Radon Transom Replacement

Questions about boat repairs with our resins and fiberglass: hull patches, transoms and stringers, foam, rot etc.
Fuzz
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Re: Radon Transom Replacement

Post by Fuzz »

Gerr's numbers make for short and fat stringers in smaller boats. If you have the height room I would go thinner and taller. If you match what came out of the boat it is hard to go wrong. Lasted 30? years right. JMHO

fallguy1000
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Re: Radon Transom Replacement

Post by fallguy1000 »

Fuzz wrote: Tue Aug 02, 2022 10:30 am Gerr's numbers make for short and fat stringers in smaller boats. If you have the height room I would go thinner and taller. If you match what came out of the boat it is hard to go wrong. Lasted 30? years right. JMHO
Agree fully. We were trying to establish the laminate thickness.

Gerr's book has a 10 stringer rule. I don't get the stringer chapter at all.

My intuition says 4 layers 1708. How about you David? Any gutcheck?
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Fuzz
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Re: Radon Transom Replacement

Post by Fuzz »

If my memory is correct 4 layers of 1708 will be just a little over 1/8 of glass. That much glass standing 8-12 inches tall on each side of a former would be darn stiff. I would be happy with it in my 32 foot work boats.

bigtalljv
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Re: Radon Transom Replacement

Post by bigtalljv »

thanks guys, I appreciate it. The only issue with putting back what was there is, they were all hacked to heck, the extra three feet of hull I added, and the swap to outboards :-) I do know that I am in the ball park with the guys that restore these professionally and I am copying what they do. 1-3/4" x 7" LVLs are popular with them. I'll go three layers of 3/4" ply and 4 layers of 1708 and if it break in half I not sure what else I could have done....

fallguy1000
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Re: Radon Transom Replacement

Post by fallguy1000 »

Seems good to me. Gonna take a lot of work to laminate those pieces. I like to hit both sides with a 1/16" vee trowel and use vacuum to press. 2-4 psi is ideal, but hard to attain without vac. 9" of mercury

Also want to avoid hardpointing. So when you go 3 wide, you'll wanna 1/8" shim under to get the dims and allow for putty. But you probably know all of this. Just ez to make 3 of them and think you can push them down on the short side to touch and that is a major no-no bcuz the hull can crack there then.

And pin them when bonding the stack. They will look great and you come back and more than once, I said, how did that move.. I like aluminum nails. I drill a hole and drop them in and leave em.
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bigtalljv
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Re: Radon Transom Replacement

Post by bigtalljv »

Well, I already have two layers done and I have shaped the two stringers I built already so I just need to add the third layer. I laid them up on the floor and stacked just about everything heavy I had on them, when you start figuring PSI it takes quite a bit of weight. Like 4000lbs for 2psi….I didn’t use that much. After I stacked the weight I also lightly clamped them to nice straight 2-1/2”metal square tubing I had so they would have a flush edge and not be able to move. After cutting the shape in them it looks like I did a good job, no voids. I thought about vacuum but that seem like a lot more work. Pulling up 40’ of butyl tape doesn’t sound fun. Although with the pins I guess you could use a tube bag….

fallguy1000
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Re: Radon Transom Replacement

Post by fallguy1000 »

Just avoid laying them down so they touch the hull when bonding. A gap is essential and then putty fills the gap and a fillet. A small contact area of stringer is what you want to avoid.
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bigtalljv
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Re: Radon Transom Replacement

Post by bigtalljv »

I was actually going to go with the foam padding method under them, which still needs some putty but hopefully less...

fallguy1000
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Re: Radon Transom Replacement

Post by fallguy1000 »

bigtalljv wrote: Tue Aug 02, 2022 1:01 pm I was actually going to go with the foam padding method under them, which still needs some putty but hopefully less...
Foam is great insurance, putty the foam down. If you cut the pads out right; the angle of the pad also can replace some fillet. Think 2.25" of flat and a 3/4" wide piece of 45 degree for 1/2" pad is close. Marine foam, not xps. Xps will not hold shit, pardon my french. If you pad with cheap foam, just pad and no fillet. Fillet with epoxy and make them big enough to bury the xps so you are not tabbing to it.
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OneWayTraffic
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Re: Radon Transom Replacement

Post by OneWayTraffic »

On Gerr stringers: Two or three on hull bottom, one at chine, two on the sides. The rules are mainly used for boats larger than any we have here. Hard chines with extra reinforcement act as a stringer as does the turn of the keel, and tabbing of sole to the sides.

So for a hard chine planing craft with a sole sitting directly on the stringers and mudded down with epoxy, then tabbed in to the sides all around. will be at least as strong as the stringers specified. If the boat has high sides you might want to glass in a shelf to further strengthen it, and act as storage.

It seems fairly straightforward to me, except when one would use two or three stringers on the hull bottom. I'd probably set it at two for most trailer boats. My 17' has only one each side and it seems enough.

There's also this article from Gerr where he mentions and details an older, simpler rule of thumb which just works for most boats.

https://www.gerrmarine.com/Articles/boa ... thibex.pdf

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