Nose diving/increased pitching moment at speed uni progression, tuning

Foils and Boards - Gear Talk
1

Hi folks.

What’s your understanding of how to prevent my progressions (mostly 125 winging) from nose diving at speed close hauled.
It seems it’s a combination of the front wing doing this, increased drag and maybe tail wing and front wing having different lift/drag curves through the speed range?
Currently mostly using Kanes’ 13R at 1deg shim. I might actually try reduce the shim, as i was all at the front of the tracks with the katana but gained several centimeters with the different hole pattern of the new nolimitz, so might move the mast forward and be able to reduce the need for addded front foot pressure through shimming. I feel i might have ben stuck in a bit of a weird tuning because of the mast tracks in may board being a tad too far back, not sure. When i tried the mast for the first time i mounted maybe 2cm more fwd because of the pattern, felt a bit overpowered at times with the push of the windswell but also had more control in turns. Will need to investigate this further, maybe need to get used to more front foot.
Will try the progression tails soon, also interested in how people would compare the KD R series or Marlin with the Progression tails.
Cheers, Andi

2

Have you checked out KDMaui’s tips on tuning?

"diving at high speed = too little angle

breaching at high speed = too much angle.

by angle I mean negative angle (front pointing down)"

You either need a higher degree shim or a bigger tail to counter act the forward pitching moment at higher speeds.

3

Yeah thanks of course i know Kane’s info. Although he left out some bits, probably not to overcomplicate things…if the stab and front wing aren’t develloped together/are designed with a very similar Cl/Cd curve over the same speed range, the nose diving will be amplified a lot so that you can’t decrease it by shimming the stab as you will have too much front foot pressure at lower speeds…i was wondering if the progr stabs would be better …actually i had ordered some but ups delivered to the wrong adress in another part of the country so probably lost and not in time for my upcoming trip to Greece on the weekend…idiots…

4

I’ve been liking the kd marlin 14 with my p170 + p140 at high speeds while winging and down winding. definitely settles down the pitch axis. still like the shiv for prone.