Hobie/J24 Trimaran Conversion

[Delane]

I've just bought a j24 and have a Hobie 20. I'm thinking about converting the J into a Tri. The thought is to use the rear traveler as an area to tie in a spar and go under the hull on the front end jsut behind the mast. I think this would be a very fast stable boat. I love speed with a little comfort. Any thoughts out there?

[DaveB]

Great to think about ideas like that, but it might be more involved than you realize... Might wind up costing you more than it would to go out n' buy a tri... after trading in what you've got n' buying used of course... I think that tri hulls are designed knowing that they will have the outer hulls for stability... A J24 isn't... it's pretty beamy in comparison so it has form stability... it also has a whopping big keel! To take advantage of the hulls you'd want to increase the size of your rig which isn't trivial... new sails, new mast, new standing rigging, possibly re-inforcing required... The keel'd have to go too... I guess it just seems like a lot of work for a non-ideal solution... A purpose built tri like a dragonfly'd perform much better... Also, your boats are popular classes and by modifying them as required you'd destroy the resale value... If I were you I'd think about selling them and buying a used tri... dragonfly, farrier or something like that...

Just my two cents...

Dave

[Doug Lord]

I think Dave is 100% right. In addition, the beam to length ratio of the j24 hull will not be very good compared to a boat designed to be a tri keeping speeds pretty slow.

[yokebutt]

Somebody did mate a wabbit with a hobie 16 a few years ago, don't know how the offspring turned out though.

Yokebutt.

[mackid068]

Not worth it. 2 boats are certainly better than one.

[Delane]

Thanks guys for your imput. I know the ration isn't close to ideal, and planned to remove 90% of the keel and add a foam and fiber stub of maybe 2 feet and use daggers on the Hobie hull for pointing. Without changing the mast and reducing the weight of the keel (900), figure I could at least reach speeds of around 10 knots up and 18 down. The center hull minus the keel should plane at around 12.

[CT 249]

Reducing the wieight of the J keel by 90% saves....what about 800 lb?

Adding the weight of the Hobie 20 and crossbeams of sufficient strength adds what, 350 lb and a lot of wetted surface area? So you've taken 550lb out of the boat, BUT added foils that will be very highly loaded (only the lee one will be in the water and it was designed for much less sideforce at higher speeds) and windage and wsa, and you expect to increase speed? Umm, sorry, I've seen a couple of attempts at this and they are utter failures.

Re speeds; a Farrier F720 trimaran is about the same pace as a J/24 all round the track and it has a much slimmer main hull and bigger, better outer hulls, plus a better rig IIRC. The J/24 rig is not much chop when it comes to low drag sailing which a tri needs. The J/24 hull is a fat little thing, it's nothing like a real tri hull.

[mackid068]

do what you like, but post pics...PLEASE!!

[Chris Ostlind]

There's a guy near Perth, named Barry Sanders, who was building a wild thing tri from a sharpie skiff, I believe, and a Hobie 18. This boat has yards of aluminum structural rigging and is set to run with a dual H18 rig set as a schooner setup. I haven't seen or heard from him in a year or more, but I would hazard a guess that his stuff can be found with a Google of some sort.

If that doesn't work you can post a query with the Multihull Boatbuilders site on Yahoo. Someone there will know how to find him.

Chris

[Delane]

CT 249, thank you for the imput. I disagree about a F720 pacing around at the same speeds as a J24, and I'm pretty sure the H20 hulls can take side loads at any speed. I've had two on the wire a me at the hot seat, flying a hull in heavy seas to windward and just pounding the waves at 24 knots. I'm certain the H20 will take the loading of the J rig, especially when reducing the load with bodies on the windward side. I'm in the process now of determining the best location to bolt in the main cross members to the J hull. I plan to have the J hull projected out in front of the H hull to allow more initial loading (learned this from another site) and allow easier tacks. Also thinking a full batten main will help performance. Cris, thanks for the info. I'll try to find that guy, and let you know. Later

Delane

[lanekthomas]

I have effected a similar conversion of a 16 ft Lone Star mono and Hobie 16s. Speed is less than the Hobie 16, but greater than the Lone Star. Very pleased with the performance, just more weather helm than I care for.

[CT 249]

Re "CT 249, thank you for the imput. I disagree about a F720 pacing around at the same speeds as a J24"

You may well be right, but US Portsmouth yardsticks put the TT 720 at 79.X, and the J/24 at 80.X. So Portsmouth thinks they are the same speed. Most Australian races give the TT720 a rating in that sort of speed and when I sailed the agent's TT720 we were about that pace and the Trailertri agent reckoned that was the normal speed. Ditto when I raced against TT680s and TT720s, mainly on a 26' Mull. I see that Mull is still rated faster than Farrier 25s in the biggest Australian race. Then again, a lightweight and modified TT720 rates very quickly. The TTs are wonderful, wonderful boat (I want one, I have advised friends to get one, I really enjoy sailing them) they are just an older cruiser/racer and that is reflected in their performance.

They are also pushing the limits in terms of having an unusually beamy main hull, but it's still much, much narrower than a J's hull. Considering how much importance multi designers like Nigel Irens, Peteghem/Proviot and Dick Newick place on having a narrow beam/length ratio, it would seem highly unusual that a much beamier boat would go all that well.

"I'm pretty sure the H20 hulls can take side loads at any speed."

Sure, I was just wondering about the sideloads of the rig; not structurally, but in terms of overloading the optimum lift/drag ratio for the Hobie centreboards which are smaller than the sort of board you'd put on a boat with the J style of rig.

[Delane]

The start of the J conversion is near with most of the other items finished. I've completely refurbished nearly everything on the boat to include electrical, wood, tabernacle deck step, spreader thru bar mod, paint, etc. I've cut the cross bars to 18ft each. Next is fabricating a jig to accurately mark the locations for cutting the holes for the cross bars. Have a plan and drawings of how to support the cross bars through the hulls. No less than bullet proof will work since I ocean sail to local islands in varing conditions. The aluminum pipes are 5.5 inches accross and 3/8 thick, each weighing about 90lbs. Considering drilling litening holes to reduce weight by 25% and yet maintain at least 80% strengh. Rear cross bar just under the companion way and the other just in front of the compression post. Next remove the keel and seal up the keel stud holes, and launch with the approximate weight of items not on board to measure the new waterline. This will determine exact hole locations for the bars and mounting distance to hulls. My guess is it will float about an inch higher than before with a reduction of about 650lbs. Then fabricate a foam and fiberglass foil that will help with leeway and in addition dagger boards for the outer hulls. I welcome any helpful suggestions.

[tspeer]

Put the saw down and step away from the boat. Keep your hands in the air, and nobody gets hurt.

You're missing the whole point of a trimaran - how to have a narrow hull without the excess weight of a heavy keel to keep it upright. Converting a J24 to a trimaran is preserving the worst features of both types. You have the high wetted surface of the floats and the beam of the monohull.

You've refurbished the J24 - you now have a nice monohull. If you want a trimaran, sell the J and get a trimaran. Despite the common cliche, a trimaran is not really "a monohull with training wheels." These mono-to-tri conversions inevitably end up as dogs. And they ruin a perfectly good monohull.

[frosh]

Hi Delane, excellent advice from Tspeer; take it before it is too late. When you find out after spending your hard earned money and countless hours of work, that the new boat doesnt really work you wont be able to give it away. It is inevitable that such boat wont come remotely close in performance to any Farrier Tri. Either get one of those, or build one if you want a construction project, or stay with a J24.

[Delane]

Tom/Frosh,

Thanks for your input guys. By the way Tom, I was checking out your web site today, very interesting. This past weekend the J went on a crash diet of about 950lbs after a lot of cutting with speed grinders and a chop saw. In the end I may realize your predicted result or at least in part. I'm commited to seeing the project through though I expect the result wont be optimum. Having said that, and now that you see I,m really stuborn please bare with me. I,m thinking about projecting the mast about a foot or so higher to give a higher sail projection and higher boom clearance. Good or not worth the effort? Also reading forum threads on lifting foils, Moths and others. Here's a ?, would it be feasible (barely Ok) to build a foil or foils to the keel stub fixed or variable pitch to achieve lift, speed and all that stuff. Or possibly a V foil in the front with a T-rudder and or T-daggers. Consider the total weight at approximately 2700lbs with 3 soles. Just looking a options to enhance performance of a non ideal solution.

[sharpii2]

Along with the genral consenses, I have to relutantly agree.

What is really being done here is the design of a new boat, not, as it appears at first glance, the combination of two old boats. This can create some interesting problems. One of which is rigging stresses.

When the J24's rig was designed it was designed for the very limited initial stability of a keel boat plus a few hundred pounds of moveable ballast (the crew).

This determined everything. It determined the size of the shrouds, the size of the chainplates, The size of the rigging screws, not to mention the amount of reenforcement the sections of the hull that take the chain plates needed.

Now this careful engineering is being thrown out the window. This is because a trimaran can have up to three times the righting moment of a similerly sized mono. So even if the sail plan is not changed, the failure of rigging parts can be confidently predicted.

Early multis were well known for rigging failures as their builders tried to ape the rigging sizes of the monos of comparable sizes they were sailing against. After all, length for length the early multi's were from 1/3rd to 1/2 lighter than the monos.

But the absolute loads were considerably higher and easily overwelmed the safety facters put into the same rig on a mono. Then, of course, there were the shock loads. These accured when the multi was hit with a gust of wind.
The mono, in the same situation just rolled over on its side until the gust passed, shook itself off, then continued on. The multi just stood there and took it (and converted it to additional speed, if the gust lasted long enough).

You can probably frankestein this thing together and it may actually perform reasonably close to your expectations, but as the weather worsens the nasty surprises can too. And the worse part is, that without a careful load analysis of the whole structure, there is no way to predict which part will fail first. Will the mast buckle, the shroud snap, or will the crossbeam fold?

I do, however, have great sympathy for the idea that multis are designed too much for speed and too little for payload. Going very fast as opposed to going sorta fast is not much fun when you have to weigh your provisions with a gram scale.

[frosh]

Delane, have it your way, it is your boats and money. It worries me that not only are you going ahead to morph a unhealthy hybrid which will inevitably break ( but not when conditions are smooth, but when you you sailing in horrid wind and water conditions) and put human lives at risk, but you are now talking lifting foils. As far as I know no craft no matter how well designed has ever benefitted from lifting foils when the power to weight ratio is as low as the boat you are creating. You say that you need a sea worthy craft for inter-island passages. Sounds like you have a death wish or you believe that you are right with your concept no matter what others who may have more experience than you might advise.

[Delane]

Well, now you guys have me a little worried or sobered up anyway, but I have the keel cut off and there's really no turning back. To address the issue of shock load, I'll up the size of the upper shrouds (or all?) and possibly run shrouds out to the hobbie hulls as well for additional support. I've already replaced the chain plates, thicker, longer and well supported on the front side. Not too worried about the cross beams folding as they are really beefy. Also adding foam blocks to several compartments to insure positive flotation. Also well equipted with VHF, GPS, Epirb, Cell, flares, and all the other usual stuff. When completed, I'll test structural integrity with baby steps close to shore to get a feel for handling, performance or any signs of stress or weekness. I appreciate your concerns for safety and performance but this is something I've wanted to do for some while. The hobie I rescued off of a beach, minus sails, daggers, rudders, boom and some hardware. Just need dagger boards. By the way, I'm retired Air Force (Jet Engines) and have enjoyed sailing here in Okinawa for 17 years. Started with a Hobie 16, J24, Yamaha 36 (sunset cruise business, racing, etc) and now back to a J24. We frequent a small chain of islands about 25 miles away called the Kerama's. Great sailing when we aren't having typhoons.

[SeaSpark]

Need i say more.

[sharpii2]

Delane:

Even though I sided with the others on this thread, I did so reluctantly. And I did so exclusively for safety reasons.

But now that you're rally going to do this, let me make a few suggestions:

1.) Find youself an experienced NA or boat designer who has experience with multi's and have him or her calculate the needed hull reenforcements. The few hundred you'll have to pay this person will be more than made up for in peace of mind. (I would offer to do such work myself, but am afraid I am not qualified. I have some training but no experience)

2.) Prepare yourself for a lot of boos and hisses from both the mono and the multi cultures. Everybody hates a half bread. (But mutts are considered by many vetrinarians to be the most healthy and often also the most intelligent dogs around.)

3.) Prepare yourself as well to laugh as you blow past a mono j24 on a broad reach (and as a similer sized multi blows past you). Speed is cool, but it aint everything.

Best of luck.

Bob

[Delane]

Bob,

I'm going to take your advice and get a proffesional opinion on reinforcements for the main hull. I found a guy (boat builder/designer), I think Ted Brewer on the web that for 300 bills will assist. I'll draft up some KAD drawings of my interpretation of strength and see how I measure up. One positive side of a through hull spar is the forces generated on either side is distributed to all four points where the spars enter the hull. I'll keep you updated on my progress and post pics when completed. Thanks

Delane

[Yacht Skipper]

Hello Delaine,

How is your convertion going ?
Will be interested to hear results

regards,

[Delane]

Hello,

Plan to seal up the keel stub this weekend, hang the motor, add all the gear and equivelant weight of spars, amas and support stuff and mark up the water. This will determine how far down I cut the holes for the spars. Initial measurement is 2 inches below the top of the hull lip. Would like to go to 3 inches if the waterline will allow, meaning enough to allow the amas to barely clear the water when the boat is level. And then again it probably wouldn't hurt if the hulls touched the water. After all when loaded, the windward hull should fly around a foot higher. Sound good to you?

[dem45133]

Interseting thread, as I myslef had the idea too. Sounds as though were trying in a sence to mix oil and water and build a boat.

How did your endevor work out? From the time stamps on these I suspect your sailed her by now.

Dave
Hillsboro, Ohio

[Delane]

Hi Dave,

Not finished with the project. Found a house with a Million $ veiw and had to do it. Have about a dozen more small projects to complete in and around the house until I resume on the boat. I'll keep you updated.

[MichaelTK]

"a trimaran is not really "a monohull with training wheels"

Glad to here this as I just spent a chuck of money on F-22 plans :)

[frosh]

"a trimaran is not really "a monohull with training wheels"

Glad to here this as I just spent a chuck of money on F-22 plans :)

IT IS (a monohull with training wheels) if you buy a monohull and catamaran and join the whole damn thing together as best you can! :eek:

[Delane]

The tri conversion is moving along well after many delays doing other things. I want to use lifting foils and have several ideas I would like some feedback on. Configuration 1: Built on a small thin fin/dagger to the keel stub and add a lifting foil as well to the stub. Next add plug in lifting foils that enter the end of the cross bar pipes at the amas and led down the side of the outer hull and under the bottom, then turn inward about 50 degrees for about 3 ft. Configuration 2: Build lifting foil to the bottom of the keel stub and use original (not purchased yet) daggers for the H20 hulls and add a foil to the rudder with a flap to control pitch when needed. Not looking to go totally foil borne, just assist and increase speed a little. Any ideas are welcome.

[frosh]

Delane, If you have been reading the forums at all over the last few years you will know that there is one un-surpassed expert who regularly posts articles about fitting lifting foils (both fully, and partially). I suggest that you ask Doug how to design them; he is an expert, and he also has close relationships with at least one Naval Architect, so you might get a design from him free of charge. Best of luck!

[Delane]

Thanks Frosh, I appreciate your imput. I'll contact him off line.

[Delane]

Finally, some pics of the progress.

[Delane]

Original plan for the front spar was to thru bolt the PVC pipe using wood and fiber. The inner sleeve piece I had machined to slide over the pipe making a very tight bearing surface. Thought about it for a while and decided to just fiber the whole thing as shown. Change 2. Planned to tie in the rear spar using the Mahogany blocks and large stainless strap thur bolted into the cockpit. Wouldn't you know it a fellow boater (power boater at that) showed up to look at the fiber job on the front and commented as to why use the whole wood block deal if the fiber job is so great. He happened to be very drunk after drinking a lot of wine. So why listen to a drunk, well he made since about the whole deal and straight to the point. So I swallowed my pride and removed the one block that was pre-positioned and being shimmed into place prior to bolt up. Will soon fiber up the rear using also nearly the same as the front.

Plan to use 3 trampolines on each side and either remove the stanchions and life lines or just remove the lower wire making it a little easier to access the amas and forcing one to keep their CG low when moving around.

Also would like to use a full roach main thus removing the original back stay and going with a split connected to the H20 original side stay straps. Those line up exactly with the spreader angle allowing the main to swing the same as before. Another thought was to split the stays between the strap and the rear spar like you see on other tri's.

Any thoughts out there with this idea!.......Mount two each aluminum pipes standing about 2 feet high to the outer edge of the front spar. Support with struts going aft and to the side. Then slide on wind surfer mast and support the top with small struts to the mast. There you have it lots more power and down low. The Leeward sail may very well be blanketed on some points of sail but overall should provide more power making foil assist a reality given proper design and placement. Yes I got the idea from looking at the Trifoiler.

Suggestions are welcome.

[frosh]

Hi Delane, having a look again at your project after quite a while. These are my general impressions.
(1) PVC pipe has no place on a boat except for dunny wastes.
(2) You should have used alum tubing without the holes. These holes reduce ultimate strength of the tube a lot, hastening it's crumpling and complete collapse if ever over loaded. The alum tube must be high tensile grade. Is it?
(3) How are attaching to crossbeams to the catamaran hulls? Surely not as shown in the photos!
(4) You are still toying with ideas of gimmicky add-ons to improve performance, when the performance will be very flawed at the outset as I explained a while ago.
It is a bit like putting little wing tip extensions on an aeroplane to theoretically improve aerodynamic efficiency when having so overloaded the plane with cargo, that it might never take off, or worse still, crash catastrophically soon after takeoff. What good will the winglets do now?
Please! don't venture too far from shore, and carry a good quality radio transmitter. P.S. It is ultimate irony, or high comedy that a random drunk man gave you construction advice. Are you going to use the advice?

[Delane]

Geeez Frosh from the sounds of it, I’d better sail it around in a little pond for a while. You know one that’s only five feet deep so when it explodes and sinks, I can simply stand on the bottom and walk to shore. No, I won’t try to swim, that sounds dangerous too. :)

There’s risk in everything we do. Driving on a two lane road is much more dangerous. Look at the trust we take with people we don’t know. Can’t you find anything positive to say about the project? I’m not putting together some little carbon fiber pretzel stick that needs weight just to keep it from flying away. And I’m not spending tons of money to design and construct a master piece high performance craft. This is all about thinking and acting out of the box with reasonable respect for safety, performance and cost.

I’ve been reading the thread your participating in “Hull Drag”, and gather from its content that you realize many things are possible given the correct balance, weight and application of materials to achieve a desired result.

Safety is always a concern of mine when going to sea in any craft and won’t be any different with this conversion when completed.

To address your concerns:

1. The PVC pipe flange I originally intended to use to secure the forward beam would have provided plenty of strength given the application. This was simply using the resources around me that would work. This is not some flimsy trash can plastic type material as you referred to.
2. The holes in the cross beams were placed there by me. 14 inch sections where the beams receive the most loading have no holes. Can’t one place lightening holes in structures and yet provide a strong enough result to get off the ground. Referring to aircraft of course. Not sure of the hardness and plan to have it tested and crunch it up with “Beamboy” analysis.
3. Gimmicky add-on……..I could say the same thing about a craft that’s being designed with planning amas that have very little volume and noticeably placed to far behind C/G. Sounds like a recipe for pitch pull. Know anyone doing this?

Now seriously don’t you feel I can achieve some measure of increased performance, both speed and stability while keeping cost a minimum and maybe live to tell about it. As is the hull should float nearly 1 inch higher than before with a weight loss of 500 lbs. Properly designed and fitted foils should provide enough hydro assist further reducing the overall wetted surface thus making it easier to transition from displacement to planning mode.

Thomas J. Watson
If you stand up and be counted, from time to time you may get yourself knocked down. But remember this: A man flattened by an opponent can get up again. A man flattened by conformity stays down for good.

Dale Carnegie
Take a chance! All life is a chance. The man who goes the furthest is generally the one who is willing to do and dare. The 'sure thing' boat never gets far from shore.

[frosh]

Delane, I don't think that there is even the slightest validity in comparing your tri with mine. I don't want to elaborate as you might take umbrage. To be fair on the governement authorities, you could inform them that if anything goes wrong on an inter island voyage, you do not want then to spend any money trying to rescue you! :cool:

[lane]

Delane,
What is the latest in your J24/Hobie conversion. This type of construction keeps me out of the bars, that is why every trimaran is required to have a fully stocked bar.

Eager to see your creation in the water...
Lane in Austin Tx.

[Delane]

Hi Lane,

Launched her to see the almost new water line. At present the amas have an air space of about 2.5 inches at level rest. With the added weight of the mast, boom, sails and other stuff, she should settle down another inch leaving still a little space. Here are some pics.

[lane]

Good pics, Deland.

Yours is a roomier project than mine. I currently have a Hobie 18 hull as my vaka (Center Hull) and GCat 5.0 hulls for the two amas. We only have a tramp to sit on, just like a Hobie 18. So I am envious of your comfortable cockpit.

As for sail plan, I have used parallel rigs on a prior trimaran and was pleased with the results. It takes a lot of adjustment in the mast placement fore/aft to get the proper balance, and a daggerboard really does improve pointing.

Do you have your sail rig complete and ready to mount?

Lane

[frosh]

Hi Delane, congrats on launching the hulls. Geez--- it looks like your vaka needs to be put onto a extremely low calorie diet!

[Delane]

Hello Lane,

Plan to use a sutable fully battened roached main, and move the back stay to a split between the rear cross beam and the original shrould chain plate/strap on the Hobie hull. It should allow full swing of the main and provide enough support. Also have a new Pro Furl unit and a cut down 130% roller furler jib.

Frosh,

Yeah she looks a little pregnant compared to most tri vaka's. She's really lite on her feet, however I'm about 300lbs minus ready to sail weight.

[pjhrn]

It gets worse Tom S, on the conversion. A kid on our lake built an outrigger canoe using a hobie. Damn him to hell.

[lane]

So, now that the hulls float, how is your rig comming along? More Pics please.
Lane
Austin TX

[dem45133]

pjhrn;

Why would you "Da_m him to he_l" for being creative... H is real and you don't want to go there or send anyone there.

You wouldn't believe some of the ideas I've thought about. Oh and I am an engineer type...

[dem45133]

Actually, I like the idea... since all sail is slow... this allows for a more level deck which my wife would like. Her Maneirs Desease (an inner ear problem) has trouble with balancing. But tri's and cats generally are larger higher end priced boats if they have any live aboard capability. NOT EVERYONE has 5 and 6 figures for play. IN FACT the vast majority of us do not. So we get creative and improvise.

Delane... one thing that I thought of is the mono hull twisting about her longitudinal axis... in higher forces and extent of travel due to the independent motion of the outer hulls... the original design likely was not designed for any great amount of that. Something maybe to thing about stiffining... (but not rigid... all hulls have to flex a little).

Looks like you've done a good job so far. Although I to wonder too about the aluminum tubes being strong enough. Look pretty thin walled. Also aluminum has fast fatique rate relative to other metals... something to think about. Exposed like that I believe I would have considered a straight grained hardwood... yea it would add a little weight... but will be strong and more flexible...and does not have the build up of fatique weakening... Thats one of the primary reasons air frames have a max life span.

She looks good on the water doesn't she?

later

dave

[Delane]

More Progress,

Here are a couple of pics of the rear beam tie in. Adding struts or inner reinforcements to the front beam is next, followed by glassing and bolting up the Amas to the beams.

[Meanz Beanz]

I reckon that this will be really interesting to see how she sails. The J24 can plane as a mono with all that extra weight of the keel. Tris are traditionally built with very narrow hulls for all the obvious reasons... but what will be the reality of having an central hull with a bigger planning surface area? It might surprise in some ways, I can't wait to hear how it actually works... maybe we will learn something from Delane's efforts!

Cheers
MBz

[surf boat man]

hi there
I am doing something similar in australia.
I am converting a 26 foot surf boat (4 man + skiff row boat) into a tri. Using a hobie 16.

[Meanz Beanz]

Where abouts?

[Delane]

MBz,

Yes the jury is still out on the performance and only time will tell. I supect that anything from beam to broad will be exciting with at least 15 knots. I'm hoping that the transition from displacement to planning will smooth and without a large hump time.

Surf Man,

Way to go there. Sounds like it could really fly. Are you using a Hobie mast and sails also? Hope your Half Breed or Cross Breed turns out well.

[Hellkell]

Do you have the aluminum beams plugged so that water will not come through and drain into your center hull?

Nice looking work.

[surf boat man]

HI there Meanz Beanz and Delane.
I am in Sydney.
Yes I I am going to use just about everthing from the hobie 16. Hulls- one out either side, rigging and sails, rudders (two out back of the main hull) for a double rudder set up (should give a little more upwiind preformance and steerage), mast step etc. I might even used the tramp cut down wnd between each hull.
I am actually about to buy 3 surf boats. Another one I want to do an outrigger on just one side and swing up a lateen rig A real islander style boat that should still fly especially when the ourrig is on the windward side.
I am engaging with the forum for support, ideas's and run project reports.
I am not sure but I might start a new thread.
Its an interesting project becasue you can pick these boats up very cheap here. I paid $500 for my first surf boat and another 500 for the trailer. I figure I can buy a an old hobie 16 without a trailor for under a grand and hope to bring the whole porject (the honie hull one ) in at under 3,000.
Thats pretty good fopr a 26' tri on a trailer.

[waikikin]

Sounds like fun Surf boat man, I've seen those boats for cheap too, & read about someone turning one into a electric, maybe solar boat, post some pictures if you can or I might come for a look. All the best from Jeff.

[Meanz Beanz]

http://www1.istockphoto.com/file_thumbview_approve/1293033/2/istockphoto_1293033_surf_boat_ii.jpg
http://www.siliconcoach.com/news/images/thunder.jpg
http://members.iinet.net.au/~jscott/city/cpsc0021.jpg

Aussie Surf Boat for anyone who has not seen one.

A surf boat trailer for $500... I would be interested in one of those! Any pointers? I'm in Melbourne but can pick up from Sydney.

[Delane]

Surf Boat Man,

Sounds like your on your way. Using the existing tramps is clever and probably needed. You might be able to get by with using one rudder or a slightly deeper one due to the length. But since you have them, might as well may use of them right. Those boats look really solid.

Hellkell,

Yes the beams are sealed with 3, 2 inches thick peices of foam. Also will end seal with the can foam for a final sealer.

[lane]

Your hulls look great. When do you anticipate having the rig up for testing?
Lane in Austin Tx

[Delane]

Hi Lane,

I suspect in a few months I'll be down to the last of the details. Waiting till near the end to assemble the furler, step the mast, position compression post and so on. Also dumping a lot of time and money into a home as well.

Laters

[catsketcher]

Surf boat man

Your tri is a god idea that has been done pretty well a few times. I would recommend that you buy a Hobie 18 as it has much larger floats and a larger rig. I got a friend a free surf boat and looked over a Hobie 18 version. It was featured in the Australian Multihull World mag over a year ago. It was a good boat.

I would stay away from twin rudders as the transom is pretty thin as you no doubt can tell. There is a fair bit of rocker in the main hull so the boats turn okay. Twin rudders only seem to be used on Open 60s which are very wide and heel a bit. If you put them on the floats then they will be a long way forward of the main hull stern and they won't turn the boat well.

The boat I saw used the Hobie 18 centreboards which worked well and meant that he didn't need to include a board in the main hull. If you go the Hobie 16 route you will have to include a board case which will compromise your interior.

cheers

Phil Thompson

[lane]

On using Hobie 18 hulls as amas, they are a far better choice than H-16 hulls. I used H-16 hulls, hopeing they would provide enough bouancy for my vaka. Carrying a load onboard caused significant submarineing of the leward ama, tons of spray and an upset crew. So, we now are rebuilding with H-18 hulls and hope for the best.

Good Luck,
Lane

[Delane]

Lane,

Sure, the H18 hulls will provide say maybe 15% more volume and should do the trick. Question: is there another solution. Maybe using tramps to reduce spray and try a little more weight shifting to the windward side or even trapezing. Might try extending the Amas out a little. Simple seems better for your already built design. Make it easy on yourself and explore all your options. My hulls are H20 and will provide about 2200lbs of bouyancy.

[Meanz Beanz]

Try looking at NACRA's and Tornados as well, H16's are not the best even in there original config. Also the center board cats offer the option of using the boards in the Alma's (there are pro's and cons), maybe you can avoid having a cb case in the main hull. If you do get a 20' cat like the Tornado you may find that the Alma's can be placed far enough back to use the rudders as you initially intended.

http://amtrup.seilmagasinet.no/images/seachart30_1146553160.jpg

MBz

[Meanz Beanz]

These are some shots of a Typhoon, it's a Tornado conversion that might yield some ideas.

Cheers
MBz

[lane]

Delane,
It has been 6 months since we saw pics of the tri in the water. What is your current status this Christmas?
Lane in Austin, TX

[Delane]

Lane,

Nothing new to report this Xmas. Will glass and bolt up the Amas before too long.

[lane]

Where are you on the trimaran project. Just thinking about how much fun you must be having.
Lane in Austin Tx

[surf boat man]

Hey- just a quick thank you for the responces to this thread. My plans to turn my 26foot surf boat into a multi hull continue to gian traction.
I am torn between simply modifying and bolting the 18' hobie across the top of the surf boat hull and using the hobie rig and rudders- it seems like the simplest yet less astetic of two options.
The other option is to turn the surf boat into a large sailing canoe with just one out rig hull off one side. I like the design of the old malabu out rigger. I would dearly love to create a more traditional outrigger witha lateen style rig. The hull lends itself to this- it woould look absolutly beautiful. Not a high performance tri (but who cares I am 51 and slowing down a bit) but something very pretty.
My heart is l;eading me this way even though building the tri with the hobie rig would be easier because I don't have to build the rig (which scares me)

[boat fan]

Hey- just a quick thank you for the responces to this thread. My plans to turn my 26foot surf boat into a multi hull continue to gian traction.
I am torn between simply modifying and bolting the 18' hobie across the top of the surf boat hull and using the hobie rig and rudders- it seems like the simplest yet less astetic of two options.
The other option is to turn the surf boat into a large sailing canoe with just one out rig hull off one side. I like the design of the old malabu out rigger. I would dearly love to create a more traditional outrigger witha lateen style rig. The hull lends itself to this- it woould look absolutly beautiful. Not a high performance tri (but who cares I am 51 and slowing down a bit) but something very pretty.
My heart is l;eading me this way even though building the tri with the hobie rig would be easier because I don't have to build the rig (which scares me)


Follow your heart , I think it could look stunning.

[surf boat man]

Dear Boat Fan- thanks for you encouragement- and you are right.
The only thing that worries me is getting the rig right.
I will start up another thread around that next week.

The main hull (surf boat) is starting to look great. I have just stripped and varnished the teak gunnels and red cedar decks and seats- she is a very pretty boat.

[surf boat man]

thanks for that- you are right

The only thing that I am worried about is building the rig.
I am going to set up a new thread on this forum to help work out how to approach it.
I have fixed up the tatty old teak gunnals and red cedar deck on the main hull and it is looking really nice- I am getting more motivated as the project moves forwards

[boat fan]

I am envious surf boat man ! :D

You have got an advanced start to a very , very nice build.

If I could find a hull like that , I would not hesitate to make a serious effort to produce something very easy on the eye.:rolleyes:

A traditional looking rig would be the way to go IMHO.


http://www.mit.edu/people/robot/malibu/willison/images/030.jpg

I would look toward the Malibu Outrigger :

http://www.mit.edu/people/robot/malibu/willison/images/026.jpg

http://www.mit.edu/people/robot/malibu/willison/images/025.jpg

http://www.mit.edu/people/robot/malibu/willison/images/032.jpg

http://www.mit.edu/people/robot/malibu/willison/images/021.jpg

http://www.mit.edu/people/robot/malibu/willison/images/023.jpg

Don`t forget you have a superior hull than that already , at least in terms of roominess , you can sit IN your boat instead of ON it.:)

I`m sure if you think about it a while ,it will all come together .

[surf boat man]

Thanks for the pics Boat Fan- nice boat!

This is exactly the direction that i want to go in. building the outrig arms in timber and putting on a simple rig.
You are right I have a great platform to start with in a surf boat. I can't believe there are not more of these surf boats conversions around. I haven't been able to find anything on line- all I have is a distant memory of one I saw in the Brunswick river 15 years ago and it was absolutely gob smackingly gorgeous.

Do you have any pics of your sail and the full rig- thats the bit that I am having trouble

[boat fan]

It`s not my boat surf boat man, it`s a Malibu outrigger.

You could build a simple box section mast fairly easily.

A boat designed in the fifties by Warren Seaman.

Most were home built. ( very simple hull shape ).

You can actually still get plans for $ 50 : 00 US

This is their Yahoo group Easy to join )

http://groups.yahoo.com/group/malibuoutrigger/?yguid=171083269

And this is the link to those photos in above post, and other pics :



http://www.mit.edu/people/robot/malibu/willison/index.html

Warren Seaman actually built a version around 36 ft ? long:D

[boat fan]

I almost forgot surf boat man :rolleyes:

You could go with a high peaked standing , or balanced lug rig too.

In my humble opinion it`s a good choice for your boat , because :

1 : Your spars would be shorter .

2 : Easier to rig up.

3 : Rig would stow inside boat , easily.

4 : Easy reefing

5 : Cheaper to build.

6 : Looks , and is traditional.- suits the look of your boat.

If you want to go this way here is a good place to start :

http://www.storerboatplans.com/Faq/tradrigperformance.html

Reefing a lug sail ( jiffy reefing ) :

http://marina.fortunecity.com/breakwater/274/2000/0615/index.htm#BALANCED%20LUG%20JIFFY%20REEF

You can make the sails for a lug rig too , it`s not that hard to do :

http://members.aol.com/polysail/HTML/lug.htm


http://marina.fortunecity.com/breakwater/274/1998/1015/index.htm#Lugsails%20From%20Polytarp%201

http://marina.fortunecity.com/breakwater/274/1998/1101/index.htm#Lugsails%20From%20Polytarp%202


Lateen Sail:

http://members.aol.com/r7dg/lateen.htm

http://jimsboats.com/burtona.jpg

http://www.jimsboats.com/15mar08.htm#Rigging%20A%20Lugsail

Try these links also :

For working out spars :

http://marina.fortunecity.com/breakwater/274/1998/0901/index.htm#Sail%20Rig%20Spars

http://homepages.paradise.net.nz/garyd/

http://homepages.paradise.net.nz/garyd/24TackingSail.pdf

[surf boat man]

Dear Boat Fan

I can't thank you enough for your feedback and for sharing your research.

I love the last rig link- the 24'tacking sail- it looks more the business if you know what I mean.

I will keep in touch and let you know how we go and post some pics.

I wlll be away on a month or so- First down the far south coast of NSW then India (if i see any interesting boats there take pics and post them).

Anyway I will come back to this thread when I am back- Or I might start a new one for this project and any interesting indian boats that I see.

For now thanks again and happy boating!!! You certainly do have the spirit of a true boat fan!


BTW- here are some of my fav boat sites- just in case you haven't seen them-

http://www.adventuretrimaran.com

http://www.holopunicanoes.com/hss.html

http://www.holopunicanoes.com/hss.html

http://www.boat-links.com/Sails/

http://www.boat-links.com/Sails/

http://outriggersailingcanoes.blogspot.com


ttfn- Surf boat man

[boat fan]

Glad I could help surf boat man ,

I believe that sharing is what this ( or any ) forum should be about .

And yes , please start a new thread when you get back .

Best of luck on your travels , thanks for the links. :)

[bill broome]

why? got an excess j24? sell it, buy/build a tri. this kind of plan converts money and effort into a garden ornament.

[surf boat man]

these are the pictures of the surf boat when I bought it

[Delane]

“Vitamin Sea” is near completion and should launch around the first week in June. Ordered and received a foil section, NACA 66-0012; 50cm root X 25cm tip X 71cm length) dagger board. Also utilizing H-20 daggers for the Amas and have a question regarding placement of the foil section relative to the original position of the as built J-24. Decided to use a standard J-24 Main, 110% Roller Furler and utilize water stays in addition to the existing new rigging.

Once the position of the foil section is decided, I plan to butt weld a 25mm steel rod to the flat 4mm steel plate. Next fiberglass the foil section and glue to the rod (gussets included) and then epoxy and glass up all to the bottom of the keel stub. The thought is to make it relatively strong and yet not make holes in the stub as with the original lead keel. The attached pics illustrate the foil section and plate minus the 25mm rod. The rod will protrude into the foil section 15 inches. Question is where I should place the section relative to previous. I’m thinking as far forward as possible but it looks right positioned a little further aft.

[BWD]

The foam in the picture looks light and non-structural (but very nicely shaped).
But even if it's strong foam, it's only foam, and putting metal rod in it seems a waste. The problem is there is nothing strong connecting the 2 skins.
Unless that foam is really really strong!

Under sailing or grounding load the fin could flex and the rod could tear the foam apart, unless the glass skins are very thick and strong, in which case the rod is not needed at all.
What I might put in there is a solid wood spar replacing all the foam at max chord, helping with grounding loads as well as serving as a sheer web.

But if you ground hard, I think you could really trash this kind of fin anyway, unless the skin thickness was truly enormous. Even without the lead, it's no dinghy.
The normal "light" alternative to a lead fin is a hollow steel one.
I would have considered using a daggerboard that could crush or kick up. Feel like building a trunk?

[Delane]

Yes it's true!

Had two good runs in a bit of a breeze and a great celebration barbeque with family and freinds at the Marina.

Speed to wind about 8 knots on the first run with the throttle at about 70%, sorry in the habit of translating for my power boater buddies who demand I break it down in those terms. Off wind seemed to be about the same but didn't have a JPS to verify the first day.

Well, I'll let the pictures speak a little.

Enjoy!

[Delane]

Here are some other shots of the first day!

[Zilver]

Congratulations on the completion of your project ! Nice idea and boat.

It looks like you were having a lot of fun on the maiden trip.
Please report some more observations about how she sails when you can.

Cheers, Hans

[mihari]

Congratulations!!!!!
Now we want to hear about how Sea Vitamin sails...
She looks like a fun boat...

[sharpii2]

Congrats.

I bet it even planes quicker than it did with a keel.

It might be interesting sport to race it against keel versions to see how the performance compares.

[aussiebushman]

Hi All

I'm new to this forum but not to boatbuilding or to the idea of building a tri from donor parts. Unfortunately, I have to sell the Simpson catamaran I built(see www.mainproject.info for details) and now want to build a trailerable trimaran. The idea of using a surfboat is really interesting and stops me having to find a suitable trailer sailer to convert. The advice about using Hobie 18 amas instead of the 16's I was considering is very sound.

I'm located near Sydney so if anyone knows where to locate a suitable surfboat or Hobie 18 at reasonable prices, please let me know.

Regards to all

Alan

[GOTTABSOMEWHERE]

Hey AUSSIEBUAHMAN



See my pics with 18' HOBIE and DORY lashed inside with "A" mast

[lane]

How does she sail, this J24/H18 trimaran?

[bill broome]

don't listen to these people, they are the same ones that said 'an elephant can't fly!' for the same reason, too, and then dumbo came along and showed them that an elephant can fly. hah!

[Delane]

Hello Lane,

She sails great and so far have hit 10 knots on a reach in about 17 or 18 knots of wind. Will soon finish fabricating an articulating bow sprit and try an symetrical spin.

Laters,
D

[lane]

Hey Delane,
Glad you tri is on the water. I should have my Hobie 18 based Tri on the water in February. With 16 ft of beam, she is VERY stable and gives a lot of walk around room on the tramps. Will post pics soon.
Lane

[oldsailor7]

Hi Delane.
Glad your conversion worked out to your satisfaction.
One thing bothers me though. Your unsuported crossbeams.
Where are your waterstays. :?:

[lane]

Here is a pic of my "new" trimaran named "Tri Again". 18 feet of Hobie 18 main hull, with two 5M GCat hulls serving as amas. The boat trailers at 8.5ft beam and then telescopes to 16ft beam for sailing.

Here is a pic, fully rigged with the Hobie 16 mast and ready for fitting the sails from a donor Hobie 16.

Lane

[oldsailor7]

ZED.
Thats not a Catamaran----Thats a Proa.

I wouldn't think much of a sailboat broker who didn't know the difference. :eek:

[oldsailor7]

.....

[Zed]

ZED.
Thats not a Catamaran----Thats a Proa.

I wouldn't think much of a sailboat broker who didn't know the difference. :eek:


That will be the Boatpoint mob, their system never had an option for Proa so I guess they called it a cat, kinda lucky it didn't get listed as a power mono hull really! <--- This is a reference to the abilities of BoatPoint dataentry staff in ID'ing such a craft!

Edit: but the description is from the owner... I guess?! A 'SHIPWRIGHT' so I dunno what that says!

I thought it was interesting given the surfboat discussion!

Further Edit: To the sad sack that zapped me for this post ---> Get A Life! :rolleyes:

[Zed]

Back to the PROA and my originally unposted thoughts....

20K for an old surf boat cobbled together with a surf ski! Not of my money mate! You have to be kidding me!

Enough of a contribution for you? Well you asked for it!

[harrygee]

Hi Delane
I'm interested in your conversion as I've done a similar thing with a Soling for similar reasons. I designed and built my own floats and beams, removed the keel, installed a c/board and dropped about 500 -600lbs. I kept the same rig (restayed) and sails (20 years old, I'm on a budget) with these results that may be of interest to you.
I race in a mixed fleet with a "by guess" handicap which has gone up 10% since the conversion. Not much of an improvement there but the boat is so much more fun to sail. Last year, as a stock Soling, I was slower than the other Soling in the club, slightly quicker than a J24, both of which could outpoint me easily, a big advantage around the buoys. This year, I've been quicker in all but two races, sometimes by big margins. My advantage is most obvious in winds above 20 knots. Above 25 knots, I can go to windward with Etchells, not pointing as high but footing at speed, 9 to 10 knots tacking about 100 deg. Running square, I am hardly any faster (the boat sits 1.5" higher) but the spinnaker is easier to use (no pole). On a reach, there is no contest. I've also done four races against a well-sailed TT720, which I used to own, with two wins and two losses. The most I've seen on GPS is 14+ knots, at which speed the spray is blinding - she throws a bit of water around. Ease and fun of sailing, whether with crew or single-handed, has transformed the boat.
So stick with it, it's all about having fun.
Harrygee

[Delane]

Harrygee,

Our boat are comparable in speed and handling from the sounds of it, although I haven't seen over 10 knots yet. I'll soon try out my spin on a bow sprit soon and post some pics as well. I've added water stays as well and plan to add strut wires at the front beams. Wanted to be able to handle more shock loading due to the current configuration. I would love to see pics of your creation.

Yes it is all about having fun!

[harrygee]

Hi Delane
I'll try to send some pics and, if that works, I'll follow up with a description.
Harrygee

[harrygee]

Hi Delane
I managed to get a pic to fly. I'm no computer nerd so that impresses me no-end.
The tri does everything I was hoping for, at an affordable cost. The Soling cost very little, about the price of a mast so it was a good place to start. I've done nothing to change the basic hull shape, though it could be made quite a bit faster with a bit of scalloping. That would make it slower to tack and I get a lot of fun out of spinning fast 360's - it'll spin in ten seconds or so and keep doing it until I get sick of it. The jib is self-tacking so the boat is very easy to single-hand. I'm currently cutting a couple of feet off a J-24 genoa to fit, it will be about twice the size of my self-tacker and will help in light winds.
She goes well in a breeze, hitting a wall of spray at about 14 knots, trying to plane. There are no signs of stress anywhere, though I've only had one racing season so far and the most I've experienced is 30-something knots of wind and 3' seas. The beam-ends are a tight fit into tapered sockets for trailing and they seem okay. I don't have structural stays on the beams but I can't detect any movement. The beams are just low-tech laminated oregon and gaboon ply with double-bias skin. The floats are stone-age csm and wr, all polyester, 150 lbs each.
I'd like to get hold of a proper roachy main or an Etchells rig and sails. Even better would be a conversion of an Etchell, they're fast boats and, with nearly a ton of keel, there's a lot of potential. As a bonus, their keel is lead, whereas the Soling keel is cast-iron. A good mooring, not much else.
I'll try to get some more pics.
Take care
Harry

[Delane]

Harrygee,

That looks like a very fun boat. Yes I think an Echells would make a great converion boat as well. Lots of potential with that hull.

Take Care!

[Delane]

Planning to modify the Vaka in the following way and wish to gain some insight. The plan is to add a hump section to the center of the main hull in an effort to add buoyancy and in effect take out the inherent rocker design of the boat. Basically I want to stop the suction action that is created by the fat rocker design and reduce friction. Another way of saying is I want the hump to do what the hull did previous but in a more efficient manner so to speak without all the spray and drag factor. The rear U section (frame) would measure somewhere on the order of 16” wide X 23” deep. All frames forward would off coarse reduce in size due to hull shape to the center and then increase again forward before becoming narrow into a plumb bob wave splitting nose. The idea is to calculate enough volume to lift the Vaka about 8 more inches dry. With that said I’m sure I would need to offset the Ama’s as well to compensate for the titter factor. I’ve been thinking about this for a while and during a 25 mile broad reach leg last weekend I was convinced that the hump would provide additional speed. We hit 10 to 12 knots several times in about a 16 knot blow. Of course flying a Gennaker, 115% Jib and Main helped with speed. If anyone wants to see I’ve got Video of that day. Do you think I’m on the right track?

[Delane]

Here's an idea of what I'm talking about from a profile view.

[oldsailor7]

Why does this thread leave me shuddering. :rolleyes:

[bad dog]

...maybe because, as my kids would say, "you're old" ??:p

[oldsailor7]

Right On.
Like-----Bin there, done that. :D

[oldsailor7]

Bad Dog.
Will you be sailing your Dragonfly today in the 11.30 multihull race. ?
I watch that most Saturdays as I live directly opposite to the RMYC. :D

[lugnuts]

My neighbor, who has nutjob tendancies, just gifted me this conversion. Venture 21 less swing keel (replaced by daggerboard) with 16 foot long cat hulls. I'm a monohull guy and I had my doubts but I have to admit, it's a blast to sail. Pix attached for your viewing pleasure.

[cavalier mk2]

Glad to see it, I have a Macgregor 23 I've often thought would be a good tri as they are pretty tender with the keel. The down side is the small section mast . It's fine for a boat that heels in the puffs but I don't think it'll take the high loads for long.....

[Delane]

It's good to see other transforming mono's into tri's. As for this boat it too could benefit from a modified center section of the Vaka.

[lugnuts]

It's good to see other transforming mono's into tri's. As for this boat it too could benefit from a modified center section of the Vaka.


I guess. It's a helluva lotta fun as is. Planes pretty easily and has a lot of giddyup. The real enjoyment from sailing a mutt like this is politely tolerating snide comments from blue bloods at the yacht club bar and then completely blowing them out of the water later in the day. He also gave me Chris White's book "The Cruising Multihull" and after reading it, I do believe that I'm about to drink the Kool-Aide on multihulls.

[cavalier mk2]

The ventures are a easy planing hull, nothing wrong with the shape except to fill in the recess where the keel used to be. Should go a lot faster than a J-24 conversion as they can pass 12 knots on a downwind plane stock. The 21 is the most dinghy like model but the others can plane too.

[Delane]

It looks like a lot of fun. Do you know if it has Tramps. Those are great for rail meat or sleeping on when camping. For those participating in the thread, what do you think about my recent plan to modify the Vaka?

[lugnuts]

Yes it has tramps. He used a section of old mast at the bow end for the front of the tramp and the rear is attached to the rear crossbeam. Also, the mast is from a catamaran-can't remember which one.

[cavalier mk2]

I'd find a boat with more of a planing hull and save on some work. Adding windage and weight is a hard way to try to go faster so you'd have to think about cutting the old bottom out. Remember you're carrying around a fiberglass layup that was designed to handle the racing loads of a keel. Taking out the swing keel trunk of a trailer sailor and putting a new bottom over the slot is a easier way to lose some weight though there needs to be enough support/stiffness for the bottom. Bulkheads should be glassed in where the akas are etc....

[lugnuts]

. Bulkheads should be glassed in where the akas are etc....

Could you explain? Do you mean bulkheads in the vaka where the cross beams attach for more stiffness? I'd like to upgrade my conversion since I've been so impressed by it.

[cavalier mk2]

In the Vaka, I'm presuming you are using beachcat amas with their stock aka attachment areas but if building from scratch those points need to be strong too. Boats like the Venture 21 typically had bulkheads (sometimes of not great ply) fastened in with machine screws. They can be relieved for passage but should reinforce both sides of the vaka as well as the deck. The aft bulkhead that supports the front of the cockpit back edge of the cabin should be upgraded to better ply and tabbed/glassed in too. The internal hull liner is plenty strong so it is OK to tab to it to avoid bulkhead print through on the Vaka skin. The deck,hull and internal liner are through bolted/screwed at the sheer with adhesive goop which may have dried out. If so it may leak at the sheer so use a adhesive caulk, you'll see where check a fastener for condition while you're there.

[lugnuts]

Thanks for the good advice. I would eventually like to take her out in open water but I'll be beefing her up first. Also, I'm toying with the idea of converting to a Chinese lug (junk) rig. Not the old fashioned kind but the modern cambered junk. I have Hasler and McLeod's bible but I'm unsure as to where to reposition the unstayed mast on a tri. Anyone care to guess?

[cavalier mk2]

They don't really work that well on multihulls because of the further forward apparent wind but I haven't really checked out the cambered version.. You need to be able to point, an unsupported luff tends to get turbulence. If you go to a free standing rig you'll need to beef up the area to put it because the boat isn't designed for it. If you are balanced now figure out your new rig CE and locate it in the same area as your current one.

[lugnuts]

I notice that Delane's link to his conversion on you tube has been deleted from this forum. Is it against forum rules to link to youtube? Just wondering...

[Boat Design Net Moderator]

I notice that Delane's link to his conversion on you tube has been deleted from this forum. Is it against forum rules to link to youtube? Just wondering...
No there is nothing wrong with including a youtube video. Delane started a new thread here:
http://www.boatdesign.net/forums/multihulls/vitamin-sea-j-24-tri-conversion-videos-38807.html

[Delane]

Well here we go!

In the planing stages of determining materials, construction method and dimensions for the soon to be added hump section for the Vaka. Yes, I'm effectively going to change the shape of the Vaka by adding the equivalent of another Ama under the Vaka thus changing everything, and hopefully for the better. In the end I intend to achieve a dryer, faster boat with minimum added weight. Initial thoughts are to construct in a (U) shape blumb on both ends thus taking out the rocker in the hull. Studying Canoe building methods now which I hope will prove helpful for my endeavor. Considering using either one of the following materials for the formers (sheet FRP, epoxy coated ply, thick surfboard foam, aluminum ) and would appreciate some suggestions there. Also haven't decided which material to sheet with (thin ply or foam ) before glassing up. Thanks in advance for any help!

[harrygee]

Hi Delane

The work on your modification might be easier with the hull inverted or you could make a mould, using cheap junk ply faired with plaster or cornice cement. Then you could make a bolt-on conversion, which could be bolt-off if it's a flop.
Taking out all the rocker, as it appears on your profile, will make it a bit reluctant to tack.
I can understand your comments about the wet ride; my own soling conversion throws a bit of water around above 12 knots, becoming a fire-hose at 15 knots. Great fun though. It's a bit more of a "mongrel" now, as I broke the mast a while ago, caught in a 40 knot blow. The soling sails had no reefing and dropping sail would have been dangerous, so nature dropped the rig. The cheapest replacement was an old dragon rig so I now have 20% more sail. That's what you do when the rig breaks. I also have a big reef.
I love my boat. It's cost me half the price of a ply trailer tri, even with the broken rig and I've had a lot of fun building and sailing her. Highest speed recorded on the GPS is 24 knots on the day the rig went, when I suspect there was very little of the soling in the water. I'll try to get an action shot to post, she looks the part when the spray is flying.

Take care
Harry

[upchurchmr]

I hope you draw this up before you start making things.

If you put an ama under the Vaka you are going to float this very high. There is no purpose in doing this. If you are going to build another ama anyway, just make a whole new Vaka.

I suggest you just use the J-24 hull without adding the hull changes. It has worked for one guy. Be happy with that.

If you put a bottom hump on the J-24 how are you going to attach the aka's? Sloping down to the amas?

Bad.

Marc

[Delane]

Hello Harry,

Sounds like you're having a blast with your creation! Would love to see some action video some day. Thanks for your suggestions and yes I thought about different methods of building. I'll post some visual aids of my building plan when finalized. Simple, strong and effective is the goal.


Marc,

Thought about drawings and I'm not adding a huge hump so large that it's going to float me up over more than a foot. When I build the form I can roughly calculate the volume and this have an idea how much rise to expect. The goal is to minimize the drag effect of the (mono hull) and cause the hull to perform more like a purpose built Tri with a similar shape. Will also drop down the Ama's to compensate for the rise. Think when i post some drawing this will become clearer. The boat will reach her full potential, I won't be happy with anything less.

Happy New Years Everyone!

[Delane]

And with that said, the trailer/boat is leveled and hardback is constructed for lack of better words and soon will finalize the fabrication of my station jig pattern thingamajiger that will slide down the hardback to each frame location. I'm looking at two options for the stern most frame. 1. Start out fat and plumb with the stern (U shaped measuring 22D X 20W) and continue forward until terminating in a sharp wave cutting nose that will extend past the original waterline by nearly 16 inches. Or option 2. Start with a tapered stern frame ( 10D X 10W) to reduce the affect on rudder control and to control excess volume in the stern. On the web I encounter two schools of thought on stern profile and the answers vary based on the boat era, type of Tri and the Author. I've decided to use 10mm ply for the frames and sheeting prior to layup but may consider other options. And because many will ask, the hardback is only there for determining the shape and exact location of the frames. Afterwards I'll set up the hardback next to the boat, narrow the top pipes and slide the frames (each having two each alignment holes same as the pipe) into position upside down, add stringers/sheeting and begin to glass. When completed I'll cut the slot for the dagger board, lift the boat up and slide the completed hull assemble up to the original hull and tab it into the hull and glass around the dagger board slot opening. I welcome and suggestions that may help achieve the desired goal. I've never built a hull like this and only going with what I know and have studied on the web/forums.

[Delane]

Thought I would post some photos of the beginning phase of the project. Still debating on exact hull shape and would appreciate some input. One thought was to make it the same as the H-20 hull but maybe 20% larger.67099

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