Balsa Composite Sandwich

[Surfdad]

Hey Jason, there is about 3 inches of nose rocker and maybe 1/2" of tail rocker - it does look flat thought doesn't it? Just poor picture taking on my part.

[Surfdad]

Another project is this Core-cell skinned creation. It's a knockoff of a Firewireboard, complete with a carbon rod connecting the rails and fin boxes, Core-cell A500 in 3mm skins, balsa rails and eventually I will wrap the rails with Carbon Fiber tape. Not as pretty as the Balsa, but probably as close in functionality.

[Jason B]

I've never heard of Core-Cell. Is that a composite?

That board looks a little more rough than the balsa board.

It's very interesting. Keep posting updates.

[Surfdad]

I didn't describe that very well did I? The corecell board is fresh out of the bag this morning at 4:30 am I still need to sand the rails flush on the deck and feather it just a bit. Then it will get rid of the rough shape on the outline.

Corecell is a Styrene Acrylo-Nitrile (SAN) foam. It's not a composite by itself, but in the board you are seeing it becomes a component of the composite. In it's current state, the board is Corecell top and bottom, a 1# density EPS in between the two skins and the skins are bonded to the EPS core with Resin Research Epoxy and 2 oz eglass.

[Surfdad]

I also did a board using Divnycell skins and rails. D-cell is a cross linked PVC foam and I used the H80 grade for that construction. That is very similar in nature to a surftech construction, except that surftech's have a LOAD of polyester on the outside to give it that great finish.

It rode very well.

[Surfdad]

I have one final skin coming. It's a PMI foam called Rohacell. It had to be manufactured in Germany and they wanted a signed release to ship the stuff!!! Crazy. It's the skin that Surftech is using in it's TL2 construction. One of the attributes of the Rohacell is that it's radar invisible. For when we want to to some stealth wakesurfing - I've got the goods.

[Surfdad]

I bagged the carbon over the rails last evening, but did a LOUSY job of aligning the tape. It will need some graphics to hide the mismatch. The carbon is a great look, ut it also stiffened up the perimiter bals rails substantially. It almost feels like the carbon by itself would make an adequate rail system.

First pic is out of the bag. Second pic is a "crayola" visualiztion of painting the board to hide the mismatch tape and then a close up of the carbon.

[da.bell]

The carbon fiber will be interesting to see what happens when you surf on it. As far as I know, carbon fiber will bend slightly for that "kickback" that you might receive in the water once you hit the wake. Let us know how this one rides.

[Surfdad]

The carbon seems to have cured pretty stiff, I'm concerned that it's too locked up already. The Carbon I used was a 5.7 oz tape, so it's like having 11 oz glass around the rails. The Balsa that is underneath has a density of around 6 to 9 pounds/cu ft. The combination feels very stiff. The balsa rails by themselves are pretty stiff, in fact a bit too stiff to generate the sort of flex I was looking for.

Anyway...we'll see what it rides like - at the very least it'll give a good rail set.

[Jason B]

Very cool.

How do you keep your bag from sticking to the layup? I was under the impression a barrier layer like poly-fill or something had to be used?

[Surfdad]

I occassionally will use consumables - breather and release ply, but for the most part I don't any more.

If you look back at the picture of the corecell board under vacuum, you'll see that crazy pattern on the rocker bed - that's a piece of scrap linoelum. I use 36" Nylon Bagging tube from these folks:

http://www.acp-composites.com/acp-vbes.htm

The epoxy will cure and there is a slight surface tension, but when you pull it up it release and there isn't any resin transfer to the bag. In fact there are some release ply made from nylon. I polished the linoleum up with mold release wax. Nothing sticks to that - makes me want to run and slide on the stuff wearing socks.

I do use Perforated peel ply with a breather on occassion. Typically when I am bagging a stiff or heavy fabric that takes a LOT of resin to wet out (Like this Carbon or Kevlar or even an eglass that is 8 oz or more) When the laminate goes in resin rich and I want to pull some out I'll lay perfortated peel ply on the wetted out fabric and then breather or plain old paper towels on top of the perf. peel ply.

I wanted the rails DONE so that I don't have to try and hot coat them (that's a bear with epoxy) so I left the carbon super resin rich and when they came out of the bag they look like they've gone through a gloss coat. YEAH! No rail lap grinding!!!!

I know that folks recommend the peel and breather and maybe in an industrial situation with a mold that makes sense, but this way I can see if I am getting any wrinkles in the 'glass or anything is weird as I am pulling the vaccuum.

So...in my PRACTICAL experience, the consumables seem mostly to be a waste in practice.

[Jason B]

You've obviously gone much, much further in your "experimenting" phase than I have. I'm not sure what half the stuff you were talking about is but it sounds good

[Surfdad]

Nothing like doing it to give you some experience, but I also grew up with all of this. My father, who is 83 now, was one of the originial folks that worked with Urethane foams. Back in the early 70's he owned this medium sized rubber manufacturing company and I used to bug him for molds, bagging material, foams, etc. I tripped across a Surftech board at a Surf and Skate and it struck me that they were composites sandwiches now...so I've been off and running ever since. If you think about this corecell over eps...1# density foam surrounded by 5# density foam - light and durable. If I can get the flex and return worked out, it really holds a LOT of promise.

[Surfdad]

Finally got James out on the Balsa board over the weekend.

[Surfdad]

I think I have one more picture.