Has anyone seen any boards with fins near the front of the board? particularly small boards?
Im considering putting 2 x 2" “side bites” in line with the turning arc of my 2 keels on the 5’5" fish Im shaping
the idea being that this will help hold the nose high on steep waves if I place my front foot over the side bite…
my thought were to make them slightly curved when viewd front the front and set them at about 6-8 degrees 3 inches off the rail…
Think dick von straalen centre fin on fish, done smaller and up the front of the board - say 1’9" from the nose.
Any thoughts or pics of something similar?
riff
At one time I put the equivalent of four small keel fins on the bottom of the forward foil of my hydrofoil paipo board. While not a very similar board, the general principles remain the same.
In my case, the purposees were spray suppression and to provide mounting points for the speed sensor for a water speedometer. However, that configuration only lasted one surf session. It definitely wanted to “hold the nose high on steep waves”-- so much so that tilting the board toward shore (to keep from getting sucked up and over the face) resulted in the craft rolling over about 90 degrees. That left the craft “planing” on the two lower struts (instead of flying on the foils) and me lying on the top main strut and forward strut; leaning way over to the side (toward the face of the wave) and on the verge of rolling even more. That lasted for a distance of about 30 feet before the wave steepened a bit more; the craft rolled a little more and got out of balance; and the craft and I capsized.
The “problem” is that when trimmed for traversing across the face of a wave, the front of the board is both lower on the face and farther away from the curl. That being the case, the slope of the wave face is less near the front of the board than near the rear. Therefore the flow past the front of the board has an offshore component relative to the flow at the rear of the board (and there is a smaller vertical component to the flow at the front than at the rear). The end result is that drag on the wetted portion of the front of the board from this across-board flow tends to pull the board toward the face of the wave. With a regular board, this is compensated for by tilting the board some (shore-side rail of the board lower than the wave-side rail). This generates a shoreward component to the pressure force acting on the bottom of the board near the front that offsets the drag force toward the face of the wave. The onshore component of the pressure vector at the rear of the board created by tilting it is compensated by the generation of a small angle-of-attack of the flow past the (rear) fins–so that the whole system remains in balance.
This pull into the face of the wave characteristic is obviously exacerbated when one puts a fin near the front of the board (the resulting lift force acts equivalent to a drag force toward the wave face and can easily be much greater than the friction and form drag over a smooth bottom); when riding hollow waves; when the height of the wave is comparable with the dimensions of the board.
It is also excerbated with a longer board. I have an 8mm movie from the early 60’s of Butch Van Artsdale riding a longboard with a (large) skeg at each end. Everything was OK while the forward skeg was out of the water. But every time when he would trim to traverse across the face of the wave, and configuration of the board on the wave would change to where the forward skeg penetrated the surface of the water, the front of the board would abruptly be pulled toward the face of the board and Butch would wipe-out (towards the short side of the board).
So, in summary: yes, the addition of one or more fins near the front of the board will help hold the nose high. But be careful what you wish for and do all things in moderation (plus you might want to bring a file or some other tool that would allow you to modify the fin size and find out what works for you).
Hi Riffraff, similar to Terrys boards, Ive been putting fins, strakes, runners on the front foil of my boards.
Simple description,
without front fins, you are always pulling (turning) the board UP the wave face ,
with front fins, you are always pushing the board back DOWN the face.
Totally different riding technique needed, further forward, and you move along the wave by turning down, replacing the bottom turn but not removing it.
do you find that its more positive to turn - if you want to draw a line does the board do it by itself or do you still have controll to make it sharp or arched out and… er… swoopy (ok… swoopy may be the wrong word but… meh… wacha gonna do)
They’re gong to make the board impossible to turn in critical sections. If the nose and tail are connecting at the same time, the board will feel like it’s on rails… but you’ll have no control of the track. On steep fast waves, you’ll get stuck to the face and take many rides up and over the falls.
Have you seen what Skip Frye is doing with fins sticking out the sides of the tail on his fish? It’s in the current Surfer’s Journal.
If you want to try front fins on an existing board, I’d suggest making them stick-ons. just flare them out to a wider, flatter base and use 3M double stick adhesive (for marine use) or epoxy to attach them. That way you could pop them off, move them around, and try different setups without having to put fin boxes all over the place.
