Hobie/J24 Trimaran Conversion

[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!

[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