Hey Everyone. I recently just got done hotcoating my 3rd board and am wavering on the final fin box placement. The board was shaped from a reject blank and was originally just going to be used as a chunk of test foam for planer technique, but it morphed into a 6’6 stub/egg bellied-out wannabe hull kind of thing. I shaped it kinda conservatively in regards to the foil/belly and knifeyness of the rails since I was unsure of my planer technique, but the end result actually looks pretty fun.
Anyways, I have a bit of a dilemma. After doing a bunch of research here on sways in the hull threads, I settled on putting the 10.5’ ‘box in the 7.5-9’’ range. So far, so good.
But this is where it gets complicated- As I was readying the board for hotcoat, I remembered I had some little sidebite fins laying around that never made it to their intended destination… a little absentminded inspiriaton and 30 minutes later, my weirdo egg/hull had some sidebites lam’d on at 1 1/8’’ from the rail and 15’’ from the tail, or about 3/4 the way up from the original fin box placement.
All of this gels with the accepted fin-forward wisdom that I’ve read here about fin/sidebite placement on traditional hulls, BUT after thinking about it a little, I would definitely not call my board a traditional hull. More egg.
So should I stick with the original plan and keep the box in that forward 7.5-9 range, or move it further back on the tail for a more eggy approach and hope for the best with the sidebite where they are?
Tried to convey as much info with the pics as possible. In the fin mock up, the box is sitting at 8’’ I believe.
That's the thing with hulls. You have to play with the fin placement a bit to nail the sweet spot. That is why I like boxes. I always start out at the same place and generally move the center fin up. Depending on the board, the side bites often come out with the trailing edges even with the front (nose) edge of the center fin. Center fin front edge is +or- 13 to 14 inches from tail. That is with a 9" Liddle template fin. And an 8 foot board. This is on a true hull.
Thanks Tblank, I think I am going to stick with my original fin placement in that 7-9’’ range; anything less and the board just doesnt feel right. Sticking with this would allow the fin to hit the marks you describe, with some wiggle room. I’m just unsure how the design critieria for a longer, more traditional hull will scale down into my bastardized version. I DID design (I use that term lightly) the board more or less around the idea of surfing it from the middle… so hopefully everything comes together to acheive some nice glide and trim. Lazy cutbacks, that kind of thing.
Anyone else with advice or critiques to share would be appreciated. I wont be putting the fin box in until tomorrow at the very earliest, so fire away.
Hamrock, Just move that center fin around untill you get that feeling. Start with it rearward and move it up until it gets that loose feeling you want.
Hope you haven't set the box yet! I think your specs are off for a board your size. I set 9' LB's at 7" up (back of 10" box) and have posted lots of pics here about that particular 2 + 1 set up. I think that you should move your box back at least to 5" up. check your tail thickness to see if the box works without grinding at that distance. 2 + 1's work well when the trailing edge of the side fins are about 1" forward of the leading edge of the center fin. I would go no bigger than 7" for your center fin with this size board. I am prefering a wide base fin lately to keep the drive in the shape. Right now, the albacore flex from futures is a good fin. Any wide base fin from Larry A. (fiberglass fins) in this size is a great fin too. You don't say how big your side bites are. Fin areas on 2 + 1's are critical as you need to balance drive with paddling drag on these type of boards. Good luck, and post up what you go with and find out! Just my 2c....
Surfteach, thanks for your thoughts. I probably wont be able to set the box anytime real soon; I’m in the middle of moving and all my tools and materials are in limbo.
I took some measurements-
Sidebites: 3 1/2’’ base, 2 3/4’’ tall, 3/8 thick, 15’’ up from the tail. No cant, no toe.
Tail width comes in at 16’’
Tail thickenss @ 5’’ is 1 1/2’', so still some meat to work with if I decide to install the box that far back.
In your advice of setting the box at 5’‘, I assume that is to adhere to a more accepted LB/singlefin setup for 2 + 1 surfing? Since the board is kind of a compromise in terms of hull characteristics, would setting the box up in hull territory (7-9’') hurt it’s drive? It’s ability to turn? Both?
Can you elaborate further as to why you think it would be a mistake to put the box forward?
The board was a bit of an experiment in technique and materials. I kind of just shaped without any concrete idea backing my decisions up. But as I enter the homestretch, I don’t want to gimp a fun looking board by trying to emulate something it’s not…
Thanks, I will keep this thread posted on which way it goes.
Hello Hamrock...does not look like a "hull" to me. I'm with Surfteach..........
I'm a backyard builder working on board #40. I build three types of boards. Boards I can surf, old school fish for other people, and dream boards. Dream boards are boards I wish I could surf or I think I can surf. Your design falls into my dream section but I think I could ride it if no one was out :)......Start with a 2+1 option ala Surfteach. Cut off fins if needed or make it a quad. I have a board that was a dog...I converted it to a 2+1 set up. The side fins were moved forward 1.5". Now the board works great. As a backyard builder you have the freedom to cut up and change things as needed. I like the surfboard......I see a ProBox quad with a center box........Ray
Taking everyone’s input into consideration so far, I think I can rule out setting the box up at 9’‘… Not that big of a deal. On the flip side, I’m not entirely sold with setting it back at 5’', either. Somehow it just doesnt “feel” right when mocked up on the board. Atleast in my newb opinion, which doesnt hold much weight compared to you more experienced guys.
I think I’ll go with a compromise ~ 6/7’'. This will hopefully allow both flavors of hull/egg to come through on the board, without leaving a bad taste. Im not looking for it to do one or the other perfectly. Just surf from the middle, gracefully trim, with a lazy cutback thrown in.
One thing that has gone unanswered -or maybe just assumed by you veterans- is why it would be a risky decision to put the box in tradtional hull range? Loss of drive? Control? I understand that the flow/foil of a hull and the fin positioning is kind of an esoteric formula. I’m just tripping on exactly why it would be detrimental in my “design”.
You are right, Ray. The shaping of this one was very stream-of-consciousness. Eccentric Decision Dream board for sure.
If you haven't installed the box, my vote is for the more aft position and a smaller center fin. A 5"-6" wide base fin without a lot of 'hook' in the trailing edge seems to work best for me on 2+1 set ups. It's almost always the case where you will have room to move the center fin up in the box but if the box is set too far forward, you might not have enough rearward adjustment. An old rule of thumb was to simply measure the thickness of the box, add 1/4" and fit the calipers to the board to see where it ended up. It looks like you have enough thickness in the tail to put it where ever you want. 5"-6" from the tail is usually a good spot. Depending on if the fin has the screw tab in front or back makes a difference on placement variables. Dedicated 'hull' afficianandos sometimes ride their single flex fins waaay the fuck up.... like trailing edge 16" or so from the tail. It takes a lot of practice, skill and the right wave to make that sort of setup work.
Bottom line.... you say it doesn't "feel' right to see the box at 6". Remember that you're looking at the uninstalled fin 1" or so taller than it will be once the box is set in place.
Hope this helps a bit more. When I first looked at your shape I noticed that you didn't do an "S" deck and there appears to be only a little belly in the bottom and the rails don't seem to be 50/50 thru most of the board with a razor down rail in the tail. These are all characteristics of a classic Liddle style hull. In these types of boards, the boards are surfed in a close-in stance from around the middle of the board. A long forward placed flex fin is what makes these types work the best. The flex is key for turns. In your set-up, it is a more traditional widow-maker set-up with that wide tail. I recommended moving back the box based on your shape and the apparent size of the side fins. 3.5" base sides, subtract 1" center height from single fin size. (ex: 9' lb with sides go to a 7.5" or 8" center) Without toe or cant on the sides if you put the center way up the board will probably be real tracky. 6" would be a good compromize if you are having second thoughts. Like the guys say, you can always reset the sides. The center box is a whole different deal to reset so you want to get it right the first time. Your fin selection for the box will be really important too. Hope this helps!
Just ran out to the shop and looked at what fins I had in stock and took a pic. The 9" fin on the far right is a good example of a flex fin for a Liddle hull. The 6.5" Harbour (by Larry also) is used. The Island is a 6" fin. The 3 on the left of the flex are all considered "wide base" for drive in a 2 + 1 set-up.