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Advice, Suggestions and General Help New Topic Printer Friendly Version

  Refinishing a carbon canoe
  Posted by: windwalker on Aug-23-13 10:18 AM (EST)
   Category: unassigned 

Found a used GRB canoe, looks like its been left outside too long. Looking at the pictures it's all white and milky. The guy says it can be sanded down and a thin coat of resin will have it looking like new.

Any thoughts?

Would the carbon be affect by the UV or just the gel coat? Concerned about structural damage from the sun.

Thanks, Mike

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Messages in this Topic

 

  Carbon cloth is immune to UV damage,
  Posted by: g2d on Aug-23-13 12:30 PM (EST)
and if it's under the gelcoat, the structural resin should be protected also.

But why would someone make a carbon canoe with gelcoat? The point of carbon is light weight. Usually a carbon boat will have just a thin "clear coat" over the hull. But that wouldn't leave you much margin for sanding.

Right now I'm not remembering what "GRB" means, so I can't tell you whether the boat is worth refinishing.
 
 
  I bet
  Posted by: mcimes on Aug-23-13 12:58 PM (EST)
I bet he just means skin coat, not true gel coat. the GRB boats ive looked into are all skincoat.
 
 
  Sometimes gel coat is used
  Posted by: kayamedic on Aug-23-13 12:41 PM (EST)
http://grbnewmandesigns.com/ Dont know about GRB

But Placid uses clear gel on its CF boats.
 
 
  Clear coat
  Posted by: windwalker on Aug-23-13 1:12 PM (EST)
It is a clear coat, he just referred to it as a gel coat.

He said a coating of resin(epoxy) would make it look new.


So is clear coat the same as epoxy?
 
 
  Looks Like New
  Posted by: mintjulep on Aug-23-13 1:42 PM (EST)
Sure, it will will LOOK like new. That may not be the same as BEING like new.

While the carbon fiber is relatively immune to UV degradation, the epoxy or polyester resin is not.

Some form of barrier is required to prevent the UV rays from reaching the resin and doing their damage.

The barrier may be opaque to visible and UV light. Gel Coat and paint are examples of this type of barrier.

Or the barrier may be translucent to visible light while being opaque to UV, or while converting the UV energy to heat. These types of barriers are referred to as "clear coat" because you can see through them to the material below.

"Clear coat" may be a paint, or it may be varnish, or it may be epoxy with a UV inhibitor mixed in. None of these are 100% effective at preventing UV from passing through them, and all of them degrade with prolonged exposure. The milky appearance is a sign of this degradation.

So how much UV damage to the structural resin this particular boat may or may not have incurred will depend on what it is "clear coated" with, and how long and how intense its UV exposure has been.
 
 
  can you see the inside of the canoe ....
  Posted by: pilotwingz on Aug-23-13 11:51 PM (EST)
-- Last Updated: Aug-24-13 1:18 AM EST --

...... if so is the milky white appearance there as well , or is only on the outside ??

My only concern would be if hydrolysis has taken place in the matrix resin .

A polyester resin is more subject to hydrolysis than would be a vinylester resin . Reason being is that polyester contains more ester groups than vinylester . It is these ester groups that are vulnerable to water degradation by hydrolysis .

By degradation I am saying that the once imobilized molecules that existed at the final stage of polymerization ... are now beginning to move again , an form a new product .

It may only be a clear polyetser gelcoat that has become degraded by hydrolysis , and not effected the matrix resin . That outer layer is the 1st line of defense , and it can be refurbished enough to protect the matrix resin again .

Hydrolysis changes the molecular structure of polyester resin , and in general makes it become more acidic (ie., degrades) . Water , H2O and heat are the culprit believe it or not .

When the Sun's UV rays strike and object , the radiation of those rays are absorbed . A process termed insolation takes place within the object . This process releases heat as it's by product . For this same reason we can live in the 1st layer of our atmosphere ... the Troposphere , because it is warmed by the Earth's release of heat during the process of insolation .

The sunlight itself is not hot , but the canoe that absorbs it (especially a black carbon canoe) can get very hot .

I believe H2O and heat are the culprits if the clear coat resin has gone opaque , it's breaking down .


ps., ... "it only needs" is B.S. . Because of it's condition "as is" makes it a roll of the dice , a risk . It will take time , expense , effort and risk to restore it to possibly reasonable condition , therefore it's current value in "as is" condition is small , very small ... don't allow silver dollar eyes that see what it "might" be able to become influence the fact that it "is" an abused and degraded carbon canoe , with the majority of it's value ($$) lost . I'd roll the dice for maybe $200.- $300. bucks ...

hmmm , what do ya think of this stuff ... http://www.aircraftspruce.com/catalog/cspages/evershield.php

 
 
  Add in the cost of about $100
  Posted by: JackL on Aug-24-13 8:33 AM (EST)
for some West Systems Epoxy and their pumps and then some more for labor, and if the boat is in otherwise good shape, go for it !

Jack L
 
 
  Don't know what "clear coat" means
  Posted by: Glenn_MacGrady on Aug-24-13 8:48 AM (EST)
Gel coat is a layer sprayed onto the mold before the laminate is laid up with resin. Gel coat can be opaque or clear.

To me, "skin coat" refers to a layup without any gel coat at all. The elimination of gel coat saves weight but sacrifices cosmetic appeal and UV protection for the resin.

I really don't know what "clear coat" means unless it is clear gel coat or something slathered on after the hull is fully laid up.

I wouldn't think it desirable to have gel coat on a racing boat such as a GRB or any boat where light weight is the primary objective.

Gel coat gets milky from oxidation by the sun over the years, especially if stored outdoors. It sometimes can be rubbed off with polishing compounds, or it can be disguised with applications of Penetrol. I wouldn't find mild oxidation of gel coat on a used boat to be unduly problematic if the price was right.

I don't know if so-called skin coat layups get milky from sun oxidation, but surely the resin is damaged and weakened over time.

 
 
  I can tell you about this
  Posted by: darkstar on Aug-24-13 9:48 PM (EST)
the bane of the GRB...

Great hulls, major pain tho... My boats are stored indoors and covered, it happens to ALL of them. even the new ones(gene and john will tell you otherwise)

I started by using fine steel wool to remove a couple of times a season. that got old, I actually found that a light solvent will "wipe" it off and that a coat of wax will keep it at bay for a bit but a light clear coat of epoxy will take it away forever. go that route and save yourself the hassle.
 
 
  I recently purchased a carbon fiber hull
  Posted by: dong on Aug-25-13 11:00 PM (EST)
kayak that had a lot of white parches on the hull. I used rubbing compound on an orbital buffer and it removed all of the white with some work. I decided to use a UV resistant wax for the finish and it seems to working just fine, although I do store the kayak inside a garage. I could have applied a coat of UV resistant epoxy but I really don't want to do that much work.
 

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