Fiberglass cloth and tape? Weight does it matter?

[DWT77]

I ordered the Raka Style 120 - 3.25oz (T) x 60 in -Fiberglass Cloth to cover my teardrop.

The lightest raka fiberglass tape I can find is a Standard woven 6oz.

I assume since they don't sell a 3.25oz tape that it doesn't matter if I use the 6oz tape? Does that make the fiberglass surface uneven?

I suppose I could make my own tape by cutting 3.25oz. (cutting it diagonally so it doesn't fray) That's what I have gathered in the forums on here.

It is my first time dealing with fiberglass I just kind of figured the tape would be easier since it has the edges.

Any experience users have some advice? Thanks for the help!

[Pmullen503]

3.5 oz is a little light but adequate. You can use multiple layers in areas like the front that would be prone to damage from stones and the like. The taped areas will be higher but they can be sanded to blend in somewhat. If this is your first time, start with something small like a tongue box to get used to it. You'll want to avoid working too much air into the lay up if you are going for a clear finish.

[tony.latham]

I've been glassing for forty years. I think 3.5 oz, for sealing plywood is fine––I'd use it––and it's okay to use 6 oz tape for the edges. However, bias-cut tape rolls over corners much-much easier...



Tony

[KCStudly]

The 6 oz will require a larger radius on edges to keep the stiffness of the glass fibers from lifting the cloth up out of the resin, causing air bubbles adjacent to said edges. Experiment. Rutan instructions (plane building reference) said that they could do something like (IIRC) 1/8 inch on bias and 3/16 perpendicular, but I found that to be ambitious. I got good results with 6 oz cloth and 1/4 inch radii.

The 6 oz will stand up a bit and you will have to sand edges some, just be sure to always wear your PPE (respirator and eye protection) and don't sand down into the base fibers. I like to run a paint scraper over the porcupine edges (after cure) to get all of the barbs off before washing amine, then sanding.

[KCStudly]

...Also, for best strength you don't really want to wet out the weave to where there is no texture. That will allow the cloth to float and not be as strong, so if you are going for a clear woodie look, lighter cloth is better because it will take less filler coats to fill the weave in secondary operations (the canoe guys all seem to use 4 oz).

[KCStudly]

...also, the 6 oz might not go as invisible as the lighter cloths.

[DWT77]

3.5 oz is a little light but adequate. You can use multiple layers in areas like the front that would be prone to damage from stones and the like. The taped areas will be higher but they can be sanded to blend in somewhat. If this is your first time, start with something small like a tongue box to get used to it. You'll want to avoid working too much air into the lay up if you are going for a clear finish.

Pmullen thanks for the feedback. Raka describes the 3.25 as "Much stronger than style 1522 x 4 oz. and has excellent clear wet out but because of its tight weave is not as drapable and is harder to wet out. A great choice for many projects as it will use no more resin than epoxy coating by itself." I am hoping that is strong enough. I did order a roller so that should help. I have started a practice board but it is only flat. I was thinking of mocking up a side and practicing the edges.

[DWT77]

I've been glassing for forty years. I think 3.5 oz, for sealing plywood is fine––I'd use it––and it's okay to use 6 oz tape for the edges. However, bias-cut tape rolls over corners much-much easier...



Tony

Thanks Tony I will see if I can track down some bias-cut tape

[DWT77]

The 6 oz will require a larger radius on edges to keep the stiffness of the glass fibers from lifting the cloth up out of the resin, causing air bubbles adjacent to said edges. Experiment. Rutan instructions (plane building reference) said that they could do something like (IIRC) 1/8 inch on bias and 3/16 perpendicular, but I found that to be ambitious. I got good results with 6 oz cloth and 1/4 inch radii.

The 6 oz will stand up a bit and you will have to sand edges some, just be sure to always wear your PPE (respirator and eye protection) and don't sand down into the base fibers. I like to run a paint scraper over the porcupine edges (after cure) to get all of the barbs off before washing amine, then sanding.

I have read where sometimes it is easier to wet out the tape and then slap it on the roof edge. That will make it easier to lay down. Is that correct?

[DWT77]

...Also, for best strength you don't really want to wet out the weave to where there is no texture. That will allow the cloth to float and not be as strong, so if you are going for a clear woodie look, lighter cloth is better because it will take less filler coats to fill the weave in secondary operations (the canoe guys all seem to use 4 oz).

I will be spraying over the fiberglass with Raptor Bed liner spray. I am hoping that will cover any of my mistakes lol. I don't have the experience for a clear woodie look.

Thanks for the help KC

[KCStudly]

Yeah, Atomic (Michael) is a professional race boat builder and he said that they always wet out on a table (that has been covered with plastic sheet) and then transfer the wet cloth to the wet coated work piece (i.e. your camper) to be squeegeed down. This gives the highest assurance that there are no little dry spots, makes the likelihood of included bubbles less probable, and results in near vacuum bag lean layups (i.e. less wasted resin and highest strength to weight ratio).

I have trouble doing that because the pieces always seem to stretch and bunch when I try to move them, fibers pull out from the edges, or the cloth is just too big for me to handle by myself. On a large project (like a race boat) where they are going to use multiple plies with multiple overlaps, and are going to do full fairing and bodywork after the main layup, getting the layup right for strength takes more precedent in the early stages than the cosmetics of perfectly laid seams and laps in the final (only?) ply; compared to a woody or stripper canoe where cosmetic perfection is almost as important as the structural aspect of the layup.

There is another technique (variation on "poor man's pre-preg", PMPP) where you wet out on plastic sheet then use the plastic to transfer the parts/pieces/cloth/layup over to the pre-wetted surface. You can squeegee through the plastic sheeting before peeling it off (some leave the plastic on during cure for a smoother finish and no amine blush, ala poor man's peel ply, but with the heavy 6 mil plastic I was using I found that I got enough pooling and crease marks that it wasn't as beneficial to leave the plastic on). Using the plastic sheet "palette" to transfer helps keep all of the fibers in place, keeps the shape true, is really efficient on resin, and makes certain layup details much more manageable. The full PMPP technique, where you draw a pattern on plastic, lay up your plies, place another piece of plastic on top, cut out you pattern, peel one side of the plastic and then use the other piece of plastic as an application tool, squeegeeing thru it before pulling it and doing any final wetting, is best for tricky areas, component parts, verticals and/or overhead details.

For big layups and large pieces of cloth I find it works fine to lay the cloth on dry and wet through the cloth. You just need to allow for the substrate to absorb some resin, whether it is foam or wood (some prefer to do a filler or sealer coat before layup); I found that I would typically use about 1.5:1 resin to cloth weight, as apposed to the ideal 1:1 ratio, when doing it this way. I even did this "dry on dry" with two plies of 6 oz at a time, but probably wouldn't go higher than that. I have found a few little dry spots and "fish eye" bubbles here and there using this technique, but the worst of that can be drilled and injected if objectionable.

Might not be acceptable for a 200 mph hydroplane race boat (deep respect), or a home built airplane, but for my little 70 mph camper I think it will hold up just fine.

[DWT77]

I fiberglassed my sides while they were on the work bench. I will soon be ready to fiberglass the roof as well.

When I do the roof, is it better to use the bias-cut tape first on the roundover edges and then do the roof?

or

Is it better to do the roof and then comeback with the bias-cut tape and do the round over edges?

Is one method preferred over the other to reduce air bubbles?

Thanks

[tony.latham]

I fiberglassed my sides while they were on the work bench. I will soon be ready to fiberglass the roof as well.

When I do the roof, is it better to use the bias-cut tape first on the roundover edges and then do the roof?

or

Is it better to do the roof and then comeback with the bias-cut tape and do the round over edges?

Is one method preferred over the other to reduce air bubbles?

Thanks

Can't help you with that answer. But I'll be interested in which fork you take and how it comes out. I would probably just do the layup on the roof first and then relieve that edge slightly before laying up the tape.

You might want to reach out to Dan AKA kayakdlk about his experience with his fine fiberglassed/Monstaliner finish.

Tony

[Pmullen503]

If you plan to sand, and why use epoxy unless you want a clear smooth finish, it's better to glass both surfaces and then put on the bias tape. That way when your sand the edges of the bias tape to blend with the flat surfaces you won't cut through the glass on the flat surfaces.

BTW, on canoes, I've laid up as many a 4 layers of bias cloth, each extending about 2" less than the layer underneath. If you avoid mixing air into the epoxy it will still come out clear.

[KCStudly]

My FG is my outer structural skin, which will be painted. I have a nice generous 3/4 inch round-over on my profile edges. (Mine's a foamie, but if I were doing it again... or on a traditional build, I would do the same radius in a wood framed edge, at least using blocking between spars like Steve Fredrick's method, rather than just two plywood edges coming together, so there would be enough thickness for the joint and the larger radius). I did my walls first, wrapping the two plies of weave up onto the roof and front wall in a stagger, about 6 inches onto the roof/front for the first ply, and 3 or 4 inches on the second ply. Then when I did the roof and front wall I overlapped the first layer to butt with the second ply of the walls, and the second ply of the roof over lapped that by a couple of inches. That way I only have a narrow strip where there are 3 plies stack up, but all of the seams have at least 2 plies of coverage. This worked best with the width of FG cloth readily available. With the 3/4 inch radius, I did not need the weave to run on a bias. I did orient one of the plies on my hatch on the bias for torsional rigidity. I did the hatch all the same way, laminating it in place with the same overlap technique, then cut it away at the gaps where the hatch gasket and hinge will go.