Hey all,
I know the method of vac bagging balsa skins to eps cores with a layer of glass between is the usual, I was just wondering if there was any reason that I couldn’t just lay up the skins using good old PVA glue (I know that this sticks well enough), and would (in my imagination) just need the extra glass on the outside.
Am I missing something really important here?
This will be the first eps I’ve done and was just playing with ideas, so any input would be just super!!
Chipper, come home!
The inner layer of glass forms part of the “Composite sandwich” of the skin, so generally it’s advantageous to have it there.
It’s by no means the only way to do things, there are millions of ways that are valid.
Kit
cheers Kit, I suppose as the foam didn’t cost me anyhing it wont be a too costly experiment even if it doesn’t turn out. So, I’m going to give it a go.
Chipper, come home!
It should turn out fine, and will make a good board.
Maybe not as strong though?
I pre-make my skins with the inner glass already cured, so I attach them to the blank with a bit of glue, similar to what you’re saying
I’d reccommend having glass on the inside in the areas where you feet/knee will be, as the deck needs to be strong.
Or you could just do an extra deck patch on the outside
Sandwich skins are super cool, so many variations to try!
Talking with Danny Hess last year at the Sacred Craft Expo he said he doesn’t use inner glass. Of course , he’s using plywood (1/8" poplar bender ply, but I suspect he sands it down) and uses 4 oz S glass outside.
If you can spread it out evenly, go for it.
Yes, it will work, I’ve done it. The board works just fine and if designed properly will last. Maybe just not as long as a true composite board, as Kit said.
The board below is the only one that I made, it’s lighter weight than my other boards, moves fast and turns on a dime (give ya 9 cent change!).
Keep this thread going by letting us know how you progress and finish it up with a ride report.
Les
Thanks all for the replies and encouragement. I will post some progress stuff as I go through but anyone who knows me will vouch for this, it will not be a quick build.
I’ve started shaping the blank, and gone for a 7’ 6" mini-mal kinda thing.
What thickness of balsa would people recomend; bearing in mind all of the glassing will be done on the outside, (and bearing in mind that this is England and balsa is reet scarce in anything other than modelling packs).
Les, that board looks great, what are the dims? I’m hoping mine goes as well as you say that does. You say its lighter than your other boards? What kind of construction are your others?
Oh the ride report won’t mean much as I’m about as talented a surfer as my gran was.
Chipper, come home!
“Talking with Danny Hess last year at the Sacred Craft Expo he said he doesn’t use inner glass. Of course , he’s using plywood (1/8” poplar bender ply, but I suspect he sands it down) and uses 4 oz S glass outside."
Gold!!!
I have been wondering, because the typical .6mm veneer just would’nt cut it as a sandwich skin.
Danny’s boards are Lush, I’m taking a bow to the man…(And sneaking off to find that ply!)
Josh
in shops that cater to model airplane builders you can get really strong and thin birch and poplar ply , we’ve used it in snowboards with success I suspect it is strong enough to use as a skin without inner glass but balsa is a no-go afaik since it simply isn’t strong enough. balsa is a “core” material for a sandwich, not really a “skin” as it were…
Hey Dave…
Yes, I’ve been aware of it as aeroplane wing skin material, but so far I’ve been spooked by the reported expense, and never actually asked!
Maybe I’ll be brave…tommorow…
Josh
hi, lardass,i would think twice before you decide what to do with your skins , if you use glass under with epoxy it only adds a small amount of extra coat and the benefit far out weighs the negative , by useing cloth under you add loads of strength and the resin is spread thin to give an even coat throught the cloth,
you can use thinner wood as well which makes it easier to conform to your shapes , i have used 0.8 mm balsa on some boards ,
if you want to save a bit of cash you can glass the outside with polyester, i have done a few this way and they are just as strong, the plus point is you can polish it up good ,
a higher density blank like a polyurathane is probably ok without glass under but i would still use something like 2 oz just to give an even spread of resin, pete
Yep, it ain’t cheap…
We are looking at approx 40 euro m2 for 3ply 0.4mm and 0.6mm, the 4ply at 2mm is too thick to flex properly as a skin without making cuts but is cheaper at about 24 euro m2 for ski’s and snowboards however it is durable as hell and gives a “pop” to the flex like you could never get with vertically laminated solid pine wood cores at a price premium though…
Hey Dave, any chance of a look at some of your snowboards? Or is that for a different forum?
Chipper, come home!
I’ve got one of the first in the resources, yes it is also a different forum www.grafsnowboards.com and www.skibuilders.com
I’ll get some more piccies as soon as the workshop gets sorted, we have an issue right now with workshop space here…
Cheers Dave, I’ll take a look when I get home later.
Chipper, come home!
It’s 8’x23"x3" Construction was 1 lb. EPS, Pu glue, 1/16" balsa, 4 oz. S glass over. Rails are Redwood.
Weight is about 12 lb.
The construction I use now is 1 lb. EPS, 4 oz. S glass, 3/32" balsa, 4 oz. S glass, and Cherrywood rails. I don’t seal the EPS.
The boards are slightly heavier than Pu glue under the balsa.
Les
Fat, There are several reasons I would not use your method of construction. 1 Glass-balsa-glass is a sandwich and that is what gives you strenth. The thicker the balsa the stronger the sandwich. Now about PVA glue. Several possible problems here. PVA glue has a short tack time which means you don’t have much time to do your glue-up and put it in the vac back. Next PVA glue will bleed through veneers when put in a vacuum , It will bleed through 1/4 inch balsa no problem. Bleed through will give you a finish that is blotchy at best or even black spots if it is in the vacuum to long and mold spores are pressent. PVA is a soft cure glue so your glue joints with stand proud after you sand the balsa. The cure time for PVA is slow when under vacuum so it needs to stay in the bag under vacuum for over night at least to cure enough to not de-lam. Yes PVA can be a good glue for vac-vaneering because it can be sprayed on with a gun, but veneer PVA is formulated for extended tack time and the veneers used a generaly paper back or ply veneers. Now that I told you why I wouldn’t do it I am going to recommend that you go ahead and do it so I can learn from your experience ! Aloha Ahui hou- Wood_Ogre
Hey Wood ogre
Well, I think I’m going to have to re-think some of this. What I’m trying to come up with is a way of doing this without vac bagging it, and as cheaply as possible. I have four blanks cut to mess about with which have cost me nothing so I’m happy to experiment with them but the epoxy is very expensive over here so I’m reluctant to waste what little I have of that in experimentation.
I’ve just been reading a thread which has been revived from way back about figure 8 stringers which has got me thinking aswell (some serious engineering genius going on there) so may abandon the balsa skin idea for a bit anyway…or maybe not…So many choices to make. I’ll decide by the time I get home from work.
Chipper, come home!
Hi Dave, I havn’t looked at the Graf foroum in a while, are you using the ply as a core or as a skin with triax cloth. If as a core how are you foiling it? I’d be stoked to see some of the boards.
cheers
