Fiberglass cloth and tape? Weight does it matter?

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Re: Fiberglass cloth and tape? Weight does it matter?

Postby DWT77 » Wed Mar 21, 2018 1:52 pm

KCStudly wrote: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.


Thanks KC,

I have used blocking between the spars so I might mock up my wall and try different radius' to see what I like. The most common I have seen are 1/4 and 3/8 radius. A bigger radius did concern me about getting into the framing/spars of the trailer.

On a side note I took the middle ground and did a 5/16 round over on my tongue box a couple of days ago. It did seem a little small to me but like I said I don't have much experience with fiberglass.
Last edited by DWT77 on Wed Mar 21, 2018 1:54 pm, edited 1 time in total.
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Re: Fiberglass cloth and tape? Weight does it matter?

Postby DWT77 » Wed Mar 21, 2018 1:53 pm

tony.latham wrote:
DWT77 wrote: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


Thanks Tony. I had reached out to him in the past about trailer weight since we had close to the same profile. I shot him a message.
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Re: Fiberglass cloth and tape? Weight does it matter?

Postby DWT77 » Wed Mar 21, 2018 8:23 pm

I did a mock up of my side wall/roof. Just in case someone else is interested in what a different radius might look like on the teardrop. I wanted to try out my larger round over bits.

I stapled it real quick so in one of the pictures you can see how the 1/4 roof is lifted off of the side wall. I don't think that would be an issue if everything was glued and secured properly.

Mock up of side wall/roof. I have the spars with the 3/4 blocking in between them. Then the 1/4 piece is the roof
Image


Roof lifted a little on the 1/2 round over
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What it would look like on the tongue box or side wall. Also If you look on my tongue box how close to the edge I put the staples. Hitting those with a larger round over bit might be an issue. Might want to watch staple placement in the future.
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Re: Fiberglass cloth and tape? Weight does it matter?

Postby KCStudly » Thu Mar 22, 2018 7:00 am

DWT77 wrote:The most common I have seen are 1/4 and 3/8 radius.


Yeah, some of the Burt Rutan stuff said that you could take 6oz cloth down that low, IIRC his method said 1/4 for with the weave and 3/16 for bias, but in practice on my tongue box I couldn't pull it off at 1/4 inch w/o the cloth springing back and leaving bubbles along some of the edges. 3/8 is as low as I would personally go because fixing stuff afterwards takes even longer than the extra effort to get it right the first time.

Probably not good for a structural wall-to-roof joint, but if you want a sharp corner you can use the flock method. Basically you mill a 1/4 to 5/16 inch chamfer along the edge; fill that with epoxy thickened with structural binder, like West System 405 (I attached temporary dams made from scraps of thin ply on one side of the fillet to make filling easier, less messy and have less finish work to do afterward. Used a rabbeting bit with 1/16 offset to trim the dam a little proud of the adjacent surface; then removed the dams, used packing tape on them as a release agent, reinstalled and then packed the chamfer with "thick".) After the flocked corner cures you can trim the excess flush with a router or sanding block, fill any pock marks or voids with thickened 3-min, and repeat sanding flush. Now you can lay your cloth right past the hard edge; trim it close while it is still wet so that it doesn't lift from the weight of the excess cloth; and it's an easy trim once it gets to the rubbery stage, or even later after fully cured... a small hand scrapper takes the stubbies right off. Then just block sand a minimal radius to take the sharpness off the corner and you have a "hard" edge. This is good for where you want crisp gaps, like between door edges and door jambs, and/or between the side wall and galley hatch edge.
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