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hamburking · 04-08-2020, 19:31

I had something similar on my 1972 Pearson 30. There were several vertical ridges on each side of the boat, like shallow waves. Both sides, near the chain plates, but not the chain plates. It bothered me terribly. I scoured the interior of the boat searching for water or stress damage, and found none. I loosened the rig and let the boat settle, thinking it might be stress from the rigging. Nope. It seemed worse in winter, but maybe because the boat was on the hard and I could see it more easily. I envied all the other boats, with their smooth hulls.

In the end, I think it was nothing. Perhaps a manufacturing defect. I doubt it was a collision, since it was on both sides of the boat. I owned the boat 5 years and sailed it HARD. Never any issue. I consider it totally cosmetic.

Might not be the same issue as your boat, but that's my story. I posted here about it when I first bought the boat...you might find the thread if you search...lots of pictures. Good luck.

Cheechako · 05-08-2020, 07:28

Quote:

Originally Posted by Jim Cate

fiberglass shrinkage?? Never heard of that myself. Perhaps it explains boats advertised as x feet in length actually measuring somewhat less! Wait long enough and you can move into a shorter marina berth...

Seriously, I've not experienced or observed such shrinkage, and kinda doubt that it exists.

Jim

yep Jim, it's a thing. You dont think fiberglass outgasses and cures for years? In fact, that's the reason a properly fitted bulkhead has a "cushion" or gap between the bulkhead and the hull before tabbing it in. If you simply fit the bulkhead tight to the hull, the hull shrinks over time and a hard line will show on the outside of the hull.
There is a Catalina 34 right at the base of the ramp going onto the dock at my local marina. Where the main bulkhead is located there is a hard vertical line /bump showing on the hull you can see walking by. That bulkhead was improperly installed and the hull shrank over time.

Case Western Reserve University
"Pure unsaturated polyester resin having about 50% styrene content shrinks more than epoxy resin. The volumetric shrinkage of unsaturated polyester resin is somewhere between 5 and 13%, depending on the polymerization temperature. This is the reason why an additive called low profile agent, typically a thermoplastic polymer, is added to reduce the apparent shrinkage by inducing the porous morphology within the phase separated thermoplastic phase, by taking advantage of the different vitrification temperature of the polyester and thermoplastic. The thermoplastic phase acts as a reservoir of styrene monomer. On the other hand, epoxy typically shows the volumetric shrinkage between 2 and 7%."

sailorladd · 14-08-2020, 09:40

It is either a sloppy rub rail installation with incorrect fastenings or possibly the washers or fasteners are of mild steel and have rusted and swelled, distorting the rubber ...perhaps it may be worth trying to uncover one of them to see?

capnorv · 15-08-2020, 11:31

I'm thinking you've had water intrusion between laminates or laminates and core and then subsequent freezing. *****, it's fixable but a labor intensive act of love. Anything on a boat is fixable.

DeValency · 15-08-2020, 12:34

Could be water intrusion around bolts at the deck to hull joint - hence, the symmetrical appearance. So check well any leaks and moisture at these areas inside out and also the the hull right under these bumps.

Quote:

Originally Posted by ShakenSeraph

Hey Team,

I'm considering purchasing a project boat and I'm curious if anyone knows what these bumps just under the toe rail on the outside of the boat could be?

They're on both sides of the boat in the same places. I thought it could be osmotic blistering, but the symmetry across the boat has me thinking otherwise.

Anybody have any thoughts?

**Jim Cate** · 15-08-2020, 15:30

[QUOTE=Cheechako;3201974]yep Jim, it's a thing. You dont think fiberglass outgasses and cures for years? In fact, that's the reason a properly fitted bulkhead has a "cushion" or gap between the bulkhead and the hull before tabbing it in. If you simply fit the bulkhead tight to the hull, the hull shrinks over time and a hard line will show on the outside of the hull.
There is a Catalina 34 right at the base of the ramp going onto the dock at my local marina. Where the main bulkhead is located there is a hard vertical line /bump showing on the hull you can see walking by. That bulkhead was improperly installed and the hull shrank over time.

Case Western Reserve University
"Pure unsaturated polyester resin having about 50% styrene content shrinks more than epoxy resin. The volumetric shrinkage of unsaturated polyester resin is somewhere between 5 and 13%, depending on the polymerization temperature. This is the reason why an additive called low profile agent, typically a thermoplastic polymer, is added to reduce the apparent shrinkage by inducing the porous morphology within the phase separated thermoplastic phase, by taking advantage of the different vitrification temperature of the polyester and thermoplastic. The thermoplastic phase acts as a reservoir of styrene monomer. On the other hand, epoxy typically shows the volumetric shrinkage between 2 and 7%."[/QUOTE

g'day Cheech,

I believe that your bit from Chase refers to shrinkage during polymerization, not in later life. If boats shrank to the degree mentioned they would be in pretty horrible shape, not just hard spots at the bulkheads!

I believe that well constructed FRP boats are allowed to cure for some while before removing from the molds, and then longer still before the bulkheads are stuck in just to avoid such distortions developing.

I'm surely no expert, and admit to uncertainty, but I still can't believe in any substantial long term shrinkage.

Jim

boatpoker · 15-08-2020, 18:00

Quote:

Originally Posted by Jim Cate

I believe that well constructed FRP boats are allowed to cure for some while before removing from the molds, and then longer still before the bulkheads are stuck in just to avoid such distortions developing.
Jim

Nope ! They get them out of the mold as fast as possible to get the next one in.
Bulkheads are no loger "stuck in" (assume you mean glassed) for the most part they are fitted in to recesses in the liners.

**Jim Cate** · 15-08-2020, 18:50

Quote:

Originally Posted by boatpoker

Nope ! They get them out of the mold as fast as possible to get the next one in.
Bulkheads are no loger "stuck in" (assume you mean glassed) for the most part they are fitted in to recesses in the liners.

Well, BP, I did specify "well constructed" didn't I? Seems to rule out this practice!

And that just gave me a thought: when a boat is constructed around an internal grid that is glued into place with a pretty rigid adhesive (Plexus), any differential shrinkage would result in failure of the glue joins and subsequent .loss of structural rigidity. As a surveyor, do you see this ?

And what are your th oughts on long term fiberglass shrinkage as discussed above?

Jim

boatpoker · 15-08-2020, 18:55

Quote:

Originally Posted by Jim Cate

Well, BP, I did specify "well constructed" didn't I? Seems to rule out this practice!

And that just gave me a thought: when a boat is constructed around an internal grid that is glued into place with a pretty rigid adhesive (Plexus), any differential shrinkage would result in failure of the glue joins and subsequent .loss of structural rigidity. As a surveyor, do you see this ?

And what are your th oughts on long term fiberglass shrinkage as discussed above?

Jim

it most definitly shrinks for decades as the plasticizers migrate out of the resin but not so much that you'd notice.

You may have noted that I'm a bit cynical (it's been forced on me by this shabby mostly unregulated industry) however I've only ever been truly impressed by three boats and each was home built.