Made single concave depth too much for too long

General Discussion
1

I have a board that I made the single concave a little too deep for too long.

Consequently I’ve got too much lift in the tail through the fins.

This of course is creating some problems.

I am using probox fin boxes with 4degree cant inserts.

Figure I’ll slip in some 0 degree inserts to reduce some lift due to fin cant.

Any thing else I can consider like fins with greater depth?

or some bondo preparation that I can sluice on the bottom and smooth this thing out?

Does some suitable sluice exist?

Would be nice to get a coat over of something to perfect the bottom temporarily.

2

maybe rehotcoat the entire bottom and let it flood in the concave

???

3

Yo Otis,

It’s amazing what you can do with fins. If you have an photos of the board send them to me a

Putting fin boxes in the right place with fins that will give the board good release and drive is almost always possible. Boards with full length concaves can be lots of fun. I have one that has very parallel lines and full single concave. The thing goes like a rocket when the south swell is really jamin’ here on the east side of Santa Cruz. I got a wave in the last big swell where I went as fast as I have ever gone surfing. It all happened so quickly with completely instinctive roller coasters that when the wave was over I just a sat for a couple of minutes in amazement. I think I may have gone over 25 knots on the wave. The board I was ridding is a quad. IMHO quad setups are the best call for single concave boards. Larger trailers will calm things down but size and configuration depends on many things. The board outline and rocker will say a lot.

No Worries, Rich

4

You can mix up some of your own thick light “putty” with resin and “Q-cell” - fill some, more than you’d think, then try it, you can alway take it down easy.

The fin thing sounds good too.

5

Four, single foiled fins, canted even 4 to 6 degrees, creates a TON of lift alone. Combine that with some concave and you end up flying…

6

instead of zero cant you can try smaller fins for less lift.

7

All good suggestions. This is from Bill Barnfield…melt a coffee can’s worth of paraffin (wax) and pour it into the trench. You can either shape it or you can balance the board on some racks so that it flows where you want it. You can do it in stages so you can find the ideal depth and length. Then gouge it out and replace it with q-cell/resin or bondo to the optimum shape.

Or, my favorite, it’s a great excuse to make a new board!

8

Otis,

  1. Greg Loehr has said a few times, soften the hard edges of the rails.

  2. Reversed 3d fin as a trailer, i mean, shape one yourself, exactly the same, but reverse the area that creates lift.

Wouter

9

I’m loving all these suggestions.

All quite good!

Halycon thanks for the offer, but playing dentist and filling is my route.

Morever, I’m shaping another one to replace this one soon.

So I’d like to play with correcting the concave and see how it affects it.

Ive decided to backfill with sanding resin perhaps a 3 layer approach.

Qcell and resin although a good idea, I’ve seen that stuff crack from flex and stress

over time. My guess is the sanding resin will do better in that category.

10

Brushed on 4 different overlapping layers(mid pt through tail) of sanding resing with extra surfacing agent in it.

Sanding wasnt too bad, although I’m sure its not smooth as silk.

slightly overhead waves will be the test.

Figure I might have to do 2 more layers to finish it up.

One just a complete finishing–hot coat over the entire length.

Initially had .20" or somewhat greater concave depth extending too far.

Now down to .16" max and fading properly.

11
Quote:
Brushed on 4 different overlapping layers(mid pt through tail) of sanding resing with extra surfacing agent in it.

Sanding wasnt too bad, although I’m sure its not smooth as silk.

slightly overhead waves will be the test.

Figure I might have to do 2 more layers to finish it up.

One just a complete finishing–hot coat over the entire length.

Initially had .20" or somewhat greater concave depth extending too far.

Now down to .16" max and fading properly.

Followup: this totally fixed my board. However 5 layers

of sanding resin were required in the mid through tail area

and a necessary stress crack appeared between the two side

fins. So far manageable and has not run amok.