What’s the minimum overlap to provide a good bond from top to bottom?
How does the lap width affect the stiffness/flex of the board?
Could lap width be manipulated to stiffen parts of the board and loosen others (cosmetics aside)?
How does the geometry of the rail affect this performance?..if I have a really boxy rail in the tail can I just lap up the side and not come over on to the deck/hull?
The 6’5" thumbtail has 4oz bottom, 4oz top with 4oz patch…the patch laps the rails only in the center and then comes up off the deck…this is all done in resinX
Now get this…I can put the tail of the board up on a table, leave the nose on the ground and literally stand on the entire board (and bounce) and the thing only deflects like an inch…maybe. This still seems really stiff to me. I don’t want to go with less glass, but perhaps I need to dial back the depth of the lap to free up the rails a smidge?
My guess is that the more vertical surface you have, that is parallel or close to parallel with the stringer (thicker or boxier rail), the less flex. Also, the more layers of cloth wrapping the rail, the less flex. I think the width of the lap will only make a minimal change in flex.
I have made two stringerless boards with “variable” laps that don’t lap at the ends of the board.
One is 5’8" x 22" x 2.75", mini-log template, with Ice9 foam and ResinX. I have one layer of 6oz. on the bottom with full laps, and 2 layers of 6 oz. on the top, all S-Cloth. Of the 2 layers on the top, one is full laps, and the other only has full laps in the middle of the board. The board is super stiff (although it is starting to break in, and become a bit more flexy, now, I think), but this is because the rails are very boxy, and the board is thick.
The other one is 6’1" x 22" x 2.75", same mini-log template, with Ice9 foam and PolyResin. It is much more foiled out, and has a layer of 4 oz. and a layer of 6 oz. on each the top and the bottom, all E-Cloth. The layer of 6 oz. on each side only laps in the center of the board (the laps fade out 1 foot from each end of the board), and the layers of 4 oz. lap have full laps. The board isn’t done, still needs fin boxes and a gloss and polish, so it hasn’t been surfed, but it is much more flexy already than the first one.
I don't think it has anything to do with how wide your laps are. As you know, I'm no expert, but my experience tells me that if the glass covers the curve of the rail, then it is going to resist flexing.
I learned a lot about what makes a board rigid when I was building up the rails on my HWS. Here is a shot of my board as I was gluing on one strip on top of another.
The first few strips coming up from the bottom don't do much for the boards rigidity. Not until I started putting on strips that were angled over towards horizontal did the rigidity start happening. I think that if you want more flex in the tail, then you need to minimize the amount of rounding in the rails near the tail. You can do this by making the deck curve near the tail section more boxy, or by reducing the overall thickness of the rails. It's hard to tell from the picture, but it looks like you have a faily thick tail. If I were you, I would try removing the crown in the tail, and making the round-over on the rails fairly sharp.
on a side note, a neighbor has been slaying the beachies around here on a little thumb/minilog thing…do you have any comments on template/rails for someone considering building himself one?
any reason you’re back to poly?
if you were to take a stab at it, do you feel the additional flex “feels” like it’s in the foil or the lam…meaning, is the additional flex proportional to the added foil or does the whole lam just feel looser?
I think I need to elaborate, because it appears that my statement contradicts with what OB proud said. I think we are saying the same thing, but from a different perspective. Take one of those Pink Perl erasers. They have pretty boxy rails, and there is some flex. If you do a lot of erasing, and round over the edges, then it will become more flexible, but you just reduced the volume. So I'm saying... given two boards with equal volume in the tail section, then the one with no crown and boxy rails will flex the best.
Ya, too many variables to really make any useful comparisons, with that said, I did the second board in poly to see if I could feel a difference (and because I ran out of Resin-x, I have more coming for my next board).
As for the side note, the best fins are the probox flex side fins (I think they might be Greg Webber’s design) that I snaked off you over at the SurferMag forum classifieds last year. I tried the board as a single (with multiple different fins), and as a 2+1 (with different sized center fins), and it didn’t work very good (for me). I want more of a positive feeling off the bottom (which is why I like quads), so the single, and to a lesser extent the 2+1 would “drift” through the bottom turns. I think that this is because of the short rail line (less of it in the water) combined with too little side fin, leads to less than optimum lift (back up the wave) when loaded in the turn.
So I got those high aspect flex side fins, and a small sharktooth center fin, and the board is amazing. It pumps down the line, comes off the bottom like a quad and releases off of the top like a thruster (kind of…). These fins are the best of both worlds (quad, thruster)… my next board in the pipeline will be built around this setup.
As long as the deck lap passes the bottom lap you shouldn’t need to worry that your rails will split… if that’s what you mean by bond.
My thinking is that larger or smaller laps may play into flex characteristics some but, stringers play a much bigger part. Of course over all board thickness and rail density will vary flex too.
And sure, you can taper your laps wider or narrower at points along board length…. easily done via cut laps, and easy to experiment with from board to board, with variations, to test flex.
Don’t forget, different foam cores will vary flex too.
Stringer, lap width, rail thickness, blank thickness, glass schedule, etc all play combined roles in flex control but it may be that the single most important element in flex control is the amount of deck dome.
Ben Sparks (Benny1) and I exchanged ideas on this and after staging our own independent experiments basically came to the same conclusion. Once you thin out and concave the deck, you increase flex in spite of any changes in material technology including compsand. The fiberglass shell alone from a thick dome deck is surprisingly stiff.
If I remember correctly Bert Burger was keen on the concept as well.
How about tail flex when using a vanishing stringer? Do you guys think varying the size of the laps in the glassing schedule will contribute to flex changes?
