Ventral Fin and fin tests

[Eagle]

Can confirm that the Gladiator Elite is an excellent tracking stability fin.  Do use it from time to time - as well as the slightly smaller Hybrid for AW.  Even DW.

And have tried your ventral and small kicker on a Blackfish 25 without side fins.  Found that board to be extremely stable - turned ok - and felt fast.  Not my board though - so no timed GPS speed tests.  Very nice board and really liked the smoothness with the ventral.

[PonoBill]

Yes, that was one of the test variations. Not as fast: 5.10 max, average 4.95 but stability was good and acceleration was good. The blackfish 25 is the test mule for all this.

[Eagle]

Yeah correction - that board I tried was Luc's Eradicator 25 before the present owner bought it from him.   And originally was apparently Norm's race custom he used when I paddled with him up Squamish way.  Luc did the LA 4 fin mod. 

The Blackfish Luc currently has was apparently bought from another local racer I had paddled with on that same DW.  Think that was the time I shuttled with Norm.  The circle of DW paddlers and racers is very small in these parts.  Luc can chime in if different.  Have not paddled with Luc in awhile though.  Probs a couple of years.

The Blackfish has a very interesting crescent tail.  Does it do anything special from what you can tell?

[PonoBill]

I don't know. It's been challenging to steer, I'm hoping that's a fin issue. The nose and tail have funny waterflows, the nose especially (since I can see it) does this very random little flow that wraps up the rails and flings into the air like a plugged showerhead. Very odd. So far it's most redeeming quality is that it trims so well with me on it. And it's reasonably fast in flatwater. I like it. I hope I can make it work to my satisfaction for downwind.

[Eagle]

Probs if you have the right fin in there - it should be ok.  Lucky for us lightweights - we can trim most boards and balance ok.  All our boards have a ton of extra buoyancy.  It actually provides heeps of extra stability.  But if heavier - yeah very much harder for sure.  Paddled with a small boy sitting in front while I paddled the Dom - and could barely make that thing move.  So can empathize. 

My strength to weight seems really optimized at my current weight.  And add just 10 lbs and it would drop a lot.  But you seem to be doing ok in your 70s.  I am a teenager in comparison.   

[Area 10]

PB - at the risk of opening up another can of worms in the. "14fters that big guys can paddle", have you tried the SIC FX14? That seems to be a board that some pretty solidly built guys say trims well for them, and might be the kind of flat water/DW hybrid that might suit your needs, perhaps? Interesting to hear the views of some bigger guys.

[PonoBill]

Okay, I spent three hours testing today. Nice day, light wind that picked up enough for one kitefoiler to play.

I made a standard ADD screwup that was kind of revealing. I intended to try the stock center fin, two nubs and ventral combination first. I had left the ventral in the center slot after testing yesterday so I moved it to the ventral slot. Paddling up and down at Nichols the board felt sluggish and I struggled to make it past 5.0. I thought it was just a matter of warming up, so I left the Nichols pond and headed downriver into a light wind. A struggle all the way. I was pushing hard to maintain 4.5 mph. When I got to the beach (where the Gorge Paddle Challenge was held) I thought "this isn't performing as well as the stock setup. I'm going to pull the ventral and see what happens. Pulled in, flipped the board over, no center fin. I thought it might have fallen out, but when I got back to the car I found the center fin on the passenger seat. ADD boy strikes again.

While I was on the beach, I moved the ventral fin back to the center position and started paddling into the wind again. I hit and held 4.9 easily with a few forays above 5.0. Turned around and held 5.5 to 5.7 easily in the little bumps. Back at Nichols I could do 5.55 easily, either direction, and I held above 5.2 generally. I haven't downloaded the data yet so I don't have precise figures. I'll do that tonight.

I tried Single fin and ventral again, got 5.1 with great effort but averaged about 4.9. Pulled the ventral fin and had the same results with less stability.

I tried to do coastdowns, but my method isn't working, and my Paddle Coach isn't helping. I think there's a software glitch, or maybe it's configuration option or a smoothing feature. I was trying to hold 4.5mph for a few seconds, then stop paddling and see how long it took to coast down to 2.0mph. The paddle coach would dither around 4.5, but then when I stopped paddling it would hold a slightly lower value for perhaps ten seconds with no update. Then when the speed got down to about 2.9 mph it would show that and start updating every second. The times I got for coastdown varied all over the place. So that sucked.

What I learned is that the tree fin setup is fast, and it's even faster when the center fin is small. I stopped by Big Winds, hoping they'd have a little ventral fin, but no dice. I'll have to talk to Larry and maybe make something in the meantime. I'm fairly certain that for my use, the two nubs plus a small center fin and an even smaller ventral fin would be the fastest combo. Very stable.

I also noticed that when I was paddling hard with the three fin setup, that the nose of the board moves a little in the direction of the paddle. With a single fin and no ventral the nose moves away from the paddle, and with a single fin and the vental it doesn't move.

[PonoBill]

I can't figure out the data. I don't know each configuration starts and stops. I normally would have taken note of the timing, but I had that long paddle in the middle. Ah, screw it, I know what I need to know.  That's the problem with screwing up, everything turns to fog.

[ukgm]

I tried to do coastdowns, but my method isn't working, and my Paddle Coach isn't helping. I think there's a software glitch, or maybe it's configuration option or a smoothing feature. I was trying to hold 4.5mph for a few seconds, then stop paddling and see how long it took to coast down to 2.0mph. The paddle coach would dither around 4.5, but then when I stopped paddling it would hold a slightly lower value for perhaps ten seconds with no update. Then when the speed got down to about 2.9 mph it would show that and start updating every second. The times I got for coastdown varied all over the place. So that sucked.

Yep, I had problems with a speedcoach with that. The raw data would only record when I was actually paddling (I guess the accelerometer in it is a trigger) so I'd get data gaps. I've had to switch to using a conventional Garmin 910XT for those tests (I then import it in into Trainingpeaks WKO+ 3.0 software). This seemed to work when I pilot tested it with a couple of fins but the sampling frequency might not be high enough when I do all of the fins.

[ukgm]

I can't figure out the data. I don't know each configuration starts and stops. I normally would have taken note of the timing, but I had that long paddle in the middle. Ah, screw it, I know what I need to know.  That's the problem with screwing up, everything turns to fog.

I got into the habit of coming off the water and writing down the distance achieved on a notepad as I switch out each fin or after each run. I also then only paddle slowly between test runs. This allows me to pick up the runs visibly when I pull a CSV file into Microsoft Excel.

It does take time just to get a methodology right and repeatable and it can be frustrating initially. However, it can be rewarding when it goes well. Don't let this dishearten you - it just takes time.

[PonoBill]

I'm pretty happy with the results so far, I found out what I wanted to know. I don't understand it at all, but it's useful. I'm fairly certain the magnitude of the difference is wrong, but every test is consistent enough so I'm convinced the difference is real.

Which leads to the real question--how the hell does sticking a little tiny fin in between two fins make the board faster?

That just doesn't make sense to me. The board feels very draggy without it. I can't make two fins without that little fin between them work at all. What the hell is that little fin doing?

[Dwight (DW)]

Which leads to the real question--how the hell does sticking a little tiny fin in between two fins make the board faster?

I assume you plugged the empty finbox when you removed it.

I found when testing 2+1 fins in a longboard, there was a spot in the middle box, where the center fin made drag and another spot where it didn't. Felt to me like the middle fin cleaned up flow coming off the side bites when I got it right. I know that is different than your case, since my side bites are toed. Food for thought anyway.

[PonoBill]

No, I didn't plug it. The side fins are toed a little, according to my laser the intersection point of the toe is about six feet in front of the nose of the board (about 19' total), so pretty small. I'd convert to degrees, but who cares other than my old trigonometry teacher, who is probably safely dead.

I'm finding this very odd. I think your explanation might be on the money DW, which leads me to wonder how small the fin can be and still get the same result. I'm pretty certain that bigger fins are slower for me (stronger paddlers might not have the same result), but will smaller be faster. I think all the work of making the board track and resisting the torque is being done by the nubs, and the middle fin might just be a flow straightener.

I'm just guessing, but it opens some interesting options. Larry is definitely onto something.

UK, I suspect you're right about the refresh for SpeedCoach being triggered by stroke. Makes sense for what it's made for. I didn't think of tagging fin changes by distance. Duh.

[Larry Allison]

I'm finding this very odd. I think your explanation might be on the money DW, which leads me to wonder how small the fin can be and still get the same result. I'm pretty certain that bigger fins are slower for me (stronger paddlers might not have the same result), but will smaller be faster. I think all the work of making the board track and resisting the torque is being done by the nubs, and the middle fin might just be a flow straightener.

I'm just guessing, but it opens some interesting options. Larry is definitely onto something.

PonoBill, You said it perfectly.

[Luc Benac]

Hello Larry/Bill,
Just trying to reconcile this with the size of the central/kick fin having increased over the past years from the original to the current 6" Stinger.
As far as I know the 6" Stinger is the de facto recommended kick fin for the Blackfish.
Does the center fin also provide projection like the ventral or should it be kept smaller as suggested by Bill.

Cheers,
Luc