hi everyone!

i have a 23cm LW/McD speed fin and its taken some scrapes an chips over time,

whats the best stuff to use as a filler?

also the fit in the tuttle box isnt perfect, sits in a good few mm, again whats the best for building up and rubbing to fit?

thanks

Epoxy resin is the go. depending on how much build up you need, add some fibreglass. If there's not much damage, a thickening powder of some sort added to the resin, will stop it from running.
There's an epoxy product over here called "knead it". good to keep with you for running repairs. it's a little finger sized stick, you just cut off a slice and knead it to mix, then apply, sets quick and is quite sandable after it sets.

thanks,

without sounding an idiot typical sandable fillers dont work? like car body filler

also what grade papers would you recomend?

cheers

epoxy resin with a thickening powder (Q-cell or anny others) are very hard to sand is sugest just a car body filler and mabey just try a few washers to push your turtle box back out instead of trying to build it up then sanding and try to keep it square and neat ..

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nick0 said...

epoxy resin with a thickening powder (Q-cell or anny others) are very hard to sand is sugest just a car body filler and mabey just try a few washers to push your turtle box back out instead of trying to build it up then sanding and try to keep it square and neat ..

i dont know what you think Q-cell is but it is designed to to be light weight sandable filler. You need to mix it to a light and fluffy consistancy. This will allow it to be sanded very easilly. Q-cell is not water tight so it wont be good for you fin. You need to find a filler that has a closed cell such as fairing compound. i have repair many fins this way. it the nick/ gouge is biggish i usually fill it with faring compound and then glass over to top. i use Bote-Cote Epoxy resin.

To pack out the fin box I use teflon (ptfe) coated fabric (self adhesive). We use it in the composites industry as a release film rather than wax or pva. it comes in varying thicknesses. The one I use is 5 thou. The last board I did, the fin was about 3 mm too far in when the screws were firm. One layer on either side of the fin box and it's just right. Available from Dotmar enginerring plastics, they're in all states. I buy it as a 1 metre wide roll but possibly you can get it in a narrow tape.
Product name is Chemstick.

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Bender said...
[>>>> Q-cell is not water tight so it wont be good for you fin. >>>>

Not a problem Bender all it needs is a coat of paint afterwards, I use automotive sander primer spray cans. Not a bad idea after any fin repair as it shows up any defects and helps to fill those small pin holes.

I agree that epoxy with qcell should sand very easily..
Automotive body filler will work, but it's polyester based not epoxy, so there will be a mismatch between fin and filler properties. Not sure how important this is.
If you already have some in the shed give it a go, if no good you can always redo it.

I start of with 80 grit if there's a lot to sand off, 120 if there's not much, but work my down to 400/600 wet and dry for the finish.

If you've got alot of blemishes over the fin you can cover the lot with a two-pack epoxy high build primer, this is a paint that is quite thick and sands to a very smooth finish easily. I've done up an old fin by firstly filling the deeper recesses by squeegy, it dries pretty quick. then a coat of paint all over with squeegy then sand as per decrepits post.

I use super glue (Cyanoacrylate) mixed with carbon and/or ceramic powder to fill the scrapes.

Fred

Hallo Eastcoast! That what Fredstyle wrote is the shortest and the best way.
There i work carbonfins, have I enough powder. Super glue, please like water.
At first glue on the fin, than powder and glue and powder. Make it a little hot
and 5 minutes later you can work with sandpaper. The same way with the box.
In front or back side ( what is better for the position of the screws?)
If you have problems to get powder, I can send you powder. I am here in
Germany. Wolfgang