View Full Version : Any tips on fairing?

07-22-2010, 06:52 AM
I am in need of some tips on fairing.
I am working on the bottom of my tug-along and have used a notched trowel to put down the epoxy and made a long board and sanded it smooth now I have to fill in the grooves but this seems like I am using too much epoxy. Also, during my first attempt to fair the bottom I used a big metal blade to try and put the thickened epoxy on but it came out too thick and I had to use a belt sander to remove it. I am using 3m glass bubbles to thicken the epoxy.

What is the best way to fair the boat on the exterior and the interior?


wizbang 13
07-22-2010, 08:36 AM
No short answer . But I am curious,a 16' tug needs bottom fairing? More info. ,pics. I am not a fan of the notched trowel/longboard(torture board)method.

07-22-2010, 08:46 AM
A really fun looking boat you are building, nice job too.
As for fairing, the purpose, as I see it, is two-fold;A- To make it look good ie. cosmetics, and B- to increase the ' laminar flow'.
On the bottom, it is almost all about laminar flow, so it depends on how un-fair the bottom panels are and how important that is to you, as to how much compound you use in fairing.
Inside the boat is all about looks and I have never 'faired' the inside of any boat I've worked on. That is, used fairing compound, just sanded as fair and smooth as possible.
You say you troweled on the compound and sanded 'smooth'. Smooth is important but fair and smooth is the goal.
I use West and microlite (410) for fairing and trowel it on about 1/8' thick or less,depending on how much it needs, and longboard off the high spots (the flex in the board finds these) until I just 'touch' the epoxy filled glass at these high spots, being careful not to sand into the glass. The low spots will show up and need to be filled. These low spots need to be 'scratched ' evenly and lightly to accept the next fill layer.
I don't use a notched trowel because I have trouble sanding into the bottom of these 1/4" notches, but others have good results with them.
Keep doing this until you are satisfied, or fed up, which ever comes first. After which I squeegee on a thin coat of epoxy before sanding and priming.
Thats my take on it hope it helps, good luck with your project and keep up the energy.

wizbang 13
07-22-2010, 08:50 AM
smooth and fair are 2 different things. belt sander=wrong Did Jackster see some pics ???

07-22-2010, 09:08 AM
Yea, Blake has documented his build pretty well, with pictures and all!
I clicked on his name and opened his previous threads.

07-22-2010, 08:43 PM
wizbang, the reason i am fairing the bottom is to try and blend in some of the ridges from where the fiberglass overlaps and it is also a good place to practice fairing since it will almost never be seen. I had to use the belt sander because the thickened epoxy went on way to thick so I had to take it down some.

jackster, Thanks for the tips! how well does the Microlite trowel on? it probably makes no difference but can be used with other epoxy brands? so with the notched trowel, i sand it down almost all the way to the fiberglass and there will still be ridges that need filled in the low spots right?

Here are some pictures that i already posted in my build thread but it shows the shapes of the sides that i will be working on soon, as of now, the entire exterior is covered with 6 ounce fiberglass cloth and the seams have 17oz biaxial and 6 or 8 ounce fiberglass tape.




07-22-2010, 09:32 PM
First make sure the wood is fair , if you have a bump in the wood , you well have holes in your glass when you start sanding
next put your glass down and stretch it tight with no wrinkles , as you brush on your resin make sure the glass is totally wet then remove the extra resin so the glass does not float . At this point you should still be fair , when the resin has stiffened enough then apply another heavy coat to berry the glass . After curing take a sanding block at least 11 inches and try to just nock off the high spots without exposing the glass , As you start glazing the trick is the less you put on the less you have to sand off , so use a stiff wide blade and only fill the valleys , Then take you sanding block and nock off the high spots , repeat till smooth :) The thicker the fill the more chance of loosing fairing .

wizbang 13
07-22-2010, 10:15 PM
So the boat is glassed now and you need to fair the tape edges and fill glass weave?407 ( red phenolic baloons) may be better for rough fairing. 410 (microlight) is for very small thicknesses. It sands very easy but is weak/brittle. A slow speed 8" softback will perform better than a belt sander. Much better.

07-23-2010, 04:49 PM
Ramillett, i have the exterior already glassed, so you are saying to just take the blade and apply a very thin layer to just fill the valleys and sand and apply again and sand until i am satisfied with the outcome?

Wizbang, where do you get the fairing supplies? i have a 30"+ fairing board that i have been using to fair the bottom, would that be the best to use or should i use something smaller?

I am trying to end up with a very fair/smooth surface because i think i am going to go with a deep green color for the exterior and i don't want to see a lot of flaws.