Cowboy Foil Experiment Thread

[supuk]

Yes she helps me laminate my unlimiteds and get them in the vac bag and all sorts of other things. She could probably lam a board on her own now, may make her do her do her next board herself. Hotwire cutting is anouther skill she has acquired lol

[blackeye]

Sorry I forgot to post the picture of the hot wire  jig, this way is great for cutting multiples or if you want accurate cuts but you can just nail them straight to the blank. If you put markets on each template at 1/4 1/2 3/4 it helps judge your speed at ether end and it's a lot easier with two people. You can set up a pivoting arm that pulls everything through at the right speed but they can be a bitch to get right and no point for quick 1 off things. For your hot wire just use some nicrome wire and a 12v car or bike battery and resistor if you need to adjust the temp

I see you must do top and bottom surfaces separately with two templates. I used one complete foil template, but yeah, the transition between top and bottom was tricky, even with two people.

I'm trying to visualize your process. The cut-line of your two templates must hover above a standard reference point, so that when you attach the bottom template after doing the top, it aligns correctly. Or do you just eyeball the lower template such that it lines up with the leading and trailing edges already cut from the top? You must have to allow for the kerf on the bottom one, which I have found to be wire temperature dependent. You could make a convex bottom template, mate the top section with its cut-off scrap, flip it over and wire with no worries about the kerf. Then imperfections you could sand away rather than have to fill. 

The alignment with my method was by dead reckoning: I squared up the blank as best I could, then measured and marked my pin-holes from the edges. I pinned the templates to the foam with 2" deck screws. I cut about 4 pairs and was happy with 1. I cut them long so I could cut them in half and get symmetrical Port and Starboard sections. My foil wasn't tapered except for the tips.

I found that I got the best cut by starting in the middle and cutting towards the trailing edge, then repeat towards the leading edge, flipping it over and doing the other side the same way. The imperfections in the cut from starting the wire are easier to smooth out over the flattish areas of the foil rather than the edges. I see your method provides a lead-in / run-out from the template, which would be really handy.

Cowboy - as for A, B, or C, if it comes out generally resembling one of those, or an amalgam of all of them, be thrilled!

[surfcowboy]

Lol black eye, that's what I figured.

I actually need to post a pic of mine. I mounted the templates with an overhang. The bottom trailing edge is flat so I just hung the first 2" over the edge of the board so I can go around the front.

I'll post up in the am.

[supuk]

yes two templates one for top surface and one for bottom then flip everything over for the opposite side. cut the top first then the bottom. for cutting wings by hand you want to cut fairly slow with a thin wire, the temperature should cause hardly any kerf. The bottom sheet of the jig is the exact size of the wing and the blanks are cut so that just is your blank registration also. When cutting curved surfaces you have to make sure that the wire does not drag so just go at the speed it is cutting at or you will get a curve in you surface. I need to cut a new glider soon so will take some pictures
 

[surfcowboy]

Testing a photo upload here with Tapatalk.







That's just a demo piece of EPS but tonight I made a prototype out of the sculpture foam.

I'll post that up if this works.


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[surfcowboy]

Ok, so the redneck CNC works.

Here's the idea for any who want to make a flat foil.


Put a 24"x8.5"x2" piece of foam in and roughed it in with a saw blade.



Here you can see the sanding block. I stiffened a 1x4 with a vertical stringer of 1x2.



There's just over a foot on each end so it rides on the foil templates.

Sand a little holding the foam in place on a rubber no slip mat and you get this.



The only challenge is that the sculpt foam bows up (the wrong way sadly or I'd keep it lol)

I think I'm going to get some 2" EPS this week and knock one out.

In good news, if I want anhedral it'd be easy to glass this over a form and get whatever bend I want.

At 1.5" thick (38mm) thus thing should fly sloooow.

Now, to design and cut my mast and fuselage and do some glassing tests.



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[supuk]

good job, If your going to do a foam core for your mast I would ether use some hd foam or if you do you eps or xps put a stringer down the center. with eps/xps it would pay to hot wire it, it will only require one set of templates and it means you can use the cores to help bag the carbon onto it.

[surfcowboy]

Man, I'm thinking of laminating some 3mm plywood and glass/carbon just to do this one fast. Seems likely I could get the stiffness I need and then if I like the design go glass over foam ( or get crazy and mold.)

This will be my first bagging so I want to make it simple to start.

One thing I'm working out is the mount of the wing onto the fuselage and since I'm not 100% on the angle I'm thinking I'll glue on some foam and route a flat spot into the top of the wing with a jig so I have a flat place to bolt the fuselage onto. I'll do the glass fibers and epoxy fill so I can drill and bolt through the wing. That'll let me add shims if I need to get it level as I'm not really sure what "level" is on a wing.

Do I call the flat bottom level or use the straight line from the airfoils site? That seems imprecise to me.

By the way, the rest of this forum needs to start building some foils. It's just you and me now that Pono has gone to Maui. Some of you inland guys need to make some for next summer behind a buddy's boat!

[supuk]

ply and glass will work fine for a basic mast, try use good quality birch ply though it will make a big difference and is nicer to sand and finish.

 For the mount between wing and fuzz you have a few options  but you want it to be solid! The torsional stiffness is the key. The 3d printed tubes I have been using bonded into the core and glass over has worked a treat and means your not relying on just the bolts.

you want to take your airfoil centerline  from the center of the leading edge to the trailing edge. set the fuz parallel with that and then with a inverted foil on the rear about +2deg incidence on the rear wing.   

[surfcowboy]

You aviation guys know all the tricks.

As to the mount, I hadn't thought about the 3D printing idea. I might also go check my buddy's industrial hardware store for some sort of metal coupler that I could glass in to standardize the mount. Or carbon tubes or rod like a paddle handle might be a way to go with bolts through them. I'd need to reinforce most tubes I'm betting, but it's an idea and would fit nicely.  Hmm.. time for some googling here.

[supuk]

it defiantly pays to have a connection that is booth solid and allows you to switch out the wings easily.

 I would also think about your fuz at the same time and what you are going to do with that to get the torsional stiffness  to translate from the board all the way to the front wing. Its is just as important to get the connections between the components solid as it is them selfs's. even a .5mm tolerance at the connection of the wing right in the center translates into a large amount of movement at the wing tip so make it a good fit. 

[surfcowboy]

Yes, this has been something that I've considered for sure. Even at 55cm, that's a long way from plate to wing tip.

I'm going to use thin plywood as they mention in the seabreeze article, 3 layers if I can get good quality 3mm. Then use glass (or carbon?) between the layers. Then, after shaping it down, some 45° and 0° carbon on the outside with a few layers of glass over that.

One thing I'd considered as well is to route 2 or three channels into the inner ply, maybe like 1cm wide, which would give me some channels to laminate in so that the glass/carbon would have "U" channels like people do on the rails of a board. I figure that those carbon channels would help stiffen the laminated unit. You think that's overkill or something worth doing?

That's the weird thing about the Clearwater kits. I can't see that mast being stiff enough to not be a bit loose from twisting with just wood and glass.

[supuk]

I don't think you will have problems with making the mast stiff its easy to run uni and some at a bias especially using a ply core but it is harder to get the fuz torsionaly stiff itself and at the joints between the mast and fuz and the fuz and wing

[surfcowboy]

Ah, yes. I'm actually gong to make the fuselage and mast in one unit. At least for the 3 plys of the mast. I'll add a couple of extra plys on the outside to get it up to an inch or so thick but that way I won't have to mess with the mast to fuse joint at least.

I think I have a plan to mount the wing with some carbon tube salvaged from a cheap paddle. Slide the smaller tube over the front of the fuselage and embed the larger tube into a routed channel in the wing with the glass and some bog. I can then bolt bottom to top through the tube and wing. (I'm doing your epoxy fill for the bolt areas on the wing and to tie the top and bottom together.

[surfcowboy]

Here’s the idea, I’ll trim the front at an angle and glass and fair it all into the wing.  Hopefully, carefully, setting it at the correct flat angle.

The inner slide will go over the front of the fuselage to make sure it’s strong enough to hold.

I’ll drill out bolt holes and fill the area around them with epoxy and filler and fibers to tie the top and bottom together and give me 2 or 3 strong points to bolt it all together.