I am fairly new to Sways. I am a novice shaper and have just shaped a 6’0" x 21 x 2.75 with an 8.5" bat tail which I would like to set-up as a quad. I live on the south coast of England and I think a quad fin set up would be ideal here, but quads are totally new to me and I am struggling with placement. I have bought a set of Lokbox quad fins and was hoping that someone might be able to give me some standard dims for the fins. I have done a search here on Sways but haven’t come up with anything concrete. I realize that there will be a huge variety of combinations but if someone could piont me in the right direction that would be great.
Check out a thread on this forum titled “Fin Templates For Quad Fish” and its various links. Good place to start and almost more info than needed. I just marked a wide squash-tail for quad fins using some measurements off of that thread. I had to make some adjustments. Had to change the distance off the rail of my lead fins to get the “tow” right, but it got me going in the right direction. Use you own eye to make sure . It all comes down to whether or not they look right after you’ve marked them. Use whatever measurements you can glean from that thread and then “eyeball” 'to be sure. Never hurts to let a buddy take a look at them for a second opinon.
Here are the fin measurements for a quad fish with similar dims.
Front Fins: 11" from tail, 1.25" from rail
Back Fins: 5.5" from tail (half the distance to front fins), 1.75" from rail (or straight up from edge of tail, so in your case the fins will be 8.5" apart)
For the toe in find the points at which the nose is the same width as your tail. Point your left side fins toward the point on the left side of the nose and do the same for the right fins. This way both lateral pairs of fins point to the same point on the nose. The back fins will be straight, and the front fins will be toed in about 1/8" to 1/4".
I set my rear fins with a little more toe and splay
than the fronts. Makes sense to me since the
flow of water is progressively fanning out as the
board pushes its way through.
Ive been having similar thoughts except I would like to use same toe all fins but use slightly less toe and a bit more cant than the typical thruster fronts.
Many thanks to all of you who posted advice on the thread. Between you all and the links given I have finally got a position on the board that looks good. Markings are as follows: rear fins 5.5" from tail and 1.75" in from the rail, the front fins 11" from tail and 1.5" in from rail. “obproud”- I took your advice and found the piont on the nose that is the same width as the tail and lined the fins to this. It seemed to look right to me, and with the rear fins slightly further in from rail this gave them a bit less “toe” which I understand is correct.
I have a router so am ready to go. I will be cutting them freehand so if anyone has had any experience fitting boxes without the jig, again this would much appreciated. When the board is finished I will post some pics.
Many thanks to all of you who posted advice on the thread. Between you all and the links given I have finally got a position on the board that looks good. Markings are as follows: rear fins 5.5" from tail and 1.75" in from the rail, the front fins 11" from tail and 1.5" in from rail. “obproud”- I took your advice and found the piont on the nose that is the same width as the tail and lined the fins to this. It seemed to look right to me, and with the rear fins slightly further in from rail this gave them a bit less “toe” which I understand is correct.
I have a router so am ready to go. I will be cutting them freehand so if anyone has had any experience fitting boxes without the jig, again this would much appreciated. When the board is finished I will post some pics.
Many thanks everyone.
Q
Just to clarify, I am not talking about one point on the stringer where the nose width is the same as the tail width. I am talking about the two points where a line perpendicular to the stringer (at the position where the tail width is the same as the nose width) intersects with the rail line.
The fins should point to a point on the rail, the same rail as the side that they are on.
The back fins should be the same distance apart from each other as the width of the tail. If you moved the back fins in toward the stringer from this position and still pointed them at that point on the rail you would have toe-out.
With the formula I supplied your back fins should have no toe-in.
Yes I realised that you were not talking about a point on the stringer, but the points on the rail perpendicular to stringer at same width as tail. I have pointed both fins on right side to the mark on right rail and both fins on left to mark on left rail. The trailing edge of my rear fins are exactly the same distance apart as the width of the tail. Thanks again for the advice. Going to cut the boxes in today. A little nervous!!
Just a quick progress report. I eventually installed the fin boxes at the beginning of this week. Not too bad although it would have been much easier/quicker with the jig.The board is hot-coated and I am now at the sanding stage, after which I will finish with a gloss coat. Can’t wait to get it in the water.
Thanks to everyone for the help with fin placement. I will post some pics for your ammusement ( I realy am a novice) when done.
Finally, here are a few pics of the finished project 6’0 x 21.5 x 2.75 bat tail quad. Sorry the picture quality is crap. Not too good with these computers. Thanks to everyone who helped with the fin placement. Much appreciated.
hi, your board looks really good , have you tried it yet, where do you surf on the south coast, there has been a fair bit of swell on the south side in the last month or so, pete
I surf in the witterings area on the south coast. No decent breaks but better than nothing!! I havent tried the board yet but hoping for a wave this weekend. Never tried a quad so should be interesting!!