Overlapping overlaps with glass

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jbo_c
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Overlapping overlaps with glass

Post by jbo_c »

How do you do a good job with corners where the transom meets the bottom meeting the sides? Having a heck of a time getting good laminations with all those overlapping pieces.

With each joint doubled, that’s 6 overlapping pieces. Then add the folded over pieces from the angles when you wrap the corner and there are even more. Are all these layers necessary or can I feel good about trimming so I get a good full double layer there like on any other joint?

Jbo

wpstarling
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Re: Overlapping overlaps with glass

Post by wpstarling »

jbo_c wrote: Thu Oct 28, 2021 12:37 pm How do you do a good job with corners where the transom meets the bottom meeting the sides? Having a heck of a time getting good laminations with all those overlapping pieces.

With each joint doubled, that’s 6 overlapping pieces. Then add the folded over pieces from the angles when you wrap the corner and there are even more. Are all these layers necessary or can I feel good about trimming so I get a good full double layer there like on any other joint?

Jbo
When i did mine i cut the cloth so that it wrapped nicely around the corners so I didn't have to 'fold it'. My layers overlap but nothing is folded over. I did have to cut a little farther into the cloth to make sure I could get everything to lay flat but you should be able to cut a slit in it and layer it up. You can trim little bits but if you're doing it wet on wet then it shouldn't take much epoxy and you can pretty much guarantee it will never have issues on the corners. I'll let other chime in with what they did. If I can remember I'll post a picture of my 'after' so you can see
Boats restored: 1973 Glastron CV16, 1990 Proline 17 CC, 1993 Bass Boat
Boats built: custom 15ft flat bottom skiff, Soon-to-be-built TX18 (originally dborecky's build)

jbo_c
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Re: Overlapping overlaps with glass

Post by jbo_c »

I cut it, but still had a heck of a time. Maybe fold was a confusing word to use. What I meant is where you fold over one of angles, it changes directions and overlaps one of the other side pieces.

For instance, just doing one vertical along the side of the transom, if I’m doing two layers on the joint, where it actually crosses onto the bottom, I now have four layers of thickness and I haven’t even done along the bottom yet. I was working wet on wet, but still had a bunch of small air pockets.

I had intended to do the rest but didn’t want to keep burying air under more glass without addressing. Was afraid it would compound the problem on me.

Guess I’ll grind, fair, and make another run. Bah.

Jbo

fallguy1000
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Re: Overlapping overlaps with glass

Post by fallguy1000 »

You really want to practice 2" overlaps always.

So, if you have 3 layers of glass and want to finish a transom to hull intersection, the first piece is 6" over, next 4", next 2".

Glass is darted at direction changes. Cut all the way to the corner.
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OneWayTraffic
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Re: Overlapping overlaps with glass

Post by OneWayTraffic »

Just how big are those air pockets? I don't think that a few small bubbles will matter one way or the other with all the excess strength built in. Drill and fill is also an option.

In general the 2" is given as a guideline. There's two reasons: stress concentrations and bonding. You can get away with less than 2" in many cases, the important thing is not to have all the reinforcement finishing at the same spot.

fallguy1000
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Re: Overlapping overlaps with glass

Post by fallguy1000 »

OneWayTraffic wrote: Thu Oct 28, 2021 11:45 pm Just how big are those air pockets? I don't think that a few small bubbles will matter one way or the other with all the excess strength built in. Drill and fill is also an option.

In general the 2" is given as a guideline. There's two reasons: stress concentrations and bonding. You can get away with less than 2" in many cases, the important thing is not to have all the reinforcement finishing at the same spot.
Accurate, but the problem with planning overlaps is a one inch error on a two inch overlap is only an inch.
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OneWayTraffic
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Re: Overlapping overlaps with glass

Post by OneWayTraffic »

Absolutely. I once tried doing some calculations sometime on the shear bonding strength of epoxy vs the tensile strength of the relatively thin layer of glass on top.
Then I stopped worrying about whether 2" overlaps were 'enough' and used what the plans recommended. Which is a long winded way to say use the overlaps in the plans, but don't stress about the details.

Small air bubbles (say under 1/4") buried under layers of glass will not sink your boat. Laying some putty under the glass when folding over and squishing the putty into the glass will help.

jbo_c
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Re: Overlapping overlaps with glass

Post by jbo_c »

Good and true points about the amount of overlaps and the small bubbles. There are only a few bubbles that I’m currently concerned about making sure to fill. My concern was about more layers compounding the bubble issue and making it worse as I went. So, I stopped.

The filler under the glass idea is a good one and I’ve used it before with success(though I’ve never seen it officially sanctioned). I use it when not working wet on wet.

So back to the original question: How to do all those overlaps wet on wet and have a good clean, saturated layup?. - and whether all those layers are really necessary. The corners will have places that are at least 8 layers thick - 2+2+2+overlaps. That’s a beast to get a clean layup even wet on wet(for me, at least).

Are all those layers necessary if two layers are good on the rest of the joint? It’s a corner, so stresses are different, so might need more, but 4x?

And if they really are necessary, how do you get a clean layup that thick?

Jbo

fallguy1000
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Re: Overlapping overlaps with glass

Post by fallguy1000 »

The reason for laying longest first is just that...much easier to finish clean.

Have you been doing shortest first?
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wpstarling
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Re: Overlapping overlaps with glass

Post by wpstarling »

Also, what type of glass are you using? I had some small bubbles as well but I'm not using anything really thick so that helps but I did do some 1708 on the inside that overlapped (only x2 though).
Boats restored: 1973 Glastron CV16, 1990 Proline 17 CC, 1993 Bass Boat
Boats built: custom 15ft flat bottom skiff, Soon-to-be-built TX18 (originally dborecky's build)

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