the fin and box design is for the following application; still water fishing sup 11-12' x 32-34". i imagine i will find myself in shallow water from time to time and would like to have the fin pivot up to prevent most damage.
the red dotted annotations try to reflect the extra material removed from the board to encourage the fin to pivot up. the rear channel will be just larger than the thickness of the fin blade where as the front will remove more material to allow for the large trapozoidal top of the fin to move. the blue annotation is where i plan to have the fin pivot. this is my initial idea and i imagine there are better functional models i can follow.
note: i have seen the thread on home made fins and will integrate a textbook foil into my fin. the fin displayed in the attached image is more of a place holder than anything else. i plan to keep a more traditional fin shape with extra height to promote straighter tracking and more stabilization, correct? i would like to hear some dimensions i should follow for height and width. i plan to shape the hull similar to a bote hd; should help track straighter and also reduce water noise. i mention this as it might reduce the recommned height of the fin?
what advice can you offer on fin dimensions and also pivoting box ideas?
I can save you a lot of work. Look into where race SUP fin design has gone.
Really shallow fins that are very long in length.
They provide straight paddling and the shallow depth for speed. For you, the shallow draft is ideal. Plus, the ones Larry Allison is doing at Fibreglass Fin Co use ball dents to secure them in the box. That means they pop out when you run aground.
Some of the first ‘‘modern big wave guns’’, of the late 50’s, used shallow fins 4.5 to 5 inches deep with 10 to 12 inch base lengths. Re-think what you’re doing. Give consideration to the 15 inch FU box. Lots of room for a long base fin, as well as room for fore/aft adjustment. (that’s what I’d do.)
i understand the underwater world is unpredictable and would hate to jeapordise something i put a lot of time into because my fin/fins do not move. i do not mind putting a little extra time in now to cause peace of mind later.
hans:
i want to help keep the sup as stable and tracking straight as possible while fishing. my kayak i fished many years from would pivot and be blown all the directions but the right one.
dwight:
i looked into those fins and similar designs. i am having a difficult time finding an illustration of how these" ball dents" work. can you link an image of a fin setup that promote lifting upon impact with bottom?
image link...i like how these look. http://s3.amazonaws.com/true-ames-20110412/assets/uploads/4815/large/wood-fins-line-up-700.jpg?1366838985
also like shape of these fins. http://www.standuppaddlesurf.net/gallery/s-i-c_recon-10/sic-recon-10-sup-surfing-board-09.jpg
thrailkill:
these long and short fins sound like the ticket. does surface area play a large role in fin setups; suspect it does? like 2 smaller shorter fins with similar surface area to larger taller fin has similar characteristics; e.g. similar roll resistance and tracking? or does one setup tend to hold an advantage? i understand fin shapes are dynmaic and can really influece the outcome but when keeping similar profiles and surface area but comparing 1 fin to 2 fins do both setups preform similarly?
i dont think my concerns are found but i still have them untill i become informed otherwise. i guess the idea of having a fin deeper in the water would reduce the rolling of the sup. but if 2 fins can accomplish similar roll resistance and be half the height id prefere this solution. i can better visualise how having similar surface area in the horizontal axis will result in similar tracking characteristics between both 1 and 2 fin setups. in my mind it just seems like it might be different for verticle axis; lots of variables muddy this topic.
im still looking for better ideas on a how to integrate drop in the fins and allow for them to easily pop up if they contact something.
For a flat water fishing SUP you can forget all that you’ve read or heard regarding ‘surfboard’ fins or fins for SUPs in the waves… Have you watched many SUP riders paddling in flat water? The tracking capability of most designs is pretty dismal. With few exceptions, riders are frequently switching the paddle from one side to the other just to keep going straight. Vertically oriented surfboard fins are designed for maneuverability, not tracking so much.
You would save yourself a lot of grief and trouble by simply glassing several long strakes to the bottom of your hull. They don’t have to be very deep. Think of them as long shallow keels. If glassed heavily they can protect the hull when you beach it.
A pivoting retractable fin will be a pain to engineer and build. It will likely develop leaks down the road. For your purpose long shallow keel-like strakes might be a better, cheaper, and less troublesome option.
I’m not saying that this photo represents the ideal strake design but it should give you some ideas.
