1981 Dolphin 20' Commercial

Questions about boat repairs with our resins and fiberglass: hull patches, transoms and stringers, foam, rot etc.
fallguy1000
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Re: 1981 Dolphin 20' Commercial

Post by fallguy1000 » Mon Jul 08, 2019 11:32 pm

those pinholes are some type of outgassing or poor lamination issue

lotsa potential reasons

here's a few

1. holes in the surface - those can be prefilled with thixotropic material, but holes in the surface allow gaseous exchanges between the polyester and the epoxy, a hole that is very small can get larger under certain conditions...if you prefill with thixo, you need to quickly rewet before rolling out the glass or if the cure time for the thixo gets made; the glass will stick and cause a LOT of headache...prefilling is used by me often for really superb secondary bonding especially

2. contaminants in the surface - that could be water or moisture in the polyester, remember polyester is not waterproof, the job would be best off indoors for this reason, if your poly got a little damp and you close it in; you might get blistering later; be careful there

3. temperature change, usually heating up is bad

4. poor epoxy formulations, some epoxies are not as good as others, Silvertip is probably one of the best and designed to prevent outgassing, I know of a really bad one, but it is not carried by BBC

just a few

job looks good to me, keep on truckin


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MSRiver
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Re: 1981 Dolphin 20' Commercial

Post by MSRiver » Tue Jul 09, 2019 11:54 am

Got the other side laid up last night not finishing till 11:30, i dont know why i thought it'd be better than the first time as far as ease, needless to say gonna be icing my back all day today. It did came out a lot better not nearly as many small bubbles. While i was filling the fins with glue i also swiped pretty much the whole surface trying to fill any small holes i wasn't seeing. Id say i took away 75-85% of the bubbles from the left side. Only thing i did run into is bugs but without it being a inside project not much i could do about it. I will say if you see those white patches showing through those are just the areas i patched before laying the big sheets down and not air bubbles. just once you sand the new glass you can just tell the difference between the old glass and new glass.

Since i got done so late last night gonna have to stay off it today might try and do some final fitting for the new stringers to go in. Sand everything down tomorrow then get stringers laid in my the end of the week. I hope anyways.

Two questions, 1. before i put down the new stringers after i sand should i make up some glue and get a long board and make everything smooth essentially fairing or just wait till i have the stringers glassed in?
2. the hull pretty much took up my stockpile of glass, and im going to have to put another order in, i guesstimated im gonna need another 30 yards to finish stringers and floor and little bit for bulk heads and such, does 30 yards sound about right for that? I was just going to do 1708 for the rest is there any reason i should split that up between regular 17oz or 12oz?

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fallguy1000
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Re: 1981 Dolphin 20' Commercial

Post by fallguy1000 » Tue Jul 09, 2019 2:01 pm

Why are you using 1708?
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MSRiver
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Re: 1981 Dolphin 20' Commercial

Post by MSRiver » Tue Jul 09, 2019 2:45 pm

Just what i started out with. Knew i was going to use a bunch of it so figured itd be easier just get a big roll of that. Plus dont you want the matt to for the first layer on everything so it has some bite to it.

boguesounder
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Re: 1981 Dolphin 20' Commercial

Post by boguesounder » Tue Jul 09, 2019 4:02 pm

Hi, I think others with more experience will chime in but I think you will just want 17 oz on your stringers. The mat is good for adding thickness but does not offer the strength of the biax. So no extra strength and soaks up lots of expensive resin. Therefore, I think most folks just use biax with no mat on stringers. Hopefully someone will second my opinion. Super clean hull you made there...bet that back was sooooore! Thanks.

fallguy1000
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Re: 1981 Dolphin 20' Commercial

Post by fallguy1000 » Tue Jul 09, 2019 8:08 pm

Use what you have, but 1708 is a 25 oz per yard wetout at 100% which it requires ftmp.

I like it when I don't want much movement when you want to move the material wetted.

Otherwise, it is a costly and heavy option and lotsa headache to wetout.

I did use it in my build, but very limited.
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MSRiver
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Re: 1981 Dolphin 20' Commercial

Post by MSRiver » Wed Jul 10, 2019 9:25 am

i mean anything wood i need at least the first layer to be 1708 as i understand so it has bite, while also helps take care of imperfections to the surface. So roughing it and tell me if this sounds right at least if you kept up with your usage. Another 20-25 yards of both 17 oz and 1708, rouhgly might have a little extra, but the floor will take up a most of that. maybe im in the ball park.

fallguy1000
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Re: 1981 Dolphin 20' Commercial

Post by fallguy1000 » Wed Jul 10, 2019 9:48 am

The only reason to use 1708 would be if you needed the stiffness in the layup or you were using polyester and want to avoid print through or you had a spec that wanted 25 oz glass.

For your situation, it is a bad choice.

If you have a rough surface; you should be hotcoating it with thixo mix and smoothing it and then wetrolling the surface and then rolling the 17 oz glass.

Every yard of 25 oz glass v 17 oz glass is adding an extra 8 oz of glass and at least 8 ounce of epoxy, so you are adding an extra pound per yard to the boat.

I used 1708 in all of my moulds. The mould is a set size and the 1708 maintains its cut size better than biax.

The only time to use 1708 is when you are carrying wet glass around or you cannot afford the glass to shape change much.

Triaxial glass also exhibits this type of quality.
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MSRiver
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Re: 1981 Dolphin 20' Commercial

Post by MSRiver » Thu Jul 11, 2019 5:46 pm

So i gave hull a good sand in preparing to put the stringers in. Im not sure yet again how much my port stringer is 1/4" high maybe a little higher, so going to trim that up. (possible didnt measure from the correct spot on the hull) Then get them in place mark down where they should go then just run a level across to get my measurements of the 3/4" stringer. I plan on making the 3/4" stringers this afternoon and splicing them together.

Glass is coming next week so i should have all the stringers glassed in by the end of the week.

Now a quick question i see people only tape in at the corners and not go all the way up the stringer. My understanding is you want the glass to fully enclose the wood, one so no water gets to it and second you want the strength of the glass. So as far as laminating them in, my plan was to go from the top of the stringer for all 3 layers then onto the floor 1-8", 2-6", 3-4" all wet on wet. Or in the case i just need the corners go ahead and put a layer of 17oz to seal the stringer then just tape in 8-6-4 at the corner?

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Re: 1981 Dolphin 20' Commercialj

Post by fallguy1000 » Thu Jul 11, 2019 7:40 pm

It is pretty difficult to do a nice job in one shot.

The glass does not behave well in the coves each side and up and over.

Easier to put the caps on, then wet on green run the tapes.

You can try a single go, but it is harder.
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