Τετάρτη, 16 Απριλίου 2008

Filleting attempts.

Using epoxy to glue wooden parts or sheath plywood was a straight forward procedure with no secrets for the amateur builder. On the other hand, I am now convinced that making perfect epoxy filllets is quite an art! The exact amound of filler one must add to the epoxy to make the right mixture for filleting is something you only understand after a lot of unsuccessful attempts. There is no rule. You just add filler until the mixture reaches the consistency of peanut butter.
After a lot of reading I desided to make my first fillets on bulkhead No 4, which will later on be completely invisible under the bunk of the forward cabin.
The first step was to apply pure epoxy with a cheap brush on the surfaces that would be covered by the fillets. Then I should apply the filleting mixture with a round knife or spatula along the bulkhead to hull side corner. Finally I, theoretically speaking, should form the fillet by draging a round ended spatula of the appropriate radius along the corner, forcing the applied thickened epoxy to take the right shape and leaving the excess portion of the mixture on both edges of the fillet to be cleaned later.
In practice, my first fillets on bulkhead No 4 were a disaster! Although the consistency of the mixture seamed right, as soon as I applied it, it saged down the vertical surfaces of the bulkhead and the hull sides. After a lot of efforts to keep the mixture in place I finally let it cure as it was in order to sand it later on and make better fillets, as soon as I managed to figure out the right procedure.
After some thought and a few more unsuccessful attempts I finally managed to improve my technique and make some beautiful fillets on bulkhead No 2! As it turned out to be, my mistakes on the beggining were:
  • While trying to squeeze epoxy in the fine cracks between the bulkhead and the hull sides I applied too much epoxy which later on diluted the filleting mixture applied.
  • I made large quantities of epoxy which was difficult to mix thoroughly as the right mixture should be very thick. Now I never mix more than three squirts of epoxy each time.
  • Although the mixture may seam thick enough it is better to try if it clings to vertical surfaces like the sides of the mixing pod before applying it. As a rough guide I add about 6-7 full soup spoons of Low Dencity Filler (I use West System products), for every three squirts of epoxy.

The photos bellow show the unsuccessful fillets of bulkhead 4 and the very improved fillets of bulkhead No 2. There is also a picture of a broken metal baking spatula which turned out to be a perfect filleting tool and some photos of the first diagonal stiffeners I installed this past week.



Bulkhead No 4



Bulkhead No2





Diagonal stiffeners