Beachcat vs. Beachtri?

Hi again!

All of you, thanks for all your help and links! Chris, the links about the 3m Class was very interesting! And as I wrote in my mail to you Chris, really nice boats your small tris! Thanks!

Grob, whats the Idea behind having 4(i guess) identical hulls? Is it for transportation and stuff like that or is it performance oriented?
The Biplane rigs looks really cool

Yeah, maybe a cat would be best? But somehow, I prefer trimarans, think they look better.

I would like to test something like the lifting boards or is it called foils?, that they have in the amas of the 60's. Or do you guys think it would work with outwards canted boards with lifting foils like the Moths in the bottom? Or is it better as on the 60's with one centreboard in the vaka and arched daggerboards in the amas?

When I read about the 3meter class I found out that they are a bit to slow, topspeed around 6knots, but its a nice concept still.

I think something like 16' high volume amas, lots of foils, long bowsprit, two trapezes, rotaing canting wingmast, square top main, jib, and the looks of the 60's, thats what I want But also to be possible to go from overpowered catkiller for two guys, to singelhander sitting in the vaka. I mean, can always take a reef or to, and skip the jib and/or assy. Depending on conditions of course. Would like to singelhand trapeze to, need the exercise I want to both be able to sail alone and with a friend.
Would this be possible on one platform? I would be a multi in more then one aspect

And if you wonder, yeah, I´m a bit crazy

Thanks againg everyone!
Best regars
Robin Larsson

 

killer tris

I wouldn't try to directly scale down an ORMA 60 foil system which is very dependent on ama reserve buoyancy for pitch stability. I can go into that some other time in more detail.
Your idea of canted out foils like a Moth may be a good idea: to create a foiler that takes full advantage of the power to carry sail of the tri configuration. Of course, you should see Kotaro Horiuchi's boat in this forum and consider just adding significant bouyancy pods to a production Moth...
The boat in this picture is the first production rc foiler and designed by me with lots of help understanding the concept from Dr. Sam Bradfied. It is similar in concept to the Rave and Skat but the foils,rig,and overall beam are somewhat different as are the hull designs.
This type of foiler works on the princible that the differential altitude control systems create lift a well as rightig moment. I'm going to experiment with the idea(a VERY expensive idea, Robin) you had down the line and these are the mods to this design that I'd make:
1) the boat is already more "oversquare" than most tri's yet tacks very well so I might increase beam a bit more.LOA 56" BOA 71"
2) the foil system would be completely redesigned NOT to develop it's own RM: there would be two canted t-foil systems(one wand per ama like now) in each ama but the ama would be extended by use of a non immersed carbon tube so that the rudder foil was almost as far back as it is in this picture on the main hull. At static this tube would not touch the water. The reason for this is that the foil systems in each ama would now be designed to operate entirely separately as opposed to together(differentially). The new model would use a movable ballast system to move the weight of the battery. On a full size design using this concept the crew would move outboard using trapezes(maybe) instead of sitting in the center as they do on a Rave.
3) At static if the boat was balanced perfectly neither ama would touch the water and when retracted neither would the foils. But the new boat woud be designed to sail with the leeward foils down and the windward foils retracted.
The boat would be designed to fly in as little as 5-6 knots of wind due to the massive SA but the rig would be reefable/reconfigurable. The major advantage is that none of the foils lift is used to generate righting moment and that saves a lot of drag.Also when underway on foils there would be just two surface penetrations saving even more on the drag budget. When sailing in anything over 5-6 knots this thing would fly on just two foils. Also because the foils are not developing differential RM the structure of this boat could be somewhat lighter than the Rave/F3 type.
Probably enough to makeup for the extra foil set and rudder "gantries". Disadvantage: foils probably would not be retractable creating extra drag below 5-6 knots windspeed.
mfoilerf3_14a.jpg
Changed:7:04 PM on Monday, June 18, 2007

 

3 metre trimaran

Hi , I have just registered as a member, have been lurking for some time and seeing some very interesting discussions.
Re the 3 metre tris, I designed one some years ago and sold some plans in various parts of the world. Have built 3 of them one of which I sailed for a while. I decided 2 years ago that the design could be modified to make sailing it more fun. I redesigned the boat adding 500mm (1'-8") to make the overall length 3.5 metres (11'-6") and called it the SCARAB 350. The Scarab 350 can be sailed one or two up sitting on the trampoline with feet in the main hull and steered with a conventional tiller and rudder arrangement. It has a jib (self tacking) pocket luff mainsail and if required a retractable prodder with screecher. The design has been modified to cut down building time tremendously (over the previous 3 metre design) and may be built in plywood or foam sandwich. If interested have a look at the Scarab 350 at http://www.teamscarab.com.au
Regards
Ray Kendrick

 

Doug, I didnt mean flyfoils Thats not really what I want, I want atleast one hull in the water Dont know why, just dont realy like the flying och foils idea, sorry

Your pic didnt work, atleast not for me.

But the two curved daggarboards they have on the Orma 60s, arent they there to minimize the risk of pitchpoling? Wouldn´t then a narrow entry ama service even more from having said boardarrangement? Maybe not. But I´ve understood it as that daggerboards do the (more or less) same job as lots of reserve bouyanzy?

My idea was to have daggerboars canted outwards in the amas, pretty far forwards, with smallish lifting foils attached. So they would both do the job of reducing leeway and keeping the bows up when driven hard. Since that seems to be the most commonway of capsizing multis, atleast beachables.
Rudder on either all hull, och only on amas. No centerboard in vaka.
The vaka should fly most of the time anyways, so why bother having a centerbord that will only be half inmersed?

Thats my idea, if its any good, I dont now

So thats really back to my original question, why even bother having the vaka, if its going to most of the time? How can having an extra hull in the air make the boat faster than a cat? Cause that seems to be it, I mean, there arent that many Orma 60 cats, I only know of Parliers, any more out there?
Is it better loaddistrobution that makes the vaka usefull?

Ray, thanks for the info! Welcome to the forum, but I´m also rather new, so I´m not the one to say it really
The Scarab 350 seems like a really nice boat, so does your other boats to in fact. For a couple of years I have sailed a lot with my 4.8 meter keelboat, a small cruiser from the happy 70s And a tri in that size would be fun, but not now sadly...
How fast can a 350 sail? I wanna go fast you know About how many building hours would you say?


I really feel that I have to get my Wasa 55 ready, so I can sell it and build/buy myself a big trimaran instead

Regards
Robin Larsson

 

Hi Robin, I detect a strong sense that you are dreamer much more than a doer. That is OK, but in real terms, the sort of tri you want has not been built yet in the size range you are interested in. You might need to self design, and if the exercise is likely to be theoretical, then Doug might be the help you need to get a true radical multi purpose " Killer performance" boat on the drawing board.
However I hasten to caution that even if it is finished on the drawing board, it is HUGE step to translate that into a fully functioning trimaran in the " flesh".

 

Hi Frosh,
You detect right I´m afraid, I most certanly like to dream away at times, have a lot of ideas And, for sure, sometimes things dont always get done. But, I must say, when I set my mind firmly, then I get things done. Hate to leave a project half way through, so I usualy dont.

I see what you mean Frosh, and sometimes I need someone to bring my feet back to the ground, thanks
But I also feel, that if I´m gonna do something, then I wanna do it "right", see what I mean? dont know the way to say it english.

But hey, way better to have a small tri that sails good, then a half finished one on land that possibly could have done 1 knot or 3 more

If there havent been a tri like the one a envisoned built before, is it because its to complex, not enough bang for you buck, or because its a bad concept?

Feels a bit like if one should go complex, for the sake of speed, than it deserves a full carbon construction to, see where this is going? And thats something I cant do right now.
I could probably get a simpler tri built in plywood, thats far more doable right now. And thats really what I wanted, a relatively small project that could be finished "soon".

But say that I build Chrises 14footer or something like that, or Rays 350, wouldnt it be possible to test different daggerboards and such, adding complexity along the way so to say? Or wouldnt it be worth the job?

And Frosh, how is your planing tri coming along? Should be sailing soon shouldn´t it? Hope all goes well!

Regards
Robin Larsson

 

The principal reason for the four identical hulls was transportability and ease of manufacture. The boat was designed as an entry to the BMF 2002 Concept boat contest, it was a finalist and the brief for the competition was to design a transportable boat.

All the best

Gareth

 

Kiss

Hi Robin, you have heard of KISS havn't you? "Keep it simple, stupid!"
Not a bad principle to follow the majority of the time. When an International Moth changed from a simple homebuilt scow or skiff to a high tech, all carbon, lifting foil, extreme sail boat, it became about 10 times the price, and was beyond the average sailor to take out and simply have fun.
If you can build assymetric ama fitted banana shaped foils within arced centreplate cases, good luck, most of us amateurs probably couldn't. I for one have never attempted it, and would not bother, as it is now becoming extremely difficult to build and also to sail, for minimal extra benefit. Easy to draw up for fun, even I could do that in an hour.
My planing ama tri has temporarily stopped due to very heavy other committments and should be ready before the Australian Summer. The main brief to myself was (1) Try something fairly different that might have a good chance of higher than normal performance in stronger winds, which is our normal summer weather. (2) Keep it fairly simple in concept with not to many moving parts or adjustments to be made. (3) Keep the whole structure as light and strong as possible using exotics or state of the art timber boatbuilding techniques. (4) Keep the concept simple enough that one experienced and one novice sailor could go out and get considerable performance and maximum fun without a long learning period.
Keep us informed of what you are going to do.

 

Grob, thats what I thougt, smart concept! How does it it sail?

Frosh, yeah, heard that expression, we use it in Sweden to Of course that is a good way to do things, will take your advice for now

About banana foils, I´m not sure that I could do it, but a rather think so, I do have a abrasive waterjet machine to play with, accuracy about 0.1mm. Could make jigs and or mould in alu for the boards.
But as you say, probably not worth it.

But asymetric daggerboards in the amas, that could maybe be enough, if I dont build a boat with "keels" like the Hobie 16.

Of course I´ll keep you updated! But not likely that I will start building until my keelboat has hit the water, maybe around late august. But that depends on if I can get the keel casted in time, otherwise I might start building a simple tri this summer we´ll see.

Thats seems like some good specs for your boat, will fun to sail I think Hope you get it done in time, but I think you will!

Regards
Robin Larsson

 

Thanks, its a work in progress, it has high wave drag so is not great in light winds, but once it gets over the hump its pretty quick. Still needs alot of work though.

Gareth

 

How many foils is the right number?

Hi Robin, as much of your postings have been about types of positions of underwater foils on the new tri (yet to be designed and built), I thought I would give my thoughts on this topic. First decision to make is whether the vaka will be regularly flying. In a small boat I can't see the point in doing a tri with only the leeward ama in the water. It is lighter and cheaper to go for a cat and the and F16 homebuild design ( such as the Blade) probably is the best way to go.
Assuming that you want a tri and that the vaka as not meant to regularly fly, then put all foils on the centre hull, otherwise on every tack and gybe when many tasks are being undertaken by the crew in the space of a few seconds, you also need to drop the plate on one ama and raise the one in the other. Think about it! Can you achieve this as well as control the tiller, and sheets for 2 or 3 sails, rapidly shift crew weight, all at the same time. My feeling is that it will be very difficult, and becomes stressful, and for what advantage?
The banana foils on the ORMA 60 significantly add to reserve bouyancy on the leeward ama almost lifting it out of the water at high boat speed. The design and placement and exact orientation of the boards will be very critical because they will be carrying huge loadings. In other words a design error can be disastrous in strong winds. I consider this an unacceptable high risk strategy, as the chances of getting it right at first attempt are small. If doing straight boards, whether canted or not, you still get all the disadvantages without the main advantage of the banana board. (leeway resistance and lift at the same time). Then it will be almost impossible to do a minor surgery to change the position, shape or orientation of a banana board. Having foils in the amas significantly increases the structure and therefore weight of each ama, which is ultimately speed robbing. My feeling for my own boat was to do an 18ft. tri, with advanced building techniques and materials at a much lower weight than the same length F18 cat. This factor alone will probably mean that on many points of sail the much lighter tri will be quicker.
For rudder blade(s), why have two when one will do an excellent job with less wetted surface, less construction, and less complexity.
You shouldn't look too closely at extremely high tech 60 footer designs when doing only an off the beach 16 footer. Hope this makes the foil(s) thing a lot clearer.

 

killer tris

The point of using a design that allows the main hull to fly is the phenomenal increase in righting moment and ,therefore, power to carry sail. But you can't just mimic the ORMA 60's because the scheme they use to control pitching won't work nearly as well at this size.
The increase in weight is more than offset by the increase in power. In my opinion, foils on both the rudder and a single daggerboard with planing amas or as I described in a previous post are the type of solution that would allow this kind of power to be effectively exploited. Both allow the use of smaller than "normal" amas which is a weight reducing factor while using th the foils for lift and pitch control in the one case and for pitch control only in the planing ama case.
A tri that uses the trimaran configuration to maximum advantage like this will be much more expensive than a "normal" tri. And much faster than any normal tri or beach cat in light and heavy air.

 

HSP is a good base

Hello all,

I watched Frank Bethwaite get the HSP going over a few years. It went from a complicated slow arrangement to a very fast simple tri. I am a trimaran afficionado having got my first tri, a Piver Nugget when I was 15. As much as I like the normal tri configuration I wonder about its use at small sizes.

The Windrider and its ilk of lower performance but wonderfully sensational sailing are very intoxicating boats. I always wonder about the need for speed on a play boat. I go sailing to feel the boat go over the waves. It is not so much raw speed but the senses the boat delivers to me that are the reason I sail. 12 knots on our 38ft cat is nice but can be mundane. 12 knots on our Tasar is a hoot.

So for a fun boat the pursuit of speed itself is problematic. It may increase complexity, cost, skill requirement and the like. If I didn't have far too many other things to do I would like to build an HSP - very easy shpaes to build - asking for KSS. Very simple and light crossbeams - alloy tubes. The engineering of the HSP setup is far easier than a normal tri as the beams become compression members rather than cantilevers.

Scaling down the ideas in large boats can be problematic in other ways too. A friend who worked for Lock Crowther told me of sailing Shotover - the 60ft cat built in the 80's. He said they could fly a hull in that safer than a smaller boat. The accelerations were much slower than a small tri and so gave more time to react. Getting a small tri up on one hull could be trickier than it looks.

Just build whatever gets your kettle boiling. Only you have to love it. If you really like sailing it, chances are someone else will buy it from you when you get over it. Then again don't put too much money into it so that you can keep it if no one else loves it enough to sell it to.

cheers

Phil Thompson

 

The complexity thing

Excellent set of observations, Phil.

These boats actually thrive by being less complex than is being suggestd on this thread. They are easier to build, own and sail. Can be devastatingly fast when dialed-in correctly and built from simple and easily obtained materials.

The form already has a considerable righting moment advantage over cats of the same length and when built correctly, can be every bit as light as most of the production boats one sees on the beach.

There's no need to get all tricked-up with this type of boat to have a good time on the water and your comments to that effect are spot-on. When looking at the new tri being built by Sam, I see that simple approach being developed to a logical end.

Any beach style tri that emulated the performance of the French Nitro, whether slightly bigger or even smaller in scope, would yield a wonderfully fun beach boat which could easily be towed by a smallish, economy type car.

Another issue... if one keeps the design and execution simple, then it's very easy to make any future mods to the design when one finds it a potentially fun effort. Complex boats, by their very nature, design themselves right into a corner from which it is costly and complicated to emerge.

Chris Ostlind

 

Hi Guys!

Thanks for those last answers! Sorry to take so long time to respond, but I´ve been away without internetacces, Sailing and stuff you know

Of course I should build a simple boat to start with, and thats what I´ll do.
The only questions then are, which modell and when
It will probably be a tri, as Phil Thompson said, thats what would get my kettle boiling, or for that matter, float my boat

About the foils, as you say Frosh, if the vaka stays in the water, its best to have the foils there.
My reasons to build a tri would be that I like tris better, and like the idea of having a cockpit, maybe even like a kayak. Altough, Im not to keen on footsteering. So maybe one should sit on the side of the vaka, and move further out as needed. That should give alot more sailcarryingpower.
And, I want the boat to be physical sail, I need some exercise

But just for the sake of me learning some more, on a tri like that, the mainhull stays in or atleast very near the water, would there be any real gain in having daggerboards in the amas? And rudders for that sake. Of course on a tri like the Seacart 30, which fly the mainhull easily, you need the rudders on the amas to keep control, but the still have the daggerboard in mainhull.

But as you say, build simple from the begining, and I can always and more complexity later on. gets me one the water faster

But againg, I want to learn things. Why cant one build a cat that is as wide as a tri? Would there be alot of downsides to it? Cause that really feels like the biggest advantage with a tri, the width and hence have high righting moment. I mean, most cats are only about half as wide as the´re long, alot of tris are almost square.

Thanks for all the help guys! I´ll keep you all posted when and if somethings happen

Best Regards
Robin Larsson!