18' Trimaran vs F18 Catamaran

Discussion in 'Multihulls' started by Doug Lord, Jun 13, 2010.

  1. Gary Baigent
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    Gary Baigent Senior Member

    Doug, I know you're claiming complete originality with the bi-foil main hull arrangement ... but did you know that the Kelsall 52 trimaran VSD sailed by Eugene Riguidel in the early Route du Rhum, had one set of lifting foils set forward on the main hull below water (like shark fins) plus an IT rudder - there's a pioneering bi-foil arrangement ... around 30 years ago?
  2. RHough
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    RHough Retro Dude

    A bunch of us started a RC Laser fleet (13 boats) here in Mexico. Way too much fun! Been sailing that and I took the Sabre from Mexico to Canada and back on her own bottom this year. I've been having so much fun being retired that I haven't gotten to finish the Glen-L Dyno-mite I started 3 years ago ... :(

    If I ever get that done (next summer?) I'm thinking something old school like a Cross 18 for day sailing ...

  3. Doug Lord
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    Doug Lord Flight Ready

    Well, that sounds great! Unfortunately(fortunately?), I'm still working testing boats and boat parts-and writing reports but that will change fairly soon and free my time up-I can't wait. I have some interest in the Trapwing so that is proceeding albeit slowly now. I'd like to race a little one design-maybe like a 2.4 m -while I'm getting these projects together when time frees up.
  4. Doug Lord
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    Doug Lord Flight Ready

    Gary, I'm claiming originality for the system I've described here and in detail in the MPX-thread as applied to a trimaran. What you're describing does not sound like that system but it sounds very interesting. Any pictures or detail?
  5. cardsinplay
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    cardsinplay da Vinci Group

    Within this post you will see just how much time has passed since all the big loud pronouncements were made regarding the Trapwing and how Doug chose to express a personal commitment to the project.

    Do enjoy this look into the workings of Doug Lord's mind. This post, shown below, came from March 10, earlier this year and it shows the moment when Doug went "all-in" on the Trapwing... a boat that still has never seen the light of day, even though he promised to devote 100% of his time to the project. http://www.boatdesign.net/forums/sa...ge-trapwing-deck-ballast-12-22-a-29610-3.html

    One can draw one's own conclusions as to how good his word is in similar efforts such as these and there have been many projects of this type that are still relegated to the "All I have to do is make an iffy model, mount it to some wooden base and call it good" method of thinking.

    Draw your own conclusions

    It took three weeks to "develop a model" of the boat and nobody, yet, has seen a working example and likely never will. Nice cred, Doug

    So, Doug, if you have done significant work on the Trapwing project AND you can show photos that support those claims. I'll be happy to delete this post and you can bring your wonderful work to the fore. If you haven't done squat, which is what I think is the case, then you have to eat this as truth. Scuttling off to the zone of the irrelevant would be a gracious way to exit this forum after all the big noises you have made in the interim. I bet that you do not have a thing to show regarding the Trapwing that is about a real boat and yet, here you are on another thread, chuffing-on about an even more lame project, the Flash Tri.. which I guarantee will also not ever see the light of day. An 18' trimaran as described on these pages... not a chance in hell.
  6. Paul B

    Paul B Previous Member

    You are being unfair.

    You didn't mention the brass plaque.

  7. Doug Lord
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    Doug Lord Flight Ready

    18 tri vs F18-THREAD SUMMARY

    Thread Summary: 11/14/10

    This thread started out to try to see if there were any high performance 18' tris around that could beat an F18-either existing boats or designs whose numbers reflected the probable ability to do the job. To me, it is a very interesting design challenge that could produce an exciting, comfortable and very fast boat. With the numbers for the Magnum 18 tri and Wildcat F18 available to use as a benchmark it is clear that an 18' performance tri with small amas and lifting foils on the main hull(as per my suggestions earlier and below) and either foils or a planing hull to provide dynamic lift on the ama could be in the ball park pricing range of a Wildcat F18. It is further clear that with careful design and engineering the boats would be comparable in weight as well.( Keep in mind that as beachcats go the F18 is on the heavy side). The technical aspects of the boat show a high probability that the tri would be faster than the F18, would be able to sail in the same pressure as an F18 with one or two crew, and would do this while allowing the tri's crew to sit on the side of a center cockpit very comfortably:
    --the main hull on such a boat would be physically much smaller than the Magnum 18-with perhaps 20% less weight,
    --the rig with 50 sq.ft.(277 all up-1' higher CE) more upwind SA(121 sq.ft. more downwind) than an F 18 would insure the power required to be faster than an F18
    -- using carbon tubes for the cross arms would assure the strength and light weight required for a 16' beam vs the Magnums 14'.
    --Righting Moment: Max RM for the tri with two 175lb crew sitting on the side of a center cockpit would be 6700ft.lb. which means it could carry the 277 sq.ft. of sail(1' higher CE than an F18) in about the same pressure that an F18 can with two 175 pounders on trapezes (1.5lb./sq.ft. pressure). But while the F18 requires two 175lb crew to sail in this kind of pressure the tri would not. In fact, it could be sailed with a single crew in that pressure with the contribution from the mainfoil of 218.75lb. of downforce. The mainfoil, in concert with the rudder foil,(both on the main hull)act to control pitch and can be used to maintain the sailing angle of the boat with the main hull flying thru a significant variation in crew weight. The mainfoil would not be much larger than a Moth foil( 1.1=Moth; 1.4 sq.ft. tri). The F18 has 4 foils-the tri main hull four, as well, except that two of them are very small-about half an F18 foil-and lift vertically up or down. Learning from the F18 Capricorn(and other race boats) the tri would have a gybing daggerboard assuring excellent windward performance.
    -- Ama- the key to the design is that the main hull flys almost all the time. At max RM the ama must support 750lb.(boat weight+ 350lb of crew weight,or approx. 175lb crew +175lb main foil download). The ama could be a single rotating hull that would allow a displacement hull or a stepped planing hull as the case may be. Very experimental.
    OR: the ama could be a high L/B design incorporating a retractable (pivoting) foil with 1.4 sq.ft. of area in each ama. This would allow the ama foil to carry 70% of the boats weight(same % as an ORMA tri) using a proven foil system(DSS) that works somewhat differently than a "typical" curved foil: it develops no lateral resistance as a by-product so that 100% of its area is dedicated to vertical lift making it much more efficient than a curved foil. The least expensive of these two options may be the stepped planing hull but that still has to be proven. The DSS foil is proven....
    If you look at the Magnum as a rough guide only and keep in mind that we're just looking to be in the ballpark with pricing it is faily exciting-and accurate- to consider a tri such as this at + or minus, say $2000.
    If you look at the technical aspects it is undeniable that the tri would beat the cat-and that's with one hand tied behind its back! The crew of the tri sits on the side of a center cockpit while to sail in the same pressure(1.5lb.sq.ft-max design pressure for the F18) the F18 requires two crew on trapezes. Not only that but the tri can be sailed in the same pressure that an F18 requires two 175lb people on trapezes-singlehanded! More power ,more speed, much more comfort, much easier to sail fast-the tri could be a tremendous addition to "beach sailing" multihulls and the first of its kind(that I know of-even ostlind agrees with that!).
    Yes it can!
    NOTE: please see the SA/WS ratios for these two boats. They tell the story better than almost anything else showing that the tri has much less drag for its power than does the F18. And remember, this tri is not using all the power that the configuration allows-it is designed to be faster than an F19 AND extremely comfortable and much easier to sail.
    Length: 17' 11" / 5.46 m
    Beam: 8' 6" / 2.59
    Draft w/Rudder Up: 7.1" / 0.18
    Mast Length: 29' 6" / 8.99
    Sail Area:
    227 sq.ft. upwind SA
    454 ft2 / 42 m2 downwind SA
    --two hulls in water- 4.77/1
    -- single hull in water- 6.03/1

    Bruce Number: 1.66
    SA/D: 44.16
    W/SA: 3.29
    Weight (with spinnaker): 397 lbs / 180 kg
    Price as of 6/21/10= $22,500 including everything except trailer
    18 Tri
    Length: 18' / 5.49m
    Beam: 16' / 4.88m
    Draft w/Rudder Up: 6.4"
    Mast Length: 31.5' / 9.6m
    Sail Area:
    277 sq.ft. upwind SA
    575 ft2 / 53.4 m2 downwind SA
    -- not flying-5.73/1
    -- flying main hull-10.26/1

    Bruce Number: 1.83
    SA/D: 53.89
    W/SA: 2.71
    Weight (with spinnaker): 400 lbs / 181.9 kg
    Hull Construction: Fiberglass/Foam Sandwich and some carbon/foam sandwich
    Price estimate-$22,500-24,500
    (Note: Magnum 18=$19,235)
    (Note: skin area and volume of tri ama about 1/3rd that of an F18 hull!)
    Ama foil area corrected 6/22/10
    SA/WS added 6/23/10

    Note: for those that only see numbers and not the picture they paint you should really do something about that. Without analyzing the technical characteristics of a boat you know nothing about it. If you judge a boat by a pretty rendering without at the same time analyzing the technical data for the pretty picture you're not getting the full story. When comparing two boats such as the F18 cat and 18' tri the technical data is critical. You should insist that posters/"designers" who are telling you about a boat and/or comparing one with another provide the applicable ratio's and other details. You should probably make an effort to understand this information.

    SEE Design Ratios PDF below from Eric Sponberg........


    Note: the key to understanding this is to realize that the tri works like no other tri currently in existence utilizing two lifting foils on the main hull augmented by a wide beam and and VERY SMALL ama using either a small lifting foil or a planing surface-or maybe both in certain conditions. The two foils allow the mainhull to fly long before a conventional tri this small and this wide would. The two foils,and this is real important, unload the faster the boat goes! The pitch control is greater than almost any equivalent length multihull. This is a "daysailing" version of the concept since an all out racing machine could be considerably more powerful(and expensive).
    This was done to show the potential of new thinking that allows the full attributes of a trimaran to be used more effectively than they have been to date in "conventional" small trimaran designs under 20' or so. A smaller version, that is a maxed out speed machine and that takes this concept to its logical extent, is being designed in this thread: http://www.boatdesign.net/forums/multihulls/mpx-11-very-small-high-power-trimaran-33686-13.html

    Attached Files:

    Last edited: Nov 22, 2010
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