Evolution of my other fish

Here’s the rocket fish I’ve been riding on and off for the last year, now my other fish rebuild is ready to glass and I’m locked down, I thought it would be a good time to do this.

 

This one is 6x21x2.75. Belly nose to single to double and flat out the tail. 60:40 rails, and pretty low rocker. The fins are bamboo and a smaller template than the rasta keels.

 

Ive found this board to be great in a range of conditions from 2 foot to head and a half. Not guna lie, on the couple of  bihger days I I took it out, I knew it wasn’t the right board but it worked. Paddles in really well, probably better wave catcher than my egg. It does in the pocket snaps off the top, you can pump away for speed, and take the board where you like.

However I do have a big issue, when I come off the top to do a cutback and I’m turning through the apex of the turn to begin facing back towards the wave, the nose has a pretty consistent spot where it just washes out on me. This is the same front side and back side, but perhaps happens even more on the front side.

 

I have a 6’4MB, and was planning to use the template from this, but pull the tail in about half an inch, thus pulling the nose in a little and the mid point. If I do this and thin the foil through the. Nose and tail, will it allow a little more penetration in the tail and more bite through the nose rail?

Or am I looking at this from the wrong angle? 


I’m not quite certain from your description what the problem is, but it sorta sounds like a form of ‘twin spin.’  The nose is washing out because the fin isn’t holding it on a line.

I looked over your photos, and I see a problem with the foil on your fins.  I see a flat spot on the curved side.  It might be parallel through the middle.  It kinda looks like the old 70’s foils that had rounded bevels on the front, a rounded taper on the back, and parallel in the middle.  This will result in multiple locations where the flow will separate from the shape of the foil, possibly re-attach further down only to separate again.  The maximum achievable lift coefficient will only be half of what a good foil can achieve.  Our foils need to be about 5-8% thick, the thickest part needs to be at or about the 20% chord, and from 50% chord and back it needs to have a straight taper.  The leading edges should not be sharp - just a nice radius that is neither sharp or blunt.  That’ll get you in the ballpark without going the CNC milling of G-10 glass plate path.

Drela AG03 (flat aft bottom) airfoil

Thanks for reply, 

 

It think the foil is about right, just an optical illusion from the angle of the bamboo. I think I have a picture of the foil so I will try and find it so we can discuss further.

Going back to the issue, Ita a hard one to explain, it happens when the board has passed the apex of a turn where you have (front side regular foot) faced the wave, then turned off the top and are half way to facing the beach again, just passed the 45 degree mark if parralel to the wave was 0 degrees and facing the beach was 90 degree. Just at that point the nose will wash out like under steer on a motorcycle. The nose physically seems to pop out of the wave and go away from you

Does that make any sence?

Ok, now I understand and I may have an idea what is going on.  Looking at your pictures, holding a straight edge against the side view, your rocker is dead straight though the tail.  When you’re turning off the top, your tail is in the hook of the wave; the curve of that water will lift the tail and gravity washes out the nose.

The straightest, or rather least curved, part of the rocker should be somewhere from just behind your front foot to under your center of gravity.  Some shapers put it just in front of the fins, but I don’t like it there.  Behind that the rocker needs to progressively increase.  Then it’ll turn in the pocket easily.

Well that’s experience right there! Thanks Scott, I’ll measure up the rocker again today and revise my plans.

It makes perfect sence, I also remember putting the single concave in after doing the rocker, which would make a flat board even flatter! I have a recollection of 4 inches in the nose and 1.75 in the back, I know this would be a distribution  issue rather than a numbers issue but maybe a more modern rocker would suit this board, 

Put a straight edge on the bottom this morning, there is a super flat spot just under the front foot, the curve then stays steady through the tail. I will work this out the next few days

Well slow progress on this but I have now laminated the board. 

Shape wise I pulled the tail in a little, left the foil similar in the rear 3rd. Trimmed the fat in the nose. I lowered the rail, and got rid of the slight bevel too deck. I’ve left the concave as the original, single to double with. A little v

I did also adjust the rocker, moved the flattish spot to between the feet, and put the rocker dims at 4 1/4 nose, 2 1/8 tail of I rever correctly

Not sure whether to run the same fins or go for some boxes. 

 

Glass wise I used 4oz bottom, biaxial deck patch and 4oz top. Used a little biaxial around the fin area too. Glassed in poly

Digging the yellow streaked in the red man. Pretty combination