Does anyone have any advice for concaves and quads? I was thinking of trying a double concave through the tail with a quad. Should I go single instead?
Hi Deanbo,
Double concave sounds more stable at higher speeds, it depends on what you’re after…
Check Superturtle in the photo archive, for a complicated bottom shape.
Works fine at any speed
Soul
Hey,
I have a few quads and they are all single concave. They are not too deep. I also ran a straight edge along the bottom of a couple of Stretch quads and they were single. These are all HP shortboards I’m talking about…
As for the ride on the ones I own, they seem to go. So, what does this prove?
Not much.
Good Luck
I am sure that there are other here who would know better than I, but I have made a few quad semi-fishes this past year for friends.
I used a single concave starting about 8" from the nose, about 3/16" at its deepest (where the front foot would be) into double barrel concaves starting about 1/3 of the way up from the tail going to 1/8" deep to flat out the tail. (double barrel, meaning that the concaves are set inside of the side fins)
(this ones a tri-fin, but it gives you an idea of the concaves)
I have had good feedback from all of my friends on these boards.
I recently built a quad with a shallow single to double out of a fairly low rockered blank. If it had more rocker, I’d go deeper with the concaves, particularly the single.
It’s 6’4x12.5(?)x21x15x2.5 and rides really well into the 1-2’ overhead range. After that, there’s just too much width. But from thigh high to just overhead, it’s the best board in my quiver for the snappy beachbreaks we have here in NJ.
Deanbo
The most successful quads in Australia at the moment are being made using Brian Mckee’s formular. Mckee advocates vee or double concave. The reason being in the absence of the centre fin you don’t have as much of feel for when you’re in the neutral centred postion when starting or ending turns. You can sometimes see this in video of guys riding quads or twins, they kind of have this drifty look to what they’re doing whereas the thruster will look to be more direct and precise. McKee overcomes this problem by moving the fins closer to the centre line and by using vee or double concave in the bottom. With double concave you’ve got water squirting along either side of the centre line so you can get subtle cues when you’re centred. So the short answer would be use double concave.
On this point, could someone give a description of the Pavel quan (speed-dialer) concaves. Where does the double start and end and the single begin and end. The “double into single barrel afterburner!” thingy.
Just my two cents. I tried a few shapes with singles to doubles on quad round pins. I ended up going back to singles. A few of the boards had the single starting above the center line getting progressively deeper out the tail, others had the concave starting further back on the board with shallow to flat tails.
The ones with the single concave running out the tail worked the best. Those boards felt faster with a smoother carving feel on top turns and cutties. The few with the vee worked good but the feeling wasn’t as positive. Another tip is to make sure to compensate for the concave on the box/fin installation. The first few I set with the jig flat on the concave and they went o.k. but the ones I did after with the fins canted further out to compensate for the single concave went unreal.
for more of a pulled-in tail (quad shortboards) i would say a double concave through the fins.
for a wider tail (swallow tail quad fish) i like V through the fins.
I am currently building my #1 after a Speed Dialer 6’2". Mine will be a scaled down version at 5’9". The bottom contour on the Pavel is a rolled Vee entry transitioning into a light double concave under the front foot…this then transitions into a medium deep single concave. For the first part of the single concave the double is present WITHIN the single, to just in front of the leading set of fins…at this point the contour transitions into a fairly deep single concave out the tail of the board. Make sense or no?
This is the bottom contour I am chasing, but it’s a bit complicated for my first board! See attatched photos of ALMOST finished ‘Fletch-Dialer’ as I call it…
Quote:
I am currently building my #1 after a Speed Dialer 6’2". Mine will be a scaled down version at 5’9". The bottom contour on the Pavel is a rolled Vee entry transitioning into a light double concave under the front foot…this then transitions into a medium deep single concave. For the first part of the single concave the double is present WITHIN the single, to just in front of the leading set of fins…at this point the contour transitions into a fairly deep single concave out the tail of the board. Make sense or no?
This is the bottom contour I am chasing, but it’s a bit complicated for my first board! See attatched photos of ALMOST finished ‘Fletch-Dialer’ as I call it…
Hey Fletchdialer…paint your side wall and garage door flat black or a drak color so you can see what you’re doing.
I’m interested in this because I thought wisdom from 80’s quads was to avoid single concaves with quads. Something to do with having to lower the tail in order to retain drive as the single centre fin of thruster concept moves out to the rails as 2 fins in the quad concepr (and forward) .
What’s evolved to change this or is my information abot single concaves and quads incorrect?
Not sure about that one Red, putting more fin near the rail is going to give you more drive not less. When I decided to build a quad I did a lot of research, just reading every review I could find online, in mags, pros, average guys - there seemed to be more positive reviews of the McKee set up than others so I’m assuming his theory about compensating for loss of centre line feel with vee or double concave is valid. However you can see from this thread people have different experiences.
Howdy,
just to say that in my early days of quads, the first ones having larger rear fins, I had the rear fins out on the rails.
To keep the rails from pulling in or rail grabbing, I had a fair bit of toe-in on all fins.
Looking down the board from nose to tail this obviously had a wedging look, so having a nice big Vee double-concave was a way of feeding this thirsty wedge and actually I felt it generated much more speed, almost like the Vee was forcing water against the inside faces of the rear fins which was then projected rearward in a blast.
From the initial stages, all my quads were made to counteract the image that quads had as being twin-fin like. The fin positions were for power surfing and out grunted the best that three fins had to offer.
The Tom Curren at J-Bay Search 2 board had this big Vee double-concave, was a 6’11" x 18 x 2-5/16" swallow tail.
There is a foto of the same model in Mission Quattro section of the website, in a collage, with green fins.
The positions at that time were very spread out, like a limousine wheelbase, and with this, the tail fins were forced together in the narrow tail.
Being narrow, the wedging possibilities with toe-in would be even more accentuated, so the big Vee DC eliminated the possibility of hand-braking.
Time progressed and due to the moving of the rear fins away from the rail, I found that the direction could be straighter and basically the direction fell in the sweep of an arc if you focused on the same point that the front fins would cross the stringer forward of the nose of the board.
The rear fins now being away from the rail, also moved further forward, had less of a wedge effect and so I could make concave tails of any type. The use of double concaves in the tail, is just inherited from the early days, but I have since made single concaved tails that also work well. I also found that double foiled tail fins allowed a less restricted flow between the tail fins when straight running before a big bottom-turn, but in the end it’s all just combining the right ingredients depending on your projected shape.
The rear fins being closer to each other, proportionally depending on the tail width meant that after a bottom turn when you are climbing the wall, the lower side fin will enter earlier and straighten the board up preparing it for the downward turn.
In the older models, especially the more clustered ones with fins forward and with fins on a rail, the boards had the ‘stuck on one tack’ feel and needed a body gyration to bring them around. I got used to it and used a lot of rail to rail turning, but for an avid ‘Thruster’ fan, this delayed and tricky turn interchange was a No No.
People are still making boards this way and they can be fast and fun and yes you can get used to riding them and you can do things to compensate for the deficiencies and tricky areas… but in my ‘Mission Quattro’ journey, with a ‘one strike and your out’ policy installed by the majority of test pilots, I had to move forward from there. Eliminate the hit and miss.
The double concave idea is not used for any redirectional purposes, the rear fin placement takes care of that. It is just a safety measure that assures that when you need to milk the last bit of speed when the curtain is guillotining, that you pass into freedom, versus eat shite.
Here's a Video of a board with deep single to double concave 6'3" x 17-3/4" x 2-1/8" on a grunty day at Coxos. Speed to burn..need some new vids though...
http://www.mckeesurf.com/brucemckee/indexfiles/videos/tiagosession3.mp4
Too much to choose from...
Cheers.
Thanks for sharing.
By the way the footage of Curren at Jbay on that board is the best surfing of all time. Not kidding.