To Gel or Not to Gel - That Is the Question

[feelsgood]

Plaane off the gel coat repair any voids and use a 2 pack poly system try JOTON PAINTS thay have some realy great stuff and not bad prices
Regards Pete

[Maine Sail]

Originally Posted by Solitude

Fish
Is there a logical reason for the stress cracks?
Chainplates or bulkheads... I am not the expert Nick is but wouldn't it be an idea to try to stablize the cause. Add glass to the bulkhead/hull joint or stiffening it with glass over a form if there are cracks along a weaker area? On the inside.

Gelcoat crazing or cracks are often caused by a few things. Movement/flexing, gelcoat applied to thick or an improper cure. The latter two are the most common on wide spread surfaces and can often happen together (bad cure and to thick). Stress crazing usually only occurs where there is stress but thick gel or a bad cure are usually much more wide spread. Controlling the exothermic reaction is sometimes hard for boat builders with production lines and once in a while you get a hull with a bad cure.

Cape Dory was famous for thick gelcoat and many of them are quite crazed but also still quite sound and strong..

Personally I would use Interlux Interprotect 2000E. Easy system, 4-5 coats, and can be hot coated (chemically cross linked) up to two weeks depending upon temperature. Interlux recommends hot coating to avoid sanding. I have used West System as a Barrier coat before and won't do it again anytime soon.

IP 2000E is specifically designed as a barrier coat and formulated specifically for this application. I prefer to use alternating white then gray to make sure coverage is 100%, and not thin in places, IP 2KE is available in both white and gray which makes this very easy.

A one gallon kit (hardener and epoxy) of 2000E is $74.99. I can do one full coat on a 36 footer with one gallon and have a little left over.

West System:
78.99 (epoxy) + 32.99 (hardener) = $111.98

Weest and IP 2KE are about the same price but the difference is in ease of application

Here's what West System has to say about hot coating:

"Apply second and subsequent coats of epoxy following the same procedures. Make sure the previous coat has cured firmly enough to support the weight of the next coat. To avoid sanding between coats, apply all of the coats in the same day. See Special preparation-Cured epoxy. After the final coat has cured overnight, wash and sand it to prepare for the final finish."

With IP 2KE you can do your coats up to two weeks apart with no washing and no sanding and you do not need to do it all in the same day.

When it comes time to apply the finish coat even the paint can be applied without sanding or washing the IP 2KE but you need to work fast, and preferably on a cool day, to do this. The barrier needs to be thumb-print dry to apply the paint and you'll get a good solid chemical bond.

My yard is a huge user of West System epoxy but won't use it for barrier coat jobs they use IP 2KE...

Interprotect 2000E (LINK)

Pettit also makes a similar product...

[Solitude]

Originally Posted by Maine Sail

Personally I would use Interlux Interprotect 2000E. Easy system 3-5 coats and can be hot coated up to two weeks depending upon temperature. Interlux recommends hot coating to avoid sanding. I have used West System as a Barrier coat before and won't do it again anytime soon.
.

Yes Interprotect is what I used as well and would suggest it for below the water line. I believe Fish is looking for crazing fixes above the waterline. Would you suggest it for that.

[Maine Sail]

Originally Posted by Solitude

Yes Interprotect is what I used as well and would suggest it for below the water line. I believe Fish is looking for crazing fixes above the waterline. Would you suggest it for that.

A Dremel and Cabosil/milled fiber/West. I don't really like micro-baloons and find they can tend to bleed through a light color paint and even gelcoat repairs. Sometimes a mix of baloons and cabosil works well though and lightens the bleed through color. They sand great but I much prefer a mix of milled fiber and cabosil. Dremel out the crazing then fill/fair. If it is wide spread... Well that is a HUGE job!!

P.S. Before barrier coating anything the hull needs to be dry! On a badly blistered hull this can literally take years if you don't strip to raw glass and let dry for a long period.

You'll want to take moisture readings along the way to know the progress. Simply trace the meter on the hull and write the reading in the box, date it then repeat throughout the process...

[barnakiel]

not to gel

the gelcoat is placed in the mould first and binds chemically leaving smooth surface

on repairs use epoxy and then paint as applicable

[s/v Jedi]

I'm not sure if everybody knows this but Cabosil is the same thing as colloidal silica.

It is not necessary and buys you nothing to apply additional coats when the previous coat is still "green". Simply wash each coat with water and a 3M scouring pad and dry thoroughly. Remember to protect the barrier coat from sunlight and UV until you get bottom paint on. Neither the barrier coat additive from West, nor the pigments have any UV filters in them.

I'm afraid I don't agree with this at all. If you let each layer fully cure before applying the next one, you create a secondary bond. Even though epoxy doesn't do bad with secondary bonding, it is much better to create a chemical (primary) bond. So, do not let it cure, apply next layer before the previous one is fully cured.
Also, all pigments protect against UV. They simply reflect it. This technique isn't good enough for full time protection, but very valif for temporary protection and used by many incl. West themselves. Read the final fairing and finishing guide for more info.

Some must read links:

WEST SYSTEM - Projects - Adding pigments to epoxy
Fiberglass tub and shower repair
and of course: WEST SYSTEM | Use Guides

Gel coat failure: gelcoat is more brittle than fiberglass. So, when the hull works/flexes, the gel coat doesn't want to join that game. That's why you get cracks when it's too thick. Also, we have a vinylester hull but a polyester gelcoat: cracks are the result. The links above shows how to make your own epoxy gelcoat. You could do that and protect it with a LPU clear coat (but that's just silly).

I don't think the cracks on Fish's boat are due to design or construction flaws. They are caused by damage related stress, degradation of the gel coat itself and stress from nearby risers like fasteners etc. The cracks around the damaged area should be checked to see if they go into the fiber... one should do that check for every crack so don't just sand a bit but grind it out down to the fibers. Filling up is easy enough.

cheers,
Nick.

[Maine Sail]

Originally Posted by s/v Jedi

I'm not sure if everybody knows this but Cabosil is the same thing as colloidal silica.

Yup I actually use Aerosil but most people know what Cabosil is so I generally use that term... Fumed Silica, colloidal silica, Cabosil, Aerosil.....

[Fishman_Tx]

The crazing, cracks, chips, etc. is about 1/4 of the boat above the line. All blisters have been ground and "dished" to the roving. See the pix on my profile or page 3. This hull is all poly.

Re: IP2E - as we are planning to use Interlux paint, I think this will work. And it's cheaper too. Definitely no compatibility problems.

Planer: I wish I had one. I'd off the gel in a second...

[Solitude]

Originally Posted by Fishman_Tx

Re: IP2E - as we are planning to use Interlux paint, I think this will work. And it's cheaper too. Definitely no compatibility problems.

Planer: I wish I had one. I'd off the gel in a second...

With the Interprotect 2000 I bought a bunch of cheap rollers rolled it on and used the thumbprint test. Its written in the directions. Check the interlux paint guide .pdf. Its on the website. It has some good info about topside paint and stuff.

[LtBrett]

I don't necessarily recommend stripping all the gel coat--as mentioned, you'll have a lot of fairing to do afterwards. Perhaps try grinding off the gel coat over a representative sample of cracks to determine if they are cosmetic or if they go into the glass. If cosmetic, which is most likely, you can gouge them out with a dremel and fill the trough. Sand smooth and paint. I used both Marine Tex and Duraglas to fill cracks and both yielded similar results. If they go into the glass, you have to cut away until you get to solid glass. If you have a large patchof spider cracks, you can grind off all the gel coat in that area and if you are good at feathering the edges of your grind and you use white paint, the repair will be very hard to spot.

Brett

[barnakiel]

Re Jedi's comment - correct! The mechanical bond of epoxy is just on the first layer towards the damage - that's why it should have some key to grip, then it is better to re-coat before the epoxy cures - to get the chemical bond in between the layers of repair.

b.

[Fishman_Tx]

Sorry guys, no new pics this weekend due to rain and "birthdays". I'll get some new ones as soon as I can...

[utahmonty]

No boat has ever sank due to it, but to tackle properly you have a lot of hard work and patience required to do a top job.

The older the boat the less the blisters show, some not at all! that means things are pretty advanced- not good, and in real terms all bottom treatment start with a peeling back of teh gelcoat and lots of freshwater washing and drying time to get the hull ready for treatment. 3months -12 months dependand on how bad !!! soem hot vac treatments speed up the time scale but at a cost.

Treatments (epoxy) is well documented, but any treatment is a waste of time if the hull is not dry! you will just seal in water at great cost- better to leave alone and keep sailing if you cannot wait the time required.

Good luck and remember if you dont have the timenow the boat can wait a few more months longer.

Ewan

[Fishman_Tx]

Originally Posted by utahmonty

No boat has ever sank due to it, but to tackle properly you have a lot of hard work and patience required to do a top job.

The older the boat the less the blisters show, some not at all! that means things are pretty advanced- not good, and in real terms all bottom treatment start with a peeling back of teh gelcoat and lots of freshwater washing and drying time to get the hull ready for treatment. 3months -12 months dependand on how bad !!! soem hot vac treatments speed up the time scale but at a cost.

Treatments (epoxy) is well documented, but any treatment is a waste of time if the hull is not dry! you will just seal in water at great cost- better to leave alone and keep sailing if you cannot wait the time required.

Good luck and remember if you dont have the timenow the boat can wait a few more months longer.

Ewan

Oh! But it's WAY too late for THAT!

The entire starboard side below the line is skin't to the skeg. The blisters have all been drained and ground (dished) already. See the earlier pics..

[FloridaWriter]

Originally Posted by s/v Jedi

I'm not sure if everybody knows this but Cabosil is the same thing as colloidal silica.

I'm afraid I don't agree with this at all. If you let each layer fully cure before applying the next one, you create a secondary bond. Even though epoxy doesn't do bad with secondary bonding, it is much better to create a chemical (primary) bond. So, do not let it cure, apply next layer before the previous one is fully cured.
Also, all pigments protect against UV. They simply reflect it. This technique isn't good enough for full time protection, but very valif for temporary protection and used by many incl. West themselves. Read the final fairing and finishing guide for more info.

Some must read links:

WEST SYSTEM - Projects - Adding pigments to epoxy
Fiberglass tub and shower repair
and of course: WEST SYSTEM | Use Guides

Gel coat failure: gelcoat is more brittle than fiberglass. So, when the hull works/flexes, the gel coat doesn't want to join that game. That's why you get cracks when it's too thick. Also, we have a vinylester hull but a polyester gelcoat: cracks are the result. The links above shows how to make your own epoxy gelcoat. You could do that and protect it with a LPU clear coat (but that's just silly).

I don't think the cracks on Fish's boat are due to design or construction flaws. They are caused by damage related stress, degradation of the gel coat itself and stress from nearby risers like fasteners etc. The cracks around the damaged area should be checked to see if they go into the fiber... one should do that check for every crack so don't just sand a bit but grind it out down to the fibers. Filling up is easy enough.

cheers,
Nick.

I have to disagree with you regarding UV filtration and your statement that a secondary mechanical bond is somehow less advantageous than recoating when the previous coat has not yet cured to create a chemical bond. First of all, in any gluing situation, West epoxy is in fact creating a mechanical bond with either the wood fibers, the glass fibers or the metal surface--there is no checmical bond and West adhesive works as designed (and described in the The Gougeon Brothers on Boat Constuction, by Meade Gougeon). No where in the book have I found any statement that indicates that a checmical bond of a coating of epoxy over a previous coating is somehow "stronger" than the mechanical bond of a coating over a cured previous coating. Furthermore the book repeatedly describes best practices for coating wood and fiberglass and states repeatedly that once the coating is cured it is to be washed and lightly sanded prior to the next coat being applied. If a chemical bond offered any additional strength, I feel certain that would be repeated pointed out as well.

Regarding your statement that all "all pigments protect against UV. They simply reflect it...." that is patently not true. To filter UV a coating must have UV filters, regardless if is pigmented or clear. Meade states as much on page 29, when he writes:
"501 White Pigment and 503 Gray Pigment are epoxy-based liquid colorants used to tint the epoxy mixture to provide an even color base for the final finish system. The colored surfaces also tend to highlight flaws and imperfections. Cured, pigmented epoxy surfaces are not a final finish surface but require an additional paint or UV filter coating for ultraviolet protection....
None of these coloring additives provide UV resistance to the cured epoxy, so limit their use to areas not exposed to sunlight unless additional UV protection is applied."

Since epoxy degrades from UV exposure in as little as a few weeks it is very important to protect it from sunlight.

Finally, for Fish, Meade does not recommend spraying West System epoxy:
from page 154..."It may be possible to spray West System epoxy, but we strongly recommend against it. Leaving asside the practical difficulties--our epoxy is a high density material which is very difficult to atomize and reducing it with thinners will lower its physical properties (specifically its resistance to moisture)--the possible health hazards are enormous..."