High Performance MPX Foil/Self-righting Trimaran-The Test Model

Fire Arrow Test Model:


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WOLF daughter of fire arrow:

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Much design work over the last few weeks and lots of changes. WOLF is back to being WOLF though a bit smaller than the original design but not quite as small as I was considering. She would be a foiling singlehanded trimaran if she were to get built. I've resolved a lot of issues and settled on a final design that I'm very satisfied with.
The ama length is still up in the air-I'm building a small concept model to help work out the remaining problems. The boat may use a very small ama-about 7.75'-with a unitized ama/curved piece/crossarm structure that makes trailering simple OR a longer ama-about 10.25'-with the same basic folding system planned for the original WOLF. Regardless of length the ama will consist of the ama planing hull and the "curved piece"(for extra buoyancy)-a
"Two Stage Ama".(see page 171, post 2565)


WOLF specs(tentative) :
LOA 14' 8.5"
Beam 14'
Target weight 175-190lb
SA-
--upwind: 149 sq.ft
--downwind: 249 sq.ft
--max pressure before depowering/reefing: 1.58lb/sq.ft*
* NOTE-see previous page-post 2697- for max pressure comparison with an F18.
Cost about 60% of WOLF
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Advantages /disadvantages:

1-will not have the capability of taking two people for a ride with high performance upwind . Downwind will foil with a crew weight around 340lb in 6.5-7.5 knots of wind. Excellent upwind performance singlehanded.
2-Singlehanded (200lb crew) will foil in 5 knots of wind .
3-Carbon rotating wing mast, carbon cross arms and carbon foils.
4-Retractable foils(from cockpit).
5-Extremely comfortable.
6-Uses the Fire Arrow Foil System(like Fire Arrow, Gitana 17, Banque Pop and Maserati)-- the same as the original system first used on the Test Model. Two UptiP ama foils-one used at a time-and one wand controlled mainfoil for very early takeoff and capable of substantial downforce all working with a single rudder T-foil.
7-Foiling throughout the wind range -including very light air-the essence of 3D SAILING!


WOLF would look very much like this but with shorter amas(ama + curved piece) and raked aft forward cross:

 

WOLF daughter of fire arrow: I'm working on a new smaller concept model of WOLF which allows a wider, roomier cockpit permitting more crew movement outboard. But a possibly big deal is the new molded, movable/adjustable , two level singlehander seat basically supported by something like a reinforced tramp. It will be exceedingly comfortable, light and make crew movement easy. More to come....

Basic concept of the two level seat-the new version will be much different:

 

WOLF daughter of fire arrow 14 concept model progress:

 

WOLF daughter of fire arrow 14 concept model progress-frames,cockpit and keel glued in position-skinning it next:

 

WOLF daughter of fire arrow 14 concept model skinned. I'm really satisfied how it's coming alive from the plan! The new cockpit/side tanks are much different than the first concept model and the cockpit much bigger athwartship and fore and aft.
But the new type bow is a real rush to me.

 

WOLF daughter of fire arrow Epoxied the hull with resin and Q cells this morning-next sanding and filling then pulling off the board.
This model may not be finished to the level of the first WOLF model. I mainly want to work on the new seat system and study the cockpit. I want to experiment with very small amas and a 14-15' beam overall and a pivot system for trailering.
Also, the main will use a version of a wishbone boom with midboom sheeting so the mainsheet is in front of the crew as he/she crosses from side to side. A curved 3.5' traveler(vangeller) on the cockpit sole will be used.
The cockpit sides sticking out port and stb don't normally touch the water when displacement sailing(which won't be often!).

 

WOLF daughter of fire arrow First fill tonight:

 

I like the extra seat concept, if the seats are material such as tramp mesh it will add very little weight avoid filling with splash and be comfortable[your yacht has aspects of my early tremolino],you've made a lovely shape. I 've been toying with the idea of building a model with a canting keel/float, but I can't see it being feasible because there is no way of scaling the density of water. Your foil models are ingenious in that they avoid this issue in scale ,..pretty much. Those beams in full size are going to need to be seriously strong though,.. extra water stays/struts /truss? Anyway, enjoying your work, cheers .

 

Thanks! With the right diameter and carbon -the beams won't need waterstays(which I don't like). Eric Sponberg did some engineering on the crossarms and on a folding system I came up with.
When you scale something up or down the sail area varies as the square of length, weight/displ. as the cube of length and righting moment as the 4th power of length-that last one is the problem with doing a model of your hollow canting keel. You don't need to scale the density of water.
The model of Fire Arrow is fairly gigantic-5.5'LOA, 6.7' wide and about 9' tall. The point of such a large model was to ensure that model testing results would be accurate for the 19.5' full size version. The new concept model of WOLF(daughter of fire arrow) is just to help with solving some relatively minor problems-thanks to Fire Arrow,the Test Model(and Maserati,Gitana 17 and Banque Pop), I already know the system works.
So a large model of your system might work for you?

 

Thanks Doug that makes sense, I knew something was amiss, now I'll just go and work out what that means..., I asked and got a straight answer.. either way the large scale solves the problem for me . the WOLF looks great, regards

 

Say you want to scale down a 50 footer to 5':
1) 50 squared =2500, 50 cubed=125000, 50 to the 4th power= 6250000
2) 5 squared=25, 5 cubed=125, 5 to the 4th power=625
3) what you learn ,scaling down from 50 to 5':
a-sail area: 25/2500=.01. So multiply the sail area of the 50 footer by .o1 to get the exact scale sail area for the 5 footer.
b-displacement: 125/125000=.001. So multiply the displacement of the 50 footer by .001 to get the 5 footer displacement.
c-righting moment: 625/6250000=.0001. So multiply the RM of the 50 footer by .0001 to get the RM of the 5 footer.
4) what you learn scaling up from 5 to 50':
a-sail area: 2500/25=100. So the 50' SA is 100 times the 5 ft. model SA.
b-displacement: 125000/125=1000. The 50' displacement is 1000 times the 5' model displacement.
c-righting moment:6250000/625=10,000. The 50' RM is 10000 times the model RM.
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Analysis: when you scale down the sail area usually winds up being too much for the displacement with the RM way too little for the scale sail area.
For your purposes I'd just design the largest model using your concept that you can afford money and room wise rather than scale it down from any artificial length. That way you can experiment with the concept -and should the concept work you can scale it up to any length.
You have to consider this type of scaling up or down as a guide rather than the result being the final design. You still have to do the final design work to ensure that you have a viable boat whether scaling up or down. For instance, scaling down from 50' to 5 ' will produce a model that won't sail in much wind because it will have too much sail and not enough righting moment so you have to use your best judgement to try to capture the essence of the larger boat both in appearance and performance. Most models use multiple rigs for this reason.
Fire Arrow is 5.5' LOA and it is an exact scale model of a 19.5' full size boat. So because the model is so big vs the full size boat the results tend to be very accurate. For a radical concept such as yours do a large model-then if it works do the smallest full size version of it you can to start with. That way you'll be reducing the chances of any unforeseen errors due to the scale process. Many famous designers have used RC models to test their concepts including Greg Ketterman(Hobie Trifoiler), Dr. Sam Bradfield (40' SKAT foiler), Bill Burns(CBTF-canting ballast twin foil concept), Hugh Welbourn-(DSS-Dynamic Stability Systems), Paul Larsen-(SailRocket), Alain Thebault-(Hydroptere) and many others.
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Thanks Doug for this considered reply, the maths/numerical explanation doesn't mean that much to me but the practical physics I find fascinating. What really raises my interest is that you havn't dismissed the idea outright and that if it had been attempted and rejected on this forum before there is a good chance you would have read it considering how long you have been an active member. Your advise to build as large a model as feasible solves my my original problem with trying to scale and gain tangible results. This concept can be applied to an existing[shallowish draught] craft as the model/donor., All I need is a partner or group more technically minded than me and equally slightly nutty in their own special way,...ha .,regards

 

I just found out that my friend Paul Riccelli(PAR) has passed on. He was a big help to me many times and was a great help to many people on boatdesign.net. So sad to see him go........

 

What? Paul (PAR) passed on? What happened? He is simply the greatest boat design and build reference this site has seen, and may ever see.

 

I found out here this morning: RIP Mr. Paul [PAR] Riccelli https://www.boatdesign.net/threads/rip-mr-paul-par-riccelli.60437/#post-831648