Foiling Trailer sailer

I have been a little distracted work skiing f1 ordering a mast from Forte and deck jewelry from Allen brothers .

still working on foils  

re bulb cog ahead or behind centroid of rotation of keel 

depends upon how one expects to span load and whether the keel root is exposed in typical upwind  sailing and whether the bulb acts as an equal or better edge plate.  see Julian B comments re same. If the tip loss from vortex is greater than the root loss from wave depressurization  ie sailing upright  low angle of heel or ventilation you would want to reduce Aoa at the tip so that the tip doesn’t stall. If the end plate at the tip is better  or you are sailing at high angles of heel the reverse is true .

 

JulianB

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I have been a little distracted work skiing f1 ordering a mast from Forte and deck jewelry from Allen brothers .

still working on foils  

re bulb cog ahead or behind centroid of rotation of keel 

depends upon how one expects to span load and whether the keel root is exposed in typical upwind  sailing and whether the bulb acts as an equal or better edge plate.  see Julian B comments re same. If the tip loss from vortex is greater than the root loss from wave depressurization  ie sailing upright  low angle of heel or ventilation you would want to reduce Aoa at the tip so that the tip doesn’t stall. If the end plate at the tip is better  or you are sailing at high angles of heel the reverse is true .
Chris, if I may, you’re never going to "stall" the tip even if you increase the AoA a few degrees, at the speeds and the loads we are involved with, but what you will do is drop out of the bucket (drag curve) and go turbulent which is likely to be higher drag.

Placement of the bulb, so if you have the LE of the fin just in front (20-30mm) of the max volume of the blub then you will have max flow rate over the LE of the fin, certainly close to the bulb, and then, pretty obviously you will have reduced flow (can't have reduce pressure because water is incompressible) at the TE of the fin and reduced flow sort of = impossibility to have a tip-vortex. So the end plate is doubly effective.

Whether the fin then feathers, or gybes is a 2ndary factor, I always like them to feather, but who says I know what I am talking about.

                       jB

 
Thank you Julian  I stand corrected you have described the flow much better that I did   Dropping out of the bucket and increased drag is of course the issue not stall . I like your solution re bulb position and end plate .

 
Regarding alternative composites to plywood side car your are of course correct that there are many options which are lighter than plywood . I like your proa nicely done .  My point was that plywood is not hugely inferior to foam glass or basalt . It helps if you like working in wood. . Initially my prime driver was to achieve  a single skin structure  that would not suffer core failure like the imoca’s when landing  on water or my trailer. This is somewhat similar to Greg Elliot’s 7 m sport boat  done in  glass ply. With hindsight  I could have used lighter skins having found the effect of carbon biaxial more effective than anticipated .especially the 100 gm biaxial. Also 1.5 mm ply with 25 mm high density styrofoam and 100 gm carbon  could have been used on more horizontal surfaces in my interior .

 
Three old plywood multihull  for amusement 

Dragon 1988  NZ splashed at 450 kg 8m but grew and gained weight Wang computers big rig  spunspar fishing rod ply main hull and modified tornado cat AMAs in Kevlar  kinda glorified kelsall typhoon

Timberwolf  NZ about 2000  all plywood double chine mainhull torture ply AMAs and mast 800kg initially dry  weight8.5 increasing to 9.1 m 

snow leopard 2010  Canada tortured ply hulls and strip plank spruce carbon mast  8.5 m  750 kg  

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Sidecar

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My point was that plywood is not hugely inferior to foam glass or basalt . It helps if you like working in wood.
Totally agree. I wouldn’t work in anything else than wood or ply. A possible problem with (too) lighter skins is puncture resistance?

 
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Foil construction verticals 

when I was building moth foils I laminated englmann spruce blanks with pushrod Teflon tube in place then carefully cut saw width grooves of specified depth at every 10% of chord. This time I cheated and copied Burt Rutan building foam aircraft wings 

this is not as good as cnc milling !!!

I made the spars with 45-/+ shearwebs between spruce or fir longerons then carefully screwed templates on each end and checked that there was no twist . I had also pre cut 20 mm thick ribs from airfoil templates eppler 836 

Using a 2 inch aluminum angle extrusion I set each rib on the spar and glued in place 

the space between ribs is filled in with spore a 60 psi foam  which will be sanded to shape . On the leeboard vertical a 1/4 inch I’d tube is glued between the 2 layers of foam with 50 mm wide 6 oz glass tape becoming the trailing edge 

the foam for the leading edge will have 3or 4 mm thick ply  in a rebate .

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Regarding foil sections I concur with Julian B about the importance of leading edge parabolas particularly as his dad noted in High Performance Sailing page 240-241 radius 0.5 to 1% of chord.Wrt hollows in trailing surfaces I think it is worth reflecting on wortman , eppler and pfenninger’s work in the low speed wind tunnel in stuttgart as well as Bruce Carmichael’s with low drag natural laminar flow bodies in water.

it is critically important to choose airfoil sections appropriate to the Reynolds’s number your foil will operate in .  I will include some copies of their work .

Thinking more about Ian’s question re bulb placement and induce position angle of AoA with heel by having cog aft of centroid of keel torsional rotation this could induce flutter which is most destructive just like porpoising in an F1  car or an airplane exceeding Vmax . A very good reason to do like Julian B suggests and feather but keep the moment arm small

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  1. The above sections are for lifting asymmetric airfoils so one has to troll thru the eppler and wortmann sections to find appropriate section . One note worthy flapped symmetric section is the Du86-137. 

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Weekend of carbon and peel ply.  Laminated 2 layers of biaxial carbon and 1 of 100 gm glass onto the daggerboard. Then laminated 1 layer of biaxial carbon on the leeboards and rudders to consolidate and stabilize prior to vacuumed carbon outer layers . All rather tedious with more fairling to come but fairly close and straight .also made moulds for the rudder horizontal and repurposed a section of mast of snow leopard to become the boom .

I lofted out the curved box section for the prod and re bogged the inside of the cabin top to deck joint . Hopefully the boat elf might sand that if I help her lay linoleum in the bathroom !  
working up the pivot for the wands on the back of the leeboards as well as starting on the plug  for the main  horizontal foil.

last Wednesday  went over to Arcright  and helped bend up the pulpit with John . Hopefully he will pop out next weekend and tack it all in position.

Unfortunately I was unable to get any more system 3 silver tip epoxy and had to switch to entropy clear eco poxy laminating resin. Boy does it stink! Resin is viscous and hardner is thin. So bad I had to use  an organic filter respirator  and have the dust extractor on when mixing and laminating . So different from West, system 3  or ,epiglass which are almost unnoticeable unless you stick your nose in the hardner.

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Interesting weekend . Bathroom Reno’s  now finished  so the boat elf returned to help vacuum bag the skins on the rudders and the leeboard verticals .  400 gm uni on both 100 biaxial on rudder and 200 gm glass. Lee boards got 300 gm biax 200 gm carbon cloth and 100 gm glass . Previously they both just had 100 gm carbon biax to allow handling .

I have cheated and used my bimare HT 18 rudders as  a plug for the rudder horizontal. 

 
Oh thanks for the interest in this project.. Obviously there are better or different ways  of making boats and foils depending upon  resources available .  I would certainly done  something’s differently knowing what I know now and seeing JB and Jim Donovan’s builds .

The mould still needs a lot of work

I have gone over a lot of my old aircraft airfoil data and compared with bacillicus’s info from the AC forums . I have settled on a wortmann FX 62 K 131 air foil for the main foil modified with a  30 % flap . I may move the hollow slightly further forward given that the flap is not 17%. Span will be 1.4 m with centre section chord 300 mm tapering to 180 mm at the tips . However to achieve a balanced flap  both in weight and hydro I expect to extend the flap ahead of the hinge at the tips but  not quite sure how much area and leverage .I need hydro balance so that a simple mechanical wand can actuate the flap like a moth on steroids !! Well actually more like Ian Ward’s laser foil mechanism without the all flying foil.

I tried something similar in 1990 when I put Dragon Trimaran up on T helicopter foils “bell jet ranger “ initial 900 mm span 170 mm chord way too much !!  Had to cut down to 600 mm span but flew the whole boat 4 adults one baby and a large dog at 22 kt’s the the mainhull left the water and took the speedo with it . Mild ease  but no T rudders so lost pitch control when the amas lifted out ! Also with fixed T albeit incidence adjustable it was very draggy below 10 kts and splashed the windward crew.

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Wortmann section , leeboard with pushrod tube prior to skin lamination  note the thickness of the spar flanges  rudders and leeboards before reskinning 

I think Jim Donovan’s  approach for foil construction is much better than mine . A lot less fairing !

however since it would be really difficult to build the main foil that way with tip taper and I have not got  someone to  machine a mould with a CAd cam router I will make a plug and build a mould off of it .

Oh just one thought .whilst I don’t like using or wasting peel ply I certainly don’t like paying $12.50 a metre for it in BC. In frustration I went to alibaba express.100 m at 70cents a meter shipping $50 and arrived in 3 weeks  in Nelson bc .

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A little breakaway to checkout the discovery islands and the Sunshine Coast. Lovely place to sail but water access for small boats ie moths is really difficult and the skiing is not nearly as good as here. 
Before I left John from Arcright came round and kindly welded up my pulpit and anchor roller. Next are the stainless steel T pieces in 3/4 inch square SS bar stock for the demountable horizontal leeboard foil. Many thanks .

I have put sheaves in the daggerboard 65 cm down from the top so I can lift it up without a tower.

I have ordered sails from norths and a mast from forte .I am swapping trailers with a friend and then have to weld in torsion bar axle boxes so that I can keep the keel bulb really low and close to the ground 

 I am still searching for a lead bulb for the keel about 160-175 kg . I expect I will end up making it myself.

I am working on the plug for the horizontal lifting foils and expect to layup the first of the rudder T foils  1/2 s this weekend 

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