1981 Dolphin 20' Commercial

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

Post by Fuzz » Wed Jun 12, 2019 2:21 am

As Fallguy said being too smooth is not good for bonding. The thing about epoxy is it is a superior glue. I am not sure how smooth you are thinking but if using 1708 put the mat side down. The mat will fill smaller voids. If you think the voids/low spots are too big you can make up some thicker epoxy and put down a layer of that first and then lay glass over it while it is still wet. Maybe pictures of the areas would help. Real hard to tell when we are not there :wink:



MSRiver
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Re: 1981 Dolphin 20' Commercial

Post by MSRiver » Thu Jun 13, 2019 12:02 pm

The more i look at im sure it shouldnt be a problem, with all the glass dust on it just makes it look worse than it is. I put that spreader on it, and there's probably not more than a 1/16" in any spot that i didnt grind through a whole layer and will have to patch with new glass.

My 40 grit grinder disk wore out alot quicker than i expected, but i imagine if your running it 6 hours or so none stop it will do it. Switched over to my 5" circular sander with 60 grit paper, which seemed to get bigger swipes of material off quicker, as far as roughness ill probably come back over with a wire wheel as fallguy suggested.

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cape_fisherman
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Re: 1981 Dolphin 20' Commercial

Post by cape_fisherman » Thu Jun 13, 2019 5:15 pm

Replacing a floor is typically easier with the cap off...so if you haven't bonded it, try not to. Also...if you're going to remove the stringers, do one at a time. Remove one, replace it, then remove the other. That way the hull retains it's shape.

MSRiver
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Re: 1981 Dolphin 20' Commercial

Post by MSRiver » Fri Jun 14, 2019 1:50 am

I would probably agree that while the cap is off I’d be easier to work on but I’m going to just have it on the boat to help keep its shape. I’m doing the same for the stringers. The hull did have a small tendency to splay out but sure don’t want it stuck like that after I get the stringers and floor in.

I have completely sanded the hull now. Putting the cap on tomorrow and cut a stringer open to see what it looks like.

Another quick question. Since I’m going to be adding another layer of glass to the hull should I do that first then have stringers bond to new glass or stringers then new hull glass?

I’m adding another layer cause why not I’ve already got it all apart and after sanding some of the garbage work whoever did makes me feel a little better that some todays high quality glass and epoxy laid right it’s going back in it. I’ll probably add another layer to the sides help stiffen her up as well but that can wait after I get the floor in.

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Re: 1981 Dolphin 20' Commercial

Post by fallguy1000 » Sun Jun 16, 2019 8:24 am

The answer is it doesn't matter.

The ideal situation is to layup the entire hull, but the gains are truly incremental. So at the point you are at, just make sure the boat holds her shape and can be managed for the cap and stringer work.

It is all about your efficiency and general build quality at this point.

I would personally install the stringers to no movement, grind the boat rough to 40 grit or lower. Install the glass to up the stringer sides, then same day bond tapes over the top from the other side for a place to work. A common fallacy in boat building is that the tapes need to reach further and further. The strength in glass is developed in thickness; not extension. Hardspots have the opposite effect and this is why we extend tapes; not for a little extra strength. My boat tape scheme has some errors this way. I could have taped 4-6-8, for example instead of the specified 6-6-8. I'll be a bit heavy now for sure.

So you glass the bottom and up the side of the sttringer and install your tapes. Then the middle same way and then the other side.

If you are glassing extra; you really ought to consider where and why not just because you can. Most boats need stiffer bottoms than stiffer sides. If you are really wanting to seal the poly; you can also go no glass and just roll coat epoxy at 2-3 oz per yard.
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MSRiver
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Re: 1981 Dolphin 20' Commercial

Post by MSRiver » Mon Jun 17, 2019 10:02 am

fallguy1000 wrote:
Sun Jun 16, 2019 8:24 am

I would personally install the stringers to no movement, grind the boat rough to 40 grit or lower. Install the glass to up the stringer sides, then same day bond tapes over the top from the other side for a place to work. A common fallacy in boat building is that the tapes need to reach further and further. The strength in glass is developed in thickness; not extension. Hardspots have the opposite effect and this is why we extend tapes; not for a little extra strength. My boat tape scheme has some errors this way. I could have taped 4-6-8, for example instead of the specified 6-6-8. I'll be a bit heavy now for sure.

So you glass the bottom and up the side of the sttringer and install your tapes. Then the middle same way and then the other side.

If you are glassing extra; you really ought to consider where and why not just because you can. Most boats need stiffer bottoms than stiffer sides. If you are really wanting to seal the poly; you can also go no glass and just roll coat epoxy at 2-3 oz per yard.
Fall guy, trying to wrap my mind around what you're saying. So i have the cap on and boat is level.

For stringers your saying lay strips of 1708 or 12oz 6" tape up the inner sides doing 8-6-4. Now i am going to foam fill them again so i get to play and shape that right. Then come from outside all the way over the top and how far? Trying to clear it up.

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Now i have sanded the left stringer taking off the 1 layer of glass since it was horribly laid up but after than looks good, now i was just going to cut the top off bring up the front sides 2" since there is a random dip on both stringers (which does mess with floor height since they just added more puddy to reach the floor). Pour foam in and get that level and rounded then put 3 layers of 1708 over them and tab out.

Now as far as the hull glass goes it just flexes a little to much for me, and the sanding ive already done to get it smooth or take out the texture of the previous glass pretty much took one layer away so i want to replace that while a second layer will make it plenty stiff.

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Re: 1981 Dolphin 20' Commercial

Post by fallguy1000 » Mon Jun 17, 2019 7:01 pm

Get the stringers glued on.

Fillet the outside of one stringer.

Glass the hull bottom and up the stringer side say 8" or so..

Add tapes to the outside of the stringer say 6", 4" tapes over the bottom glass

Fillet the inside of the two stringers.

Glass the hull middle bottom.

Tape the stringers inside.

Allow cure.

Glass the hull bottom other side and tape.

Sand and glass the stringer caps.

Assumes ability.
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MSRiver
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Re: 1981 Dolphin 20' Commercial

Post by MSRiver » Mon Jun 17, 2019 10:36 pm

Fall guy are you assuming im cutting out the stringers completely? But the rest sounds good.

Just a thinking out loud. Say if i cut the stringer all the way out, could i put some pva down foam that then i have a mold and then ill be able to lay up everything against that? or is that just too much hassle?

Maybe itd be better form the top open so i can get the height where i want it.

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Re: 1981 Dolphin 20' Commercial

Post by fallguy1000 » Tue Jun 18, 2019 12:05 am

Post some pictures; I assumed stringers were out.
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MSRiver
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Re: 1981 Dolphin 20' Commercial

Post by MSRiver » Tue Jun 18, 2019 10:21 am

This is right after i sanded the entire hull with 40 grit. The cap was put on right after this and i have since sanded the port inside face stringer.
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