DIY Barrier Coat

[mrybas]

Here are a couple photos of the uncovered bottom.

[T37Chef]

Um...looks familiar Look on the bright side, they don't look to be anything but on the gel coat, so not a worry.

Once you pop them, rinse several times over the course of the next few weeks, then let dry (checking with Meter), followed by filling and fairing, then barrier coat/bottom paint. If you re read my post above you have pretty much what I was faced with.

BTW: If you don't already know this, please sand your bottom using a vacuum attachment, the boats near you will appreciate it very much

[Legendsailing]

I'm not sure why you would want to take off the existing gel coat if there is nothing wrong with it? Can't you simply clean down to the gel coat and paint with 4 or 5 coats of Gel Shield. I purchased a Soling Keelboat which had been treated in this way and it has stood on a mooring for over 2 years at a time with no problems whatsoever, my other Soling's on the other hand are all showing slight signs of osmosis and so I make a point of taking them off the water each year to dry out. Eventually I will get round to applying gel shield to them as well.

[mitiempo]

Legend
The existing gelcoat doesn't have to be all removed, but the blisters have to be sanded off and the hull allowed to dry out before barrier coating. Saving the gelcoat is not essential really as it is porous compared th the barrier coat that would replace it.

[KeelHaulin]

With such small blisters and in high abundance; you might want to consider using a power planer to strip all of the gelcoat off with one shot. There are tools designed to do this and they are quite expensive; but "peeling" the hull might be the best way to get all of the blisters off the hull before putting down a barrier coat. Otherwise you will have to carefully grind out each blister with an angle grinder; tapering the edges them so the fairing compound will adhere and not pop off of the hull when flexed. It's a tedious job and in addition you will then have to sand the hull smooth after fairing.

If you peel the hull you might have to re-build with a layer of thin cloth and epoxy fairing compound; but it might be faster and easier than grinding out each blister.

[mrybas]

KeelHaulin- I think you may be onto something. The blisters are far too small and numerous to individually grind-out. Do you have any more info on the tools to peel the gelcoat? If only the gelcoat was removed, and not the laminate underneath, is a layer of cloth necessary before the barrier coat?

As an alternative to peeling the gelcoat, would soda blasting remove the gelcoat that has been delaminated from blistering? Basically removing any gelcoat that has been weakened by blistering. Then I could fair and barrier coat.

[idontwantanaccount]

I have no experience with it, but you should google "marine shaver." It appears to be a relatively low cost gelcoat planer. The video on the website shows fairly impressive results. Also the company apparently will buy back the tool from you after a period of days (essentially making it a rental) for a modest cost.

[KeelHaulin]

Originally Posted by mrybas

KeelHaulin- I think you may be onto something. The blisters are far too small and numerous to individually grind-out. Do you have any more info on the tools to peel the gelcoat? If only the gelcoat was removed, and not the laminate underneath, is a layer of cloth necessary before the barrier coat?

As an alternative to peeling the gelcoat, would soda blasting remove the gelcoat that has been delaminated from blistering? Basically removing any gelcoat that has been weakened by blistering. Then I could fair and barrier coat.

I don't have specific info; but there are tools available that will remove about 1/16" of material per pass and follow the contour of a smooth surface. I would try and find something specific for planing a fiberglass hull because if you don't take it off evenly you will have trouble re-fairing the hull smooth. I have seen jobs where the mat has been stripped completely off and you need to re-cloth the hull to build a layer back; but I don't know about just the gelcoat. I would say that you should apply a thin woven cloth layer to get the thickness back to the level of the topside gelcoat and then use an epoxy filler mix to fair it smooth. Then sand down any rough spots or high spots and then apply epoxy barrier coat per MAS epoxies instructions.

I don't think I would soda blast; it might leave the surface full of craters where the blisters were, and then it would be difficult to plane or sand smooth.

I should also mention that blisters usually are down in the strand-mat; you should grind a few out until you reach dry epoxy filled glass to see how deep they are. Blisters usually form beneath the gelcoat and in the strand mat layer; where the epoxy did not fully wet out the glass.

[cutterorient]

to the OP, I just did all this this past winter / spring and my boat is from the same builder as you so you may see some of the same probs. Some of my thoughts;

1. soda blast is good as it does more than just take paint off, it revealed to me gelcoat imperfections that I then filled with epoxy thickened with microbaloons. The guys I hired were idiots but they got the paint off. If the surface is pitted who cares, more surface area for the first barrier coat. I wouldn't take anything off that is well bonded, just fill

2. neutralize the soda with cheap vinegar from the grocery for easy cleanup

3. get ready to do alot of sanding, filling, fairing, sanding, filling, etc.

4. I did not choose Interprotect for the following reasons; high cost and tight windows for recoating and bottom painting which, if done incorrectly, can mess up quite a bit of work and add more cost and work.

5. I chose MAS epoxies for the following reasons; reasonable cost, easy to use/mix, VOC free, flexible application ( you can recoat when its tacky or wait till it hardens while you are on vacation in between coats, hit it with a scruff pad and throw another coat on ) no need for crazy expensive and toxic solvents as water and denatured alcohol are all you need, on final coat after it has had time to fully cure, scuff with a scoth pad and paint with ablative paint so you never have to do this again.

5. MAS epoxies were good for filling, fairing, wetting out glass for repairs, barrier, so I had one product that I could use for all those purposes, just keep pumping 1:1

6. When unavoidable repairs are to be done in the future I can just grind, repair, re barrier without all the time schedules and recoating windows. Easy Simple, cheap.

7. You can tint the epoxy for that cool grey look - I did.

8. After full cure just paint it when you want after a scuff.

[mitiempo]

myrbas
Here's a link to a site restoring a Morgan 30. He peeled the hull and built it up with glass after drying. At the bottom of the page it goes to stage 2 - application of new bottom. Boat Peel