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Author Topic:   Proper gelcoat repairs vs. West System and Paint in and out.
thistle posted 06-28-2002 04:21 AM ET (US)   Profile for thistle   Send Email to thistle  
There isn't much I don't know about glasswork, gelcoat, epoxy and the like. However, my only experience is with racing sailboats.

I am looking at a 17 footer(I first thought it was a Montauk) with crazing and bb size checks in the blue interior gelcoat. The EXterior is an easy fix. I'll grind a few small spots, repair glass, gelcoat and either polish it all out, or wet sand for awlgrip.

The interior is a mess. I have inspected the hull, poked, prodded and thumped my way around it, in and out. No discernable delamination and no structural issues. Just failure to clean it up and keep it covered while in storage.

I will have to replace/rebuild the mahogany console, seat and likely add a mahogany or teak rear grating inside the transom. I intend to remove the rails and reinforce their anchors. I have a diagram of the wood components inside the hull should any repairs become necessary.

What is the best way to prep the textured bilge surface and interior for paint. Or, do you all advise against paint and prefer repaired and buffed gelcoat?

Either way, I don't want to find out after great effort and expense that I trapped moisture or opened the gelcoat to capillary action.

What are my options? Thank you in advance.


Cpt Quint posted 06-28-2002 09:42 AM ET (US)     Profile for Cpt Quint  Send Email to Cpt Quint     
your asking a group of whaler junky enthusiasts, however you sound like a pro at these type repairs by your questions.

You will get opinions on either side of this issue with this bunch. You can scroll through old posts and see all the debate.

My interior blue nonskid needed help and I chose awlgrip (they have the factory blue special order) because its thin enough not to build up and loose the texture of the deck.

As you probably know, you can drop a hammer on the stuff and it wont scuff.

thistle posted 06-28-2002 12:05 PM ET (US)     Profile for thistle  Send Email to thistle     
Cpt. Quint: Thank you.

When prepping the non skid - you can't sand it. How do you get an even tooth on it so that the paint will bond? Also, having used awl grip, they recommend the awlgrip primer which is light grey. Did you use that or just spray directly on the surface?


DIVE 1 posted 06-28-2002 08:39 PM ET (US)     Profile for DIVE 1    
To rough up the non-skid areas try using scotchbrite pads. Red or brown should do the trick.
John W posted 07-01-2002 10:51 AM ET (US)     Profile for John W  Send Email to John W     
As you probably know, fixing lots of gelcoat chips & crazing using new gelcoat is a ton of work, whereas fairing with 2 part West fairing compound is quite easy. We went the epoxy & paint route on my father's '68 whaler 16. We used Sterling brand paint using the roll & tip method which I highly reccommend if you plan on using a roller & brush. It looked as good as Awlgrip and was much easier to apply. If you have experience & equipment to spray Awlgrip, go for it...but if not I highly reccommend Sterling polyurethane paint.
John W posted 07-01-2002 10:57 AM ET (US)     Profile for John W  Send Email to John W     
One more already mentioned use scotchbrite pads for the nonskid areas. Using Sterling and also Interthane painting various boats we've used the primers on some jobs & not on others with no difference in paint adhesion or performance. We follow the paint's prep directions to the letter, including all the overpriced solvents. Sterling has a light blue that we used that was very close to the original gelcoat color.
Highwater posted 07-01-2002 11:44 AM ET (US)     Profile for Highwater    
To all of you--I recently bought a 15' that has a lot of crazing, or what some people call "spider cracks," in the interior. Lots of cracks. Everywhere. I was under the assumption that I would need to media blast it (like sand blasting it but with baking soda) before I could apply gel coat or paint. Is that not correct? May I send you a digital photograph? Thanks! David.
thistle posted 07-02-2002 02:47 AM ET (US)     Profile for thistle  Send Email to thistle     

I have some experience with sand blasting using some pretty fine abrasive(1200-2000 aluminum oxide). I've not heard of using baking soda but that doesn't mean much. The difficulty is that you would probably need a large pressure pot to do it and also a large capacity compressor. You can't just stand back and spray with that size abrasive. It will do nothing unless you are within 6" or so and at 6", you will be etching an area about the size of a dime.
My point: very tedious, uneven, blotchy looking substrate. I would be happy to give you an opinion on your photos, even if it's wrong:-)


thistle posted 07-02-2002 03:01 AM ET (US)     Profile for thistle  Send Email to thistle     
John W:

Can you tell me more about the Sterling polyurethane. Specifically, bonding characteristics and impact/abrasion resistance(I'm thinking of this for the bilges and non-skid not the bottom).

Re:spraying; I prep my boats and send them to someone qualified to spray. I sprayed Imron, a linear polyurethane - Once.

Also, RE: West System and fairing fillers. Please be aware that most fairing fillers that are additives to epoxies are not suited for direct sunlight. Specifically but not limited to MicroLite 410 by Gougeon Bros., MicroBalloons, and even coloidal silica(cabosil)when added in high volumn. They expand when used under any color other than bright white. FYI.

John W posted 07-02-2002 10:09 AM ET (US)     Profile for John W  Send Email to John W     
Thistle, in regard to fairing fillers, I don't recall the particular fillers we used, but they were West System brand which we mixed per instructions. Actually it may have been labelled as some type of 2 part putty as opposed to a filler, as this was not a poweder that we added to epoxy I guess I misspoke when I said "filler". (I've used those type of epoxy filler additives in rebuilding strngers, making fillets, etc on other projects). In any case we had no problems with the putty expanding under the blue paint, the boat has had several years in the hot Florida sun with no problems.

If you do a search on this board for "Sterling" you'll probably find some lengthy threads I've written on using this brand paint with the "roll & tip" method. I've done two boats with Sterling, one with Interlux Interthane, all using a roller & brush. Sterling was much easier to use than Interthane. The paint is as abraision resistant as any 2 part polyurethane paint I've seen, we used this paint to paint the hull & topsides of a 19 Mako and the 16 Whaler I mentioned...the latter was done about 3 years ago, the former was done 8 or 9 years ago. I don't own either boat anymore but I still see both of them periodically and the paint has had no adhesion problems & still looks like it did when we painted it. We used Interlux nonskid grit in the final coat of paint on the nonskid sections.

IMO sprayed Awlgrip's only advantage over Sterling or other 2 partpolyurethanes is in the slightly higher gloss & deeper shine that many feel it has. (Having said that, the whaler we did loked as good as any Awlgrip job I've seen on a small boat). I've seen more paint adhesion problems on professionally sprayed Awlgrip jobs than I have on roll & tip jobs using other brands of 2 part polyurethane paint (perhaps due to Awlgrip being more sensitive to painting conditions & prep than other brands, but I'm just guessing). At any rate, I feel confident that adhesion & abraision would not be problems for you if you chose to use Sterling. The finish is hard, shiny & abraision resistant just like sprayed Awlgrip or Imron.

If you have someone who will spray Awgrip at a reasonable price, I'd go that route...using two part polyurethane paints is a messy, smelly job that I'd rather avoid. But if you do want to do it yourself using a roller & brush, I'd highly reccommend Sterling.

Whaler Proud posted 07-02-2002 10:43 AM ET (US)     Profile for Whaler Proud  Send Email to Whaler Proud     
If I could jump in on the soda blasting. I grew up in the abrasive cleaning industry and am familiar with all types of abrasive.

To soda blast the interior of the hull you will need a small abrasive pressure pot, a 100 cfm compressor, hose and nozzle (make sure you use an approved dust mask and eye protection). With the proper nozzle and hose, you should be able to produce a 6 to 8 inch diameter blasting circle. Keep the spray at least 6 inches away from the surface and use a circular motion as you blast. Depending on how well the existing surface was applied, you will need to adjust the nozzle pressure accordingly. Do not stay in one area too long or you will create ripples in the fiberglass.

Probably the best way to soda blast is to take the boat to a sandblast shop that does this kind of blasting. Soda is used for all types of materials where you need to leave a smooth surface and minimize damage. You can probably have this done by a professional for what it would cost to rent the equipment and buy the abrasive. Even if it is more, you are saving a whole lot of time in sanding and will complete you project faster.

Highwater posted 07-02-2002 12:13 PM ET (US)     Profile for Highwater    
Whaler Proud--I'm going to email you pictures of my 15' "fixer upper." Please tell me if you think I should soda blast it. Thanks! David
JDH posted 07-02-2002 12:19 PM ET (US)     Profile for JDH  Send Email to JDH     
John W.

Do you have any experience spraying Sterling? I have a decent paint setup, but want to avoid the really nasty (health wise) 2 part paints.

I am currently specing out a console that will be fabbed out of AL, and when it is done and rigged, I will pull it and paint it off white. After that I will likely paint the inside and outside of my 62 classic. Will likely go with an off white, but haven't decided yet.



John W posted 07-02-2002 01:28 PM ET (US)     Profile for John W  Send Email to John W     
JDH, I've never sprayed Sterling or anything else but I know that yacht yards do it all the time. But I don't think Sterling is any less toxic than Awlgrip or any other two part paint, so I don't think you'll be accomplishing anything health-wise. The reason I like Sterling is that it's easier than others to apply with a roller...othrwise I don't think it's any different than other 2 part polyurethanes.

Maybe I'm being stupid, but with full clothing, goggles & a decent gas mask, I don't think you'd be risking your health. At least I hope not, since my father & I have done it several times.

thistle posted 07-02-2002 02:18 PM ET (US)     Profile for thistle  Send Email to thistle     

Thanks for the pictures.

Disclaimer: I do not yet own a BW. I have never worked on a BW. I am not an
engineer but have a good basis for understanding the structure of the BW. I
do have experience with gelcoat and GRP resins and the like, and... foam and
wood cored substrates. This qualifies me to give you only an overview. Read
as: Don't take my word for it.

In image #1; the longitudinal cracks are stress cracks. The longitudinal
cracks are indicative of structural movement of a hull component. That is to
say a stringer, bulkhead or other stiffener comes to rest or intersects, at
or near the site of the damage. This means there is movement between
structures. Since the hull is foam cored, the stiffeners, stringers,
bulkheads are pricipally built into the interior and exterior hulls. So in
effect, what you have is a sort of, boat shaped stress skin panel.

Unless delamination is apparent in the region of these stress cracks, the
liklihood of solving this problem is slim, short of rebuilding the entire
boat. These components, after your cosmetic repairs, will continue to move
absent significant reinforcement but should not get too much larger, if at
all. Even if you were able to grind and lay up more glass, all that the
newly reinforced area would do is transfer the present stresses to new

If you find delamination, it can be repaired(this subject will have to be a
different thread and is probably better discussed by an experienced BW Forum
person). I am speaking of delamination of the glass from the foam core. I am
not talking about delamination of the glass substrate itself. I suspect that
the latter is not likely in a Whaler. Some of the long time Whaler
afficianados could better respond to that issue.

Finally, in any boat of this age, stress cracks are common and do not
necessarilly cannote a defect anymore than wrinkles are a defect on old
people. Look at nearly any used boat around; cockpits, coamings and where
ever different planes meet and you will find similar occurences. Some better
and some worse contributed to by very good to poor maintenance but mostly
due to use.

The Fix:

Wipe the surface down liberally to remove the years of waxes and oils that
have come in contact with the affected surfaces. Wet sand the affected area
to at least 320# but no more that 400#. After 400# you begin polishing.
Paint needs a "tooth" to bond to. Rinse the wet sanded surface well but DO
NOT POWER WASH. Leave the boat to THOROUGHLY DRY OUT(this may even include a
dehumidifier in the garage at night(s) after sitting in the sun all day(s)).

Now, from here everyone has their own ideas and this is likely to be were
differences of opinion appear. I would wipe the entire area down with an
aromatic of your choice. I would purchase the best epoxy that you can find,
West System comes to mind but there are others out there. Using the epoxy
straight, or with very little coloidal silica filler, begin to work epoxy in
to the fissures. Be sure to "scree" in several directions to make sure the
crack is filled. Someone in another post suggested using an old credit card
which would be good. Otherwise, any automotive paint store can sell you a
few $0.59 applicators. (BTW: Find a good shop, you'll be spending some time
and alot of money there. Get to know them by name they can save you both.)
Be careful to use only as much epoxy as you need to fill the
cracks/fissures. Epoxy is tenacious and hard to sand. So don't think you can
liberally squeegee(sp?) it on and then sand it smooth. You probably will not
need more than 1-2 coats of epoxy. 1 may just do it. If you plan to search
for perfection, buy a boat in better condition. Good enough should be just
that. Finish sand to 320# for paint. Do not overly thicken the epoxy, it
will not flow into the cracks well and it will expand under the heat of the

It was suggest to me that 3M Scotchbrite pads be used on the non-slip areas
of the bilge. Be sure you have really cleaned the non-skid with solvent
also. Another addition and/or alternative, is a brass wire brush. There is
nothing worse than finding your $90 quart of paint avoiding poorly prepped
substrate. As you have likely heard, 95% of it is preparation. Don't wast
your time trying to repair cracks in the non-skid. I would clean it well and
allown the paint to fill the checks. Plus a coat or two of a good durable
paint will still allow the non-skin to remain just that.

From here follow the instructions of your paint manufacturer, they will have
a Tech Support number and all sorts of application info. Also, someone
pointed out in an earlier post, you are doing this only once. Do it right
the first time, buy the best paints and overpriced solvents that are
recommended and don't mess with any of them unless you have experience in
that area. These things will kill you, slowly. If you do all the prep work,
you can often find an Earl Schieb or similar painter to spray the thing for
$100 or so (labor only)

Again, referring back to Image #1; the finer checking is gelcoat failure.
This again is typical of a boat of this age and is due mostly to UV
exposure. Handle these also in a cosmetic manner unless you find that there
is moisture in them or you uncover voids or blisters.

Referring to Images #3 and #5; the heavy dark cracks should be ground out
with either a gouge or a small die grinder. Grind down until it is solid
maybe 1/8" deep and between 1/4"-1/2" wide. Feather the grind out to 60
degrees or more. Fill 90% of the new ground out crack with either 100% epoxy
with chopped glass fibre or polyester resin with the same. Finish in the
same manner described above starting with sand and fill, again using as
little filler as possible to keep it from running. On vertical surfaces, it
sometimes helps to apply a coat of PVA when there is a strong possibility
that the resin will run. When the resin cures it is easy to lift off the
runs and then sand. Although, paste wax performs the same function, don't
use it. We are trying to avoid waxes as best we can.

Referring to Image #3; atop the radius of the non-skid you can see a
previous repair. That is a bad repair. It is a coverup not a repair.

Good luck. It's not too hard. Just time consuming.


Given the detail and length of this, I am going to paste it into the forum
so that others have the benefit(or liability) of reading it. If you could
post the images to the cetacea pages with a link, so that people can refer to
my comments and the images, that would be great!


thistle posted 07-02-2002 02:28 PM ET (US)     Profile for thistle  Send Email to thistle     
Whaler Proud:

On the soda blasting issue: does this method just etch the surface or does it pit the gel coat. You know.. the path of least resistance thing. Based upon your description it sounds like it may be the perfect prep tool, at minumum for the non skid? Advise please.


Whaler Proud posted 07-02-2002 02:35 PM ET (US)     Profile for Whaler Proud  Send Email to Whaler Proud     

The soda blasting (performed properly and on a decent surface) will leave the gelcoat smooth. Removal of the gelcoat will require more blasting but will leave the fiberglass smooth.

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