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PostPosted: September 6th, 2021, 1:15 pm 
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Location: Freeland, Maryland USA
I’ve worked on boats with great factory gel coat jobs, and others with not so good gel coat work. More specifically, on some boats, usually thicker gel coated, with lots of spider cracks and missing gel coat chips and chunks, and some others, while heavily used and scratched, with thinner gel coat and fewer issues.

I have noticed is that some more vintage gel coat was applied thinner than as on later models of the same boats from the same company/factory, and the thinner examples seem less prone to spider cracking. It makes sense (I guess) that thinner gel coat would be more flexible, and less prone to splintering on impact, but I am far from a gel coat guru.

At the same time that thinner vintage gel coat has also proven less prone to busting off chunks; maybe it takes an unattended spider crack to get those missing pieces started flaking off. That also, to me, makes sense, and may be a reason to attend to spider cracks before broken pieces peel off entirely.

I’m thinking of a friend’s hard used and abused early glass MRC Explorer I rehabbed 20 years ago, and the ’75 Hyperform Optima I am currently working on, both with thinner, more flexible gel coat, both sans spider cracks or missing chips.

The 46 year old Optima has 1,000+ scratches on the bottom, but zero spider cracks, only a few tiny pieces of gel coat missing. Cumulatively all of those missing pieces are the size of my pinkie nail. Sanded and filled with thickened G/flex before bottom paint.

ImageP9040018 by Mike McCrea, on Flickr

Teeny tiny missing chips, nearly a “why bother?”. Eh, I have time, and G/flex, and Colloidal Silica powder, and filling those teensy chips only took a second. And some cure wait-time before re-sanding and painting.

Just curious if anyone has an explanation for gel coat variances. Was it factory prep work, process, technique, chemistry? Was there some superior gel coat used in the ’70’s & ‘80’s that fell out of favor, became too expensive compared to a lesser alternative, was banned by OSHA for toxicity or etc?

Or are some hulls just outliers, made by a careful shop with skilled employees, and some made on Friday afternoon by folks ready to call it a day?


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PostPosted: September 13th, 2021, 10:56 am 
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Joined: June 28th, 2001, 7:00 pm
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Location: Freeland, Maryland USA
Mike McCrea wrote:
Or are some hulls just outliers, made by a careful shop with skilled employees, and some made on Friday afternoon by folks ready to call it a day?


That was, as anyone who has worked on enough canoes knows, a retorical question.

I’ve seen some “Friday afternoon” canoes, or at least examples of less caring craftsmanship; wood gunwale screw holes that barely hit the sheerline edge, same for holes in thwart and yoke ends, seat drops installed catawampus.

One pricey carbon “Bell” canoe with the double hung yoke installed backwards. When I took that yoke out to turn it around it was not just backwards, only two of the four machine screws were through the yoke ends. Not what I expected to see in a $3000 canoe.

“Bell” in quotation marks, that was an end-of-brand ORC-made Bell canoe, not a Ted Bell canoe. FWIW that kludgy yoke convinced me to remove and inspect thwarts and yoke, even on brand spanking new canoes. Even if the machine screw holes were properly drilled I could lay a couple more coats of varnish over the butt ends, an unseen area where too many manufacturers skimp.

BTW, the Hyperform Lettmann Optima is very cool decked hull. This is the third one to come through the shop undergoing gender reassignment, from “Tandem European-Style Touring Kayak” to “Solo Decked Tripping Canoe, AKA the poor man’s Kruger Sea Wind.

ImageP9010010 by Mike McCrea, on Flickr

One of the past Optima conversions, with photographs:

http://scooter-bangortoportland.blogspo ... canoe.html

I liked the Haida swirls he painted on the stems, tying the black Dynel & graphite skid plates to the black coming trim, enough to do so on my ’71 OT Sockeye, the rarest (and maybe best sailing) of the ‘70’s open cockpit decked tandems.


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PostPosted: September 13th, 2021, 2:16 pm 
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Joined: January 11th, 2005, 4:58 pm
Posts: 2283
Location: Manitoba
I enjoy your vast knowledge and your C1 conversions.

_________________
Brian
http://www.JohnstonPursuits.ca

 


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PostPosted: September 14th, 2021, 2:54 pm 
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Location: Freeland, Maryland USA
Paddle Power wrote:
I enjoy your vast knowledge and your C1 conversions.


“Vast knowledge”, BWAHAHAHA!

I am at best a shade-tree boat tinkerer compared to some, and mighty damn slow at that. I really want to understand the secrets behind vintage/thinner gel coat work. I don’t want to actually DO gel coat work; getting a decent color match on old boats, even faded white, is near impossible. I just want to understand the whys and wherefores of older gel coat.

How slow? The Optima as been in the shop for 2 weeks and all I’ve done so far is halfway finish the paint job. It will be a sexy thang once the paint and “muscle car” racing stripes are finally finished, then I can move on to the funner challenges of custom outfitting. I have ideas.

The marathon outfitting sessions, as in that Optima blog rebuild, are shop partner fun, and we’ve done a few in that git-er-done couple days guise. Outfitting a Freedom Solo, with my childhood best friend (and brother-in-law), was another fine weekend of non-stop tinkering and logistical scheduling.

https://www.canoetripping.net/threads/m ... hon.74835/

Like the Optima outfitting yet to come it really helped speed things along to have a same make, same model, agreeably outfitted boat resting alongside in the shop.

Screwing around with boats is my version of doing jig-saw puzzles or Sodoku; every rebuild or outfitting session is a little different, and I learn something new every time. After 30 years I’m still getting better at it.

Much of that “better” is simply figuring out best sequence and timing from past experiences; do this, then that, then flip the hull upside down, then right side up. Do the epoxy or paint work shortly before it is time to walk away and call it a day; screwing with wet paint or epoxy rarely makes it better.


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PostPosted: September 15th, 2021, 9:57 am 
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Mike McCrea wrote:
I have noticed is that some more vintage gel coat was applied thinner than as on later models of the same boats from the same company/factory, and the thinner examples seem less prone to spider cracking. It makes sense (I guess) that thinner gel coat would be more flexible, and less prone to splintering on impact, but I am far from a gel coat guru.


ya i think your intuitions are good Mike.

https://www.youtube.com/watch?v=trPnY0a2Ibg&t=271s
(back to the old days. along with everything else)

(the world keeps turning over so that it doesn't go stale)
(like a pancake, so that it doesn't go burn)

Mike McCrea wrote:
At the same time that thinner vintage gel coat has also proven less prone to busting off chunks; maybe it takes an unattended spider crack to get those missing pieces started flaking off.


ya i'm sure these chunk busts are just another perk of the thicker coat. like an eggshell on a hard boiled.
verses thinner shell. you'd have to press the egg deeper.

eg, we could imagine no laminates involved, just the gelcoat in the shape of a boat.
so, thick or thin,

if you push hard on a chine, the thicker coat will produce a steeper turn into that pushed point.
the thinner coat a gentler slope i bet, for that same push.
(eg, it does not crack because it bends gradual vs. sharply)

and so the particular laminate will either promote or suppress these effects as well,

Mike McCrea wrote:
..That also, to me, makes sense, and may be a reason to attend to spider cracks before broken pieces peel off entirely.


agreed,


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PostPosted: September 17th, 2021, 10:42 am 
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Joined: August 28th, 2004, 5:26 pm
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Location: n/e ontario
We bought a Kevlar Langford 16.6 about 22 years ago. It has the thick gelcoat. It got spider cracks within the first few months. They seemed to be cosmetic…and we never got around to taking it back to Langford (long drive).
Over the decades, it’s had some rough use…but most of the damage happened during transport and once when a wicked wind blew it off the canoe rack.
I’ve been doing random repairs, sometimes every spring, sometimes not. The spider cracks have never resulted in flaking off. However, there are odd little spots where there are chips in the gel coat.
JB waterweld is a perfect solution. I’m not concerned about colour matching, but I think a permanent marker could colour the spots close enough. Not interested in painting. I don’t want to carry the extra weight. - https://www.canadiantire.ca/en/pdp/j-b- ... 3792p.html


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PostPosted: September 18th, 2021, 2:58 pm 
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Location: Freeland, Maryland USA
red pine wrote:
JB waterweld is a perfect solution. I’m not concerned about colour matching, but I think a permanent marker could colour the spots close enough. Not interested in painting. I don’t want to carry the extra weight.


JB Weld, PC-7 epoxy, thickened G/flex will all work, and once cured accept paint. Even little covering dabs of enamel paint pen or Rustoleum.

But sometimes a full on repaint is the way to go. I’m working converting on a 46 year old Hyperform Optima tandem to a decked sailing tripper.

The bottom, after washing, scrubbing, and filling tiny gel coat chips still looked rough.

ImageP9040016 by Mike McCrea, on Flickr

Two coats of gloss white EZ-Poxy paint later.

ImageP9140007 by Mike McCrea, on Flickr

The decks were badly faded, approaching pink. Removing the he old logos show the original shine.

ImageP9030003 by Mike McCrea, on Flickr

Two coats of Fire Red EZ-Poxy and some white “muscle car” stripes and she is a sexy thang once again.

ImageP9160002 by Mike McCrea, on Flickr

I don’t know what the paint weighed, less than half a quart all total.


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PostPosted: September 19th, 2021, 4:09 pm 
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Joined: May 22nd, 2020, 9:25 pm
Posts: 42
Mike, I’m sort of hijacking the thread here,

I’ve seen your work on a few forums now, and I’m curious about what you look for in your tandem kayak to decked canoe conversions. I’m interested in the idea of converting one myself and any advice you have on selecting the right candidate boat all the way to modification advice would be greatly appreciated

P.S., I’ve been following your advice while repainting a canoe of mine and it’s working out great, so many thanks!!


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PostPosted: February 21st, 2022, 6:04 am 
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i think what's going on, might be this:
(about the thick vs. thin gel coat). say you hold a dry stick horizontally in your hands, and you bend it so it cracks in the middle clean,
but you don't bend it so far that it cracks complete through, but almost through.

now, if you look down this crack, you see it's wide at the entrance and then gets narrow.
like a crevasse on an ice berg.
(the hole is in the shape of an upside down triangle).

why a triangle and not, say, a square?
because, the higher part of the stick that cracked, was stretched more during that bend.
the mid part, less. lower part, even less.

like a race car on outside of a turn, loses to the car on the inside of that same turn. because the outside means more distance to travel.
the top part of the stick stretches more, travels more, hence wider gap there.

so, if stick was gel coat, same thing would be true.
thin gel coat represents the lower area of the thick gel coat. so, the thin gel coat travels less, has narrower cracks, and all this = less crack prone.

(given the same bend/bang).


thick
Image

thin
Image


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PostPosted: February 21st, 2022, 7:21 am 
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Location: Freeland, Maryland USA
remogami wrote:
i think what's going on, might be this


Those bendy photos tell the tale. As does this; very thick gel coat.

ImageP5292859 by Mike McCrea, on Flickr

Those aren’t “spider cracks” those are crevices.


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PostPosted: February 21st, 2022, 7:51 am 
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When you start to dig into gel coat and vinylester applications it becomes quite complicated with a lot of engineering considerations. Most notable the gel coats density, tensile strength , Young's (elasticity) modulus etc....

Here is vinylester resin spec sheet:
https://www.composites.dk/wp-content/up ... 2016UU.pdf

Gel coat spec sheet is harder to find since I don't have a brand name. I'm guessing the gel coat's mechanical properties should at least equal that of the underlying resin. If not, spider cracks in gel coat. So, I'm inferring that the quality of the gel coat is very important. A good reason to find a reputable canoe manufacturer for long term reliability of the gel coat.

Please note I have only enough info to be "dangerous". LOL


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PostPosted: February 21st, 2022, 8:25 am 
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RichardW2 wrote:
So, I'm inferring that the quality of the gel coat is very important.


ya, completely agree.

RichardW2 wrote:
A good reason to find a reputable canoe manufacturer for long term reliability of the gel coat.


this is why i am so wary of new brand canoes. nothing beats experience. that said, i'd experiment with anything for the right price.


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PostPosted: February 21st, 2022, 3:45 pm 
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RichardW2 wrote:
When you start to dig into gel coat and vinylester applications it becomes quite complicated with a lot of engineering considerations. Most notable the gel coats density, tensile strength , Young's (elasticity) modulus etc....

Please note I have only enough info to be "dangerous". LOL


Me too, “just enough”. I’ve been told by folks in the industry that, beyond the product being used, how the gel coat is applied and by whom is a potential issue. Age and mix of the gel coat, temperatures, skill level of application.

remogami wrote:
this is why i am so wary of new brand canoes. nothing beats experience.


I too am leery of a new start up, just finding out the whats and hows of canoe construction. And I’m leery of companies that have relocated, needing to hire new staff. Some things you can tell from a careful inspection. The quality of gel coat work isn’t always one of them.

I’m not saying the craftsmanship will be inferior, but there is a chance it will be unlearned.

Back to the start of this thread; Mad River did superb gel coat work in the Vermont days. Maybe not in the last months before the move to North Carolina, when folks on the shop floor knew they would soon be looking for work, but MRC’s earlier composite work was always top notch.


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