Forums > Stand Up Paddle Foiling

Foil Sup DW

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Created by frenchfoiler 2 months ago, 10 Aug 2021
JB
NSW, 2192 posts
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25 Sep 2021 6:17PM
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And the Southerlies just keep blowing = Soo good!

Here's today's run from Brown water to Mona basin.

SE wind around 18-20kn.
Swell 1.5m ESE

Riding the Naish Hover 125, JET 1800HA/280HA on 64cm Fuselage and 75cm mast. Plate shimmed 3 degree and rear wing shimmed 2 degrees. Mounted an inch further forward than maximum.

enjoy,



Ride safe,

JB

JB
NSW, 2192 posts
Site Sponsor
25 Sep 2021 6:19PM
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JB said..
And the Southerlies just keep blowing = Soo good!

Here's today's run from Brown water to Mona basin.

SE wind around 18-20kn.
Swell 1.5m ESE

Riding the Naish Hover 125, JET 1800HA/280HA on 64cm Fuselage and 75cm mast. Plate shimmed 3 degree and rear wing shimmed 2 degrees. Mounted an inch further forward than maximum.

enjoy,



Ride safe,

JB


Here's the stats from the run. Was good to give the 1800HA a run. Bloody nice foil!


Ride safe,

JB

kobo
NSW, 685 posts
25 Sep 2021 6:30PM
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Great stuff JB, you have the DW formula worked out and all the gear to match the conditions.
Do you find there is enough energy when the wind has only been blowing for one day ? I have found the easiest conditions are when we have a NE of 15-20 kns that has been blowing for 2-3 days and there is only wind swell and no ground swell to confuse things, would you agree ?

what do you think is the ideal DW conditions?cheers Kobo

JB
NSW, 2192 posts
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25 Sep 2021 7:26PM
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kobo said..
Great stuff JB, you have the DW formula worked out and all the gear to match the conditions.
Do you find there is enough energy when the wind has only been blowing for one day ? I have found the easiest conditions are when we have a NE of 15-20 kns that has been blowing for 2-3 days and there is only wind swell and no ground swell to confuse things, would you agree ?

what do you think is the ideal DW conditions?cheers Kobo


To a degree it's not a matter of days, but more strength of wind over fetch (distance). That pittwater run was only a few hours of wind over a 1-2km fetch. So it doesn't take long. But you're right, the run would be extremely well groomed if the wind blows the same direction for days. There's a great site that will calculate the swell/chop over given strengths and fetch's.
if I find it, I'll link it.

JB
NSW, 2192 posts
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25 Sep 2021 10:04PM
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swellbeat.com/wave-calculator/
this site calculates, size, speed and period.

kobo
NSW, 685 posts
26 Sep 2021 7:41AM
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Select to expand quote
JB said..
swellbeat.com/wave-calculator/
this site calculates, size, speed and period.


Thanks JB, that's an interesting tool do you use it much and find it helpful.
Im guessing you input data from MHL buoys ?

JonathanC
VIC, 948 posts
26 Sep 2021 8:45AM
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Awesome JB
Can you please go through the rationale for the shimming of the mast and the stab. Why you are changing them and what you are looking to achieve with the changes. Great to see you achieving this with pretty 'standard' gear and not custom DW boards etc

Thanks

JB
NSW, 2192 posts
Site Sponsor
29 Sep 2021 12:46PM
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Select to expand quote
JonathanC said..
Awesome JB
Can you please go through the rationale for the shimming of the mast and the stab. Why you are changing them and what you are looking to achieve with the changes. Great to see you achieving this with pretty 'standard' gear and not custom DW boards etc

Thanks


Hey Jonathan,

Shimming in a way or increasing/decreasing a set AoA (Angle of Attack).

Rear Wing is like the flaps on an aeroplane. Increasing the AoA will apply more down force aiding the front wing to rise/lift. Sometimes this can be too much when surfing and the added drag can be counter productive, so you have to be careful. I have 1 & 2 degree shims. I have found using the smaller rear (280cm2) and the 2 degree shim works quite well at DW speeds as I guess there's no real pitching sections or when there is, they're only momentary.

Base plate shim is changing the entire angle of attack when the board is in the water. This way when I am paddling for a bump just want as much lift as possible at a slow speed to break the hull free, I can achieve it, then as soon as the hull is free the plate shim does not affect the AoA theoretically. It will affect my flying angle a little bit by making me fly nose down a tiny bit, but that's a small price to pay for an easier paddle up (I actually do not notice it). But the key thing is it theoretically gives me a 5 degree rear wing AoA increase and a 3 degree Front Wing AoA increase before lift off and then 2 degree rear wing and 0 front wing increase at lift off.

To get this much kick (like shimming the rear wing at 5 degrees) would have way too much rear wing pressure once you got up speed. I love front foot and lift, and this is a great way to achieve it so it's massive at paddle up and just big when flying.

I hope this makes sense?

Ride safe,

JB

JB
NSW, 2192 posts
Site Sponsor
29 Sep 2021 12:50PM
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Select to expand quote
kobo said..

JB said..
swellbeat.com/wave-calculator/
this site calculates, size, speed and period.



Thanks JB, that's an interesting tool do you use it much and find it helpful.
Im guessing you input data from MHL buoys ?


Yes you can inout from MHL or any of the weather forecasters that give you more than once swell. Also using the other calculators and Wind forecasts will determine before the fact what MHL should get. Knowing where the wind will blow from and roughly how long (fetch), you can work out the rough bump size. Using Windy is good for that as you can see where the wind line moves in from and to. Quick calc on the fetch and bobs your uncle. Then use the other calculator the measure the speed, pick the right foil and go

mcrt
308 posts
29 Sep 2021 12:18PM
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Select to expand quote
JB said..


Hey Jonathan,

Shimming in a way or increasing/decreasing a set AoA (Angle of Attack).

Rear Wing is like the flaps on an aeroplane. Increasing the AoA will apply more down force aiding the front wing to rise/lift. Sometimes this can be too much when surfing and the added drag can be counter productive, so you have to be careful. I have 1 & 2 degree shims. I have found using the smaller rear (280cm2) and the 2 degree shim works quite well at DW speeds as I guess there's no real pitching sections or when there is, they're only momentary.

Base plate shim is changing the entire angle of attack when the board is in the water. This way when I am paddling for a bump just want as much lift as possible at a slow speed to break the hull free, I can achieve it, then as soon as the hull is free the plate shim does not affect the AoA theoretically. It will affect my flying angle a little bit by making me fly nose down a tiny bit, but that's a small price to pay for an easier paddle up (I actually do not notice it). But the key thing is it theoretically gives me a 5 degree rear wing AoA increase and a 3 degree Front Wing AoA increase before lift off and then 2 degree rear wing and 0 front wing increase at lift off.

To get this much kick (like shimming the rear wing at 5 degrees) would have way too much rear wing pressure once you got up speed. I love front foot and lift, and this is a great way to achieve it so it's massive at paddle up and just big when flying.

I hope this makes sense?

Ride safe,

JB


It is easier to draw this than put it in words clearly :)

If you are using a Mastplate shim with the thin bit forward (like i do with the Takuma):
-When floating it will increase the AOA of front wing but decrease the AOA of stab (because it works with downforce).

So if you are using a -2 shim on stab (raises stab trailing edge for more downforce) and a +3 shim on the Mastplate (thin end forward,lowers both trailing edges) the net result for the Stab is +1 (probably neutral ,zero downforce) when floating and paddling for a wave.
Once up only Front to Rear wing relative angles matter.

BTW i am still scratching my head at the upwind angles i measured on one of your recent wingfoil tracks,really really good.Like 8-10* more than i do :(




kobo
NSW, 685 posts
29 Sep 2021 5:23PM
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Select to expand quote
JB said..

JonathanC said..
Awesome JB
Can you please go through the rationale for the shimming of the mast and the stab. Why you are changing them and what you are looking to achieve with the changes. Great to see you achieving this with pretty 'standard' gear and not custom DW boards etc

Thanks



Hey Jonathan,

Shimming in a way or increasing/decreasing a set AoA (Angle of Attack).

Rear Wing is like the flaps on an aeroplane. Increasing the AoA will apply more down force aiding the front wing to rise/lift. Sometimes this can be too much when surfing and the added drag can be counter productive, so you have to be careful. I have 1 & 2 degree shims. I have found using the smaller rear (280cm2) and the 2 degree shim works quite well at DW speeds as I guess there's no real pitching sections or when there is, they're only momentary.

Base plate shim is changing the entire angle of attack when the board is in the water. This way when I am paddling for a bump just want as much lift as possible at a slow speed to break the hull free, I can achieve it, then as soon as the hull is free the plate shim does not affect the AoA theoretically. It will affect my flying angle a little bit by making me fly nose down a tiny bit, but that's a small price to pay for an easier paddle up (I actually do not notice it). But the key thing is it theoretically gives me a 5 degree rear wing AoA increase and a 3 degree Front Wing AoA increase before lift off and then 2 degree rear wing and 0 front wing increase at lift off.

To get this much kick (like shimming the rear wing at 5 degrees) would have way too much rear wing pressure once you got up speed. I love front foot and lift, and this is a great way to achieve it so it's massive at paddle up and just big when flying.

I hope this makes sense?

Ride safe,

JB


Interesting you are playing with base plate shims too JB, I have been doing it on my boards which all have too much tail rocker to get the to board deck level with the top of mast plate.
I thought Naish boards were like most others ( flat with no tail rocker ) and don't need mast plate wedges, or are you wedging past level so to get 'extra' lift for early takeoff ?

JB
NSW, 2192 posts
Site Sponsor
29 Sep 2021 8:21PM
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Select to expand quote
mcrt said..

JB said..


Hey Jonathan,

Shimming in a way or increasing/decreasing a set AoA (Angle of Attack).

Rear Wing is like the flaps on an aeroplane. Increasing the AoA will apply more down force aiding the front wing to rise/lift. Sometimes this can be too much when surfing and the added drag can be counter productive, so you have to be careful. I have 1 & 2 degree shims. I have found using the smaller rear (280cm2) and the 2 degree shim works quite well at DW speeds as I guess there's no real pitching sections or when there is, they're only momentary.

Base plate shim is changing the entire angle of attack when the board is in the water. This way when I am paddling for a bump just want as much lift as possible at a slow speed to break the hull free, I can achieve it, then as soon as the hull is free the plate shim does not affect the AoA theoretically. It will affect my flying angle a little bit by making me fly nose down a tiny bit, but that's a small price to pay for an easier paddle up (I actually do not notice it). But the key thing is it theoretically gives me a 5 degree rear wing AoA increase and a 3 degree Front Wing AoA increase before lift off and then 2 degree rear wing and 0 front wing increase at lift off.

To get this much kick (like shimming the rear wing at 5 degrees) would have way too much rear wing pressure once you got up speed. I love front foot and lift, and this is a great way to achieve it so it's massive at paddle up and just big when flying.

I hope this makes sense?

Ride safe,

JB



It is easier to draw this than put it in words clearly :)

If you are using a Mastplate shim with the thin bit forward (like i do with the Takuma):
-When floating it will increase the AOA of front wing but decrease the AOA of stab (because it works with downforce).

So if you are using a -2 shim on stab (raises stab trailing edge for more downforce) and a +3 shim on the Mastplate (thin end forward,lowers both trailing edges) the net result for the Stab is +1 (probably neutral ,zero downforce) when floating and paddling for a wave.
Once up only Front to Rear wing relative angles matter.

BTW i am still scratching my head at the upwind angles i measured on one of your recent wingfoil tracks,really really good.Like 8-10* more than i do :(






The rear wing shim is relative to the front wing. So the 2 degrees still affects the the front wing even when tilted with the base shim. Try to think of an aeroplane flying, it doesn't matter whether it's in a dive, climb or level flight, the flaps have the same affect. The base shim just gives it a turbo boost right when you want it. Yes once up, the base shim as far as lift goes is irrelevant. Some will say they like it for pumping or turning, but that's just personal boards angle preferences.

Yes, I smoke upwind . Not many will beat me upwind. But I am a sailor, Windsurfer, Kiter. One trick I like to use is board/mast twist! We used to use this on 505's by allowing the centerboard to twist underload and actually angle upwind. I try to twist my hips forcing my mast and foils to turn slightly upwind. This raises my upwind VMG, increases height and power in the wing. Also do not oversheet, let the wing breathe, keep your speed up, even luff it a little every few seconds to ensure you have the maximum amount of flow. Sheeting in too far will feel good, but you're dog slow and low.

Hope this helps,

Ride safe,

JB

JB
NSW, 2192 posts
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29 Sep 2021 8:23PM
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Another video (sorry) from Yesterday's Nor-easter.

About 18kn NE. Swell ESE 1.5m. A little tricky with the angles out there, but some good glides. Came down once unfortunately, I got greedy and went into a dead spot.

Riding the Naish Hover 125 with 1800HA/280HA on 64cm fuse and 75cm mast. Shimmed again 2 & 3.



Ride safe,

JB

JB
NSW, 2192 posts
Site Sponsor
29 Sep 2021 8:30PM
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JB said..
Another video (sorry) from Yesterday's Nor-easter.

About 18kn NE. Swell ESE 1.5m. A little tricky with the angles out there, but some good glides. Came down once unfortunately, I got greedy and went into a dead spot.

Riding the Naish Hover 125 with 1800HA/280HA on 64cm fuse and 75cm mast. Shimmed again 2 & 3.



Ride safe,

JB


Here some stats.

Not a bad run. Wish I didn't come down in the middle.

Here's a few splits. Obviously in the 3rd km I came down .




Ride safe,

JB

mcrt
308 posts
30 Sep 2021 4:59AM
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"But the key thing is it theoretically gives me a 5 degree rear wing AoA increase and a 3 degree Front Wing AoA increase before lift off and then 2 degree rear wing and 0 front wing increase at lift off."

Nope JB,sorry to insist but you are doing this right (as your riding proves) but explaining it wrong.

Front and rear wing create lift in opposite directions,with opposite AOA's.

A mast shim cannot increase the AOA of both wings,it is impossible.

If mast shim increases Frontwing "takeoff" AOA by 3* it has to decrease the Tailwing AOA by the same 3*.
If your tail had a -2* relative to the Frontwing and you add the mastplate +3* you end up with a "takeoff" AOA of +1* for the tail.Which is probably zero tail downforce (on takeoff only).

Comparing foils to an airplane is something i do all the time,i have been driving an airliner for +20 years,plus 4 crazy wonderful years as a Hang glider & Paraglider pilot (not anymore,too risky).

Foils have the config of a typical airplane,but without control surfaces so we use Weightshift like a Hangglider,but from above instead of below,in water...many similarities but many differences too.
We ride pretty incredible,weird pieces of tech :)

Thx heaps for the Upwind tips!.
When you say "twist" the board&foil upwind you mean in the yaw axis or roll axis?.
I will look through your vids to see if i can spot this technique.

JB
NSW, 2192 posts
Site Sponsor
30 Sep 2021 2:59PM
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mcrt said..
"But the key thing is it theoretically gives me a 5 degree rear wing AoA increase and a 3 degree Front Wing AoA increase before lift off and then 2 degree rear wing and 0 front wing increase at lift off."

Nope JB,sorry to insist but you are doing this right (as your riding proves) but explaining it wrong.

Front and rear wing create lift in opposite directions,with opposite AOA's.

A mast shim cannot increase the AOA of both wings,it is impossible.

If mast shim increases Frontwing "takeoff" AOA by 3* it has to decrease the Tailwing AOA by the same 3*.
If your tail had a -2* relative to the Frontwing and you add the mastplate +3* you end up with a "takeoff" AOA of +1* for the tail.Which is probably zero tail downforce (on takeoff only).

Comparing foils to an airplane is something i do all the time,i have been driving an airliner for +20 years,plus 4 crazy wonderful years as a Hang glider & Paraglider pilot (not anymore,too risky).

Foils have the config of a typical airplane,but without control surfaces so we use Weightshift like a Hangglider,but from above instead of below,in water...many similarities but many differences too.
We ride pretty incredible,weird pieces of tech :)

Thx heaps for the Upwind tips!.
When you say "twist" the board&foil upwind you mean in the yaw axis or roll axis?.
I will look through your vids to see if i can spot this technique.


Good conversation. Interesting take on it. And definitely not doubting your experience and knowledge.

I understand your reference from the hull on on the wing AoA, and maybe I am not technically correct in the way I talk about it. When lift is increased by a shimming I call it positive (i.e. 2 degree shim on the rear as opposed to -2 degree).

I like to seperate the front and rear wings as a lifting agent to the board. The relationship between the front and rear wings is really what effective lifting potential of a given wing set. If we go off what i think are the actual angles of the wings, I think Naish said each wings CL is 2 degrees (+ front - rear if you like), so a difference of 4. When I add another 2 degrees (-2) to the rear wing, this effective difference becomes 6 degrees. The rear wing is acting against the front wing and not the board in my opinion.

It is the effect of the combined pair that is affected by the base plate shim when the board is in the water before take off and I guess against the actual direction of travel.

Again I could be totally wrong here, and I will try it out physically by removing my plate mount shim to test my theory. But from what I have noticed since shimming the plate, it has decrease my lift off and lowered my base speed required. I have been using rear wing shims for a long time before using a plate shim, and do not recall any sensation of loss of rear wing kick. But like all good theories they deserve to be challenged.

So again to clarify. I believe the lifting force applied to the board is that of a combination of the entire foil seperate to the lifting force of the entire foil which is a combination of the relationship between the two wings (along with a whole bunch of other stuff like fuselage length, mounting placement etc...).

I use the plane analogy having never legally legally flown a plane. But when you take off on a plane and the front wheels are lifting, this is kind of creating the same affect and I am guessing to a degree here that the rear stabs are still up on the trailing edge during lift off??

Upwind. Yes, your yaw angle. Definitely roll over to windward (axis roll) as this aids lift to push you upwind also, but twisting your line of flow to windward greatly increases your upwind angle. It is only a slight twist in the hips and kind of pushing to lee with your back foot, but it really helps.

Anyway, off to study areo/hydro dynamics some more...

Regards,

JB

JonathanC
VIC, 948 posts
30 Sep 2021 3:54PM
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Thank JB and mcrt for the attention to detail and all the effort of explaining - kinda think you guys are saying the same thing but looking at it from a different place!

mcrt
308 posts
30 Sep 2021 2:56PM
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JonathanC said..
Thank JB and mcrt for the attention to detail and all the effort of explaining - kinda think you guys are saying the same thing but looking at it from a different place!


Agree :)
It gets really complex to put this into words,makes it sound super complicated.At the user ,practical level foils are simple,but they can be annoyingly counterintuitive.

I will try to make some graphics to illustrate my point.

BTW i have been wrong before many times, being a pilot does not make me an expert in foils :)

kobo
NSW, 685 posts
30 Sep 2021 6:22PM
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Select to expand quote
JB said..

mcrt said..
"But the key thing is it theoretically gives me a 5 degree rear wing AoA increase and a 3 degree Front Wing AoA increase before lift off and then 2 degree rear wing and 0 front wing increase at lift off."

Nope JB,sorry to insist but you are doing this right (as your riding proves) but explaining it wrong.

Front and rear wing create lift in opposite directions,with opposite AOA's.

A mast shim cannot increase the AOA of both wings,it is impossible.

If mast shim increases Frontwing "takeoff" AOA by 3* it has to decrease the Tailwing AOA by the same 3*.
If your tail had a -2* relative to the Frontwing and you add the mastplate +3* you end up with a "takeoff" AOA of +1* for the tail.Which is probably zero tail downforce (on takeoff only).

Comparing foils to an airplane is something i do all the time,i have been driving an airliner for +20 years,plus 4 crazy wonderful years as a Hang glider & Paraglider pilot (not anymore,too risky).

Foils have the config of a typical airplane,but without control surfaces so we use Weightshift like a Hangglider,but from above instead of below,in water...many similarities but many differences too.
We ride pretty incredible,weird pieces of tech :)

Thx heaps for the Upwind tips!.
When you say "twist" the board&foil upwind you mean in the yaw axis or roll axis?.
I will look through your vids to see if i can spot this technique.



Good conversation. Interesting take on it. And definitely not doubting your experience and knowledge.

I understand your reference from the hull on on the wing AoA, and maybe I am not technically correct in the way I talk about it. When lift is increased by a shimming I call it positive (i.e. 2 degree shim on the rear as opposed to -2 degree).

I like to seperate the front and rear wings as a lifting agent to the board. The relationship between the front and rear wings is really what effective lifting potential of a given wing set. If we go off what i think are the actual angles of the wings, I think Naish said each wings CL is 2 degrees (+ front - rear if you like), so a difference of 4. When I add another 2 degrees (-2) to the rear wing, this effective difference becomes 6 degrees. The rear wing is acting against the front wing and not the board in my opinion.

It is the effect of the combined pair that is affected by the base plate shim when the board is in the water before take off and I guess against the actual direction of travel.

Again I could be totally wrong here, and I will try it out physically by removing my plate mount shim to test my theory. But from what I have noticed since shimming the plate, it has decrease my lift off and lowered my base speed required. I have been using rear wing shims for a long time before using a plate shim, and do not recall any sensation of loss of rear wing kick. But like all good theories they deserve to be challenged.

So again to clarify. I believe the lifting force applied to the board is that of a combination of the entire foil seperate to the lifting force of the entire foil which is a combination of the relationship between the two wings (along with a whole bunch of other stuff like fuselage length, mounting placement etc...).

I use the plane analogy having never legally legally flown a plane. But when you take off on a plane and the front wheels are lifting, this is kind of creating the same affect and I am guessing to a degree here that the rear stabs are still up on the trailing edge during lift off??

Upwind. Yes, your yaw angle. Definitely roll over to windward (axis roll) as this aids lift to push you upwind also, but twisting your line of flow to windward greatly increases your upwind angle. It is only a slight twist in the hips and kind of pushing to lee with your back foot, but it really helps.

Anyway, off to study areo/hydro dynamics some more...

Regards,

JB


I agree with the effect it has 100%A mast plate shim or wedge at the rear , swings the foil set forward on the board , so when the board is increasing speed on the surface of the water it lifts off earlier. Once up ,it makes the board travel more nose down but no other effect. (except improving the pumping) The opposite effect if your board has tail rocker , the foil set is swung back which delays lift off , and the board travels nose high when up riding.This is helpful taking off in larger/ steeper waves as it reduces the ' launching' effect of the foil.(and reduced pumping)Not sure of the hydrodynamics in play but I can guarantee that is the effect you will get.

mcrt
308 posts
30 Sep 2021 10:42PM
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So this 3 pics represent how i have understood your setup "evolution" JB,and the resultant forces at the takeoff phase only,with board accelerating parallel to water surface.
-Fig 1 is factory,no shims.
-Fig 2 is with tailshim added for more downforce

-Fig 3 is Fig2 plus a mastplate shim addef,to takeoff earlier.

The setup is,by the way,almost exactly what i use on my Kujira 1210.

My only disagreement is when you added Tailshim and mast shim angles to get the Tailwing AOA, i believe they substract not add.As in Fig 3.

Moot,nitpicky point,it does not change anything and your setup seems dialed in from the way you ride :)

In a wingfoil takeoff (very progressive acceleration) the tailwing has very little influence IMHO.It has small surface,little AOA and slow speed.Cannot create much lift with those ingredients.
In DW SUP and mostly in surffoil/supfoil it will have a lot more felt effect as the accelerations are much quicker.








If i have made any glaring errors in my reasoning please let me know,i will take it like a man (as in go drink and grumble).

Will try to add the yaw to my next upwind runs,see if angles improve Thx!.

Winsup
32 posts
1 Oct 2021 1:23AM
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Yaw pedantry is evident and though you say it's well meaning does contain glaring error
Fig 3 is not fig2 with a mast shim
It is fig 1

mcrt
308 posts
1 Oct 2021 1:26AM
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Winsup said..
Yaw pedantry is evident and though you say it's well meaning does contain glaring error
Fig 3 is not fig2 with a mast shim
It is fig 1


Nope,tail is shimmed.Look again.

kobo
NSW, 685 posts
1 Oct 2021 6:56AM
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Select to expand quote
mcrt said..

Winsup said..
Yaw pedantry is evident and though you say it's well meaning does contain glaring error
Fig 3 is not fig2 with a mast shim
It is fig 1



Nope,tail is shimmed.Look again.


Looks good to me mcrt ! that extra aoa on the front wing is exactly what you experience in real life.Interesting the decrease in the tail angle too which I didn't think about but makes sense.Its all about the relative flow of water to the wing while the board is on the water surface . Great stuff !

JB
NSW, 2192 posts
Site Sponsor
1 Oct 2021 11:10AM
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mcrt said..

So this 3 pics represent how i have understood your setup "evolution" JB,and the resultant forces at the takeoff phase only,with board accelerating parallel to water surface.
-Fig 1 is factory,no shims.
-Fig 2 is with tailshim added for more downforce

-Fig 3 is Fig2 plus a mastplate shim addef,to takeoff earlier.

The setup is,by the way,almost exactly what i use on my Kujira 1210.

My only disagreement is when you added Tailshim and mast shim angles to get the Tailwing AOA, i believe they substract not add.As in Fig 3.

Moot,nitpicky point,it does not change anything and your setup seems dialed in from the way you ride :)

In a wingfoil takeoff (very progressive acceleration) the tailwing has very little influence IMHO.It has small surface,little AOA and slow speed.Cannot create much lift with those ingredients.
In DW SUP and mostly in surffoil/supfoil it will have a lot more felt effect as the accelerations are much quicker.








If i have made any glaring errors in my reasoning please let me know,i will take it like a man (as in go drink and grumble).

Will try to add the yaw to my next upwind runs,see if angles improve Thx!.


Man I love those diagrams. I usually do poxy pen drawings and use highlighters .

I do understand what you are saying. And agree with the principle. But my point is that the affect is a two stage effort. What you are saying and depicting is spot on. I guess the other reality is your foil does not just travel along parallel to the water surface as you are paddle to get up. You are proposing a lot, diving and ollying your foil. The only real relationship of the rear wing and its angle is to the front wing. This is my point. We do not just slide along flat and lift off, our foils get driven by the down force produced by the rear wing to counteract the pitching moment produced by the front wing resulting in thrust.

So I did a mini practical experiment yesterday afternoon as you got my noodle baking challenging my thoughts. I went out to paddle up in near no wind and near no bumps (it was really hard). But what I did was tried in two sessions. Firstly I removed my plate shim and rode the foil with just the rear wing shim. the result I could not get up. I had 10 attempts and did not get up even once.

Then I went in and put my plate shim in. Again tried 10 times but got up on 3 of them. If anything the conditions were worse when I went back out. All in all this was not a controlled experiment, and I would have been more tires the second go and still had far more success. Even on some of the tries were I technically didn't get up, I did break the hull free on most and got super close.

Attempts without the plate shim.

Attempts with the plate shim.

Now, what does all this mean??

For DW, I like to shim my rear and plate . I feel it increases the lift affect before take off then reverts back to just my FW and RW setup at flight. I still think the front and rear wings work together to produce their lifting effect, it is the relationship between them that drives the lift created. The plate shim just intensifies it in relation to the board.

Again, great discussion. I will try this again on a better day when it is easier to get up (this nearly killed me) and add in removing the rear wing shim and do 4 runs (god help me). I really thought I was going to get up without the plate shim. A lot of what you say did make sense, but I know from practical experience that what you feel and what you expect to feel are often different.

Anyway, for now both shims stay in for me.

Ride safe,

JB

mcrt
308 posts
1 Oct 2021 10:47AM
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By all means ,do not remove any shims ! :)
I am riding pretty much the same setup,on a diff foil and with far less skill,but it works very good.

As you say ,what works on the water trumps any on paper analysis or cutesy drawings.

And the graphics i did are just a snapshot of the simplest takeoff possible.Everything is constant except increasing speed.

In a "pumped" takeoff everything is a variable,speed,pitch,load...i would love to better understand how it all fits but it does my head in :)

Please don't go nuts changing your setup because of anything i wrote,unless you really want to play with it.The shims and your reasoning seem spot on to me.
Saludos !


JB
NSW, 2192 posts
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1 Oct 2021 12:57PM
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mcrt said..
By all means ,do not remove any shims ! :)
I am riding pretty much the same setup,on a diff foil and with far less skill,but it works very good.

As you say ,what works on the water trumps any on paper analysis or cutesy drawings.

And the graphics i did are just a snapshot of the simplest takeoff possible.Everything is constant except increasing speed.

In a "pumped" takeoff everything is a variable,speed,pitch,load...i would love to better understand how it all fits but it does my head in :)

Please don't go nuts changing your setup because of anything i wrote,unless you really want to play with it.The shims and your reasoning seem spot on to me.
Saludos !




I will probably still play around more. It is not the first time that a theory has played out different than expected. I have tried most things foiling, gone back and forth, and as you mentioned, not everything makes sense.

JB

burchas
114 posts
4 Oct 2021 7:15PM
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JB said..
And the Southerlies just keep blowing = Soo good!

Here's today's run from Brown water to Mona basin.

SE wind around 18-20kn.
Swell 1.5m ESE

Riding the Naish Hover 125, JET 1800HA/280HA on 64cm Fuselage and 75cm mast. Plate shimmed 3 degree and rear wing shimmed 2 degrees. Mounted an inch further forward than maximum.

enjoy,



Ride safe,

JB



JB = Jolly Bumps? Great stuff!

i know your brand but you run with such a talented crew there with access to some cool gear,
do you switch gear with others just to get a different point of reference? Since we're talking technical now.

Dpap
29 posts
5 Oct 2021 1:08AM
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JB said..

JonathanC said..
Awesome JB
Can you please go through the rationale for the shimming of the mast and the stab. Why you are changing them and what you are looking to achieve with the changes. Great to see you achieving this with pretty 'standard' gear and not custom DW boards etc

Thanks



Hey Jonathan,

Shimming in a way or increasing/decreasing a set AoA (Angle of Attack).

Rear Wing is like the flaps on an aeroplane. Increasing the AoA will apply more down force aiding the front wing to rise/lift. Sometimes this can be too much when surfing and the added drag can be counter productive, so you have to be careful. I have 1 & 2 degree shims. I have found using the smaller rear (280cm2) and the 2 degree shim works quite well at DW speeds as I guess there's no real pitching sections or when there is, they're only momentary.

Base plate shim is changing the entire angle of attack when the board is in the water. This way when I am paddling for a bump just want as much lift as possible at a slow speed to break the hull free, I can achieve it, then as soon as the hull is free the plate shim does not affect the AoA theoretically. It will affect my flying angle a little bit by making me fly nose down a tiny bit, but that's a small price to pay for an easier paddle up (I actually do not notice it). But the key thing is it theoretically gives me a 5 degree rear wing AoA increase and a 3 degree Front Wing AoA increase before lift off and then 2 degree rear wing and 0 front wing increase at lift off.

To get this much kick (like shimming the rear wing at 5 degrees) would have way too much rear wing pressure once you got up speed. I love front foot and lift, and this is a great way to achieve it so it's massive at paddle up and just big when flying.

I hope this makes sense?

Ride safe,

JB


What you explain here is like trying to liftoff with an airplane at lower airspeed than indicated by forcing the elevator up...think about it .thank god it is not an airplane you would stall and die damaging the runway....
Another food for thought about shimming to change the AOA at the takeoff... while you pump the AOA of the foil is going from about +20 degrees to -20 degrees until you reach a decent speed so what exactly does a +-2 deg !!???
Just my 2cent..

PeterP
717 posts
5 Oct 2021 3:17AM
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I find that the shimming of the plate, which allows the board to release easier, has more to do with the effect on the board moving through the water. Without the shim and LE of foil pointing further down, the board is being pulled down as one tries to increase forward speed, increasing drag (until sufficient speed allows the foils lift to release board). In this set-up board feels glued to the water

Get LE to point upwards towards board and any forward motion is working to release the board.

mcrt
308 posts
5 Oct 2021 4:31AM
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Select to expand quote
Dpap said..

What you explain here is like trying to liftoff with an airplane at lower airspeed than indicated by forcing the elevator up...think about it .thank god it is not an airplane you would stall and die damaging the runway....
Another food for thought about shimming to change the AOA at the takeoff... while you pump the AOA of the foil is going from about +20 degrees to -20 degrees until you reach a decent speed so what exactly does a +-2 deg !!???
Just my 2cent..


I am not sure if you are referring to the mastplate shim or the tailshim?.

Anyway,i do not think our foils will travel through a -20*/+20* AOA range
My guesstimate would be more like around -5* (zero lift,as it is an asym foil) to +20*/25* stall AOA?.

Mind you,i have never seen a C.lift graph for any of the foils we use but those figures should be in the ballpark.Probably very big stall angle differences between thin HA shapes like an Armstrong 1125 and thicker ones like a LOL or Gong Allvator.

For wingfoiling takeoffs i have not noticed any major effect from screwing around with the tail size or shim.Once in flight yes,a lot.

But if JB says it makes a big difference in SUP DW takeoffs i will take his word as gospel.He can DW really good.
And DW or flat water SUP takeoffs are the most demanding by far,with little power available for very little time.

The effect of the mastplate shim can be quite dramatic with med or hi aspect foils.They can change the takeoff from frustrating to really friendly.This is easy to test with a DIY shim, 6mm on the thick side tapering to 1mm should give about a 3* angle.Try it if you haven't already,might surprise you.



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"Foil Sup DW" started by frenchfoiler