Dunning-Kruger problem with my rudder

[JoeRobertJr]

Posting in Sailor's Confessional, because I am not seeking advice so much as admitting ignorance and/or lack of skill.

I bought a new rudder for my Mariner 39. It came with pretty simple instructions: Scrub the PVA off the gelcoat, lightly sand the gelcoat to remove the shine, then apply the barrier coat. No problem. I can do that myself. After all, I stripped the swing keel on my previous boat to bare metal, then faired, then applied 6 layers of resin epoxy, then primer, then anti-fouling. I've got some experience. I've read the rudder manufacturer instructions. I've read the West Systems fiberglass manual. It all sounded straight-forward.

After preparing the surface, I started the barrier coat sequence. The first two layers were plain resin epoxy. The plan was to include a barrier coat additive in the next four layers. However, when checking the cure of the 2nd layer, I saw a problem. The epoxy was pulling away from spots: "fish eyes".

Clearly, I did not prepare the surface well enough. Maybe I did not get enough of the gloss off the gelcoat. Maybe my solvent wipe was not thorough enough. The only thing I am sure about is that I overestimated my ability to do the barrier coat.

The epoxy has had a week to fully cure now. I've had a week to reread all the instructions, review every CF thread discussing resin epoxy issues, and watch every YouTube video on barrier coats. So, the next steps are to thoroughly remove the amine blush, do another solvent wipe, then go back to sanding and much more careful attention to the pre-epoxy preparations. Wish me luck. And maybe some skill, too.

[s/v Jedi]

I have found the best steps are to first rinse with a water hose, then wash with dish washing detergent, then rinse or even pressure wash.

After drying, I prefer a wipe with denatured alcohol, not acetone/MEK etc.

Also, for barrier coat, using TotalProtect or Interprotect is much easier and performs as good as West System. Make sure the first coat antifouling goes on before the epoxy fully cures.

[JoeRobertJr]

Thanks, Jedi. I took your advice on using denatured alcohol vice acetone, advice I had seen elsewhere also.

Given the pattern of the fish eyes, it seems that my most likely failure was not removing enough of the gloss off the gel coat. An insufficient wipe-down could have contributed, too.

This past weekend, I started over and gave a lot more attention to the preparation.
1. Thoroughly scrubbed off the amine blush from my failed epoxy attempt.
2. Completely sanded off all the failed epoxy and the original gel coat gloss.
3. Cleaned by blowing off sanding dust with compressed air, then washing and drying overnight, then wiping with a rag soaked in denatured alcohol while drying with paper towels shortly before restarting the epoxy sequence.

After applying the six layers of resin epoxy, the outer four layers with barrier coat additive, the end result looks great. I've read over and over that attention to the preparation is key, but still underestimated that step originally. Lesson learned. Hopefully.

[s/v Jedi]

Originally Posted by JoeRobertJr

Thanks, Jedi. I took your advice on using denatured alcohol vice acetone, advice I had seen elsewhere also.

Given the pattern of the fish eyes, it seems that my most likely failure was not removing enough of the gloss off the gel coat. An insufficient wipe-down could have contributed, too.

This past weekend, I started over and gave a lot more attention to the preparation.
1. Thoroughly scrubbed off the amine blush from my failed epoxy attempt.
2. Completely sanded off all the failed epoxy and the original gel coat gloss.
3. Cleaned by blowing off sanding dust with compressed air, then washing and drying overnight, then wiping with a rag soaked in denatured alcohol while drying with paper towels shortly before restarting the epoxy sequence.

After applying the six layers of resin epoxy, the outer four layers with barrier coat additive, the end result looks great. I've read over and over that attention to the preparation is key, but still underestimated that step originally. Lesson learned. Hopefully.

Great! I find that finishing a good barrier coat is very satisfying.

I sand with a very course grit, like 50 or even 36.

[more]

Originally Posted by JoeRobertJr

Given the pattern of the fish eyes, it seems that my most likely failure was not removing enough of the gloss off the gel coat. An insufficient wipe-down could have contributed, too.

This past weekend, I started over and gave a lot more attention to the preparation.
ly.

no your problem is x3 maybe x4 Dunning-Kruger problem.
what **** base resin,1-6 coat you talking.
one cheap mix be componenta A

bisphenol A-(epichlorhydrin)
epoxy resin MW =< 700

≥25 - ≤50

titanium dioxide ≥10 - ≤25


formaldehyde, polymer with
(chloromethyl)oxirane and
phenol

≥10 - ≤25

1,6-hexanediol diglycidylether R
≥5 - ≤10
oxirane, mono
≥5 - ≤10 Skin Irrit. 2, H315

bis(isopropyl)naphthalene
≥5 - ≤10
C12-14 alcohols E 0,2%
4,4'-isopropylidenediphenol 1%


or ****ing pick one brand and folow Anti-Osmosis Epoxy Primer program

do you whant one cheap.

for new from factory boat with gloss gel coat.
wash boat with cheap liquid soap(without any wax)
hand sand paper with speed 3-4 m2 per minute.
wash with water
dry

Hempel's High Protect II 150 µm 2 layer

Hempel's Light Primer 150 µm 2 layer
or pick one company and folow program.
you,me all guys from this forum,all guys combined from internet ,your profesor of chemistry from colege, your paint guy from shipyard . you never know data from whorst chemistry guy working in this company. more data this guy forget what we ever know.

[s/v Jedi]

Originally Posted by more

no your problem is x3 maybe x4 Dunning-Kruger problem.
what **** base resin,1-6 coat you talking.
one cheap mix be componenta A

bisphenol A-(epichlorhydrin)
epoxy resin MW =< 700

≥25 - ≤50

titanium dioxide ≥10 - ≤25


formaldehyde, polymer with
(chloromethyl)oxirane and
phenol

≥10 - ≤25

1,6-hexanediol diglycidylether R
≥5 - ≤10
oxirane, mono
≥5 - ≤10 Skin Irrit. 2, H315

bis(isopropyl)naphthalene
≥5 - ≤10
C12-14 alcohols E 0,2%
4,4'-isopropylidenediphenol 1%


or ****ing pick one brand and folow Anti-Osmosis Epoxy Primer program

do you whant one cheap.

for new from factory boat with gloss gel coat.
wash boat with cheap liquid soap(without any wax)
hand sand paper with speed 3-4 m2 per minute.
wash with water
dry

Hempel's High Protect II 150 µm 2 layer

Hempel's Light Primer 150 µm 2 layer
or pick one company and folow program.
you,me all guys from this forum,all guys combined from internet ,your profesor of chemistry from colege, your paint guy from shipyard . you never know data from whorst chemistry guy working in this company. more data this guy forget what we ever know.

WTF is this rant?! The OP used West System products incl. their barrier coat additive which is a top of the line product. Hempel is fine but so is TotalProtect and Interprotect 2000 which is the first one to innovate into a specialized barrier coat product I think.

[more]

Originally Posted by s/v Jedi

WTF is this rant?! The OP used West System products incl. their barrier coat additive which is a top of the line product. Hempel is fine but so is TotalProtect and Interprotect 2000 which is the first one to innovate into a specialized barrier coat product I think.

West System has <25 employees no lab,no testing site. this is simply warehouse who import from china india epoxy https://gougeon.com i think total have 30 employers. pizza restourant close my house have more employment.
pick any brand with over 1000 employer and go with this program. normaly I and milions comercial cargo ship more trust heempels brand (only 6500 employer) ws garage mix west System.
But West System company marketing is best, product s solid 3 in scale 1-5, you have lot better epoxy in germany (germany home of epoxy resins) but you du not make anti-osmosis with epoxy resin, you must convert special epoxy resin in durable underwater primer ,
some people trust delivery guy without school for medical advice , i not.

Interprotect good trusted brand also huge company lot bigeer from hempel.

[team karst]

Test surface with pure water. If it beads up, there is still a contaminate issue. Wax, silicone or other. Silicone mold release can be a challenge to remove. Sanding only can imbed. I have had silicone containing caulk migrate several inches from original placement, causing severe paint issues.

[s/v Jedi]

Originally Posted by more

West System has <25 employees no lab,no testing site. this is simply warehouse who import from china india epoxy https://gougeon.com i think total have 30 employers. pizza restourant close my house have more employment.
pick any brand with over 1000 employer and go with this program. normaly I and milions comercial cargo ship more trust heempels brand (only 6500 employer) ws garage mix west System.
But West System company marketing is best, product s solid 3 in scale 1-5, you have lot better epoxy in germany (germany home of epoxy resins) but you du not make anti-osmosis with epoxy resin, you must convert special epoxy resin in durable underwater primer ,
some people trust delivery guy without school for medical advice , i not.

Interprotect good trusted brand also huge company lot bigeer from hempel.

A small company, but they wrote the book on wood-epoxy boat building while your buddies were chipping rust off steel bulk carriers thinking on how to protect it better.

[catsketcher]

I sometimes get fisheyes but I don't think it is amine blush - I get amine blush from when the temp goes cold after curing and then when I sand the paper all gums up - fish eyes I get from the slightly cheaper epoxy resin I tend to use.

If I was you I would not gently scuff the gelcoat - I would get right into it. 80 grit and get the surface totally matt, eat right into the gelcoat with your sanding tool - lots of dust required to ensure a good job. I just put clear epoxy straight over some filler I used 26 grit paper on (but it would have been better to go over the filler faired with 60 at the end).

I also don't get what the barrier coat additive will do. After three or so coats of epoxy there should be not water doing anything anyway. Then you hit the rudder with two coats of epoxy high build as well. I sure hope two coats over filler is okay because that is all my cat got and she is still all good after 23 years (plus lots of high build and then antifoul primer)

I check for amine blush by sanding gently with 120 grit. If it gums up then I know I have to get it off. I usually do this by gently scuffing with something rough - like 60 grit, this tends to remove the blush, then I can use 120 or so after.

I have tried water and scotchbrite pads but they don't work for me. I know it says to do so in the articles but the blush is a wax - and waxes are non polar and don't dissolve in water. I find it easier to abrade with old 60 grit.

PS - you are not dumb - things going wrong is boatbuilding

cheers

Phil

[JoeRobertJr]

Originally Posted by catsketcher

...If I was you I would not gently scuff the gelcoat - I would get right into it.

Thanks, Phil. I did a more aggressive sanding the 2nd time around, and no more fish eyes. I was too conservative the first time, influenced by the rudder manufacturer's instructions saying that a "light sanding" was all that should be needed.

Originally Posted by catsketcher

I also don't get what the barrier coat additive will do.

Per West Systems, "422 is used as a barrier coating additive to help prevent gelcoat blistering. 422 also increases the epoxy's abrasion resistance." I have no personal experience to weigh how much it actually helps.

Originally Posted by catsketcher

I have tried water and scotchbrite pads but they don't work for me. I know it says to do so in the articles but the blush is a wax - and waxes are non polar and don't dissolve in water. I find it easier to abrade with old 60 grit.

Yeah, I am found it difficult to tell whether the plain water, over even hot, soapy water got the blush all off. After doing the scrub and wash and dry, I followed up with a denatured alcohol wipe down as Jedi suggested. That seemed to do the job.

[s/v Jedi]

Originally Posted by JoeRobertJr

Thanks, Phil. I did a more aggressive sanding the 2nd time around, and no more fish eyes. I was too conservative the first time, influenced by the rudder manufacturer's instructions saying that a "light sanding" was all that should be needed.

Per West Systems, "422 is used as a barrier coating additive to help prevent gelcoat blistering. 422 also increases the epoxy's abrasion resistance." I have no personal experience to weigh how much it actually helps.

Yeah, I am found it difficult to tell whether the plain water, over even hot, soapy water got the blush all off. After doing the scrub and wash and dry, I followed up with a denatured alcohol wipe down as Jedi suggested. That seemed to do the job.

Yes, aggressive sanding is better.

Yes, the 422 additive works very well.

Yes, water easily removes amine blush, even with a regular sponge. If it seems it doesn’t, then there is something else contaminating the work, often silicone oil.

[catsketcher]

I have built 4 largish epoxy boats and made many thousands of mixes, but sometimes I get a waxey build up on the cured surface. It happens after high humidity and then cooling.

With the resins I use, washing with water does not get the build up off. It just makes the surface cleaner but still it still gums up paper when sanding the surface. Of course alcohol could work for me - it can dissolve both water based and oil based substances. I should try that next time. It could be because I don't use WEST 105 anymore - it is too expensive for me. But there may be some people who find the build up hard to remove. I do know some Chemistry (I teach Science) but don't know the process of how the blush occurs, I know that amines are used as curing agents but how the different types cause the blush is beyond me.

cheers

Phil

[Distant_Shaws]

In preprinting molded GRP use a kitchen scrubbing sponge and running fresh water until water beading stops.

Allo to dry then continue