Foiling Trailer sailer


I wonder if any of you  maybe interested in my 7.5 m foiling trailer sailer project. I know strictly speaking it is not a sport boat but it does have twin trapezes!! And headroom for short people ! And I could use some help sourcing a 150-175 kg keel bulb and a 9.5 m carbon mast .

7.5 m long plus 350 mm boarding platform 2.5 m wide  draft 2.0  headroom 1.75m sleeps 4 nominally  light displacement 850 kg   sailing 1100 with 2 crew 115 kg !!!  2 Invert T hydrofoils  with 35% flaps and 2 t rudders  with variable AoA like a moth  or maybe like an A class.  Sail area  main 20 m2 jib 13.2 m2  Fro and kite to be determined.

Construction is 6 and 9 mm ply over stringers with 100 gm carbon biaxial inside and 300 gm carbon biaxial outside with 100 gm glass cloth on outside . Plywood 1.5 to 4 mm with high density styrofoam 60 psi and carbon  for the bulkheads and  berth tops and sides.galley and loo similar  construction .cabin top is carbon  styrofoam 60 psi  carbon with   Foam replaced with shear webs and uni carbon caps .I only wish  Julian B had started his 89er sooner and I would have  reduced a lot of my laminates and used more Basalt and pet foam. However I got the carbon really cheaply . Currently weighs 520 kg with all interior in place  and most of the fairing done.

I have been working on this for 2.3 yrs so this is slow  going for me  after building the NZ tris Dragon and Timber Wolf much faster .Guess I am getting  old  but it  is taking longer than building Free Radical  10.5 m cat .

I have more photos but no videos 

Cheers chris 





Super Anarchist
Park City, UT
Ironically...I may be able to help.  I'd have to run it by the rest of our Board first if you have interest but we have an Elliott 6meter bulb and mast that could be for sale. We had a poor decision made last season when dragging a boat off of the mud and the keel fin was broken. I was able to find the bulb in the mud and the mast was taken off the boat safely. 

Good luck with the project otherwise.  Definitely fill this thread in with pics and let us follow along and cheer you on.

Thanks for the comments I am guilty of designing my retirement boat .As an explanation I live  these days  just above the US border 1/2 way across BC . Lots of lakes great skiing and hiking but not a lot of high level yacht racing.  I have built  4  multis 3 in NZ  one Snow Leopard here and  rebuilt  2 keel boats in NZ. Currently I sail a Foiling moth self designed and built ,a Modified Bimare 18HT  cat with exploder 3  Z foils t rudders  and stern extensions as well as a windfoiler.

So to slow down !!!  My wife and I wanted a  boat that we could trail to the ocean and all the interesting lakes   sailing  and racing mostly 2 handed.We want to be able to comfortably sleep in  it on the road or in the water. This means being able for us to standup inside  have a head and a galley and a double berth . We wanted self righting but didn't want a swing keel or the space restrictions of water ballast. Invert t leeboards  like Will Sunnecks cat with flaps gives us more stability 600increasing to 1200kgm RM  ride height control if used with T rudders with global AoA and the possibility of low flying down hill.Aero drag  and minimum  useful volume inside dictated the rather ugly if purposeful cabin arrangement.

Hull form is an extension of PeterMilne's Virago followup to the Fireball ie a pointy scow  with enough rocker not to drag her ass in the very light  but a very straight chineline to sit on until  the foils lift up .2 rudders  so that the roll axis on foils is not as divergent as the AC 76s hence simplifying roll pitch control .Lots of things to play with !!  Probably won't rate PHRF or IRC.



Super Anarchist
Park City, UT

how much does the bulb weight on the Elliot ?
I think it's 600lbs.  I don't have the exact measurement and we could reach out to Elliott for that, but they may not share the info.  I do know that four of us struggled to move it on a pallet at the end of the season.  It may need some shaving of lead. 

Current moth is knot mellow but now has a 

prod extension for the wand . Wooden one is the first one I built to take to the gorge in 2009  .there were 2 more one sold in between one of which was a true front steering canard . It flew but underdamped in pitch so I reverted.




Started work on the dagger board/ drop keel. I am building it like an aircraft wing  spar with 45 degree 18 mm ply side  end grain cedar core and carbon caps . 94 mm fore and aft 46 mm thick with  staggered step down. 7 mm thick 94 mm wide carbon caps  15 layers of 400 gm uni sm one. 300 gm  biax Ian carbon  and  200 gm glass cloth over prior to vacuum at  about .9 bar 



Machined 2 fir 18 mm by 60 mm  planks  to specified bevels   And glued onto spar . Then cut foreword ribs old fashion way with a  jigsaw as my bandsaws blade is cooked .  Rupees sander to even them all up and check with foil cross section   I am using an Eppler 836 foil section for the verticals. Daggerboard and leeboards  possibly rudder vertical and horizontal 

I plan to use a FX 62-K-131 /17 modified with a wider flap  approaching 30%.with aero balanced tips so I can use a a trailing wand off the vertical strut . This is like Ian Wards approach on the laser foils but principle is like the vampire project regarding foil positioning . Calculating lift at 6 ikts gives 118 kg lift at CoL at .0.8 probably capable of CoL at nearly 1.6 with 3000 cm2 single foil area .

By 8kts 212 kg lift @0.8 or about 424kg @1.6 pretty scary 1/2 displ  1.1 m off centre line   L/d should be better then 50 at this sort of Reynolds’s number versus reduced hull drag . 


Lots of long board sanding using a  5 ft Long 2 inch square steel tube with 100 grit  sand paper glued on . Checking with templates   especially for thickness because the case is 68 mm wide 550 mm long and the spar is 59.9 mm thick . 1.5 mm plywood skins will be perforated then vacuumed on to the frame  . Then fairing the leading edge with scraper templates and wrap with  biaxial carbon  . All I need now is more epoxy . the trucker protest  has rather slowed transport in Canada !!


I also made the  spars for the rudder  vertical  and the  leeboard  vertical  on the right . These are  spruce and fir sandwiching 9 mm of +/- 45 degree  meranti plywood as shear webs. Rudders will get 10 layers of 400 gm uni carbon per side and the  leeboard get 12 layers  all vacuumed on .

 These  foils  will only have carbon skins mostly +/- 45 degree  but some uni and 0/90  cloth over foam and ribs . I have to put a 1/4 inch id hard plastic tube  in  the foam on the  trailing  part of the leeboards  so I can actuate the flap like a moth . I am looking at getting stainless steel T's made in bar stock so I can detach the horizontal foil from the vertical. That is why there is a foam insert in the bottom 100 mm of the leeboard  spar . It will be melted out  after the carbon is on .

Over the weekend John Wright from Arcright  came out and we [mostly John] fabricated my anchor roller and forward base for  pulpit in 3/16 aluminum mig welded . Photos next week.

I have also  drilled on the 3/4 inch holes for  the stanchions  which have 240 mm 3/4 inch glass rods insert thru the deck and down to a doubler pre glued 100 mm below the deck. Ie Tube posted. The stanchions are 1 inch od 3/4 inch ID 500 mm long  glass tube  which slip over the glass rods.NO leaks  light  and flexible stanchions for less than 5 dollars each . I will glue the rods in with G flex and have created an chamfered edge to hold the glue ie large countersink .



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