hey,
i was riding my displacement hull yesterday(fineline MP), and noticed that the fin isnt far enough in the center(even though its as far as it goes), it doesnt really feel right, is there a way i can extend the fin box like 2 inches? i doubt it can be done, but who knows, maybe someone out there has or knows how to do that.
thanks,
tim
Hi logger -
I’d say you have two choices…
Rout the old box out and install one of the 15" boxes available through Fins Unlimted:
http://www.finsunlimited.com/boxes.html
or:
try cutting away the base so the fin overhangs the end of the box. You might have to drill and reset the pivot pin but you can generally get a bit more adjustment that way.
Johns’ recommendation, above, is bang-on. Try adjusting the fin first, it’s the easiest to do. Go for the box replacement, if necessary.
Hi…
Long time ago when we were using FinsUnlimited boxes, we’d run into this problem occasionally, and the most obvious fix is the long box…BUT…
Those long boxes weren’t nearly as strong as the black FU boxes, the plastic was white and brittle so we… routed the front of the box, installed a partially cut FU black box surrounded by multiple layers of glass and big woodies, and we’d end up with a custom box the length we’d hopefully needed.
Obviously, we’d need to seal the boxes during installation of the extension box, and some care was needed to insure alignment. But it was pretty straightforward and held up just fine with those big, flexy, 10" high aspect curved sabre fins.
I suspect the current 15" longboxes are still not very strong.
Also, adding any extension to the box usually required not only layers of glass, woodies, but also posting thru to the deck at the joint and also every 4". Post material can be just a block or post of ABS or polyurethane plastic…anything to tie the two boxes together and reinforce for stress at the joint. Woodies thru to the deckskin can work just fine.
LeeDD - welcome back to Swaylocks!
Hello LeeDD!
I second Keith’s welcome back. I have referred (myself and others) to your past posts on board design many times. Stuff you’ve posted on semi-gun design is timeless.
Me three - I had to check the date to see if I’d entered a time warp.
Glad to see the old DD there (No offense Lee"V" - that’s always a favorite too! Ha!)
The 15 inch FU box is available in black. So, is now as strong as the other boxes.
Frick! Welcome back LeeDD. I wondered what happened to you. Mike
Hello LeeDD!
I second Keith’s welcome back. I have referred (myself and others) to your past posts on board design many times. Stuff you’ve posted on semi-gun design is timeless.
Historic Day, for sure
Thanks guys !!
Back to boxes… if it’s black and shiny, it’s still the same weak pure plastic. If it’s black with glass reinforcements, which you can detect as less black strands in all directions, it’s a strongbox. Better still, a Chinook product strongbox with serrated outsides, 3 posts thru to deck, and reinforced plastic for the 10"+ sizing fins, reefs, shallow waters, and big strong surfers. Try not to shave the box fitting into thin tails. Instead, for strength, not looks, it’s better to have the box protrude thru the deck and anchored with 4 more layers of fiberglass 3" around the protruding box…use woodies as well, of course, and more cloth than pure resin for installation.
Hey LeeDD - Sorry for my ignorance, but what do you mean by “woodies?”
Howzit Thrailkill, I have installed those 15" boxes a few times and they work great, no failures to date.Aloha,Kokua
Good to hear the black 15" boxes are strong enough, possibly.
The real test is to try them on sailboards, as they are stressed waay beyond surfing stresses, even Wiamea conditions.
Woodies are the wood strips, usually 1.25" deep and more than 1/8" thick, the full length of the finbox, to help spread out the catastrophic loads caused by the fin when it’s loaded sideways by the force of the turn and the rider’s weight.
Most guys who want a real strong finbox, but not willing to go to Tuttle, PowerPox,TrimBox, MeritexBox (did I miss any?) go the route of the woodies, then spider leg short, 3" woodies emanating outwards from the stress area of the box, normally about 2/3rd forwards lengthwise.
Spider leg because 8 is plenty enough.