Home |
Search |
Today's Posts |
#11
posted to rec.boats.building
|
|||
|
|||
Gelcoat question
On Sat, 16 Jun 2007 16:39:25 -0700, LouiSurfer
wrote stuff and I replied: As has been said, the first batch was too old. Don't feel too sorry; I have had 200 litres of resin go hard on me....once G! The trouble with Gelcoat is that it's really designed for working inside a mould, and not for brushing. It has additives that make it flow more the longer you work it, but also make it stop flowing almost as soon as you stop. The beauty of this for inside moulding is that it will not run or sag, and of course the mould's surface gives a smooth exterior appearance. Wall plaster has the same tendency. If you are really worried about finish then either very finely (600+ grit) sand and polish the area (practice on something that does not matter first! You will also have to affect the surrounding gelcoat), or I would ask around and find a basecoat and (pref 2 part) paint that will do a better job if brushed, and are meant to go on polyester/gelcoat. The 2-part urethanes are good. About 3 months ago, I bought 1 quart of clear gelcoat. Didn't get around to using it for about a month. When I went to open it up, it was pretty hard and unuseable. I bought another quart from the same seller about 2 weeks ago, and opened it up within a week. This time, the consistency was about that of grape jelly. At no time was any of this liquid. I've worked with surfboard fiberglass resin and thought gelcoat would be similar liquid consistency. Am I wrong or: a) Was unlucky, got two bad batches and need to take it up with the seller? b) Waited too long to use it? I don't see how it can harden up like that within a week. c) Need to add something else to liquify it or thin it, like acetone. I tried acetone, but it doesn't take out clumping. d) Leave gel-coat repair to a professional. I've done plenty of fiberglass repair and didn't think gelcoat would be that different. A little advice is much appreciated. L. Human bevaviour: Bestiality with a brain |
#12
posted to rec.boats.building
|
|||
|
|||
Gelcoat question
Put the open container in a pan of water on the stove and warm it up.
Old dry hard crystallized polyester resin will liquify and can be used when heated. Not sure about gelcoat but worth a try. Also worth a try is hacking some out of the container and warming in a microwave oven on low heat. Gotta move with the times. |
#13
posted to rec.boats.building
|
|||
|
|||
Gelcoat question
"sherwindu" wrote in message ... Hi Arnold, How would you compare the looks of a painted boat to one sprayed with gel coat? Sherwin Hi Sherwin, absolutely no comparison. A gel coat sprayed boat will look like awful. See Oldnick's post below. Good info there. But I am about to spray gel coat on a small boat. I expect to spend many hours sanding and fairing and polishing it after. I make a lot of GRP plugs so all that sanding is no big deal - kinda used to it. But I won't want to do it on anything more than 10 feet or so. Arnold |
#14
posted to rec.boats.building
|
|||
|
|||
Gelcoat question
"sherwindu" wrote in message ... Hi Arnold, How would you compare the looks of a painted boat to one sprayed with gel coat? Sherwin Also, if you intend to use gel coat this way. make sure you add wax to the gel coat. You can buy liquid wax from a grp supplier or you can use any kerosene based wax (I use floor wax frequently). This is to inhibit air from getting to the gel coat. The wax rises to the surface and blocks out the air thereby alowing a full cure. If you omit this step, your gel coat will remain tacky for a LONG time. But you can also wax the part liberally after the gel coat has cured. This will also keep the air out but its an extra step. Arnold |
#15
posted to rec.boats.building
|
|||
|
|||
Gelcoat question
Arnold,
I think you missed my drift. I was thinking about regular paint vs. gelcoat. I suppose that gelcoat is used for repairs or when the original gelcoat has worn through. In my case, the gel coat is probably still intact, but there are numerous tiny crazing and the original white color has faded to a dull yellow. I guess regular paint is the way to go, but can it be applied with a brush and still come out streak free? Any special tricks to make this happen? Sherwin Ystay wrote: "sherwindu" wrote in message ... Hi Arnold, How would you compare the looks of a painted boat to one sprayed with gel coat? Sherwin Also, if you intend to use gel coat this way. make sure you add wax to the gel coat. You can buy liquid wax from a grp supplier or you can use any kerosene based wax (I use floor wax frequently). This is to inhibit air from getting to the gel coat. The wax rises to the surface and blocks out the air thereby alowing a full cure. If you omit this step, your gel coat will remain tacky for a LONG time. But you can also wax the part liberally after the gel coat has cured. This will also keep the air out but its an extra step. Arnold |
#16
posted to rec.boats.building
|
|||
|
|||
Gelcoat question
"sherwindu" wrote in message ... Arnold, I think you missed my drift. I was thinking about regular paint vs. gelcoat. I suppose that gelcoat is used for repairs or when the original gelcoat has worn through. In my case, the gel coat is probably still intact, but there are numerous tiny crazing and the original white color has faded to a dull yellow. I guess regular paint is the way to go, but can it be applied with a brush and still come out streak free? Any special tricks to make this happen? Sherwin Hi Sherwin, you're opening up a can of worms learning to paint! I'm guessing you know about surface prep etc. Here's a tip when prepping - use as fine a grit paper as you can stand. 300 plus grit will be ok but your paint will flow better if you go higher, say 600. Custom car guys will sometimes go to 800 but we don't need to aim so high. Some people are happy with 220 grit. The finish will be ok, just not stunning. Your prepped surface has to be near perfect because paint will not cover up any surface imperfections; that's what a hi-build primer is for. So any crazing, nicks etc will have to be filled first. Now to the painting! The most important thing you can do is to thin your paint properly. The manufacturer will have a recommendation but I've found that they are almost always cautious. You need to buy or make a vicosity measuring device like a Ford cup or a Dean cup. You fill this up and time how long it takes to empty. Write this figure down! Roughly you can expect a Dean cup to empty in about 18 secs (very big +- ). I like the roller brush method (lots on Google). But use the softest brush you can find and treat it to some hair conditioner (really!). The theory behind getting a flawless finish is like this - You need to apply enough paint such that it almost wants to sag and /or run but doesn't. If you have enough paint on there, the brush marks will "flow" and even out. This is how you get a mirror finish. Too much paint and you get runs. Too little and it won't flow out. Fun, huh? Don't forget that vertical surfaces will flow out much easier! So how do you aid flow out? Thinning! But that's not all, you need to know how viscous to keep your paint at different temperatures. You need to know how much time you have before the thinner flashes off. Once the thinner has mostly evaporated (flashed), you're out of luck - the paint will be too tacky to flow. If using polyurethanes, buy the slowest harderner they have. Good quality paints flow better than cheaper ones. Matt and semi-gloss paints show fewer flaws. Might be something on youtube to further confuse you! Feel free to mail me directly if you have other questions. Arnold |
Reply |
|
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Need a Sources of "Styrene" for Gelcoat Repair | General | |||
On matching gelcoat | Cruising | |||
gelcoat | Boat Building | |||
gelcoat | Boat Building | |||
Another strip-plank question - a bit long | Boat Building |