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I'd like to get any tips on filling in the fiberglass weave on big panels, as I am glassing the cabin tops and decks right now. I have tried a squeegee as well as a foam roller with the roller being easier, but it is taking a lot of coats. Any tips would be much appreciated! I thought I was done with the BS after finishing all of my beam fillets, yet the weave filling has me just as annoyed.

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From your post it sounds like you are trying to fill the weave with just resin.. if so you are on a hiding to nothing and all you'll end up with is high blood pressure and a heart attack......

Mix micro balloons with your resin, or a specialist "fairing powder" like awl-fair or something similar,  there are quite a few products out there from powders to ready mixed stuff.) specialist fairing products are often a darker colour like brown / tan.. Depending on the depth of the weave try different amounts of microballoons from quite runny to relatively thick. If its runny you can spread it with a squeegee, I preferred a thicker mix more like soft margarine / thick yoghurt, but runnier than fillet mixture, and i applied it with a wide spuckle as i think the more balloons the easier it is to sand afterwards. We also used a custom applicator - a 3 inch wide, 10 inches long piece of thin stainless. Look in DIY stores for the widest possible scraper-like tool, A good random orbital sander with a course disk 80-150 is good and should make short work of it and you'll have a nice smooth panel in no time. To save time you can apply the "fairing mixture" on top of the freshly glassed surface and therefore no sanding required between applications. Just wait till the original glassing is tacky and then apply the fairing mixture. For vertical surfaces add a bit of Fumed Silica to stop it running / slumping. The more silica the harder it is to sand so add just enough to stop it running. Trial and error will teach you the right mix. Id say no more that 5-10% silica at the most. If you want a "perfectly" Flat (Faired) surface then you'll need to use a longboard to sand. Google "Yacht fairing techniques" and i'm sure you'll get the idea.. You could write a book on fairing and there probably are plenty, Its bloody hard and quite frustrating work to get a good flat faired finish but gets easier with practice.

As they say - Practice makes perfect.

Another way, if you only have a fine weave showing, is a good coat (or three) of High Build Epoxy Primer like Jotun Pengard HB, available in white and grey. Again, apply multiple coats while not quite cured ( i found it was "touch dry between about 10-20 minutes and was ready for the next coat), for the least sanding possible (150 grit discs are great and give a perfect finish and key for top coating).  For any pin holes you can mix a bit of micro balloons into the high build primer and use a spuckle to fill the pin holes. If you let it dry then the primer should be sanded between coats to give a good key for your next coat.

I applied my paints by spraying as it gives a better finish (much less orange peel) but please make sure you read the health warnings regarding spraying paints especially those containing Iso-cyanides. However you apply it, use the best vapour masks you can get to protect yourself from the solvents and cover all exposed skin....

Hope that helps


An excellent reply from Marty.

I can confirm all that's been said, especially regarding Jotun Pengard HB. I used this on my renovation which included filling weave on replaced/repaired sections. The Pengard is excellent. It covers many smaller blemishes. I applied with a roller and cut back the coats with 120 grit on the orbital. The result was a boat with a smooth, hard, egg shell like finish which took the top coat very well. (I used Jotan Hardtop Flexi applied with a roller with very good results)


Thanks for the help, guys! I have a bunch of phenolic microballoons sitting in the shop, so I'll start on fairing with those guys. For some reason I was thinking you had to at least fill the weave a little bit with just resin before using fairing fillers. All I have left is glassing my hulls, so this should help speed that process up quite a bit.

I agree... I cannot find an old post from Boatsmith regarding this subject anymore, but I made a copy for myself. Here is Davids method:

"We wet the ply first and then position the fabric and wet it out completely. We then wait only a short while (in our climate 10 minutes) and roll on more epoxky thickened with microbaloons and a touch of silica to completly fill the weave. We usually do this twice. Then when it's time to sand tou are sanding low density epoxy and not the glass. This is one of the places where you get to decide just how perfect is perfect is good enough. Time spent with guide coats and a long board can be demoralizing or therapeutic, it just depends on your attitude. Sand off the highs and fill the lows and eventually you can end up with a beautiful fair hull. Or you can stop sooner and end up with a beautiful hull that is not as fair.It's just a matter of cosmetics. David"

Do the microballoons need an epoxy seal coat?

Likely just an epoxy primer coat, Roger.

Filling small voids and glass weave with fairing compound:

•Mix epoxy as normal.

•Add low SG fairing ballons (.25-.32 sg) to near peanut butter consistency (DO NOT use higher SG filleting balloons (.55-65 sg) as they are much more difficult to sand.)

•Add silica to reduce sag. (Silica makes the compound harder to sand, so be FRUGAL. Add only just enough to keep it from sagging. Filling small voids of less than 1/8" depth will nearly be sag free with just the balloons, even on inverted surfaces, but a small amount of silica is still required.)

•Spread the mixture over the surface with a broad putty knife to a maximum depth of 1/16" above the surface. We even use 12"-20" concrete spreaders and trowels on broad surfaces.

Properly mixed fairing compound will sand with extreme ease, even better than automotive bondo type fillers, so be careful until you are familiar with how quickly the excess material is removed from the surface.

We use Progressive Epoxy micro-spheres (.28 sg) to create fairing compound.

Once applied and sanded to desired finish, only primer and paint is required to protect the surface. NO SEAL COAT is required.

For those seeking a truly professional surface, use 3M Acryl-Red Glazing Putty (or similar) to fill the small pinholes and sandpaper scratches in the surface. This product is not for filling weave, but to fill the tiny voids (air bubbles that form) in the fairing compound, or small shallow depressions in the surface (usually caused by overzealous sanding.)

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