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 » Tue Apr 09, 2019 3:49 pm

Stop.

You need to build a mould of the cap. Almost impossible to get the cap on if you change the shape at all.

Forget that wood insert.

It is a really complex thing to build or rebuild a deck cap.

Consider a mould was used to build it.


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fallguy1000
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Re: 1981 Dolphin 20' Commercial

Post by fallguy1000 » Tue Apr 09, 2019 3:50 pm

Basically, the existing cap needs to be put on a strongback that cannot move.
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MSRiver
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Re: 1981 Dolphin 20' Commercial

Post by MSRiver » Tue Apr 09, 2019 5:32 pm

Fallguy1000 as far as a mould i dont know how I'd even start to build one for it not to mention serious time of getting it perfect to match, not sure if it would payoff for time spent doing so. I figured and while another source said as along the cap holds it shape for the most part ill be able to work with that. As far as the shape goes or contour to match i didnt just lay it flat. While it was on the boat i took measurements from ground to a common line on the cap every foot. Now that its on the ground i did the same thing except in reverse order you could say so that the nose curves up (or down for when its on the boat) Id say the cap is fairly stiff and still has a memory of where it should be. After getting it level on the ground and raising the nose with spacers and added supports where needed it matched up pretty close to what it was on the boat. Meaning if i moved one support the whole thing wouldnt just flop around so to say.

I remember when taking the cap off it flex a good bit that's not what you want but as along as it can flex or move somewhat say 1-2" at most i think i shouldn't have a problem going back on the boat as far as matching what the caps original shape was.

That being said it originally having wood for the core putting wood back for strength is what id want. I know that the wood can twist enough naturally to get where it needs to be without putting excessive force on the back 8' section. The Forward side peices I just didnt know if i need to pre-mold or twist the wood to match or if i cant just clap in down accordingly and the wood shape the cap and not the other way around. Id say the board needs to twist 2" out of datum and curve roughly 3" Theres definitely more of a curve there which is what im really asking about.

(I thought about cutting 1/4" 1/2" slits on the down side with a skill saw so that the would better mate the cap.) Of course i have to make sure those slits are epoxied well to not take away strength of course if i did that. two layer or a third layer of glass would go in that area.

fallguy1000
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Re: 1981 Dolphin 20' Commercial

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

You have to build a mould, of sorts.

The mould you build will be a strongback that will keep the cap in the shape it must end up in.

Wood will not twist much my friend.

I just used plywood in a place where I need more, not less like you, rigidity.

Do not infill the cap with wood. Add a layer or two of 1708 glass inside it on your strongback/mould/shapekeeper. That will stiffen it up some and then cleat it to the hull. You can raise the cleats up or down to suit. Use backers if you have any hardware attachment and install those after the cap is fitted dry to your liking.
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fallguy1000
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Re: 1981 Dolphin 20' Commercial

Post by fallguy1000 » Tue Apr 09, 2019 8:09 pm

You'll screw it up if you add timber.

You will need some give.
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MSRiver
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Re: 1981 Dolphin 20' Commercial

Post by MSRiver » Mon Apr 29, 2019 12:57 pm

Bad weather put me off for a little while but got to work on the center console and fill up unwanted holes. Pretty pleased how they turned out. I used Luman board to use as a backing, put 3 layers of PVA over it and screwed down then laid glass over it. In the pic is just the first layer. The day after i got to lay up the remaining layers to make the the surface flat if i recall it was 4 or 5 layers total.

As far as the cap goes i used the same luman board and pva to make the mold for the new sides where it was cut out for rod racks. Best way i could come up with holding the form in place without screwing was just your handy dandy duck tape. Laid 2 layer of 1708 for now will be follow up with 2 more layers along the whole cap. The back left kinda opened up a little more than i liked but ill address that in a min.

So not doing wood in the cap at least not in the sides. I will have once piece in the back at the motor well and another piece in the front cap. Those two areas will constantly be stood on so i need the support. For everything all along sides ill put 2 layers of 1708. I cut them in 8' sections (to not waste a bunch of glass cutting odd shapes) to where they will over lap about 4-6 inches where they will be spliced. Should be strong enough I'm hoping. Now back to the areas in the back where it opened up on me. As i lay the new glass in I'm planning on using a clamp to compress that area until the glass sets up and hope it stays in shape. So that should finish up the cap minus the cosmetics for now.

Fallguy i think i got what you were saying about setting the cap on blocks. I was looking the the Aquasport rebuild that is on here and when they were doing the cap, they had a combination between small plywood that was glassed to the hull, i also saw they replaced those with making a 90 degree bracket made of foam and glass and glassed those in(I have attached both pics below). I'm guess i could just leave the wood ones in there and just glass those in with 12oz tape. They are going to be a little finiky to make since its not just a 90 or a 45 all going to have to be cut just right. Along with those small blocks for the cap to sit on I'm going to have at least two per side full length side stiffeners/rod holders. One question i do have is what should the spacing between the small blocks should be? I plan on having the full length stiffeners in the same place as the other dolphin (which looks to be just forward of the CC and just back of the CC. After the cap is on those i plan on using 2 layers of 12oz tape to glass the inside and outside for it to be completely glassed together and not just screws holding it on. Not to mention it will help cover up all those holes from the screws and have a seamless look from hull to cap.

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fallguy1000
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Re: 1981 Dolphin 20' Commercial

Post by fallguy1000 » Mon Apr 29, 2019 8:02 pm

You will sort of learn the block spacing as you go.

Start with a plan of 2-3 feet and adjust accordingly. If the cap is not cooperating fitwise; more blocks.
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cape_fisherman
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Re: 1981 Dolphin 20' Commercial

Post by cape_fisherman » Thu May 02, 2019 6:12 pm

Or just build new covering boards and toss that old cap.

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Re: 1981 Dolphin 20' Commercial

Post by MSRiver » Wed May 22, 2019 6:58 pm

She's starting to take shape
Last edited by MSRiver on Thu May 23, 2019 1:51 am, edited 1 time in total.

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Re: 1981 Dolphin 20' Commercial

Post by MSRiver » Thu May 23, 2019 1:48 am

MSRiver wrote:
Wed May 22, 2019 6:58 pm
Cap is finished up! Laid down two layers of 1708 did 8 ft sections with 4" of overlap so i wouldn't have to deal with long sections. I did get a few air pockets which you might be able to see. I was pretty disappointed with myself when i saw them the next day. By all mean it wasn't due to not rolling it out correctly. 100% positive its due to the old glass being as wavy as it is. I sanded as much as possibly without completely taking off the old glass. But it really wasn't laid right the first time i feel like so there air pockets it in already. Right when you think itd be all glass and flat you go all the way through one weave and there will be gap going to the next layer of weave either that or there pinholes(btw i dont know what oz glass they used in 1981 but looks to be like 30oz) all joking aside as far as that goes i do believe i have plenty of contact area, and the air pockets are only in a few sections and not all the way down the cap, for it bond not to mention it stiffened up the cap plenty and still have plenty of flexibility. Its at least 2x more stiff than when i first pulled it off

Now for the motor well and front i decided to glass wood in because those are the area that are constantly be stood on or a boat having to tow me in or whatever and wanted the strength there. For the back I decided to not deal with the same problem as i had above being that the old wavy glass and having tons of air pockets, so sanded all the old woven down to matt glass. From there i put 1 layer of 1708 while still wet and then put the board with some epoxy glue down. As you could see i only put 5 holes it where i clamped down the board with other strap 4x6 of board( the peices i was going to use for the cap, need to find some use for em) on the back side so that the glass would lay flat underneath. Next day made my fillets all around the corners of the board and acutally tapered the board to help make those curves and put 2 layers of 12oz tape along the perimeter and followed that up with 1 layer of 1708 over the whole board. I also dressed up the starboard back corner i was getting a little to much play for comfort throwing off the levelest of the board. The front was the same process except i had to have another board under the main one to help take up the gap since the front is curved. The first board down had a bunch of sanding to try and match the top of the cap. Laid the first board down put a ton of glue in there where i did not feel like sanding a 3/4" board down to 1/4" over a good area so just packed glue in it. Then the big board went down and put some weights on that to hold everything down since i couldnt use the same technique as the back by clamping. Then sanded and did the same tapper to the board corners to make take less fillet, tapped with 2 layer of 12 oz and 1 layer of 1708.

For the last step i already knew where rod holder and cleats were going on it i used the scrap boards( that were suppose to go in the cap) tapered those off put glue down followed by 2 layer of 12oz tape over it overlapping 1.5" for each layer. There's a white film that happened again on a few of those backing boards because it wasn't suppose to rain till early in the morning and should have had plenty of time for the epoxy to set up but a small little storm came through and it got sprinkled on, it sanded right off and the epoxy is hard so it finish curing just had that humidity film on it. As you can see the front has no white film, other than the few sanding marks due to me spilling some glue on it. All of it was laid in 2.5-3 hrs i believe only piece i didn't get on in that sitting was the starboard back. Low and behold should have just waited but live and learn. But anyways, depending where the blocks go i'll have to sand it down anyways but other than it i should be fine. Now i did think i might need to wait before i put those in to make sure they don't interfere with the blocks, but i figured im going to have plenty of spacing to move a couple of inches either way. If i do have to put them on the backing board it would just give it more support since it will attached to a greater load area. I also got some 1" PVC (which i probably should have used conduit and not pvc) to be able to run wires under the cap out of the way and have areas for lights and what not. Which there i just put MORE glue down so glass would wrap around those and put 1 layer of 12oz over that. I put 1' sections at the front another 1' section in the middle between a midship cleat and rod holder and then 1 18" in the back. I still plan on adding another 2' section on between the front and middle pvc but didn't want to put those in yet to make sure i still have the flexibility i need for it to fit.

I plan on doing a few more things on the transom, clean up a few air bubble spots and I'm going to add another 2 layers of the 12oz tape on the corners with 1 more layer of 1708 (for a total of 3 layers of 1708) and lay 1 layer of matt over that so i can finish it pretty and not have alot of weave. I did start to notice earlier when i over lapped the glass over the transom to the back side i was going to have to either add glass all over the the back to make it easier when fairing or put a bunch of fairing to make the back flat. So i decided to sand all the high points down which was pretty much both 1708 layers on the right side I'll have to add that picture later. The plan then is once I get the inside completely done I'm going to just put 2-3 layers of the 12oz tape over the top to get that right and hopefully not have to deal with the same problem of adding a bunch of fairing to make it flat. ( If anybody has any input on that I'm open ears.)

Now yesterday i did go ahead a fit the cap on the boat to make sure i didn't mess anything up and SHE FITS!!! It was a tight squeeze put i think i know the problem for why its a lot tighter than it was before, at least in the front where she was a little pain to make it fit. You can see on the starboard side where some of the 1708 got a little wavy so it shortened the inside to inside measurement but think i just sand those down and that give me a little more room that or my straps did not hold the hull together as well as i planned, but she still fits regardless. I still plan on taking off the cap one more time so that once i get all the blocks where i want them I'm going to epoxy them to the cap first, since it will be easier to epoxy them down while its off so i don't have to work upside down and deal with all that. Then it should be as simple as raising or lowering the cap to my pre-marked spots and glass to the hull. Unless i should just tap the blocks to the hull first. I'm just trying to avoid trying to lay up glass upside down. From there plan on epoxy probably 2 layers of the 12 oz on the outside for a seemless fit, which will also take care of some of the garbage glass on the outside of the cap, and tap the inside as well. That way i dont have to ever have to deal with the cap coming off again and no water is going to be creeping in the boat that way. But shes coming along slowly but surely

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