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Failed trying to cap stringer with fiberglass tape and epoxy

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Failed trying to cap stringer with fiberglass tape and epoxy

Old 07-13-2019, 06:35 AM
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Default Failed trying to cap stringer with fiberglass tape and epoxy

I am wondering what I did wrong, and what I should have done differently. I have some 60” x 3/4” x 12” stringers I am going to install. I am trying to prefab them so they are ready to install. I want to cover the long ends with fiberglass tape and and epoxy. I am using what I think is called 1700 cloth tape. I am using West System. I THOUGHT I had all of the air out of them, and it looks like as it was curing, it slid and left me with an air bubble from one end to the other. The cloth did not want to take the 90 degree angles of the 3/4” wood. I am probably going to slightly router a radius to the boards to help eliminate the sharp 90’s. I was thinking maybe I should have coated the board, let it set up “tacky” for 20-30 minutes, and then installed the tape and wetted it out? Any helpful tips for me?
The other option would be for me to forgo using the tape altogether, and just use either 1700 cloth or 1708 (I have some of both) and drape a larger piece over the future stringer, maybe using a piece of cloth 20+ inches in width.? Basically totally encapsulate the board in two steps. Thoughts?
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Old 07-13-2019, 06:45 AM
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Glass of any flavor doesnt tolerate sharp bends and 17 oz - forget it.

I would forego trying to get any glass on the top of the stringer and just get the sides covered, and then tab/tape it to the hull bottom
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Old 07-13-2019, 06:53 AM
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I get it. I am trying to install these two stringers while not removing the deck. These are the side stringers on the sides of my gas tank. I have the tank removed. The existing stringers were punky. I plan on shoring up the deck, and sneaking these into position, and then tabbing them in, and generously covering the side facing the gas tank in 1708. I have no access to the other side of the stringer, so I was just going to bed it into a glob of Epoxy thickened with fiberglass 1/4” fillers. I don’t want to take the whole step of ripping out the deck.
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Old 07-13-2019, 06:54 AM
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Like HTJ said about sharp bends, both convex AND concave. It won’t stick to the inside bend where the wood meets the hull either. You need to build a fillet there.

Remember when you are making stringers the wood is NOT the structural part. The is the job of the fiberglass. The wood is just a mold. Perfectly good stringers can be molded from foam, pvc, or even cardboard.

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Old 07-13-2019, 07:03 AM
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If it's fibers are +/- 45 degrees and theres no chopped mat stitched to it then it may very well be 1700. 1/4" roundovers is about the smallest radius corner you can get away with. Coating and letting it get tacky will help but once you wet with resin, that goes away. A strip of saran wrap over them will also help but you still need that 1/4" radius.
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Old 07-13-2019, 07:03 AM
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Originally Posted by thefishingsailor View Post
Like HTJ said about sharp bends, both convex AND concave. It won’t stick to the inside bend where the wood meets the hull either. You need to build a fillet there.

Remember when you are making stringers the wood is NOT the structural part. The is the job of the fiberglass. The wood is just a mold. Perfectly good stringers can be molded from foam, pvc, or even cardboard.

To carry that thought a little further.... If you only attach one side of the stringer then you won't come anywhere close to the strength of the original installation. To do it right you need to glass both sides.
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Old 07-13-2019, 07:11 AM
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Originally Posted by 74lbSteve View Post
To carry that thought a little further.... If you only attach one side of the stringer then you won't come anywhere close to the strength of the original installation. To do it right you need to glass both sides.
I know. The stringer buts up to a shelf where the hull steps up (chine?). Between this vertical shelf and the stringer is where i was going to use the thickened epoxy. These stringers really only support the deck/floor around the gas tank. I was always planning on using fillets and cloth on the inside stringer areas. I was thinking of bracing the inside of the stringers to force them to stay in shape and hold the weight from the deck. Essentially building a “box” around the gas tank.
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Old 07-13-2019, 07:57 AM
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"I was thinking maybe I should have coated the board, let it set up “tacky” for 20-30 minutes, and then installed the tape and wetted it out?"
Was the wood dry when you taped?
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Old 07-13-2019, 08:36 AM
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Originally Posted by bosshoff View Post


These stringers really only support the deck/floor around the gas tank. I was always planning on using fillets and cloth on the inside stringer areas.

Glass both sides of the stringer out of the boat, glue to the hull bottom with thickened epoxy and fillet/tape everything you can reach. Epoxy 1" stock for cleats to the top of the stringer so you will have reasonable support for the sole.

You're on track
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Old 07-13-2019, 03:21 PM
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Originally Posted by HTJ View Post
Glass both sides of the stringer out of the boat, glue to the hull bottom with thickened epoxy and fillet/tape everything you can reach. Epoxy 1" stock for cleats to the top of the stringer so you will have reasonable support for the sole.

You're on track
HTJ, What do you mean by: “Epoxy 1.” stock for cleats”?
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Old 07-13-2019, 05:38 PM
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Originally Posted by bosshoff View Post


HTJ, What do you mean by: “Epoxy 1.” stock for cleats”?
Regular ol 1 x 2 yellow pine from Lowes, hot coat with neat epoxy and then glue to the side/top of your of your 3/4" ply stringer - easy way to double the bearing/glue surface rather than having your sole only on the 3/4" width of the ply - I'll try to scrounge up a pic.
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Old 07-13-2019, 05:46 PM
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Like this, note the 1"x stock on the frames


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Old 07-13-2019, 06:27 PM
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HTJ, so you are basically saying to “sister in” another piece of wood to add width at the top of the stringer to “spread” the load from the sole. I can do this with an additional strip of 3/4” Marine Plywood as I have some scrap sections. I can glue and screw with silicon bronze fasteners and epoxy.
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Old 07-13-2019, 08:57 PM
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Originally Posted by Barnacled View Post
"I was thinking maybe I should have coated the board, let it set up “tacky” for 20-30 minutes, and then installed the tape and wetted it out?"
Was the wood dry when you taped?
Barnacled, sorry, my ipad hazes me and sometime I can’t figure out how I am not reading things in order. The stringers were coated with CPES. Then, brushed with epoxy, and then the tape applied, brushed with epoxy, squeegeed, rolling with finned roller, and left to cure. In the morning, I had the mess.

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Old 07-13-2019, 09:28 PM
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Just so you don’t buy any more, CPES is worthless in this project, it adds no value.

Always coat the wood prior to laminating, then let the epoxy at least gel before applying more epoxy and glass.

Depending on the glass, 3/4” ply can be very difficult wrap over the top for a rookie, the top should be rounded over with as large of a radius as possible. Many people double up the ply so the top is easier to cover.
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Old 07-14-2019, 01:56 AM
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Originally Posted by bosshoff View Post
HTJ, so you are basically saying to “sister in” another piece of wood to add width at the top of the stringer to “spread” the load from the sole. I can do this with an additional strip of 3/4” Marine Plywood as I have some scrap sections. I can glue and screw with silicon bronze fasteners and epoxy.
Strips of ply will work, the 1 x 2 is just a lot easier as its already the perfect dimension. And no need for screws - the easy way is to have a hot melt glue gun on hand and put a dab at each end to hold the cleat in place while your thickened epoxy cures.

Yeah shit can the CPES, it's terrible at what it advertises and worthless outside of that. The words thin/thinning and epoxy don't go together.

Grind that poo off the top and move on, glass on top of a ply stringer adds nothing but a potential failure point.

Treat us to a few pics of the entire project.
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Old 07-14-2019, 02:49 AM
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Originally Posted by thefishingsailor View Post
Like HTJ said about sharp bends, both convex AND concave. It won’t stick to the inside bend where the wood meets the hull either. You need to build a fillet there.

Remember when you are making stringers the wood is NOT the structural part. The is the job of the fiberglass. The wood is just a mold. Perfectly good stringers can be molded from foam, pvc, or even cardboard.

then why replace rotten stringers ?
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Old 07-14-2019, 06:20 AM
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You could use a vacuum bag to eliminate the bubbles and voids.Trying to make wood into something indestructable and immortal is a waste of time.Think 10 years and go with that.
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Old 07-14-2019, 06:23 AM
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Originally Posted by bosshoff View Post


Barnacled, sorry, my ipad hazes me and sometime I can’t figure out how I am not reading things in order. The stringers were coated with CPES. Then, brushed with epoxy, and then the tape applied, brushed with epoxy, squeegeed, rolling with finned roller, and left to cure. In the morning, I had the mess.

That cloth is NOT 1700, just some finish cloth. It is fine for a protective layer to hold reson and keep water out but has virtually no structural value. I hope that's not what you plan on using to tab them in!
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Old 07-14-2019, 06:36 AM
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Originally Posted by HTJ View Post
Like this, note the 1"x stock on the frames

​​​​​​HTJ, I'm an Electrical contractor and I'm hiring you on my next conduit job.You have it covered!
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