Since It Is Still Locked - Multihull Plans Info

MultiHulls General Discussions (MultiHull/MultiOne)
21

Simply amazing at how someone can make these quantum leaps from 60 foot long boats to 4 foot long ones and expect the same handling and characteristics.

First off - to my knowledge the 60 foot tris (or cats) are not designed, nor do they race closed course regattas on a consistent basis. This means, like a dragster to put it into common detail, the 60 foot multihulls aren’t designed to race closed course with fast and multiple tacking. They are designed for straight line speed. If I am wrong, please show me an article that suggests or implies any of them will be racing closed course around buoys. Again, to use the dragster analogy, I don’t recall any of them racing SCCA road courses - and would appreciate being corrected if wrong.

So here we have a 60 foot multihull, as wide (or wider) than it is long. “It ain’t supposed to turn quickly!”

Most(I guess I might be inclined to say ALL cats) except the lease/cruisers are narrower than they are long. Why - because it makes it easier to tack on a tight, closed course, and I will concede “easier to tack” is a relative term here. So “all” cat manufacturers - save perhaps the Microsail boats - are left narrow for one specific reason - and that would be tacking.

As previously pointed out, there is a mechanical/physical fact which takes place and that is the wider the hulls are apart, the more difficult to tack the boat. The outside hull MUST (a fact) move faster through the water than the hull on the inside of the turn. This particular fact causes catamaran owners to develop a method for rudder alignment much as one does the steering on a car. The “Ackerman” theory is to have the outside wheel turn in further than the inside wheel. It is also why GM has been fooling with 4 wheel steering on some of their trucks - to reduce the turning radius, and if that can be done, the turns are made faster, easier and with less friction of the tires (or hull of a cat).

Since you feel it necessary to refer to the big boats here, let me point out that the 18 Square Meter class had unlimited beam. This means there was NO BEAM WIDTH LIMIT! The original NACRA 5.2 at about 8 feet in width, was widened to 10 feet of beam. It still tacked well, but stability upwind was greatly improved by the wider beam, and hence the longer axis arm of rotation. Then the guys decided to see if even wider was better. The hulls increased from 5.2 Meters (17 feet) to 5.5 Meters (18 feet) and the beam increased to 11 feet or more. I was witness to a 13 foot beam that raced in one of our North American Championships, and the owner had all sorts of problems - one was tacking, and the other was the cross beam distortion even with a dolphin striker bar. Sail control, especially the leech was impossible.

Along came the SuperCat 20 - and it only had a beam of 12 feet. A 25 foot C Class boat has a beam limit of 14 (maybe 15) feet. By Doug’s reasoning using a straight line 60 foot ORMA dragster, the C Class “should” be 25 feet wide - or more. I think when the rules were written, the designers knew that “Too wide” hindered tacking, so they wisely kept the beam less than the length. And in the 18 Square Class, this was proven out time and again. Remember, the 18 Squares and the C Class were technology leaders in multihull development, with the 18 Square being a smaller platform test bed for the bigger C Class.

Now - back to r/c multihulls - and cats in particular, I will grant cats are faster than a tri in a straight line, with the proper winds and an experienced driver. When it comes to tacking, it is a heck of a lot easier to get a multihull that is just over 24 inches wide through a turn than it is to get a 48 inch beam boat through a turn. Add in the fact that on a tri, there is only one rudder (usually) and a cat has two which further impacts the turning ability versus the stalling ability of a tri versus a cat. And if the tri doesn’t have 3 rudder steering, once the center hull and board and rudder come out of the water, it’s all over except to see if it was a knockdown or if the skipper managed to dump power and get it back in the water and on its feet.

Finally, it takes much more of a heel angle in a trimaran to reduce wetted surface than it does on a cat. Thus my recommendation to consider a tri as the first boat for someone new to multihulls. Things happen (relatively) slower.

Cat versus Tri - heeling angle versus wetted surface area:
[ graph with cat and tri wetted surface area.jpg](http://www.rcsailing.net/forum1/data/dick lemke/2004472287_graph with cat and tri wetted surface area.jpg)
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Apologies - I don’t recall where this chart came from. I’ve had it for quite some time. Note the huge difference it takes a tri to get rid of surface drag - and the amount of heel to do it. Having a bit more drag certainly might be a benefit to a new sailor as well, in my opinion.

22

You seem to have focused on just one analogy ignoring the other: rc trimarans that fly the main hull are sailing just like cats do and yet they seem to tack well even with a center rudder and board. And we know that foilers without any center daggerboard tack on a dime when on foils.
So what is the difference between a cat flying a hull and a tri flying the main hull? If you remove the main hull from the tri then you have a center rudder and board and a very wide cat that everybody agrees tacks well…At least in conditions that allow the windward hull to fly.
Again, we know that an rc tri flying the main hull will tack well so why wouldn’t an equivalently wide cat tack just as well? (in hull flying conditions)
I know that my D4Z tacked exceptionally well in light or heavy air and I think it would have with even more beam but I haven’t tried it yet. The key to the light air cat performance is having it designed to take a Power Ballast System; that way in light air(with PBS removed) the hulls float high a turn easily…

Doug Lord
–High Technology Sailing/Racing

23

The reason an equivelantly wide cat wont tack as well is when a cat tacks (one hull in water to two hulls in)wetted surface goes up but when a tri tacks (float/mainhull in to main hull only in) wetted surface goes down.
The tri will tack better purely because of a centrally based pivot (disregard centreboards when considering this) similar to a monohull, whereas a cat has a large polar inertia to overcome causeed by its wide hull seperation

24

Tranth has a great point here. Another way of thinking of it, might be that in the middle of the tack, a tri actually becomes a mono for a short period of time. I wonder how much of an effect this really has. Tranth do you have any hard numbers that you could give us to ponder?

-Dan

25

I have never seen a catamaran go from one tack to another without having two hulls in the water at the same time somewhere during the tack. It is impossible - neither “real” crew nor “inert ballast” can be moved fast enough to allow this to happen.

A radius of an inside turning hull can be 24 inches. If the beam of the boat is 48 inches, then the turning radius of the outside hull will be 24 inches plus 48 inches = 72 inches. If you reduce the beam of the boat to 24 inches, then the radius the outside hull must sail through would be 48 inches not the original 72". I haven’t yet found any changes to mathematical principles and rules that indicates a distance from point A to point B on a large radius is less or even equal to the distance on a shorter radius. Thus the hull on the outside MUST turn and move faster than the inside hull if the boat is going to turn at all. The wider you make the beam, that harder (and faster) the outside hull must move. Since there is no differential on a cat like on a car, the inside hull (short radius) cannot back up while the other hull goes forward like the wheels on a car. (In reality, the tighter the turn on a cat, the inside hull may acutally BE backing up slightly) and this is one reason experienced cat sailors know to “carve” into a turn - not “slam” into it like you were sailing a monohull dinghy! Trying to tack too quickly and too tightly is a guaranteed way to stall out the boat and frustrate the new skipper. The longer you can make the radius, the easier it will be to successfully make the tack.

I ignored the foiler for a specific reason - the topic discussion was on cats versus trimarans NOT foilers. Accordingly, a foiler (when up on foils) as you say has NO hulls in the water - thus how is that even relative to this topic? Remove the foils and stop referring to “flying” trimarans, and you are back to a situation where all three hulls are in the water at the same time - and then the principles as outlined earlier apply. Sorry Doug, but no matter how hard you try, there are certain rules of physics and mathematics that you will not be able to change.

If a trimaran (not a foiler) is flying both main hull and windward hull, there is a point when the rudder will leave the water and there won’t be any steering. Meanwhile on a cat - it has the leeward hull/rudder in the water and that will provide steering. In most conditions, a cat will be able to fly a windward hull much sooner than a tri can get the main hull out of the water. Weight is one factor. Back to my first point - try as hard as you can, and you will not be able to get around a closed course on one hull - be it cat or tri. For the 60 foot ORMAS, they are straight line hundereds of miles on the same tack, and it makes sense for them to reduce wetted surface when possible and for as long as possible. Now even this concept begins to be questioned with the new “planing hulls” that just arrived on the scene. If one can reduce wetted surface area, increase speed and NOT worry about flying a hull and it’s inherent problems and dangers, I would submit there is a benefit to doing that. Two hulls on the water are a lot more stable of a platform than only one.

And while two hulls in the water is slower than one hull (or none) I still feel it is better for a beginning multihull sailor to chose the trimaran for a first effort - instead of a cat. Just as much can happen with the tri and with the cat, but it takes a few seconds longer, and recovery might be possible. That said, I again recommend a trimaran for a beginner - not a cat. Once you get comfortable sailing a tri - by all means give a catamaran a try if you wish. I just don’t think it’s a good idea to start out there until you have a feel for a boat with no lead keel to cover up mistakes made on the transmitter.

26

Guys please get back on track. We have two non multihull sailors here who want to give multi’s a try. Let’s don’t alienate them again by argueing over the same isues, They are asking for help.

I have sailed cat’s and tri’s. The cat I sailed was 850mm wide, it had twin rudders that were set up to allow the windward hull to turn with a smaller arc than the leeward hull. It tacked slower than a tri, and didn’t accellerate out of the tack as quick.

In certain conditions the cat matched the tri’s for straight line speed, but lost out when the breeze picked up as the same sail area couldn’t be carried. Cat’s are very hard to sail when compared to tri’s, however, depending on your “normal conditions” may be beneficial as the two designs are quite evenly matched in upto 10 knots.

The ulitimate aim of the multihull sailor is to have (for cat’s) the windward hull just kissing the surface of the water and for the tri sailor have the main hull just kissing the surface of the water. This can’t always be achieved due to race conditions, wind strengths etc.
The cat will always tack with both hulls in the water, as the tri will always tack with the main hull in the water.

The cat will have the overpowered pitchpole,capsizing problem earlier in the wind range than a tri, however some design concepts can assist this.

From a personal standpoint. I think that the tri is the best way to go to enter the class.

Foilers, movable ballast systems etc are find to play with once you have learnt how to sail a multihull. Things happen with a multi much faster than with a mono, and having simple controls, (two channel) radios make things a lot easier.

You aren’t restricted to just two channels, but I suggest starting out there(one for sails the other for steering) and master the boat before adding extras.

WE can all offer opinions of which way is best. At the end of the day it is up to the person who is sailing the boat to decide what they will build, sail and to what level of technology they wish to go.

Peter

27

Tranth’s, comment on the reduced wetted surface of the tri in the split second in the middle of a tack is an astute observation. However, then he said:" the “tri will tack better purely because of a centrally based pivot similar to a monohull,whereas the cat has a large polar inertia to overcome caused by the wide hull separation”. The ineretia to be overcome is almost EXCACTLY the same between a cat and a modern tri when tacking from a position of flying the windward hull for the cat and main hull for the tri if they were the same beam and less for a narrower cat.
Tranth excluded boards from consideration in the above example but it is important to know that board position whether center or in the outside hulls has NOTHING to do with tacking speed. I (with some help) compared two identical 68" trimarans: one with a center daggerboard, one with a daggerboard located in each ama. There was no difference in tacking speed!
Another important point: a modern tri is never designed to have all three hulls in the water at the same time!
If one was to consider two “normal” multihulls of the same length- one a cat and one a tri I would recommend the tri to the beginner as does Dick because of it’s less critical stability in medium wind.It is important to recognize that a cat can be built lighter than a "normal"tri and in the “normal” case this would contribute to lack of power compared to the tri.
However, if one wanted a cat to be competitive with a “normal” tri then the addition of a Power Ballast System would do the trick improving handing in EVERY condition as long as the boat was designed for it.
I think(and could be wrong) that a “super wide” cat(at least square) could be designed using a PBS to be competitive with a “normal” tri in every condition and tack just as quickly.
But if you realy want the best-and least expensive(compared with movable ballast) boat(multihull) for a beginner a trimaran foiler(retractable foils) wins hands down because of it’s superior stability in all conditions…

Doug Lord
–High Technology Sailing/Racing

28

Can anybody help me in the purchase of a ready to sail cat or tri?

29

Stuart, contact Ian Sammis; he is a member here so look at the members list or send me an e-mail and I’ll send you his address. He was recently advertising a ready to sail tri on Windpower for around $1150 I think. He is currently bulding mostly trimaran kits.
I will have an F48 trimaran foiler available before too long…

Doug Lord
–High Technology Sailing/Racing

30

<blockquote id=“quote”><font size=“1” face=“Verdana, Arial, Helvetica” id=“quote”>quote:<hr height=“1” noshade id=“quote”>Originally posted by stuartcasteel

Can anybody help me in the purchase of a ready to sail cat or tri?
<hr height=“1” noshade id=“quote”></blockquote id=“quote”></font id=“quote”>

Doug assumes your are in the U.S. - if you are not, try Anthony Wright in the U.K., Pierre Bonnet in France (I don’t have any email for him) or Peter Birch in Australia. I would add Alan Hayes in New Zealand, but not sure of multihull activity there at this time. Any of them can tie you in to someone who builds “custom” for you, or who may have a used boat. Often used multihuls are sold almost at cost to recoup materials and hardware, so a new boat with new ideas can be tried out. Nothing wrong with the old boat, just that it is a way to finance a portion of the new one.

Keep in mind, if you have someone build for you, there are charges for labor (in some case significant) that will up the cost. Likewise, there are free plans avialable, and even a “Box Trimaran” that was very easy to construct for first time builder. Those were available too.

Here is a photo of a homebuilt trimaran. Based on the “BoxTri” design, it is rigged with a SeaWind 1 Meter sail. Completed photo shown on the home page for MultiONE Class - owner/builder was the late Jim Lestos. This photo is during construction. Note the simple lines and fairly flat surfaces that contribute to easy building.

Download Attachment: [ smr0300289.jpg](http://www.rcsailing.net/forum1/data/dick lemke/20044814126_smr0300289.jpg)
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31

The rantings yet again of someone who has never competitively raced either an r/c cat or tri. Racing multi’s is totally different to monohulls. You don’t have time to tinker with theories that aren’t proven under race conditions. Racing in a highly competitive fleet you need to be on top of your game otherwise you will very quickly be playing catch up.

FACT
square cat’s have been tried many times in different styles and DO NOT WORK, they are great in a straight line, have good stability, but take ages to tack. Tacking quickly is an essential part of racing.
Tri’s now tack as quick as monohull’s, cat’s will never do that as there configuration just doesn’t allow it. In the right conditions cat’s can match tri’s for straight line speed but lose out in the tacking.

Retracting foils on multi’s, yet to be proven in race conditions to be any good.

Foilers are a waste of time around courses. They don’t go well enough to windward to be competitive. When racing, most courses are set so that there is more windward work than reaching etc. The foiled multi’s I have seen whether live or on video don’t point high enough to be competitive.

Cougar and Wis, I am not trying to tell you to go with a tri, that decision is yours, but from the stand point of someone how has raced both go with a tri, they are easier to sail and are more forgiving. Buy or build one that is simple, both main and jib on one channel the rudder on another.

Doug is still making unproven claims(advertising). In my opinion his comments should really be taken with a grain of salt. Doug until you have raced your multihull class boats (mini40/F-48 or multione) against someone else, the words MY OPINION should always be included in all your posts.

Why do you continue to try and get new people interested in sailing multihulls to go with YOUR unproven ideas. Is it so that they can build these ideas and give you feedback to how they work?
I say again, build one, race it and then post the facts yourself. Otherwise BUTT OUT. The class doesn’t need people like you.

Peter

32

Peter; (Dick);

Well; to be honest; I asked a quote last year from Doug…the X3…it sounded nice (that time)!
But; after some reading and more…it seems that there is no X3!..PEACE

Anyway; I always dreamed about a tri[:-angel]…I am not saying that a tri is better then a cat…I have no idea[:-?help][:-?help][:-?help][:-?help]…its just; some time ago (back in Europe); I saw a racing tri…and I was so impressed by it![:-bouncy]
So yes; I will probably get a tri…not only because they seem to be more easy to sail…
the one thing is just the price…yes I know I could build it myself…THAT IS NOT POSSIBLE…why? 'cause I am very bad and have no experience with scratch building[:-censored]…one day maybe…I hope [;)]

So; now the question is:
Should I wait till I have enough $$ or should I get a cat (maybe Matt’s who kindly proposed to make some hulls [;)]??

Other thing; my conditions are usually medium to strong wind…and even choppy time to time…the pond/lake where I sail has no weed; just clean water; fresh from the mountains…almost perfect conditions…lucky me[;)]

Thanks

Wis

PS: I might get into troubles…THE wife is suspecting something[:-fight][:-sonar]

if it isn’t broken, don’t fix it!

http://wismerhell.esmartdesign.com/index.htm
http://public.fotki.com/wismerhell/

33

Answering as a personal answer, not as F-48 representative.

You have several “bucks down” opportunities, but many (all?) might be negated by freight costs, My guess is freight to Japan is probably as much as freight from U.K. to here.

  1. Write Peter and see if there are any used boats available from his fleet or contacts. I will touch with both my U.K. and French connections for same. Does it have to be a Class Champion? NO ! Not for your first one.

  2. Maybe Peter can provide you with a modified Marblehead as a starter boat, especially if you can shape 2 floats and cover with glass. Most M boats will probably be sold with sails and rig - and maybe even with radio gear. Remember, you only need 2 channel AM and since there seem to be few sailing over there, interference may be a lot less too. Since you aren’t class racing, forget bobbing the stern to bring you into 1.2 meter complaince (48 inches) and just sail it as a 50 incher. Just remove the lead and keel and install one without lead. Add two wooden (or carbon) cross tubes and go at it and see if you like it. Don’t worry about weight, width or other technical issues. Just throw it together and give it a try. You can always go back later and begin modifications. If you buy a Marblehead, I would get something no older than the early 1990s designs. Might be surprised at how reasonable in cost these might be.

  1. You can always purchase a complete boat from Anthony Wright in the U.K. - but cost and resulting freight might be high and put it out of your budget range. I had a Northwest pilot set up willing to carry one back for me from the U.K. - perhaps you can find a similar approach with travelers going back and forth (business) on a regular basis.

While it would be nice to purchase an X3 - given all it’s advertising, I am surprised your name wasn’t one that was added to the registration list given to me - but that’s another story. In the meantime, I just wouldn’t sit there waiting - as anything coming from Microsail will be a long time coming, and if/when it should arrive, the cost will be way too much for what you are getting and what use you will get out of it. If the idea was so splendid, there would be a lot of them sold to Europe where the hardcore multihull racing really takes place. (No offense Peter [:D]) And again, if France sponsors their international trophy among nations, it is also stange to note that none of the competitors are using foils - at least according to my spies. And lastly, if you were to buy an X3 - you would be one (and perhaps only) owner. You can do that right now by building one of Greg’s 2x4 wooden plank boats that we had so much fun with here on this site several months ago.

In the most logical of the above, my guess is that Peter plays an important key to one or more of my suggestions. Also - isn’t Australia closer to you than the U.K. or the U.S.?

34

Hey guys I think it is really cool that there is so much support and “opinions” out there. I think it would be far better for me to build my own boat and I believe that boat shall be a tri and that tri shal be called Silentflight. Next step is to point me in the right direction as to the available kits and or plans. I am an expeirenced wood woorker and handy with my hands and imagination. However I have no clue as to the RC world. I just bought a megatech narvana over the winter and there she sits on her stand. Never been sailed yet as I live on the shore of Lake Superior in Marquette Mi USA. I sail Hobie 16s almost every day during the season and really want to get into the RC circuit. Please dont think of me as a silly man.
Love and Light.
Stu

35

I won’t respond to Peters unfortunate comments in kind but I will say this:

  1. I have raced many different multihulls over the years especilly in the last five or so in the development of the Flyer -a 68" spinnaker equipped trimaran and in the development of the F3 hydrofoil. Both those boats went thru extensive two boat testing for a year in one case and several months in the other. Testing consisted of racing a “normal” rc course.
  2. A foiler multihull using an automatic stabilisation system will sail upwind with a VMG better than any “normal” multihull; that was shown in races between the F3 and the Flyer an between the F3 and the local F48 catamaran-which the F3 would sail a circle around.
    The foiler described by Peter on March 26th under General Discussion: “Marblehead vs Multi” could not possibly compete with or sail like a Bradfild type foiler: it had no altitude control system using differential automatic lift and it had four foils! The video of my boat,if that is what he referred to when saying foilers don’t point, is a ridiculous comparison: when that video was shot my boat never went upwind! So its clear that the descriptions in Peters post are not based on modern Bradfield type foilers.
  3. My boat was the first rc foiler to use the Bradfield system and I have made it a point to publish on this forum the details of how it works so the average person could at least understand the concept and at best, if sufficiently skilled, could build one.
    I believe that a foiler- retractable or non retractable- can be the best introduction for a beginner to rc multihulls because they are so stable and so very easy to sail compared to normal rc multihulls; I think that eventually they could have a dramatic effect on introducing people to and keeping them interested in fast multihull sailing on the water.

edt:sp
Doug Lord
–High Technology Sailing/Racing

36

<font color=“red”>EDIT:
After work, I ran at home and studied my idea, I checked the hatch…and its going to work…way too weak…plan B!! so forget the multi36/600…sorry!
</font id=“red”>

Wow so much! and so many great ideas!!!

Ok; I really really like the idea with the M’s…
why not having a multi36/600 ?? [;)] lets say I could try to modify the mainhull (that I can do)…
crossbeams…I still have some carbon tubes hanging around (kite’s) or aluminium…that shouldnt be a problem…

The floats…thats the hard part! maybe I could make some out of wood…no idea! thats where I need your help!! [;)]

now that you got me INTERESTED…its building time…I almost have multi…I have the main…with the gear and the rig!
My idea is to modify a bit the hatch from my 36/600…and on it attaching the crossbeams (I will make a new hatch).

I take away the bulb…and I got the fin…so happy I didnt epoxy the thing!

Waiting for your replies guys…with one hull; 2 boats…yahoooooooooooo

Thanks a lot!

Wis

if it isn’t broken, don’t fix it!

http://wismerhell.esmartdesign.com/index.htm
http://public.fotki.com/wismerhell/

37

I questioned the word of GOD and he got upset.

Wis
Nice to here that your going multihull. I am quite willing to help any way I can.

Peter

38

Peter,
well, yes you could…

Could you send me (again) a mail with some details about the multi you offer in your club [;)]??

Thanks

Wis

if it isn’t broken, don’t fix it!

http://wismerhell.esmartdesign.com/index.htm
http://public.fotki.com/wismerhell/

39

A word to the wise: in considering a multihull the idea of piecing one together based on a Marblehead is areally bad idea if high performance is what you’re after.
If you build or buy a multihull get one designed and built as a multihull.

Doug Lord
–High Technology Sailing/Racing

40

Doug…as a first multi…who cares about perfomance???
not me! perf is for later!
EDIT:

If I want performance, I know what I should get [;)]
Wis

if it isn’t broken, don’t fix it!

http://wismerhell.esmartdesign.com/index.htm
http://public.fotki.com/wismerhell/