OK it's time for a light wind board that fits in the wagon.

Ordered a 2400 X 600 X 150, 13.5kg/m^3 blank this morning.

So design questions for an early planing light wind shallow flat weedy water board.

Tail width is my main concern, wider should help early planing, but does that mean it needs deeper fins?

If running with short full on deltas, will make trimming hard, it would be better off narrower.

Has anybody had experience with wide boards and short fins, is it a struggle to keep the windward rail up?

I guess I could put the straps inboard a bit to help with that?

I'm fairly sure the planning area needs to be dead flat, for max efficiency in flat water, but a bit of concave V further forward won't hurt.

All thoughts and comments welcome.
I'll probably pick up the blank Monday some time.
Could be Wednesday I'll be ready to start cutting out the profile, so I'd like to have my mind made up by then.

Can you play with the cutouts ?

I haven't thought about the cutouts, but I don't think they'll have any bearing on the fin leverage over the board width at the footstraps.
I won't have to think about them till I shape the bottom.

twin shallow fins?

Hey Ben!!!! great to hear from you.

I've tried twin fins, without a lot of success, and I don't think they will help with the axial rotation issue.

So here's basically what I have in mind. It' s based on the Radix 100l slalom.
it will fit in the van and it's the right dimensions.
Wider than my 55 and narrower than the 65.
I've drawn the tail more narrow, but I'm wondering if it would be better at 450, rather than 400

you know I have an outline much like that which you could use if u want?

www.seabreeze.com.au/Classifieds/Windsurfing-Boards/~kd1s3/2022-MOz-Customs-Octane-97L-60Cm.aspx?_page=1&search=HeR%2FrT06AEs%3D

you can just take the template when we talk about other stuff

Is a Fangy 28 cm too long and beasty?
It's got more than enough grip for the fattest board , sailer and sail.Grippiest fin I have ever used.
A friend uses the next size down Fangy , 24 cm ?..on a 90 wide SLW with a 7.5 and never spins out. Fires up wind.
Deltas .yuk
Your making the board , so long rocker and square edges. All my boards have square edges and I don't need much fin. Id go the wide tail , inward back strap with short fin.
What I've found with this kind of board , is it's important to have your feet at the right angle because you're not hanging on the edge against a long fin. It's not a powered up speed board and you need to keep the board flat and be comfortable in light wind. So inboard straps with lots of angled pads or deck.
This combo works for me , shallow water light wind. Totally different specs to using a long fin that you have to lever against. I don't use a long fin anymore , too much hassle changing strap positions, that and there is so much wildlife and stuff to hit where I sail.

On our first Oz trip, I used the Fangy 22 with a JP Slalom 112, which was about 68 or 70 cm wide. Almost all sessions were with a 7.0. I needed to be a bit careful with back foot pressure, but not too bad. I switched to a larger weedie only in chop (Cervantes and Lancelin).

For you on a 60 cm board, something like the Fangy 22 should work beautifully. I think your fins have thinner profiles than Fangy's, so you'll have a bit less lift at low speeds, but you're quite a bit lighter.

Select to expand quote

Mark _australia said..
you know I have an outline much like that which you could use if u want?

Thanks Mark, that does look very close, can you get tail width at 300 in?

Select to expand quote

Imax1 said..
Is a Fangy 28 cm too long and beasty?

Yes I think so, biggest sail I'll use on it is a 6.6 My biggest deltoid is 23cm, that is fine with my 65 that has a 41 tail, not sure if going to 45 would be too much for it. But as you say, having straps more inboard should cope with that

Select to expand quote

boardsurfr said..
For you on a 60 cm board, something like the Fangy 22 should work beautifully. I think your fins have thinner profiles than Fangy's, so you'll have a bit less lift at low speeds, but you're quite a bit lighter.

Thanks Peter, I think my 23cm deltoid will be OK. Maybe I'll go inbetween my two extremes and make it 42.5 wide at the tail

You could perhaps get some inspiration from the modern Race-board designs?
I.e. narrow tail for the feet and wider against the water.

We need a build thread with lots of pics please.

Select to expand quote

SurferKris said..
You could perhaps get some inspiration from the modern Race-board designs?
I.e. narrow tail for the feet and wider against the water.

Thanks Kris, I hadn't seen that before, but I don't think it's a good implementation for a new design, more of an add on to convert an old design. The traditional rails aren't good for the feet, (well mine anyway), but it's the same effect as shifting the straps inboard. The deck just needs to be shaped to match the feet where they will go

Select to expand quote

Imax1 said..
We need a build thread with lots of pics please.

Of course, I'll try to record this all the way. Especially weights through all the changes. This should give me a fairly accurate volume amount.

This is the same dilemma I faced at Lake George a couple of years ago but with and even larger board. The isonic 117 which. was 73cm wide from memory and quite a wide tail, with which I was using a 7.7m on in 11-14 knots. All the fins I had with enough lift/area were too deep for what I wanted to sail in, not so much hitting to bottom, but because the weed was so thick! I tried the big Fangy Fin and it certainly worked in that it griped and went upwind, and got me planning early and easily. But, probably due to lack of talent, I could not get any top speed out of it. I was struggling to get much more than mid 20's, even off the wind. In the end I borrowed Waricle's 21cm prototype Pepe fin and they worked very well. That fin is very low aspect, so lots of area and rake but still not very deep. It went just as well as the Fangy in most other respects but increased my top speed to low to mid 30's!!

Your board is smaller, but I suggest the principle will be similar. In weed, lower aspect 'delta' type fins work a lot better than you might suppose they should. The advantages of shallow draft/low aspect and more than offset by the low weed drag and still have enough lift and area. I think there is also an efficiency gain from the 'endplate effect' of the weed. It's noticeable to me that when you encounter weed free water, they lose this benefit to some extent.

So I would say, dont worry about the tail width. Make it as wide as you like to gain early planning and just use a larger area, low aspect 'Delta' type fin. You should be able to use 18, to 22cm depth fins with good power, as long as they have enough area and good foils.

Windsurfer LT

Select to expand quote

AUS4 said..
Windsurfer LT

you've got to be kidding!!!!
There's no way that will fit in the back of my wagon, even if it will get me planing in 10kts

Select to expand quote

sailquik said..
This is the same dilemma I faced at Lake George a couple of years ago but with and even larger board.

Thanks Andrew, it wasn't the area lift that concerned me, it was the decreased leverage of a shorter fin.
But I guess if the shorter fin has more lift, that compensates for less leverage?

I'll have a look at waricles pepe and see how it compares to my deltoids.

Would lowering my feet, (making the tail thinner) decrease riders leverage as well as, moving footstraps more inboard would?
Seems only imax, has found this problem so far.

Select to expand quote

decrepit said..

boardsurfr said..
For you on a 60 cm board, something like the Fangy 22 should work beautifully. I think your fins have thinner profiles than Fangy's, so you'll have a bit less lift at low speeds, but you're quite a bit lighter.

Thanks Peter, I think my 23cm deltoid will be OK. Maybe I'll go inbetween my two extremes and make it 42.5 wide at the tail

With Flex's construction technique, we can design and print a few different prototype fins with different lift co-efficients for a given depth if you need more/less grunt etc., so you can get a Goldilocks fin/board/sail match up with whatever width tail you decide upon.

Select to expand quote

fangman said..
With Flex's construction technique, we can design and print a few different prototype fins with different lift co-efficients for a given depth if you need more/less grunt etc., so you can get a Goldilocks fin/board/sail match up with whatever width tail you decide upon.

Fantastic Ross, beats me messing about with off cut palm and carbon.
Not sure when the board will be ready to try.

Can you think about finbox position for me?
Ideally the box should be at the thickest part of the fin, so I can position the box to accommodate that.

Mike my lightwind kit is a 2013 JP 102 L 66cm wide, 7m KA & FF22. I get going pretty early compared to most & the fin works well. It will break out if I get to heavy on the back foot when only just planning but once you get to 22-23knots and above it's good.

On flat water I have not really felt any disadvantage as far as leverage is concerned). On my Isonic 80 with 5 .7m, the 20cm is fine and I could even rail it up a bit to windward. On the IS87 with 22cm delta and 6.3m sail, same thing. And those are widish tailed boards (with a significant Vee cutaway) with very outboard straps. That is normally as Large a board and sail as I go at LG. But as I said in the previous post, I experimented with the IS117 and the 7.7m sail in really light (and super glassy conditions) and found that great fun in 11-15 knots of wind. I found no use for me IS97 and 7m sail for the last few years jumping straight from the IS87/6.4m combo to the big gear.

I thought a LOT about moving fin boxes forward for weed fins, but after I acquired an IS110 board where fin box had been moved forward by the distance between the Tuttle bolts, I found that even with big, deep, highly raked fins (eg. Tribal 34cm deep Weedspeed), the Centre of resistance was still far too much forward and the board is very hard to 'fly' and steer in balance. I have come to the conclusion that with fins up to around 24-25cm depth, we gain back some advantage (lost with low aspect fin) by the centre of resistance being a bit further back - as long as I can get the mast base far enough back to compensate and not drag the foot of the sail in the water by having too much reward rake on the rig. This somewhat feels like the feeling of 'flying' in the fin that one gets from a deeper more vertical fin, and seems to be an advantage in really flat water. Bottom line - I would put the Tuttle box in the normal position and use a normal, forward set Delta type fin. If you need to change things after that to fine tune, change the fin base position on the fin. And make sure you have a nice long mast box to get the mast base a couple of inches further back when you find you need it. Of course, this all only applies to our rather unique thick weed, flat water conditions we love so much.

I love Fangys idea/offer of custom prototype trick fins to tune up your new sled!

^^^^How bloody fast are you going , railing up a 20 cm fin ?
Definitely go the long mast track.

Select to expand quote

Imax1 said..
^^^^How bloody fast are you going , railing up a 20 cm fin ?
Definitely go the long mast track.

Upwind, @ exactly 23 knots board speed on LG with the 5.7m on the 2017 IS80 in 20-25 knots of wind - Love the GPS-Logit 'speed talk'. Did that with the 21cm Techtonics Speed Demon Delta initially, and later the 20cm Atomic Nuclear. (Remember I am around 73KG).

Select to expand quote

decrepit said..

Can you think about finbox position for me?
Ideally the box should be at the thickest part of the fin, so I can position the box to accommodate that.

I reckon put your board box where ever suits your existing quiver of fins and construction. I will work with that, it should be no probs because your boxes are a little further forward than most, so it puts the thick section in the right structural sweet spot by default. Also, my prototypes might be rubbish.. Hopefully some TOW soon to see if it's a concept worth pursuing.

Select to expand quote

Imax1 said..
^^^^How bloody fast are you going , railing up a 20 cm fin ?

I don't think the two of us are ever going to have this problem.

Bugs came round this arvo, and we sorted a few things out.
From the master,
Early planing needs front area not tail, tail area is for once on the plane.
On flat water, not a lot of nose rocker is needed, that just pushes water.

So we've gone with a 43cm tail and a 47cm nose, with widest point forward
And only 10cm nose rocker. (I definitely won't de surfing with it!)
So here's what we've come up with.

The red line is what we're going with

Not that clear , concrete and template are the same colour.

I pick up the blank tomorrow, will hotwire the rocker and cut out the profile.

I'm thinking of adding floating carbon stringers either side of the fin box and about 1.2m long.
Will help with vacuuming and keeping the bottom straight.

I won't shape any cutouts initially, but use closed cell foam through the tail.
Helps to support the fin box, and allows me to tune the board after trying for a few sessions.

I'll try loading into the wagon, once cut out, in case it needs shortening slightly.

With any luck more tomorrow.

That's so ace, agree with everything.
Pics please.
ps, what's with the rear closed cell foam ? What foam , where from , how far back ?
pps, so that early planing section around the mast , are you going almost square or a bit of tuck ?
What I've found with my experiments is that area between the front straps and mast is what determines how smoothly I flow along. I think this area is important. Super square rails is best. But then you have to turn at one point. So tuck mellows things down.
I believe a low wind speed special is about less rocker and sharp edges. That way you don't need much fin.
I seem to kinda plane as early as the lighter weights, sort of. That's because my light wind board is half a meter longer than standard.
I believe the same can be done with lighter pilots , just scaled down.
For a super special light wind shallow fin board , I'd go square edges , less rocker and comfy rear feet angles.

I use a 23cm Pepe pizza cutter fin on my SLW which is 92 wide, only compromise I have to do is stand a bit more upright compared to my normal dragging my arse in the water