twinkeel, have a look at the pics and tell what's wrong

Hi everyone

Well I foiled a fin (keel), I attached 2 pics so you may see what it looks like and for you to see the mistakes I made.

For the plywood I used, the layers didn’t have the same thickness.

I guess I made something wrong when foiling.

It looks like an airplane wing, thick at the base and thin towards the end (tip)

for the foil I guess the leading edge is not round enough.

When I started the foil I drew a couple of lines so the thickest area would be in the 20 or 30 % area.

The thing that happened :

The thickness when looking towards the leading edge I noticed a thing. from the base it is thick and when reaching the red arrow it get thinner and thinner.

To me it looks good, I like the foil but I guess it is wrong because I think there will be a problem once in the water.

Your comments are more than welcome.


You made two mistakes…

#1… Never admit you made a mistake.

#2…Those red arrows are really ugly…

One or two layers of cloth on each side to seal the fins. Two layers of 6oz cloth and some fin rope when installing the fins. Some hot coat and a guy going crazy with a power sander will change everything. You’re Twin Keels look fine to me.

Ray

thank you very much for your pertinent comments.

This time I attached a pic from the leading edge so you may see the foil, I know the pic is not that great but with the red arrow (I know :)!!!) you have the thickest section and then you see the foil getting skinnier and skinnier.

I just wanted it to be like an airplane wing.

Was I supposed to have the foil all thick all the way up to the tip?

Any comments more than welcome, thank you for considering that request.

If it’s killing you, start over. You only into it for 2 small chunks of plywood, and about 20 minutes of cutting and sanding so far.

I don’t really see the problem. They are keel fins, keel fins are not high performance. Just rudders, like the 60’s logs with D fins. Your mainly going for the cool wood look. If you were going for performance you’d be using a Probox, or futures type set up, and you’d be doing a quad.

So the important thing with wood keels is that you got the ply grain even and straight. You did a pretty good job there, but does it match with the other fin? If you want to refoil those, just like the “stingster” said slap some glass on them and start grinding. Adding more glass isn’t going to effect the performance of keel fins.

thanks for having considered my issue.

well I will leave it that way since you don’t see any problem.

I am a rookie so with the overflow of infos available I end up wondering.

I will use those keels and see the result once in the surf :slight_smile:

it took me more than 20 minutes :slight_smile:

I cut the shape with a jigsaw but then used the rasp and a sanding block with 80 grit on it and finesanded it with 120

Last question :

What do you think of a double foil (asymetrical) but still using toe in (1/16") and cant of 2°?

I am aware that with the double foil I have to foil a new pair.

Oceanpearl,

Take a look at the Gephart rudders(keel fins) on the True Ames website. Better yet, buy a set and study them. Yours are foiled pretty well compared to some of the keels I have done and mine worked good. Maybe they are just cool looking rudders… mike

Quote:

thank you very much for your pertinent comments.

This time I attached a pic from the leading edge so you may see the foil, I know the pic is not that great but with the red arrow (I know :)!!!) you have the thickest section and then you see the foil getting skinnier and skinnier.

I just wanted it to be like an airplane wing.

Was I supposed to have the foil all thick all the way up to the tip?

Any comments more than welcome, thank you for considering that request.

ok…

take for example the fin’s base section.

lets say the chord ( leading to trailing edge) is 140mm.

the max thickness ( somwhere at the 30% of chord) is 7mm .

this means that the thickness of the foil is 5% of the chord ( 7mm/140mm)

now if you want to maintain an effective foil along the fin, every section of the fin has to be

at he same thickness ratio as the other sections.

this means that a 140mm chord has a 7mm thickness and a 40mm chord(tip) has only 2mm thickness.

ya did just fine, mate!

now glass it on and go surf…