posted 11-21-2002 05:43 PM ET (US)            

I used Spectrumcolor's www.spectrumcolor.com gel coat and did not have any trouble with it curing. In Spectrm's information sheet on using their gel coat they state the following: "Gel Coat will not fully cure without adding a surfacing agent (1/2 and ounce per pint) or overspraying with PVA before gel coat reaches its gel stage (approximately 5-10 min)."

I used the surfacing agent they supplied which is made by Fiberlay. The name of the agent is Surface Seal.

Hope this helps.

posted 11-21-2002 06:28 PM ET (US)            

What are you redoing and what is the purpose for the boat? You need to ask yourself that to see how much $ you want to put into it.

posted 11-22-2002 12:15 AM ET (US)            

As others mention above, you must provide some air seal, either with wax additives, PVA, or mechanical covering.

posted 11-22-2002 10:10 AM ET (US)            

Mini-Craft of Florida, 800-282-8244.

posted 11-22-2002 10:18 AM ET (US)            

Depending one where you purchase your Gel-Coat, it is NOT more expensive than Awl-Grip or Imron. The last boat I did, A Mako 19, a Gel Coat jobwas 1/8 the price of an Awl-Grip job (doing it myself)

Granted we used plain white gel-coat.

The prep work was easy.

1. Sand to original gel-coat (if previously painted), fill cracks dings etc with a polyester based filler or resin.(some say you can use Epoxy, just get rid of the ameine(SP??) blush.

2. Sand entire hull with 80 grit sand paper. Make sure you keep the sander flat against hull.

3. Wash hull with Acetone Tape boat. Trailer etc

4. Figure your working time with the gel-coat. Mix enough Acetone into the gel-coat so it will pass through your sprayer. I add the following way in a 2 quart mixing pail:

1: Add Gel-Coat
2: Add reqd' amt of MEKP
3: Thin with Acetone
4: Mix Thoroughly

Mix a small batch and time how long it takes to kick. REMEMBER this time. Temps Humidity, etc change things.

5. Mix a batch and begin spraying/rolling. Stop 1 min before the kick time and run to a waiting batch of ACETONE. Empty sprayer and douse everything with acetone, run acetone through sprayer assuring nothing will cure in sprayer.(VERY IMPORTANT)

6. While cleaning have someone mix another batch and begin spraying / rolling again.

7. Do this process until the boat is cover to 22mils of Gel. Took 3 coats on a Mako 19 using 1 gallon of gel coat.

Now the hard part:

The boat will now look terrible depending on your spraying skills, all orange peel, some runs etc. I am not a skilled sprayer so your skills may be better. Do not fret if it looks bad. The beautifying stage with gel-coat comes last. (for me at least)

1. For white/light color boats: rum Dye-Kem over the entire hull. Dye-Kem is a blue dye used when cutting sheet metals.

2. Begin sanding, making sure you keep the sander flat against the hull. Begin with a grit you feel comfortable with, do not cut too much. Some start with 120 other 100 and some 80 grit.

3. Stop and move to next section when the blue dye disappears. The blue dye shows the peaks and valleys so when it is all white you know to stop.

4. Switch grits up to desired finish, some 1000 others 1500 2000 etc.

5. Compound entire hull and wax.

Thinking about it,Gel coat is more expensive for a professional job as it is labor intensive. Material wise I have found it to be much less expensive.

1. Gal of Gel-coat w/ MEKP plus wax additive $50.00 From LBI Fiberglass

2. Acetone LOTS OF IT!!! $30-50

I am sure there are other ways of doing this process. This is the way that works for me. I have yet to roll gel-coat but plan on doing rolling the next boat.

Good Luck

I was unable to spell check sorry for any issues.

posted 11-22-2002 10:51 AM ET (US)            

I have a "thing" (sorry I do not know what it is called) that you push into the gel coat. This "thing" has different measurements on it. When you push it into the gel-coat you can see the measurements in mils. Similar function as a spark plug gap tool, but much different looking tool.

Very hard to explain this tool, sorry. It cost about $0.35 at a fiberglass store.

In the test stage, I spray a coat on a board and measure the thickness of the coat. I can then determaine approx# of coats to reach 22mils.

I am unable to test the hull of the boat as the gel-coat hardens between coats.

It is also important to remember to "hot" coat (apply next coat when the previous is tacky) the gel-coat between coats.

For me, 3 coats is the ussually the magic #.

I will search the web to see if I can find a pic of the tool.

posted 11-22-2002 10:56 AM ET (US)            

Scroll down and it is the last item. Looks like I was WAY off on the price, sorry. it is $3.56. They through one in for free when I purchased my supplies last time.

http://www.lbifiberglass.com/lbiproducts/tools.html#anchor611318

posted 11-22-2002 01:45 PM ET (US)            

Time is most important for your spray gun. If the Gel-Coat Kicks (hardens) in the gun, it is game over for the gun.

Kick time is specific to each gel-coat and every temp/ humidity condition. This is why I stress a test batch to figure the excact time.

I have never done gel-coating below, maybe, 68 F at the lowest.

To the best of my recollection, when spraying the last job, the Mako 19, I had 7 minutes and 30 seconds of working time. It was a low humidity day and the temp was roughly 70-75 F.

At 7 min 30 secs I stopped, emptied out the remainder of the gun in a pail and ran the acetone through the gun.

I would fill the spray gun roughly 3/4 full of the Gel-coat, MEKP, and Acetone mixture. This amount would do 1/4 of the boat. (I had someone mix this concoction seperatly for me as I was cleaning the gun)

Spraying 1/4 of the boat at a time I worked my way around the boat three times.

That was it.

I let it sit overnight and began sanding the next day. I am pretty sure I could have sanded that day but I let it sit.

One other note on this job: after it was done I had to thouroughly wash the boat with Acetone before sanding to remove the excess wax that came to the surface. This was the only time I had to do this, rather odd, just keep this in mind in case you begin to sand the boat and your sandpaper is getting clogged frequently wash it with Acetone. It took care of the issue very easily. Unfortunatly, I had to re-apply the dye-kem because I put the dye-kem on and then realized the wax issue so I washed with acetone which took the dye-kem off.

One other note is the more people helping you the better. I did this project with 3 people. All I did was take care of the spray gun, a friend did the mixing, and a third to help out when needed.

As for "kicking" I have found that with the gel-coat, I use, it goes on wet, then after time becones tacky, but not for long, and then kicks rock hard.

"Kicking", to cure, is when it starts to cure.

posted 11-22-2002 02:06 PM ET (US)            

I have never gel-coated the inside of a boat. Not saying I wouldn't, I actually am plainning on undertaking it to two boats this spring, but I have yet to undertake that project.

Curves and corners makes fairing much more difficult. Flat sides of a boat hull are much easier.

posted 11-22-2002 02:41 PM ET (US)            

I did state it starts to kick within 8 minutes and does not stay tacky for long. Technially, This is wrong, I am sorry for the confusion. The gel-coat begins to kick in 8 mins and is pretty hard by 10 but chemically stays tacky and can be hot coated for 1-2 hours.

When a gel-coat is tacky it is different than paint. If you have worked with polyester resins, gel coat is the same. When tacky it is very dense and if touched it is a little "sticky" but would not rub off on your finger.

After 8-10 minutes it will probably have Kicked/cured enough to destroy a spray gun. After 10mins to 2 hrs you can still re-apply over a previously applied coating.

After 2 hours? No problem, just wash the area to be gel-coated with Styrene to liquify the wax on the surface of the previously applied coating and off to the gel-coating races you go!

Shoctor-

What ever works for you, I get close to the previously applied area but if you overlap you will have an area with perhaps 7x the thickness as the rest of the boat. Come close but try to keep things even.

posted 11-22-2002 03:25 PM ET (US)            

There is no way I would try to gelcoat a boat over 30 ft but for smaller boat I like the gel-coat. I think a gel-coat job has a factory new finish.

posted 11-23-2002 12:56 PM ET (US)            

I wear an inexpensive disposable filter mask.

posted 11-24-2002 02:45 AM ET (US)            

Lots of very good and very useful information - thanks! I have a 15' hull to shoot next spring (this winter if I can line up a heated work space) and this information will definitely help.

A few questions if you don't mind.

What type of gun did you use, who's the manufacturer and how well did it perform? From your description it sounds like you were using a cup gun, but that's just a guess. After shooting a few hulls, do you have any recommendations on guns. ES Mfg, Glas-Craft and BODI are just a few of the cup gun builders out there - any of them or others that make a better product? (BODI also makes the disposable Preval sprayer for small areas referenced by Taylor and Tom W. Clark in their excellent piece on fiberglass
repair.)

What size compressor are you using to push the gun? Is it adequate?

I'm assuming you stripped off all hardware and rubrail before shooting (duh?). What's your recommendation on how to deal with the brass through-hull fittings on a Whaler? Remove and replace even if they are in good shape? Taping wouldn't seem to be an effective option on a gelcoat shoot - but I don't know.

Thanks again. Your heads-up on the wax removing acetone wash prior to sanding and the Dye-Kem tip are just a couple of examples of why this is such a valuable site. sammy

posted 11-24-2002 10:59 AM ET (US)            

Two of the top producers of air compressors and spray equipment are:

www.binks.com and
www.devilbiss.com

If you go to these two sites you will find a lot of information pertaining to their products and how to use them

When selecting a conventional (as opposed to airles) spray gun you may use an internal-mix-nozzle or an external-mix-nozzle. Both may be used with a cup. An internal mix nozzle will usually require less air than a external mix nozzle. However, an external mix nozzle will produce a finer finish than the external nozzle. These air nozzles will require a certain amount of air to operate efficiently at a given air pressure.

In addition to the air nozzles, you will have a fluid nozzle. Fluid nozzles have orfices that regulate how much fluid may be applied at given time. You need to determine what size fluide nozzle is appropriate for the material being used, and then choose an air nozzle that will properly atomize the amount of fluid you are trying to apply.

Once you have determined the above you should then choose a compressor that will deliver enough cubic feet of air, and air pressure, to accomplish what you want to do. Most people, when choosing a compressor, want to know how much air pressure will the compressor put out. A better question is, will this compressor supply an adequate amount of air ( C.F.M.), at the pressures I need to perform the task.

Hope this helps.

posted 11-24-2002 12:10 PM ET (US)            

The spray gun I used was from Crafstman, built for Crasftman by devilbiss. It is run of the mill, the gel-coat was put in the silver part of the gun that resides on the bottom of the gun. I am unsure but I think a cup gun is the type with a disposable cup that mounts on top of the gun?? If so I did not use a cup gun. I think Devilbiss manufactures most outh there, but I am not a spray gun guru.

I did not purchase anything special as the spraying part of gel-coating is not when I am concerned about finish. It is just how the gel-coat gets on the hull. Were I spraying Imron or AwlGrip I would be far more concerned with a quality gun because the application with the sprayer is your final finish.

The compresser again, Craftman, I do not have the model # but it is a 6hp and is more than I needed. When buying the gun the required aircomp specs are on it so all you have to do is match it all up.

The one thing I did not mention is I did use a water seperater inline with the spray gun. this is important, you do not want water contaminating your gel-coat.

On the boat I have sprayed thus far, I never had the brass thru-hull issue. Good Question. On the Mako 19, the owner did not want to remove the rub rail so we taped that up and removed the tape after the gel-coat had hardened. No problems. I just sanded in the tape lines and it came out surprisingly well.

posted 11-24-2002 12:34 PM ET (US)            

Thanks for the reply. I appreciate you taking the time.

The variables you listed regarding the gun and air/fluid nozzles (i.e. internal vs. external mix, size of fluid nozzle, etc.) are the specific types information I was trying to elicit from someone who has practical experience using the equipment. In other words, what specific equipment was used and how well did it perform. I probably didn't do a very good job of wording my original post.

As for compressors, I'm running three small portable pancakes that are great for framing, finish and siding/roofing nailers, but would be useless for this application. I also have a somewhat larger commercial grade portable with a SCFM rating of 8.1 @ 40 psi/6.4 @ 90 psi, 125 max psi, 20 gallon tank with a Doerr 5hp, 15 amp electric motor rated for continuous duty.

Equipment recommendations from the manufacturer are often right on the money. Other times there is a significant variation when it comes to practical/field/jobsite applications. Comparing pactical experience to manufacturers' recomendations can be very useful.

Spending money for necessary, quality equipment has always made good sense to me. Buying the wrong or unnecessary equipment is aggravating, buying crummy equipment is worse and all are a waste (I have a little of each that I have to look at almost daily) and avoiding mistakes is always a goal.

Thanks again, sammy.

posted 11-24-2002 12:52 PM ET (US)            

Appreciate the follow-up. So taping will work with gelcoat - that's great info. The in-line water separator is another good heads-up. If run-of-the-mill equipment does the trick, even better.

I was a little surprised about using 80 grit to prep the surface. Apparently 3 coats of gelcoat are enough to bridge that sort of surface. It ought to provide a good bite for the new material.

posted 11-25-2002 09:29 AM ET (US)            

I feel that I may need to clarify my previous message. I recommended that you look at the DeVilbiss and Bink websites because of the information that is available there, not to infer that you should buy their equipment instead of others.

The reason I elaborated so much on the different requirements of the spray guns, was so that you would not buy a compressor that wouldn't be adequate for what you may wish to do. I the past I have seen so many people go buy a relatively small, inexpensive, compressor and then wonder why they had to wait for the air supply to build back up before they could continue spraying. i.e., I have seen compressors rated at 1.5 to 2.5 SCFM being used with a spray gun that needed 4 to 6 SCFM to operate properly; you spray a little bit, wait for the pressure to build back up, then spray a little more, etc.

The compressor you already have "I also have a somewhat larger commercial grade portable with a SCFM rating of 8.1 @ 40 psi/6.4 @ 90psi" will most likely be adequate. As Contender 25 says, just choose a spray gun that will work with your compressor.