Tools For Fibreglass and Gelcoat Repair

[Sonosailor]

I'm going to be doing a few square feet of fibreglass repair on the boat, then re-gelcoating about 60 square feet, which will include the repairs and some messes former owners tried to cover with awlgrip. I hope to use isophthalic polyester resin and isophthalic polyester gelcoat, but it shouldn't matter as I believe they all act the same during repair, sanding, grinding. The fibreglass repairs will involve sanding out cracks down to a depth of say 1/4+" , building out with matting and roving, and sanding down to a uniform surface.

What ELECTRIC tools would you folks purchase to assist you, if you had none to start with? eg: palm sander, grinder, drill attachment, and appropriate power level; brand name, grit level, etc.

I'm also interested in what you folks might use for a filler for fairing before gelcoat application, and if there are any power tools that work well for sanding down gelcoat for uniformity prior to the use of wetpaper.

I'll accept any other tricks of the trade, as well;e.g.: if you have a special low-cost sprayer, or an air-dry product that worked better than others.

[GordMay]

On the Mark: Sanding tools? ~ by Mark Bronkalla
Boat builder news letter #26
and
Sanding tools - WL26

Hull Fairing; Resurfacing , Part 3 ~ by Mark Angliss
Hull Fairing; Resurfacing , Part 3

[knottybuoyz]

What part of the boat are you working on? Working overhead, say on the bottom is a royal pain.

Originally Posted by Sonosailor

What ELECTRIC tools would you folks purchase to assist you, if you had none to start with? eg: palm sander, grinder, drill attachment, and appropriate power level; brand name, grit level, etc.

Look for a 7" variable speed sander/polisher something like this....

Milwaukee - New - Heavy Duty 7/9 " Polisher

If you search e-bay you may find cheaper options. This one will probably pay for itself in your first repair.

Smaller palm/orbital sanders can be handy for feathering out the edges of the repair. Any brand will work. A selection of grits from 80 through 1200 will be needed for the various stages of the repair. The larger 7" polisher/sander will be your best when you get near the finishing stages you can switch to buffing/polishing bonnets.

Originally Posted by Sonosailor

I'm also interested in what you folks might use for a filler for fairing before gelcoat application, and if there are any power tools that work well for sanding down gelcoat for uniformity prior to the use of wetpaper.

As far as I know most pre-made fairing compounds are epoxy based. As you're using other resins you'll probably have to make your own. A mixture of colloidal silica and micro-balloons will work. Mix to your desired consistancy which will depend on which surfaces you're working on. You can avoid a lot of sanding and fairing in your repair if you use a peel-ply and vacuum bag to even out the surface of the repaired area especially if working overhead.

Originally Posted by Sonosailor

I'll accept any other tricks of the trade, as well;e.g.: if you have a special low-cost sprayer, or an air-dry product that worked better than others.

A HVLP (High Volume Low Pressure) paint sprayer might be a good choice. I hear it puts the paint where you want it and not atomized into the atmosphere. Here's a low cost option.

HDC - Electric HVLP Paint Sprayer

Again, there are others if you do a few Google searches.

A long board sander might be useful. Depends on your preference for elbow grease or power tools. You can make your own as well from some thin ply and some drawer knobs.

Neiko USA - 17" AutoBody Hand Sander

Again you're going to need a variety of grits working down from probably 80 for rough work to over 1000 for final fairing before buffing/polishing.

Good luck.

Rick

[Richhh]

Depends on the 'span' of the repair, but usually the most important for filling, fairing and polishing will be 'long feathering boards' for wet-sanding. Sorry (but to pardon my expression) this is a 'hand job' to get a fair and dead-flat surface. Just like autobody shop work the next to final sanding and leveling is usually done 'wet' and by low pressure pneumatic power sanding; the final sanding is usually done solely by hand to achieve the necessary FLAT surface .... If possible consider to spray the final gelcoat on once you get a dead-flat under-surface, then final polish, etc. If you dont want to spray the final coat consider to have a gel 'artist' do this for you.

8ft x 8ft. although not entirely impossible to get 'flat' will require some extra long feathering boards .... long thin wooden boards/battens to which you 'glue' waterproof sandpaper (1300 - 2000 grit for the final 'wet-sanding'). If you 'rush' such a job at the end you will wind-up with a wavy surface; as the human eyeball can discern 'unevenness' almost down to the micrometers range-difference using strong light 'incident' to the surface. If you want a 'quality' flawless job that rebuilds the original to 'new - from the mold' quality ... take your time with the 'final' steps. The finer the grade of paper the faster the 'cut'; but, you have to change paper more often the 'finer' the grit you use. Can be done but think 'precision' not 'production-speed'. Go to an autobody shop supply for wet&dry paper on 'rolls' to apply to your feathering boards - they will also have the proper (but weak) contact adhesive.
Once you get a FLAT surface, then you can power buff (variable speed auto body shop polisher and 3M 'knobby' foam pads) with the final 'buffing compound .... for fiberglass gel the best is probably a 'Super-duty' (3M #05964) then 3M 'Finesse-iT' followed by 3M 'Perfect-it'. Obviously, you want moderate speed/rpm but not pressure to final flatten the gel with the polisher. Dont mix polishing pads and grits .... use a new/clean knobby pad with EACH grit; dont mix!!!!!!!
hope this helps.

[seaclusion]

1. Use isophathalic gelcoat. Do not use orthophathalic gelcoat. They do not hold up as well. Fortunately they are not common, but I have seen some low priced gelcoats that turned out to be orthophathalic so buy a premium well-known brand.

2. Skip the peel ply. Do like the pros. On the last coat of gelcoat before you start sanding, add wax to the gelcoat before adding catalyst. The wax is sold under different names (Modifier-C, Sanding Aid). The wax will inhibit the oxygen in the air from reaching the surface of the gelcoat and allow it to thouroughly harden thus not gumming up the sandpaper. If you must recoat, sand thouroughly and clean thouroughly before reapplying more gelcoat.

3. Get a catalog from Fibrglass Coatings Inc. in St. Petersburg, Fl (sorry I don't have the address at the moment but they do have a website ~ Fiberglass Coatings Inc. Your Single Source for All Your Fiberglass Needs ). They sell everything that the profesionals use and in the catalog is an instruction manual on how to do exactly what you are attempting. It is the best quick and dirty guide to working with fiberglass I have come across. If you follow their guide your repair will come out looking as good as a professional.

Richard

[Sailormann]

What ELECTRIC tools would you folks purchase to assist you, if you had none to start with? eg: palm sander, grinder, drill attachment, and appropriate power level; brand name, grit level, etc.

I have found that the best place to buy Power Tools in Canada is PRINCESS AUTO. They have stores across Canada, and I believe you can order online as well. The prices are great and the quality is on a par with DeWalt and several other brands costing three times as much. Avoid Black and Decker - they are toys for light duty home repair.

Princess Auto sells a small grinder that is very powerful, yet light enough to use for long periods. They also have a circular power sander/buffer with variable speed. Their house brand is called Powerfist. As far as filler goes - there is a product called Marine Tex that is basically a marine version of Bondo. Have not used it myself but plan to in the near future.

Density is an issue to consider when you're filling. i.e.: if you fill an area with something that is a lot harder or softer then the surrounding material, it is hard to fair it smoothly as you need to use differing degrees of pressure in the same stroke, which is hard to do consistently. It is pretty soul-destroying to work on something for a few hours and then ruin it because you get a little tired and unintentionally gouge a hole.

The previous post suggesting you make your own filler is a good idea. I have had some success mixing resin with colloidal silicca and "pureed" fibreglass. I cut roving up into small pieces, fill a kitchen blender about two thirds of the way up with water, throw in the chopped roving and put the blender on puree until it really gets chopped up, strain it through a nylon stocking, let it dry out, and then am really careful not to inhale it. (sometimes I get bored and like to experiment....)

Good luck !