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Author Topic: Axis Foils  (Read 273408 times)

Alysum

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Re: Axis Foils
« Reply #705 on: December 31, 2020, 04:26:24 PM »
Are you a 116 lb 65 year old female?

She is stoked.
lol well done to Jacky 8)
« Last Edit: December 31, 2020, 04:34:42 PM by sydney.winger »

Dwight (DW)

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Re: Axis Foils
« Reply #706 on: January 01, 2021, 12:12:46 PM »
I finally tried the HPS980 and HPS1050 without shim (420 tail). It did not work for me. Felt all wrong at my weight.

Meanwhile Jacky has been doing great on the HPS980 without shim, but still had some hobby horse syndrome under certain conditions. So I installed the shim reversed and trimmed the plastic to work backwards. She liked it. That is probably the lowest angle possible for the 420 tail.


Today
https://www.instagram.com/p/CJg5GhNrhxT/?igshid=12h49fwjopwi7
« Last Edit: January 01, 2021, 01:12:12 PM by Dwight (DW) »

deja vu

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Re: Axis Foils
« Reply #707 on: January 01, 2021, 01:01:24 PM »
DW I'm confused -- I thought you liked the HPS980 Axis with the low drag 420 tail with no shim?  Now you seem to be saying that the 980 + 420 stab, without the shim, doesn't work for you.  Please clarify which Axis front wing and stab (shim or no shim) you like.  Thanks.

Dwight (DW)

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Re: Axis Foils
« Reply #708 on: January 01, 2021, 01:08:05 PM »
Admin likes no shim. I always run shim. Letís not forget 420 tail is already super low drag at only 7mm thick. Many other Axis tails are 10.5mm thick on average.

Axis supplies shim as standard with this setup. In fact, I was told by Axis to use the shim, so it took me a awhile to get around to trying it without.
« Last Edit: January 01, 2021, 01:09:48 PM by Dwight (DW) »

Admin

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Re: Axis Foils
« Reply #709 on: January 01, 2021, 01:46:45 PM »
So I installed the shim reversed and trimmed the plastic to work backwards. She liked it. That is probably the lowest angle possible for the 420 tail.

 Nice, I am stoked to try that. 

Tail on the new board looks great!
« Last Edit: January 01, 2021, 02:24:06 PM by Admin »

Alysum

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Re: Axis Foils
« Reply #710 on: January 01, 2021, 03:27:11 PM »
I would like to better understand the conditions too in which the "hobby horsing" syndrome happens.

For me:
- Definitely a lot less when using the rear shim (the one supplied), I do need to try back to back with and without to be certain.
- I get less with a flat stab (custom) than the 390GAP rear (too much drag from the thickness?)
- Smoother/flatter water means less hobby horsing too

This is all on the ultra short fuselage.

I am wondering whether the short fuselage would still be better to mitigate this ? I am enjoying how loose and how much I can pump with the US but I wonder whether it's more to do with the high aspect wings then the US fuselage (well probably both).... How long is the black series short fuselage ?

PonoBill

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Re: Axis Foils
« Reply #711 on: January 01, 2021, 03:47:25 PM »
Sidney, I read a lot of your posts and you seem like a smart dude technically. I'm not buying that you don't know what causes that. Any relative incidence angle between the stabilizer and the wing means a force is applied to increase the angle of attack. That has to be countered with front foot pressure to keep the wing flat. As you increase speed the force increases and you either under- or over-compensate.  Probably under. The nose rises, you press down harder, the nose goes down. speed increases, nose rises. And as the shampoo bottle says, Lather, rinse, repeat.

To make it go away you shim the stab to decrease the relative incidence angle. Now you need to go a lot faster to get up. You finally do, and with the lower drag (high AOA is super draggy) you get more speed = more lift. Now the board stays more or less flat but eventually rises until you hear the dreaded slurping. You push down, save it, and start a new round of nose down hobby horse, this time at a much higher speed so when you toss it all away the water has all the forgiveness of a concrete tennis court.

Not that I've ever done that. I'm just living with a permanently cricked neck because I'm watching too much TV.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

Alysum

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Re: Axis Foils
« Reply #712 on: January 01, 2021, 04:16:50 PM »
What is actually confusing me is which way to the angles of incidence change with shims.

Admin posted this info a while back:
Quote
The 980 front wing has an incidence of +.54 degrees.  This is notable.  That is 1/2 of a degree !
The 420 rear wing has an incidence of -1.91 degrees (on the black fuselage only).

Shimming the back of the rear tail increases the negative AOI doesn't it ? (say it goes from -1.91 to -2.91) so how does it make it more stable with bigger numbers (or perhaps it's the other way round  ;D)

Scratching my head with all the numbers  :o

Vancouver_foiler

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Re: Axis Foils
« Reply #713 on: January 01, 2021, 04:23:44 PM »
The different stabs are setup with different AoA(1-4degeees) As well i think Adrian mentioned the front wings have some variance in their AoA-somewhere between 1-2degrees.

Dwight (DW)

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Re: Axis Foils
« Reply #714 on: January 01, 2021, 05:00:26 PM »


I am wondering whether the short fuselage would still be better to mitigate this ?

YES!

When I demoed the 980 ultra short with 370 or 340 tail (forgot which one it was) it was such a hobby horsing cluster F*** there is no way I would have been converted back to Axis with that setup.

The short fuse and 420 tail was a whole different magical world, that completely sold me on Axis

Califoilia

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Re: Axis Foils
« Reply #715 on: January 01, 2021, 05:34:08 PM »
Today
DW, is that a camera angle optical illusion...or are the fuse and bottom not parallel to one another?
Me: 6'1"/185...5'1" Kings Foil Board...5'7" Kings Foil Board...9'6" Bob Pearson "Laird Noserider"...14' Lahui Kai "Manta"...8'0" WaveStorm if/when the proning urges still hit.

Dwight (DW)

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Re: Axis Foils
« Reply #716 on: January 01, 2021, 06:08:18 PM »
Today
DW, is that a camera angle optical illusion...or are the fuse and bottom not parallel to one another?

optical illusion. Even the board looks very distorted to me.

« Last Edit: January 01, 2021, 06:11:23 PM by Dwight (DW) »

flkiter

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Re: Axis Foils
« Reply #717 on: January 01, 2021, 07:09:26 PM »


I am wondering whether the short fuselage would still be better to mitigate this ?

YES!

When I demoed the 980 ultra short with 370 or 340 tail (forgot which one it was) it was such a hobby horsing cluster F*** there is no way I would have been converted back to Axis with that setup.

The short fuse and 420 tail was a whole different magical world, that completely sold me on Axis

370 shimmed rear on my Mr Toad's wild ride. Just got the crazy short from axis to try next week.

daswusup

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Re: Axis Foils
« Reply #718 on: January 01, 2021, 07:39:18 PM »
Holy heated shim talk!!!
I rode my 980 on US fuse with 460 stab no shim all the way back in finbox and the first thing I felt way that on the surface just putting along, there was a dramatic lifting of front of board. It took me a bit to figure out how to scootch all my weight farther forward to combat this. What started all the hobbyhorsing was the nose lifting out before I wanted it to or before it had enough speed to get on foil. I think a big part of this is how much less drag  the foil has even before liftoff. This was foreign to me as I have only recently come off of large draggy foils. I remember my Slingshot 84/48 doing this too. Infact, I wasted an entire Maui trip on fighting with this a year and a half ago. Its different reason its happening on the 980 although a similar tendency to want to come up sooner and then stall. When I had decent wind with the 980, this went away. So, my solution, without trying the shim was keep heavy front foot pressure until board speed hit a certain threshold. The 980 is a squirrely beast to get up compared to my other axis foils 1150/1010/920 but once up, I had no problems with it. I do think that suttle inputs helps compared to other wings. Once up, its just mind foiling. It goes where I think about going. Mindblowing!!!!

PonoBill

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Re: Axis Foils
« Reply #719 on: January 01, 2021, 08:03:23 PM »
What is actually confusing me is which way to the angles of incidence change with shims.

Admin posted this info a while back:
Quote
The 980 front wing has an incidence of +.54 degrees.  This is notable.  That is 1/2 of a degree !
The 420 rear wing has an incidence of -1.91 degrees (on the black fuselage only).

Shimming the back of the rear tail increases the negative AOI doesn't it ? (say it goes from -1.91 to -2.91) so how does it make it more stable with bigger numbers (or perhaps it's the other way round  ;D)

Scratching my head with all the numbers  :o

Yeah, you've got it backward. shimming to reduce porpoising and make the foil work better at higher speeds is shimming the front of the stabilizer to reduce the total incidence, in other words, to reduce the amount of up elevator that is built-in that helps beginners and people going slow to get their board up out of the water and flying.

Most axis foil/stabilizer combinations wind up with about 5 degrees total incidence, in other words, 5 degrees of up elevator. Shimming the front of the stab to reduce that to 2-3 degrees makes the porpoise calm down until you get going fast enough, and then it comes back, but it's more controlled.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

 


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