I’ve been thinking about my next board, a 7’6" tri-fin with forward V gradually running into a mild single concave in the tail.
Here’s question #1: Should the V persist longer on the rails or down the stringer as it approaches the tail? So, for example, if the V persists longer on the stringer, I’d end up with two concaves coming in from the rails, merging into the single concave in the tail. Perpendicular transition…an abrupt step into a concave. If the V persists longer on the rails, then I’d get V running directly into a single concave with a convex step into the concave.
Q#2: Has anyone tried this. I know Maurice Cole did the reverse V, I’m just not sure what the tail configuration was. I have a feeling this could be straying from the “keep it simple” philosophy, but I have high hopes.
Well Peter, it’s like this: You’d have an odd bottom configuration, since the water would flow away from the stringer, then toward the stringer. It’s simple, your board would explode.
Cole is explained in the archives, and you could do it… do what ever you want. If it’s not to drastic, no problem, and even if it is, so what - smooth out the transitions and go for it. Taylor
I have just done a 7’6 pintail for a guy (tried to post). had a double concave . He rode it last week in cyclone surf ot eimeo and said it cranked. double concaves are similar to reverse v (close ) maybe. they are fast.
Thanks for the input. So what about that transition between the reVee and the concave? I guess having the vee fade out along the rails first would actually make it a reVee to double concave to single concave.
Pandanus: Was your double concave just in the tail? What was up front?
Greg: What would it look like under a straight edge in that transition zone?
Rickholt: Same question: How do you transition from the reVee to the concave?
Thanks again.
Peter
P.S. From mayhemb3 (Greg Webber) in a discussion about reVee.
“One thing to think about is when you change the tilt of the vee from posative to negative and even back again the water is being being asked to conform to an altering angle of thet plane. I did a roll nose to a tail concave both about 3/8”, and the transition between the two did’nt feel great. For whatever gains may be made by forgivness curves (roll/soft rails)at the front there is a significant loss in balance, making the sweet spot smaller…but who cares, it’s just a different feel anyway! GW"
P.P.S Okay, I suppose I could have trolled the archives a bit more, but in the same discussion, Greg Webber gets to my point:
“The flat panels meet at the stringer to create an angled join, and the best combo i found was to carve out the stringer at an accelerating rate as you head off the tail.ie don’t bottle-neck the water flow, or like concaves that do the same thing, they will lift more than they bite.”
The transistion is very smooth. It runs from a vee in the front to a flat at about the mid point then gradially to the concave, which is deepest between the front fins then back to flat at the tail. I did so many that I got to where I could shape the whole thing in one pass adjusting the planer foot as I went. They were real smooth when I finally figured that out.
Aloha! Greg is right about the transition through the length of the bottom. What I mean about the importance of the nose and tail kick, is you need some room to engineer the contours into. I think that it’s important to keep in mind the stringer line curve, and the bottom outline curve. That helps to blend it all together. I always start with rail to rail flat and then add the extras, to maintain control and exactness. Over here, I usually put the RV on 7’ and up gun types, and it’s also a good feature on wider ‘manhandler’ types, to help maintain looseness with the extra width. Aloha…RH
Rick and I are really in agreemant here. I also like RV in guns, makes them tube ride nice and just sit down in the water better at higher speeds Running a concave through the tail maintains the drive charateristics that tail vee would take away. I too start with flat and the difficulty in RV to CC is that the rail rocker in the front end is going to be changed by vee and the stringer rocker in the tail is changed by concave so you have to set up the blank for this when the contour is still flat. Not real difficult but it does take some planning.
Getting the rail line right first sounds like good advice. I’ve got a good mental picture of how it ought to go now. Thanks for the excellent feedback. I’ll post pics when I’m done.
I’m an ex-windsurfer, who builds kite-surfboards, I’ve always been interested in reverse V as applied to wind driven surf craft that will see a crap load of wind chop on the nose of the board… I’ve been working on a nose v to double con .( or single out the back ) kite surfboard…
Wind chop is a big factor here, and the rev.V might be the ultimate answer to the wind induced side to side “nose wag” experienced when heading out through the waves… You ex -windsurfers know what I’m talking about…
I’ve been considering a V to triple concaved bottom of late…
All my boards are under 6’ long, no need for longer…
Any ideas/comments will be greatly apppreciated…You ex windsurfers know how the chop affects the ride going out, as well as coming in… I don’t surf, never have unfortunately… I jump to attention when it’s windy, usually cross on…