You say that you know what you are doing when it comes to repairing boards?? You should NEVER EVER ever use a heat gun to soften up a box to make your fin fit in it. The box has to be heated up considerably more than the surrounding materials can handle to make the box material soften. The heat can/ will either lift the lamination cap and/or distort materials such as EPS,pvc that are in the area of the box.
The corecell inside the tuttles is 3/4" (2 cm) unless it was heated up by your heat gun technique and shrunken or distorted. If you did this originally to make your fin fit in the box, you caused the damage and the shrinking/burning of 2cm of corecell.
Since you have mentioned this technique on this forum, you have probably recommended it to others before, so I want everyone to know not to ever do this to your board if your fin does not fit.
The remedy to making your fins fit is to :
1st check the top lamination of the box (we call it the cap) covering the box. Sometimes this top cap has not been sanded or filed enough out of the way when the cap was originally routed open. You want to make sure you do not lift this lamination cap by forcing the fin in and out. File or sand this cap at an angle so your fin cannot grab it. Caps are generally less than 1 to 2 mm of glass and/or filler.
2nd Check inside the box for extra resin, paint etc that might be causing the problem and carefully sand or file it out. Do not sand thru the Carbon. If it is a plastic Chinook brand tuttle , then there is less chance of hurting the box.
3rd Check the fin itself and you can you start sanding the fin base itself carefully checking it's size in the box as you sand it.
Many fins are made with the different and sometimes wrong sizing of the bases. For instance, what we call a Cobra box (boards made at the Cobra facility) have a smaller sizing of the Tutlle specifications. You can take your Starboard fin and it fits very loosely in the real size of Tuttles and visa versa a real size Tuttle will not fit all the way inside a Cobra made board.
So please everyone, do not use a heat gun to make your fins fit into a box on any board you own, this does not refer to only race boards, any board can have problems when using heat to soften up a box.
The heat gun was set at 80 °C. There was no damage to the Corecell and the Board is fine and everything worked. I was very careful and made sure that it didn't get too hot.
Your way of solving it would have ruined the Base of my fins as I would have had to sand off about 5mm each side to make it fit. Just man up and admit that there may be a problem with the Board I have and that the Box is not reinforced like it should be.
Just let me explain the exact sequence of events.
1) I bought the board at Sylt from Bjorn. Fins fit fine
2) In Italy it took in a lot of water.
3) I let it dry out in the sun the last day and about a liter of water came out.
4) Back home I let the board dry out for a week. I am sure the Gore Tex Valve was not working properly as after the drying the walls of the boxes had been compressed together and the fins did not fit at all, not even close.
5) Slowly and carefully heated the area in the boxes and forces the fins in. This worked pretty easily. The board has been fine ever since. The rest of the KTE tour and the PKRA Germany and no problems with the boxes since. I did replace the Goretex Valve with a normal screw insert.
I do know what I am doing when I repair the boards and I am pretty damn sure that I know what I am doing when it comes to construction.
Just a question on the Board I have: It's basically just EPS One layer of very thin carbon and Glass. There is no Corecell shell or anything to protect the eps like on Sandwich boards I have been making. Was that how it was supposed to be made, or did Cobra stiff you on materials? It's a pretty fragile way of making a board and its super susceptible to pressure dents. Are your new Boards the same or proper Sandwich construction.
A note on the Boxes in the board. They are Deep tuttles and there is only about 2mm worth of Glass and Carbon that the Screw and Washer lays on. In Italy I snagged a platic bag and that thin layer under the screws broke. That is where water was getting into to board too.
And one more time before you tell me I'm an Idiot again: THE BOARD IS FINE NOW AFTER MY REPAIRS TO IT!
If it interest you which board it is: https://vimeo.com/32115045 you can also see that I have laminated 600g glass over the boxes to reinforce the top deck so the screws don't break the deck the next time I snag some thing on the water.