How much carbon needs to wrap around the leading edge of mast?

[opie]

I am ordering some 400 g biax and 200 g uni for the mast and fuselage which I will make as one piece with a wood core.  Does the carbon that wraps around the leading edge of the mast add strength, or is it just to smooth it out?  How much of my carbon needs to wrap around?  Will the 400g/12 oz biax bend around, or should I add some thinner stuff to my order?
Maybe I should mention I have no experience so any help is appreciated.  My Fusion 360 skills are coming along so I think its time for me  :)to learn to work with composites.
Thanks.

[surfcowboy]

Good timing, I'm about to do this part too so I got nothing lol. I'm going to try a "strap" on each side that doesn't really wrap over and then a layer that wraps from front to back covering both sides as a sandwich so the layers meet at the trailing edge. Wondering if I should just do 2 of those. My glass will all be wrapped around like this too. An important idea is that you lay the carbon on a 45° angle to fight the torsion of the wing twisting. That's key.

I'd love to hear from the carbon heads but I don't know how much it'll help but it seems like it should as more of a tube feels like it'd be stiffer. I will say that this stuff is way stiffer than I ever expected it to be.

[supuk]

Yes it would help a lot with fatigue if you have something wrapping the leading edge weather its all or just a number of the outer layer of your laminate. 

[opie]

I added some thinner carbon to my order.  I've ordered lots of stuff, so far just a belt sander, a jig saw and some Birch plywood has made it here.
I am wondering how I'll deal with inserts in the fuselage.  I imagine I should place them before I add the carbon, then drill holes in the cured carbon skin for access.  If so, how do I keep the epoxy out of the inserts?  Something like Play Dough?
Also, what's the best tool to trim the cured carbon from the  edges?  Since I probably need to buy something I might as well get the right one.  I've been considering a Dremel or a vibration cutter.
Thanks

[surfcowboy]

Clay should keep the inserts clear for sure.

It's funny, I couldn't get my head around the whole insert thing for the main wing. I probably should have but I really didn't want to have that wide of a fuselage. Probably would have been easier in the short term. I do need to put some in for the tail wing, but I've also considered running holes through the fuse and filling them with epoxy and then drilling them out and just using bolts through the fuse to hold it on.

I just grind carbon off with 60 grit myself. The thing about not sanding carbon is that it frizzes on a surface but I've had no issues with the edges, but I'm just getting started so what do I know? I could be off base. Seems like a plug in Dremel would do great. I have a battery one and hate it, btw.

[supuk]

I would defiantly put a multi tool on the list there great for cutting composites and sanding.

[container]

400g is way too heavy! stick to 200g for everything, bi-ax will only work if it is wrapped around in one piece. short 45 degree fibres laying flat on the side wont do anything for strength or stiffness. my 900mm foam core mast has 5x 300g double bias (too heavy but was all i could get) and 5 or 6 200g unis, all wrapped around the leading edge and meeting at the trailing edge and it is nearly unbreakable, you can jump up and down on it all day no worries.
set the mast up horizontal on some mounts with the leading edge up and drape the cloth over then clothes peg or small plastic clamp the cloth all the way along the trailing edge, this will keep the cloth pulled tight around the front. tie weights to it if you have to
candle wax works great for keeping resin out, light the wick and dribble it in
+1 on the multi tool, i dont know how people built stuff without them!

[container]

i like go foils method for threaded inserts, just drill a hole through the side after you have done all the laminating and push a barrel nut in. job done. wish i had seen that before i f**ked around setting nuts into the structure and what not

[blackeye]

bi-ax will only work if it is wrapped around in one piece. short 45 degree fibres laying flat on the side wont do anything for strength or stiffness.

disagree - the 400g will be stiff around the leading edge, yeah, probably too stiff, but flat shapes on either side of the mast will be like a snow ski construction, used to control twist / torsional flex.

set the mast up horizontal on some mounts with the leading edge up and drape the cloth over then clothes peg or small plastic clamp the cloth all the way along the trailing edge, this will keep the cloth pulled tight around the front. tie weights to it if you have to

Good idea and the clamps help a ton. Wet out then drape it over the core. Hard to vac-bag but I don't think that was mentioned. Can be done with the right clamping.

Nothing fancy is needed to trim and sand carbon, but I'm sure fancy is fun. Good scissors or shears work when still green, or a sharp knife, or coarse sand paper when its cured. I have some well used 10 and 20 grit for manual grinding. I recall someone using a "cheese grater" (sure-form?) for knocking down the bits that stick up everywhere, but my coarse sandpaper is fast. Watch out for your fingers as that carbon can be sharp.

[opie]

i like go foils method for threaded inserts, just drill a hole through the side after you have done all the laminating and push a barrel nut in. job done. wish i had seen that before i f**ked around setting nuts into the structure and what not

You are talking about cross dowel barrel nuts, right?  That sounds like a great solution but I can't find a source in the U.S.  Is there another name for them? 

I may end up just using through bolts but I am hoping to learn inserts this time so that when I do version 2 I will already know what I am doing.

I am putting together a vacuum system, might as well learn everything, but I bet I can still use the horizontal jig and clamp idea.  Somehow.

Multi tool has just been added to the list.

Thanks everyone!

[surfcowboy]

I picked up some brass inserts in the furniture hardware section of my local Lowes. I think I might use those as you can totally install them post lam as was said. They are 1/4-20. Since I'm not using them to hold my wing on I think these will do me fine.

Container, thanks for the tip on the hanging the mast. I was gonna bag mine in a big bag but this might be easier actually. I like it. I want to build a foam or 3D printed mast next and yours sounds bomber.

[opie]

I found the  brass cross dowel barrel nuts.  They are Chinook brass inserts for windsurf fins.  There were also titanium barrel nuts used in bicycle seat posts, but I ordered the Chinook.

[opie]

So far I am not getting anything done, just learning from my mistakes.  Sanding the cores has been the only thing that worked but it's so messy I am going to avoid it at all costs in the future.
I drilled holes for reinforcement where the bolts will go in the plate.  The tape on the back of the holes did not hold the epoxy so I ended up with a bunch of epoxy stalactites holding the tape to my now uneven plate surface.
Sanding epoxy also makes a mess. 
I mixed a paste and filled the holes with that.  It was not easy to work with.  It left voids, stuck to my scraper and it was impossible to get the right amount in.  When it dries I'll be sanding again.
I've also learned that I need much more room to work.
I did glass a front wing but it literally weighs 10 lbs.  It came out messy and I tried to clean it up (and add thickness) with car bondo.  I thought that would be easy to sand, but not so much. So I just added a hot coat on top to try to smooth it out some more. 
I am worried that with all that weight it might rip the tracks out of my Takuma board, so I think I will dig out my through bolted Vesl sup and use it for the test.
On the plus side, I can only improve.

[jrandy]

Oh man. Bonus points for honesty in the face of adversity.

If it were mine to do (over), I might sand the wings smooth and prep them as a plug. Coat with PVA and #2 mold release. Lay up/ vac bag a couple layers of carbon over the wings from tip to fuzz. Pop the wings off the plug, fill with Great Stuff for windows or pour foam except last 2.5" at the wing roots . Cut the wood +Bondo wings off the fuzz leaving 2" of the root. Sand off all the mold release and epoxy the molded wings to the fuzz +wing roots using the 2" overlap.

Of course this is all hypothetical since I don't foil and therefore have not built a foil...I know of a series of surf fins built that way (hollow carbon foil solid base) and it's not altogether different from modern paddle assembly methods.

[opie]

Thanks jrandy for the idea with some specific instructions.  I was thinking that if one of my wood core wings worked well I could make a plug out of it, but exactly how I would do it I haven't been able to wrap my head around.
That idea is a lot like when Supuk used the 3d printed plug to make a shell he filled with foam. 
Coincidentally my mold release wax and PVA came in the mail right after I read your post.