15 replies to this topic

[Heriberto]

I'm laying up carbon floorboards. I'm using 2 plys of carbon (2 plys of 3K plain weave on bottom, 2 plys of 6K twill on top), sandwiching 1/2" polypropylene honeycomb. I measured the carbon (573g) and honeycomb (556g) to estimate epoxy, wetted it, vacuum bagged it, and the unfinished part came out at 1520g, which means 391g of epoxy. That equates to 40.5/59.5 epoxy to carbon ratio. Approx. 40/60.

My question for the experts: is this too dry? Especially for honeycomb core that seems to have a somewhat abosorbent laminating surface?

Total Panel weight is about 3.351kg/sqm (0.67lbs/sqft)
Cost is equating to about $20/sqft.
About an hour- two hours of preprep (prep surface, cut peel ply, breather, plastic and carbon*) and 30-45 minutes of laying down two layers of ply, honeycomb and hooking up vacuum bag system.


*Biggest time was cutting the templates (paper) and sizing the foam to fit in the boat. This is the same time it would take no matter what the floorboard material.

[festus]

The ratio seems a bit dry - prepregs are 35-40% resin. It is not a structural part so not much risk. (I would put the heavy ply down in tension). May want to try a different core next time - PP does not stick to anything w/o pretreat.

[Heriberto]

[Heriberto]

PP doesn't stick to anything? This stuff has a find of fuzzy coating that wicks epoxy. I was doing everything as per instructions....

[Heriberto]

This was the very first panel I've ever made, I was shooting for 50/50, and yes, this is not really structural and is also the most hidden of the panels I will do, so I'm not super worried about this one. Just like sending a newbie to floor the closets, I want to get the techniques down.

Ultimately if I do structural panels, it would be good to know the right target ratio because there seems differing opinion. I could maybe use a film that limits epoxy release, but the breather wasn't completely saturated, so I don't think it was the vacuum (plus it was pretty warm here). Also, this honeycomb was picked because of the purpose, for structural panels I would likely use a different core depending on what is recommended. Whether that is aramid or Penske or whatever.

[_Vegas_]

I'm laying up carbon floorboards. I'm using 2 plys of carbon (2 plys of 3K plain weave on bottom, 2 plys of 6K twill on top), sandwiching 1/2" polypropylene honeycomb. I measured the carbon (573g) and honeycomb (556g) to estimate epoxy, wetted it, vacuum bagged it, and the unfinished part came out at 1520g, which means 391g of epoxy. That equates to 40.5/59.5 epoxy to carbon ratio. Approx. 40/60.

My question for the experts: is this too dry? Especially for honeycomb core that seems to have a somewhat abosorbent laminating surface?

Total Panel weight is about 3.351kg/sqm (0.67lbs/sqft)
Cost is equating to about $20/sqft.
About an hour- two hours of preprep (prep surface, cut peel ply, breather, plastic and carbon*) and 30-45 minutes of laying down two layers of ply, honeycomb and hooking up vacuum bag system.


*Biggest time was cutting the templates (paper) and sizing the foam to fit in the boat. This is the same time it would take no matter what the floorboard material.

Hey Herbi - Wet layups usually yield a 50% fiber to resin ratio - Vac bagging you get a slightly lower value (like what you got) - and a properly prepared infusion will get a slightly lower than vac bag - 35% ish. there are a bunch of factors that can contribute to higher or lower contents, but I'd say you are in the ball park indeed

[festus]

PP doesn't stick to anything? This stuff has a find of fuzzy coating that wicks epoxy. I was doing everything as per instructions....

Looks like it has a nonwoven scrim for adhesion - should be fine if you followed the directions. Shorty has new teak and holly floor boards this year - they look nice. Attach some pics when finished - do you plan to leave the carbon in a clear finish?

[Heriberto]

PP doesn't stick to anything? This stuff has a find of fuzzy coating that wicks epoxy. I was doing everything as per instructions....

Looks like it has a nonwoven scrim for adhesion - should be fine if you followed the directions. Shorty has new teak and holly floor boards this year - they look nice. Attach some pics when finished - do you plan to leave the carbon in a clear finish?

Saw Shorty's pics, that looks cool!

Here's what happened with mine, I was going to go with a single layer of carbon and put a layer of bamboo veneer on top, but then I got the sticker shock! $180/4x8 sheet! Holy fuck! since my floor boards would be 28" wide in most points I would have tons and tons of waste and it would have taken me three sheets. So I bagged that and put an extra layer of carbon on both sides. I suppose one layer on the bottom would have been fine (in tension) but I figured to play it safe.

Haven't decided on a clear finish or not, I'm actually thinking about painting the tops to put non-skid in it. But I suppose I could do that in the clear coat. What do you think? Vegas?

Oh, and Vegas, thanks for the info!

[abc123]

If the floorboards are truly flat...you might consider using pre-cured facesheets secondarily bonded to the honeycomb core. With good wet-out, squeegee, and proper vaccuum-bagging you can easily obtain a 35% resin content in the facesheet and have high confidence that the laminate is not dry/voidy. Then, with perhaps some slightly thickened glue (mix in some microballoons) lightly applied to the scrim of your honeycomb (or the inner-sides of your facesheets) you can consolidate the facesheets and core into a nice, rigid panel. The worry with a wet layup over honeycomb under vacuum is the possibility of depositing a BUNCH of adhesive INTO the honeycomb cells rather than into the lamintes. Your weight ratio quotes may or may not be accurate as you don't really know WHERE the glue ended up. (In the lam or in the cells??)
(main reason solid core, be it foam or balsa, or whatever is TYPICALLY used with vacuum infusion techniques...the honeycomb cells are seen as VOIDS when under vaccuum and unless specific efforts are made to avoid doing so...will collect A LOT of excess resin)


Interlaminate (layer-to-layer) compaction of fiber (and consequently interlaminate shear strength) is also a challenge over honeycomb as the 'layered' contact BETWEEN cells is somewhat minimal...a pre-cured laminate on the otherhand is uniformly consolidated...CAVEAT: cell size of the honeycomb can play a huge role in the final results as well....I would argue that wet layups do better with smaller cells whereas precured laminates can bridge larger cells more readily....

My $.02 (...but probably worth about what you paid for it!....Your mileage may vary!)

Good Luck.

[Heriberto]

That is really interesting. This honeycomb product does have a scrim that soaks resin (see the picture above), so that part I think is "safe", but I understand what you are saying about uneven compression/consolidation. In fact, on the top side, there is a patterned print-through of the cell structure where the carbon was sucked down very slightly into the honeycombs.I have no idea what that does, but it creates a less flat surface. It would significantly increase the production time and cost to create flat plates and secondary bond them to the honeycomb. Twice the surfaces needed, three times the bagging. Not worth it for what I'm doing, but it's an interesting and useful idea.

[El Crapitano]

Beat the crap out of the test sample. If it survives your resin ratio and wetout is good.

Carbon and honeycomb comes with the unavoidable pinhole issue. The simple answer is to put a layer of thin, thin fiberglass scrim in there. The carbon weave is coarse and you can't get the interstitials to consistently wet out. The thin layer of scrim will wet out fully. If you want proof, weigh your trial horse then immerse it in water for an hour and reweigh. Don't want the honeycomb cells to fill with water.

Getting the epoxy to grab the relatively small surface area of the honeycomb can be tricky. I would use a generous quantity of thickened epoxy on the side of the carbon that bonds to the honeycomb.

Use shower board from Home Depot under the vacuum bag to eliminate dimples. Stuff is $12 for a 4x8 and is perfect for the job. It's masonite with one hard, white surface.

[_Vegas_]

PP doesn't stick to anything? This stuff has a find of fuzzy coating that wicks epoxy. I was doing everything as per instructions....

Looks like it has a nonwoven scrim for adhesion - should be fine if you followed the directions. Shorty has new teak and holly floor boards this year - they look nice. Attach some pics when finished - do you plan to leave the carbon in a clear finish?

Saw Shorty's pics, that looks cool!

Here's what happened with mine, I was going to go with a single layer of carbon and put a layer of bamboo veneer on top, but then I got the sticker shock! $180/4x8 sheet! Holy fuck! since my floor boards would be 28" wide in most points I would have tons and tons of waste and it would have taken me three sheets. So I bagged that and put an extra layer of carbon on both sides. I suppose one layer on the bottom would have been fine (in tension) but I figured to play it safe.

Haven't decided on a clear finish or not, I'm actually thinking about painting the tops to put non-skid in it. But I suppose I could do that in the clear coat. What do you think? Vegas?

Oh, and Vegas, thanks for the info!

Hell if it doesn't see sunlight peel-ply the business surface and wha la - lowered resin content and a non skid surface - done...go sailing

[Heriberto]

So I looked in the mirror, found 222lbs of dumb meat and had it jump up and down on this piece as hard as possible on the center of it with support only on 28" centers. Next to no flex, no creaking, cracking or weird sounds. I could probably drive a truck on it. I think it's good....

[Heriberto]

[_Vegas_]

Looks good by me eyes

[Heriberto]

This piece wound up right at 50/50.