Hobie Cat Forums

It is currently Sat Aug 30, 2014 5:23 pm

All times are UTC - 8 hours [ DST ]




Post new topic Reply to topic  [ 12 posts ] 
Author Message
PostPosted: Fri Dec 28, 2012 9:47 am 
Offline
Site Rank - Captain

Joined: Mon Jun 25, 2012 9:56 am
Posts: 29
As it is winter here in Michigan I don't have much do to besides restoring my 72 Hobie which has been in bad need of a new paint job. I have already started the process and over the Christmas holiday I got one of the hauls sanded and ready to fill the little spots with epoxy filler (doesn't have any soft spots).

Anyways my question is Brushing a viable options for putting gelcoat on for a complete repaint? I have pondered this and I think its my current best option. I absolutely realize that the sanding process (I'm assuming between coats as well) will be a lot more intensive, but I have plenty of time until sailing weather returns to Lake Michigan. Some of the things which are shying me away from spraying are the cost of the spray gun, I might have access to an air compressor which is capable enough, the difficulties is thinning the gelcoat to make it spray-able, and the necessity of constructing a spray booth. With applying it with a foam brush I'm guessing that I wont have to worry about thinning, just not too put it on too thick per coat. I'm assuming that the orange peal effect only happens with spraying as well, and I'm guessing that the only mixing I would have to do would be for the final coat with the hardener.

I'm going to shop around to see if there is a place around here which I could hire to spray it on after I have done all the prep work, but I would really appreciate any input.


Also on the topic of epoxy I thinking of using #205 Fast Hardener since I'm working in a 40 to 50 degree garage while running a heater. I know that epoxy is the thing to use as opposed to something like bondo as its a boat....that's in water...but what is the viscosity that I would be working with. Can I apply it like bondo by scraping it over a low spot to fill it in and would it be able to be used to fill in any nicks out of the lip of the hulls and not just drip away?

_________________
'72 Hobie 16


Top
 Profile  
 
PostPosted: Fri Dec 28, 2012 10:45 am 
Offline
Hobie Approved Guru

Joined: Mon Jul 14, 2003 7:11 pm
Posts: 4590
Location: Detroit, MI
There's so much about to go wrong here, I don't know where to start.

If you're going to re-do the gel coat, don't use epoxy to fill dings. Gel coat doesn't stick well to epoxy. (Sounds like I'm already too late on this one.)

Epoxy and polyester (gel coat) resins are fundamentally different:

Epoxy is mixed with its special hardener at a pre-determined ratio that needs to be fairly exact. For example, WEST System is a 5:1 ratio. Heat is the only thing that can speed up the reaction. Too much or too little hardener will make a gummy mess. When epoxy cures, it leaves an amine blush on the surface that must be removed before anything else will stick to it.

Polyester is mixed with a catalyst (usually MEKP) that's measured in drops (usually about 12-15) per ounce of resin. You can adjust the speed of the cure by varying the amount of catalyst (within limits) or heat. You can make it go off so fast, it will catch fire. Alternatively, you can slow it down (by putting it in a freezer) so that it will take months to cure. Gel coat is just tinted polyester resin. The boat was originally built using polyester resins.

Every coat of gel must have catalyst added or it will remain liquid forever. If it's not protected from air, then it will remain tacky - it will not cure hard - which is what you want when you're doing multiple coats so that successive coats stick to each other. The only reason to go with multiple coats is to prevent sagging and drips. There is no "sanding between coats". If you are brushing, you want the gel to be thin enough to flow out and eliminate brush marks.

On the last coat of gel, you either add styrene wax to the mix or spray with PVA when the gel starts to go off. That will protect it from the air so that it cures hard enough for sanding.

Adjusting the viscosity of WEST System resin is done with additives - http://www.westsystem.com/ss/fillers-and-additives/

But like I said, don't use epoxy under gel coat. Use this instead:
Image
It's a vinylester filler that works great under gel and sets up in about 10 minutes. Don't use the blue hardener that comes with it - it's very hard to hide under gel coat. Get a tube of 3M white cream hardener (it's all benzoyl peroxide).

Or you can use this stuff:
Image
It's polyester based and somewhat softer than the 3M filler.

I cannot stress enough how important ventilation is when using polyester resins. Don't even think about doing this in a habitable part of your house - even brushing. The fumes are poisonous and flammable (styrene has a flash point of 88 degrees). Even if you're doing it outside, you should wear an organic vapor filter mask. If you're doing it inside, you need a supplied air system.

Gel coat isn't hard to work with, but it sounds like you need some practice before you take on a job as big as recoating a Hobie hull. Try working on scraps of wood first. Use the filler spread thin to "seal" the wood, sand smooth, then try coating it with gel coat.


Top
 Profile  
 
PostPosted: Fri Dec 28, 2012 12:03 pm 
Offline
Site Rank - Captain

Joined: Mon Jun 25, 2012 9:56 am
Posts: 29
Don't worry too much I have only done the preliminary sanding, and I had no intention of going beyond that until got feedback / did more research. I have just been cobbling bit of information from reading this forum for the last few months..sorry to make your head hurt, but that's why I asked. I try not to be the derp that doesn't use the search button. I really appreciate the input though. Yes I was already planning on doing a test piece. Anyways is going with the brush options that bad of an option compared to spraying? You have answers so many questions but I think the one that started it off got a little lost.

_________________
'72 Hobie 16


Top
 Profile  
 
PostPosted: Fri Dec 28, 2012 2:13 pm 
Offline
Hobie Approved Guru

Joined: Mon Jul 14, 2003 7:11 pm
Posts: 4590
Location: Detroit, MI
Brushing is fine for small areas.

The problem with large areas is that the gel will start to go off before you're done. Then you've got a gigantic mess on your hands. Even with a single pot sprayer, you've got to move fast before the gel sets up inside the gun.

Professional boat builders avoid this by mixing the catalyst in the spray stream.

With a foam brush, you have to be careful not to have air bubbles.

I suppose for larger areas you could roll and tip (a two-person process), but you'd have to move really fast.


Top
 Profile  
 
PostPosted: Fri Dec 28, 2012 2:28 pm 
Offline
Site Rank - Captain

Joined: Mon Jun 25, 2012 9:56 am
Posts: 29
Fair point. I might have a connection on a spray booth so I will see where I can go from there. Your input has been much appreciated.

Earlier I was making the biggest confusion between the catalyst and whatever it is that is needed to thin the gelcoat to make it be able to spray easier, so thats why I was questioning the need to mix anything when going to brush route.

_________________
'72 Hobie 16


Top
 Profile  
 
PostPosted: Fri Dec 28, 2012 5:43 pm 
Offline
Site Rank - Admiral

Joined: Sun Jun 21, 2009 7:32 am
Posts: 288
Doing anything with fiberglass resin of any type, including gelcoat, is very dependent on temperature. If you have an inside place to do it that you can control the temperature, it might be doable this time of year up there. Without control of temp, I'd recommend waiting until spring.

The Wagner HVLP sprayers that you can buy for around a hundred bucks are really not bad if you thin whatever you are spraying enough. To thin gelcoat, use styrene-available from suppliers that sell other fiberglassing materials.

I use that gun for spraying oil base primer on interior woodwork, since it won't raise the grain. You have to thin stuff WAY down with it. If you thin gelcoat to spray with it, don't get greedy with any pass to try to get complete coverage. It's best to avoid runs at any cost.

If you brush an entire boat, you will spend enough on sandpaper, and respirator filters to pay for the gun.

Clean the gun QUICKLY after spraying. You do not want it kicking in the gun. You can clean it out with styrene and patience, but that's the kind of thing that we only do once, for those of us who have to learn the hard way.

There is no short-cut to doing a good job. Get in a hurry, take a shortcut, or try to get too much coverage, and the penalty is some increased exponential amount of time required from start to finish.

Get set up right, practice first on something else like a big sheet of cardboard, have everything you need at hand, and it's really not that bad.


Top
 Profile  
 
PostPosted: Fri Dec 28, 2012 8:59 pm 
Offline
Site Rank - Captain

Joined: Mon Sep 17, 2012 6:56 pm
Posts: 58
Location: Durham NC
Well I just finished spraying one of my hulls and I'll be doing the second one when I get back from MN. I used the gelcoat cup gun g100 and it was extremely easy to use and clean. You should definitely consider it. You can purchase it for around $120. Just make sure you get the 4.7mm nozzle with it when you order it. I did not have to thin the gelcoat. I still got orange peel but I've been able to sand that out. Hopefully I'll do better with the second hull. I'd be willing to lend it to you but that will be sometime towards the end of January when I'm done. Pm me.

Otherwise listen to what everyone else has advised. Personally I wasn't too worried about blowing up as I was the toxic fumes in my lungs. Definitely get a respirator. I could literally feel it affecting me the couple of times I did some minor sanding without it, not worth it, just keep it handy by the boat while you work and always put it on. Try to do all our sanding outdoors to help out. Easier to do of course in nc than your neck of the woods.

_________________
1984 Hobie 16


Top
 Profile  
 
PostPosted: Mon Dec 31, 2012 10:23 pm 
Offline
Site Rank - Old Salt

Joined: Thu Apr 24, 2008 3:58 am
Posts: 575
Location: Knoxville, TN
If you haven't already, take a look at Heelcat's threads, "restoring hulls with gel coat" and "final questions before spraying gel coat". Lots of good advice on those.

Definitely spray rather than brush. Orange peel is much easier to sand down than brush strokes. And don't even think about thinning with acetone, although it is effective for cleaning spray guns and other messes.

HAPPY HOBIE NEW YEAR!!

_________________
Mark Van Doren
Division 9 Chairman
H16 #112205 (Richard Petty Signature Edition)
H14T #47787
H20 #647 (sold)


Top
 Profile  
 
PostPosted: Thu Jan 03, 2013 12:20 pm 
Offline
Site Rank - Captain

Joined: Sat Apr 14, 2012 1:38 am
Posts: 59
I foam brushed my whole boat. The only option for me as I am not willing to spray myself into the middle of a huge cloud of poison without a full supplied air system and a booth, neither of which I have. Managing the mixing and hardening was easy once I got it down. I premixed the surfacer with the whole gallon of gel coat and then worked in dixie cups. If you fill a small dixie cup about 3/4 full and add a squirt of hardner (5 to 10 drops, I think, but check the instructions) you can get it all brushed on and will finish just at is starts go hard. You will need a new dixie cup and a new brush for each batch, so you will go through a lot of brushes, but they are well under a buck. I just did a couple of coats and did not sand or polish after, although I did a bit of sanding before.

The result is.....meh. The boat looked terrible before in bright orange that had faded to a terrible brown and been much patched and such. Now, passers by think it looks great, take photos, and complement me on it. And from 10 feet it does look great. But it is definitely not a glossy shiny new boat from up close, and if I were more fussy I would be unhappy with it. It looks good enough that I can sail it without being embarrassed about how it looks and can return my attention to trying to get the rigging 100% reliable and set to my liking.


Top
 Profile  
 
PostPosted: Thu Jan 03, 2013 8:19 pm 
Offline
Site Rank - Admiral

Joined: Sun Jun 21, 2009 7:32 am
Posts: 288
This is like the supplied air hood I use. A clean shopvac, hooked up on the blow side, supplies so much air that you have to tie the hood on so it doesn't blow off your head. You do need a long hose to set the vac in clean air. I think I paid some less than this, but this was the first one that popped up with a Google search for "disposable supplied air hood". The one I use is Tyvek, and has been used many times. I think they are just called "disposable" because they would be cheap enough to throw away when dealing with hazardous materials.

http://www.envirosafetyproducts.com/dis ... -hood.html


Top
 Profile  
 
PostPosted: Fri Jan 04, 2013 12:43 pm 
Offline
Site Rank - Captain

Joined: Sat Apr 14, 2012 1:38 am
Posts: 59
Love the inexpensive supplied air system. Not sure I am capable of keeping a shopvac clean for any length of time, though. :)


Top
 Profile  
 
PostPosted: Sat Jan 05, 2013 3:33 pm 
Offline
Site Rank - Admiral

Joined: Sun Jun 21, 2009 7:32 am
Posts: 288
That's why I bought a new one just for that application. I bought the medium sized one, but could have gotten by with the small one. I don't think you can clean one, that's sucked dust up, to blow air back out that's clean enough to breathe. If it's not much difference in price, I'd probably get the medium one again. It keeps your head nice and dry.

I use it for all sorts of dusty operations-like finishing sheetrock, sanding anything, and any kind of spray painting.

I had to jury rig an adaptor from the drop hose that comes with the hood to the long shopvac hose. It's been so long ago, I don't remember exactly how I did it. It's some combination of vac fittings, pvc pipe, and duct tape. There's one shop vac adaptor that has a bunch of steps in it that you can cut that will fit a variety of different hoses. I'm pretty sure there's one of those in there.

I'd be interested in the quality of finish you can get with that gun. I use some old Binks siphon feed guns that I 've had since the '70s for gelcoat just because I'm used to them. I can spray a finish so smooth, that I can go right to PerfectIt for final finish, and a new boat never shined that much.

http://www.ebay.com/itm/BINKS-Model-18- ... 337efda1b1

and for patch jobs http://www.ebay.com/itm/BINKS-MODEL-15- ... da&vxp=mtr

I wouldn't recommend anyone go out and buy them for this, but I had them anyway. I also have HVLP and airless sprayers-even an air assisted airless, but I don't want to put something that will set up in them. I don't mind soaking the Binks parts in styrene if I need to.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 12 posts ] 

All times are UTC - 8 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 4 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group