as we in NZ have been blessed with a 4 week ‘stay the f**k at home’ order it seems like as good a time as any to bust out a few new wings, i thought i’d share how i do it- might even inspire a few to get the sand paper and glass out and give it a go.
im shit at taking pictures while i work so bear with me
the first wing is a 1 metre span seagull wing for small surf/30kt downwinders on my sup. the second one is 700mm wing span for a mate who likes to go fast and do whapaaas in the surf. both have a max chord of 190mm and a max thickness in the centre of 30mm (the thinnest you can go in order to have room for the axis fuselage mount)
if youre planning on shaping an accurate wing then a good set of plans is essential. i draw them the old fashioned way- pencil, ruler and a good eye ball- but i assume you can get line drawings off a CAD program. the 4 lines you need are the leading and trailing edges (when viewed from above and from the front/back) these are important to get the correct amount of twist along the foil, and the apex of the curves on the top and bottom surfaces of the wing (the thickest point of the foil section on the top and bottom of the wing)
draw a rectangle around the foil outline on your plans, this represents the block of foam. make sure the rectangle you have drawn and your block of foam are exactly the same size as that rectangle is now your datum line for marking out the shape. simply measure the distance from the rectangle to the outline of the foil at each station (the lines bisecting the foil front to back) and reverse the process onto your foam. connect the dots and voila- foil outline.
i prefer to do this on 2 pieces of foam (half the wing on each), easier to handle and you can keep the shape more accurate in the centre.
once the outline is drawn you can cut it out and fair it up so the edges of the foam are square and true. get this as accurate as possible as this is the finished outline of the leading/trailing edges.
repeat the above process to get the leading/trailing edges and the top and bottom lines for the foil- thats 3 lines per side (when looking from the front or back). top one is thickest point, middle is trailing or leading edge, bottom line is the lowest point of the foil.
its easiest to do this with a set square that has 0 right in the corner, sit the foam on the bench and measure up at each station. this is when i use the small spread sheet of numbers, makes it quick and easy to have all the digits for each station laid out and colour coordinated.
apologies if this is getting confusing im not a teacher and i didnt take any photos of this process
forgot to mention- make sure the BOTTOM of your foam is a factory surface and perfectly flat so it sits nicely on the bench- 100% important
and the small wing-
the next step is sand the TOP <– and only the top, down to the top apex line (pictured above on the small wing) get this accurate to the lines and as flat and true as you can as this surface now represents the thickest part of the foil. plot out the top apex line (max thickness of the foil secton) make sure the top surface is accurate as you dont want to lose this line when you shape the foil- it should be there right up till you glass
Great technique for getting a complex shape out of paper.
Thank you for this. If you have an example spreadsheet you’d share I’d make a printable copy of it and share that. Your pics are fine by the way, really clear and your drawings are way beyond anything I could do by hand. I have to use a computer to get anything that looks decent.
Can’t wait to see this evolve.Foil FeedKeymaster
HSFoils, thanks for sharing your process. This is great for everyone who has been curious about giving it ago.
What a great project for those who are stuck inside!
Looking forward to seeing more of this.
thanks boys. im omitting alot of info as this would be longer than the harry potter series if i didnt.
now the fun part- shaping the foil. take care to not take too much off to start with, i always like to ‘find the shape’ early then take that shape down to the lines (the leading and trailing edge lines) so you dont end up with any low spots.
i use a stanley sureform to take the bulk off then 80-120-320 grit sandpaper on a cork block. theres not a lot i can say about this process as it all depends on the foil section you are using.
reminder- only shape the TOP! also remeber this is only a core,the finished product will be a couple millimeters thicker once glassed so dont worry if the foil shape looks a little flat, i leave the tips more or less flat as they are so thin you can put the shape into them once the whole foils been glassed top and bottom
once the tops all shaped and sanded to 320 grit you can mark out where the fuselage goes and carefully cut it out with a knife. this is why i shape the wing in 2 halves, makes it easy to mark and cut out the rebate. take care to keep it parallel to the bottom surface as this is effectively zero degrees pitch- if you designed it correctly!
if youre making a wing with a gofoil style socket mount then it gets a little tricky here and requires a bit of pre-fab laminating.
after that mark out a square 200mm wide +/- and the full chord of the wing, leading edge to trailing edge. sand this down approx. 1-2mm to create a rebate for the reinforcing carbon, you can see this on my small wing quite clearly.
when all thats done, 5 minute epoxy the halves together and hot glue them to a FLAT- like proper flat- bench. run a strip of masking tape accurately around the foil, taking care to get it precisely on the leading and trailing edge lines as this stops the resin running down on to the foam which is a bastard to sand accurately when you go to shape the bottom.
edit: when shaping draw lots of vivid lines! its an easy way to keep track of the shape. every time you lose the bisecting lines (the ones 50mm apart going front to back on the foil) re-draw them. on a big wing you might go thru a vivid or 2, keep drawing those lines!
So what laminating schedule are you using?ericfoilModerator
Fantastic write up and photos! Glad to finally see your process. Great stuff
as we arent allowed to travel anywhere and my carbon is a 3hr drive away i used the following to glass the top of the wings. i think for the bottom ill do the same but with an extra carbon patch and possibly a strip of unis along the leading edge through the centre section.
1x 400-600g carbon double bias patch. not sure of the weight as its from off cuts out of the scrap box. definitely heavier than 300g but probably not 600g, somewhere in between
2x 300g glass bi-axial +/- 45 degree orientation
1x 300g glass bi-ax 0/90 degree orientation
1x 200g glass boat cloth
all the layers are 1 piece and go down through the fuselage socket except the 0/90 bi ax which wouldnt do those tight corners, i cut this one in half so it stops either side of the socket.
it should be strong enough but whether its STIFF enough is the question. ive done foam wings with only 6 layers of boat cloth each side and it was fine but the wing was nearly twice as thick, and my last gull wing was 2 layers of 200g carbon twill+ patches which was what i was wanting to do on these ones but i didnt want to wait potentially 12 weeks for the lock down to end so i can get my carbon.
i also didnt use peel ply as the fibreglass store is considered ‘non essential’ and closed for the duration!!?? instead i did it like a surf board, let it go off a bit then brush on a thick sanding coat. it will be a little heavier but whats a few grams between friends
And a tip from grandma- white vinegar disolves epoxy as good as acetone, gets masking tape residue off and doesnt kill your skin. You can also wash your eyes with it should you manage to get resin in them. It sucks but not as much as resin going off in your eye
Nice wings! Got any info on them?
I’m gonna do a bit of a write up about the different techniques I’ve used over the last couple of years. Just need a bit of time here lol.
Ok, great work man. But you didn’t cover shaping the bottom. Anything of note there or just flat?
Also, yes, I’ve done a rudimentary wing with glass and at least some carbon is a good idea to get the stiffness. Even if it’s just a single layer it helps. I have a patch on the bottom of my diy wing and it made a huge difference.
Cowboy the bottom should be untouched at this point! I like to have atleast 50-80mm of foam under the wing to stop it flexing while you shape and glass the top, you want the bottom to be a factory surface so it is blemish free and sits perfectly flat on the bench. The reason i emphasise that is it makes aligning the fuselage in the socket very easy. My garage floor is pretty much dead level so all you have to do is hot glue the wing to the floor, make a little plywood cradle to sit the fuse (which also holds it level on the longtitudinal axis) and set it all up plumb, true and square with a spirit level. I put a centre line mark down the fuse so you can measure in from wing tips to centre, and from wing tips to back of the fuse to get it square in plan view.
Glassing the bottom is where the tricks are for making a solid wing but you will have to wait for that as i havent shaped the bottoms yet
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