painting bottom

[skully]

hi to all
I am in the process of painting the bottom of my 1984 com-pac 19. last year was my first year with the boat
and did not get a lot of preparation . this year I scraped some of the old paint and feathered the thick build up to the gel coat
with 80 grit with a hand orbital sander. My question is when I sanded the bare gel coat I back off with the pressure of the sander but it  still
scuffed it . what are  your thoughts ? is this a problem ?    could send pix  if that  would help with your opinion.

thanks

[Bob23]

Skully:
   Not a good idea to pierce the gelcoat. That's really the protective barrier for the rest of the glass, not that I'm a fiberglass expert. I would, at the least, apply some epoxy to the gelcoat before bottom painting. At the most, consider a barrier coating of some sort like Interprotect.
   80 grit will cut though some gelcoat fast...I speak from experience (or is that inexperience!)
   Best to you, Bob23

[Craig Weis]

Guys, guys, guys, What am I gonna do?

We have no 'GEL COAT' on Com-Pac hulls. The mold is waxed, then sprayed with the tinted epoxy resign, the very same that is used to saturate the glass cloth. [As we have no chop gun use in the construction of the hull.] and the pieces of glass cloth are hand laid into the mold and rolled flat to force the air out. Colors if opted for are mixed with the epoxy saturations.

Gel Coats like on Dune Buggy's, Surf Boards, Bass Boats are as follows.
Wax the mold.
Shoot the mold with epoxy [clear].
Shoot the desired color or metal flake over this clear.
Shoot this with black colored epoxy. At this point you created a Gel Coat.
Then usually shoot over the black layer with chopped fiberglass.
Roll out the air.
Three days later pop out the hull or body with air pressure.
Trim and build the thing you planned to build.
A cheap and crappy way to make a glass 'whatever'. In one of my lives I made Dune Buggy body's for Sand Pounders, Inc. in Palatine, Illinois for Rick Murphy.

By the way Com-Pac's have no core sandwitched between glass to hold water and rot. That is a good thing. Very strong.

So if one grinds through this Com-Pac hull to a point where you see the glass cloth. Stop and fill will with epoxy resign. If you have the tint to color [you won't] then you'll not need to paint the patch. If you grind through the Gel Coat, again patch, paint and be happy you stopped prior to making a hole. skip.

[Craig Weis]

To answer the question Skully, a little 'scuff' on the fiberglass resign [not gel coat] is just fine as this provides more surface area and a bit more holding power for the bottom paint. The bottom paint will glide over the 'scuff' and lay down smooth, you'll not see the sand paper marks.

Not that you will, but if you did see glass woven fiber that would mean that the resign has been sanded away too much. At this point mix up some 2~part resgin and smooth it on. When cured sand and paint like the rest of the boat. No big deal. skip.

[Paul]

Skip and all:

With all due respect, the hull building process described above is a bit inaccurate.  Most of the fiberglass hulls constructed in the last 40 years have used polyester resin, not epoxy.  This includes Com-Pac yachts.  The quality of lay up may differ significantly between manufacturers.  This is true.  Usually, a quality manufacturer like Hutchins, will have a successful lay up.

Unlike "finishes" on cars, furniture, and houses the "finish" on a fiberglass boat is actually the "beginning."  So, the manufacturing procedure you describe is pretty close.  Waxed mold is sprayed with a pigmented gelcoat (colored polyester resin), then layers of fiberglass are applied with clear resin.

Epoxy is a wonderful product to use.  I wish all boats were built with epoxy.  However, epoxy is prohibitively expensive.  Like most things in life, building boats is a compromise.  Polyester resin is good enough to build boats at a reasonable cost.

As for the scuffs created by sanding the gelcoat a little, it's likely going to be OK.  Gelcoat on the bottoms of these boats is in the neighborhood of 1/8 to 3/16 inch thick in most areas.  As long as the gelcoat remains and no fibers are showing, things are likely OK.  One may be concerned about blisters, but there are several factors that influence this phenomena.  If, after scraping and sanding, you noticed small bumps on the hull, then you may want to investigate.  But, if there were none, and you keep the boat relatively dry both inside and out (stored on a trailer part of the year), then don't worry about it.  Just paint away.

$0.02

[mgoller]

I just did the bottom of my 84 CP19 this spring.  Its been four years.  I bought a flexible abrasive pad (the kind used for rust removal).  It is a fiber pad 5" diameter.  Its maybe a 150 grit at most.
Took about 30 minutes to strip the dead algae and loose ablative coating for new paint.  Then I used a 9" roller and rolled on the new black copper ablative paint.  Used a brush to get at some places under the trailer rollers.  Took about an hour and a half.

Well....you already were pretty rough on the gelcoat so what's done is done.  Next time be more gentle and just prep the old ablative paint.
If its adhered well you are just trying to prep the old paint for a new coat.
After you bottom paint just move on to other projects and don't worry.  Like someone else here said the gelcoat is pretty thick so you didn't hurt anything.
The only boats that can get away with a shiny waxed bottom are those that get pulled out after sailing.
Zebra mussels are pretty pervasive in fresh water now so even fresh water boats are vulnerable.
If you want a super smooth bottom.  Put one new coat on and buff with a mild abrasive pad and then apply a second coat.
One gallon of paint did my boat twice.  That works out to $100 for 8 years protection.

[Bob Condon]

I also have a 1973 Cape Dory (28') and when I purchased her, she had 14 (yes 14) coats of paint on her. The finish was now rough and affecting her performance. I tried using Green strippers and gentle products but to no avail. I was getting about 1/2 a coat off per 4 hours of work.

I also tried some of the heavy duty stripper and the problem I had was that the chemicals were eating through rubber gloves (and probably poisoning me).

The next event was a good shop vac attached to a belt sander with 28 grit paper. The story is not as scarey because each layer had a color change and the final layer was RED
so I put on a tyvek suit, put blue tarp under the boat and dampened the tarp with water
(Damp, not puddled) and then using the belt sander and vacuum to collect almost everything, went to town. It took 6 hours of work (The hull to keel area is a killer on the back) but got almost everything to the red layer and then used a green stripper to clean up the rest. 2 places I did hit the gel coat; I purchased a gelCoat repair kit at West Marine and put a couple coats on to repair that.

I now ONLY use paints where the base ablate off with the copper (Interlux Micron Extra works fine in Northern waters- look at Practical Sailor reports in the spring for advise) . I place a good coat over the entire bottom each year and then the rest of the paint hits leading edges and rudder with extra coats.

When I apply the paint, I use a roller with a 3/8" nap (smooth surfaces) and then a cheap $3 brush as wide as you can get to remove the roller bumpiness going from bow to stern (never bottom to top because those little ridges affect performance a lot (and not I do not race).

I have done this for 5 years on the Cape Dory and need to bottom paint and clean up my Compac 19... wish I had an extra set of short stands to roll the Compac off with 8-( because that makes life a whole lot easier.

===
Other projects are built a 150% genoa and now making a new mainsail from kits...

If you have any questions, let me know...   

I weighed the amount of paint and it exceeded 300 pounds.

[Gil Weiss]

Gel coat refers to a very thin layer of special resin that is sprayed into the mold which has been treated with a release agent. It provides the outer gloss layer. Colorant may be mixed in and/or colored resin may follow the gel coat. In any case the actual gel coat is very thin, maybe .030 of an inch. Behind it layers of resin and fiber glass cloth are applied. The term hand laid up glass refers to manually layering the cloth and the sprayed on coats of resin. Some boat builders use a much cheaper and weaker method by spraying in a mixture of chopped up glass cloth and resin using a large spraying apparatus. Much weaker system. Epoxy resin is flexible and forms a much stronger composite material when combined with the glass cloth compred to cheaper polyester resins. Polyester will fracture and/or much easier.

ComPac sailboat hulls are heavier than their competitors, like Precision, as they use more layers of material and resin making them much stronger. I have heard they build using epoxy, but I can't confirm that.

Using a grinder and/or high grit sanding material will go through the thin gel coat layer. What is needed to create a new protective barrier to keep moister out is to apply two coats of a good barrier coat prior to two coats of bottom paint. In reality, with few exceptions you should have a new hull bottom barrier coated and bottom painted to prevent blisters.

In the last few years carbon fiber has come along as a lighter and stronger alternative to glass cloth. CF is also layered with resins using heat and vacuum to make very strong composite products. It is light enough for aircraft fuselages and related flight parts. It is also being used to make sailboat masts, spars and other parts. CF is not as easy to use for the home builder as FG. CF, similar to glass cloth, must not be breathed in in when cutting or sanding it. Both are worse than asbestos

I have learned this from building boats and other fiberglass structures  and having some work experience with commercial aircraft manufacturers who use CF.

MY TWO CENTS, Gil

[Paul]

Not to take this too far off topic, but I did hear some information on "Science Friday" on NPR a couple of weeks ago about health issues regarding carbon fiber.  It was said that the fine dust from sanding carbon fiber lodges in the lungs not unlike asbestos.  Of course, any sanding should be done while wearing the appropriate safety equipment.

RE:  Hulls made from Epoxy resin.  My 1989 is made from polyester resin, like 99% of most plastic boats.  Maybe Com-Pac has made some from epoxy, but I'd think they were a lot more expensive.

If any are interested in epoxy, please check out the West System website at http://www.westsystem.com/index.htm

They have wonderful information on their site backed up by the science to support it.  I have several of their booklets on using epoxy plus their text book on wooden boats and epoxy.  Fascinating reading.  Another place I like to get valid information is Classic Plastic Forum

Great information out there.  Hope this helps.

[mrb]

Hello and good sailing to all,
I offer some information from a 1999 "Com-Pac Yacht Owners Handbook" by Hutchinsons co. inc. concerning construction materials used and their recommendation concerning blister prevention.  This info may not pertain to newer or older boats and I will not copy word for word as I don't want to plagiarize their booklet.

Concerning hull construction they state that they use at least one layer of 24 oz. woven roving. May be more but no less as I read it.  The wet out agent appearers to be polyester which they say water vapor can migrate through which causes blisters.

As to gelcoat they say they use a type known as NGP (neo-pentyl glycol) which is harder and brighter and lab. proved to resist ultraviolet light, corrosion and blistering better than other gelcoats.

For protection from blisters on boats that are wet moored they recommend the bottom be sealed with  epoxy coating followed by anti -fouling paint kept in good repair.  while not being 100% guaranteed blister protection these steps will go a long way to protecting the bottom from blisters.

If any one has a newer or older hand book it would be interesting to see what their's have to say concerning these subjects.

Hope this may be of use to some one out there..
Melvin

[Bob Condon]

I will look up in my 1983 manual later

Thanks for the information

Bob Condon

[Paul]

Melvin,

Thanks for posting.  I did not know what type of gelcoat they use.  Sounds like a good bet it's high quality.  Photos of new boats show well.  I didn't find info in my '89 manual, so this might be a newer technology than 1989.

[Potcake boy]

Skully,
I too am presently involved in the ardous task of bottom paint removal - which is more fun than fast food, but not as fattening ( taste is about the same).

There is traditional scraping - but I think that is reserved for adding romance to old time sailing stories.

There is sanding - slow but sure.

There is the "easy as pie and a little messier" miracle  remover in a can.

Industrial grade sandblasting.

All of which will do the job and make you take your boat to the boat yard for the next bottom job.

I have tried all of the above and none brought the kind of smile your' supposed to get when you do boat work.

What I have found that works best and most expedient over all for the ablative paint on my boat is a two step approach. That's one step forward and two back. Just kidding of course.

First I use a pressure washer (mine is a household 2500 psi) which removes the bulk of the paint and contains the otherwise airborne residue. It is also easier to take on a really hot day and you can get to more area without being on your back under the boat. Then the palm sander with 80 grit or sand blaster finishes up with relative ease. The sandblaster is easier to use but requires more equipment (or rent one)and care not to exceed the paint or primer coat.

I would like to pose a challenge - the first to finish is the looser - and has to help the other to finish.

At least when your' done it should be a few years before you have to repeat the tedium. If you time it right you may be be able to avoid it all together by moving up to a bigger boat.

May your sore back be soothed by the motion of the ocean,

Ron

[Craig Weis]

Heck, factory paint removal...nothing to it.

A dust mask, wrap-a-round safety glasses, a ball cap, sweat shirt, an old orbital sander, a can of 3-M spray adhesive, a pair of scissors, a roll of stick-on 800 grit paper, a qt of solvent, a wiping rag, a floor jack, an adjustable wrench, a bit of line, long extention cord, something to sit on, a Milwaukee SawsAll, two qts of bottom paint, a paint tray, a roller, and a garbage bag.

In a few days the ablative paint will be sanded smooth, thin and in some places sanded off the hull to the white glass of the hull.

Ok the scissors are to trim the oversized round stick-on paper to the bottom of the sander after I spray glue the paper on.

The SawsAll is to cut the keel bunks off to get them out of the way.

The floor jack and wrench is to lower all the bunk boards to get them out of the way.

The line is tie the hull from the winches to the welded rings on the trailer in case the wind wants to blow the boat off the trailer.
And it makes the wife feel better thinking her hubby will not be pan-caked under the boat.
 
I posted pictures of the boat sitting on her keel atop the trailer rollers on the Frappr link at the bottom of the home CPYOA page.

I found two qts of blue bottom paint 1/2 price at the boatyard. I took them over to Ace and had them "shaken, not stirred". I applied with a 3 inch roller.

Additionally I glued on a full length 6mm KEEL-BOOT that I made from scrap aluminum from Palmer Johnson Yachts where I provide 'involuntary labor'.
Ain't boating fun? skip.

[Potcake boy]

Skip,
My boat has a light gray layer under the ablative paint that I'm not certain if it is a barrier coat or just primer. My boat is a 2001 lightly used (seems it sat on the trailer most of it's life)so the paint I have now may be factory original. Do you know if it was customary for the factory to do a bottom barrier when they did the paint?
Thanx,
Ron