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Foil Board Tail Rocker ? (Naish L Surf Foil)

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Created by peter_w 2 months ago, 10 Mar 2019
peter_w
NSW, 65 posts
10 Mar 2019 8:23PM
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Hi Guys,

I am looking to make a new prone foil board to replace / supplement the current the current board I have (2018 Naish Hover 5'6" Soft Top Surf). I haven't got many problems with this board, except at 85-90kgs, and I feel like 50%+ more volume would be really beneficial when the waves are really small / weak.

The other thing I was planning to do was to use a really flat tail rocker (like 5mm!) to try to improve the paddlabilty of the new board, but when I checked the current board, there definitely looks like the deck and mast aren't perpendicular:


My concern is that if I use a really flat tail rocker, then the natural cruising position might end up being with the front foot in an awkward low position. Assuming your feet are 700mm apart than 2.4? equates to 30mm height differential.

Looking at all the pictures of the boards I can find, all of the Naish boards seem to have reasonably amounts of tail rocker, where as the boards from Slingshot seem to have dead straight rockers. The new model Naish boards look to have maybe 1 degree less between the deck and mast, but I really only have one picture to go off (and Im not sure how accurate that is). The Naish sups look like they have more tail rocker (again from highly reliable product images!).

Based on my experience in tuning the stabiliser angle, I don't feel like I could rely on this to counter the mast angle difference. In my experience, the sweet spot is the only place to put this (just a tad above neutral for me).

Does anyone have any experience in using a Naish foil with the Slingshot boards (or others with flat tail rockers e.g. JL super fly?)

Does anyone know where I might source some tapered HDPE to make shims if I do mess it up?

Thanks,

Pete.

toppleover
QLD, 1498 posts
10 Mar 2019 7:46PM
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Hi Pete, I had a custom prone board (5'0) made recently & I remember the shaper saying that the mast needed to be as perpendicular to the board as possible.

Another trend I've noticed of late is the position of the foil mount is moving back - closer to the tail, compared to board designs 6 months ago.

peter_w
NSW, 65 posts
10 Mar 2019 9:17PM
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Thanks toppleover,

I think I saw this too in regards to the Go-Foil, but Im also thinking all the foils are likely to be different.

The tuttle box mounts allow you to seperate the tail rocker from the foil angle, but the plate mount foils are pretty much constrained to the bottom angle at the boxes, unless you use shims, or angle the boxes differently to the bottom surface - to get a flatter mounting surface would be ok, but a steeper mounting surface would create a funny hole in the bottom surface which might create enough drag to counter all the benefit of flatter rocker???

maybe I am over thinking it.

toppleover
QLD, 1498 posts
10 Mar 2019 8:22PM
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I think you might be over thinking it a bit mate, I was recently foiling with Ben Wison - he was ripping on a Naish L & custom foilboard.
You still have adjustments on the stab - if needed.

Camarillo
138 posts
10 Mar 2019 9:35PM
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Select to expand quote
peter_w said..
Thanks toppleover,

I think I saw this too in regards to the Go-Foil, but Im also thinking all the foils are likely to be different.

The tuttle box mounts allow you to seperate the tail rocker from the foil angle, but the plate mount foils are pretty much constrained to the bottom angle at the boxes, unless you use shims, or angle the boxes differently to the bottom surface - to get a flatter mounting surface would be ok, but a steeper mounting surface would create a funny hole in the bottom surface which might create enough drag to counter all the benefit of flatter rocker???

maybe I am over thinking it.


I don't think you are overthinking it.
I only have experience with foil supping but putting a wedge between the plate of my foil and changing the angle 1.7 degrees made it much easier for me to catch small waves.
I would go for parallel deck and bottom with tailkick behind the boxes...

DWF
85 posts
10 Mar 2019 9:48PM
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Camarillo has it right. Parallel deck and bottom. Dead flat rocker. Then chop the tail angle. Kalama style shape is what you're trying to get. The rest are behind.

JB
NSW, 1948 posts
Site Sponsor
11 Mar 2019 12:44PM
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I always find these discussion interesting, as we are assuming that the foil flies parallel to its fuselage in the water. Which I think you will find is not the case. I also find a little tail rocker nice, Best to get a picture of you when you're flying. This is when you want your board running parallel with the water. To get the best control and most accurate feel, the only thing that matters is having your deck angle parallel in relation to the water during stable flight. I see so many boards looking really kooky and guys struggling to control them with their nose pointing down because they tried to level the fuselage with the deck with wedges. When you get loaded and need some front foot, it is so hard to find your sweet spot again if you already started with down tilt. The faster you go, and the more lift that is produced by the wing, the more the angle to keep control dips the nose.

Just my 2 cents,

Get photos of your board in stable flight. is it parallel with the water?

Y = trim is good.
N = something is not right (IMO)

Enjoy toying with things. (BTW, I have tried many wedges and track positions over the years. everything from 5mm down to 1mm and using the full 10" of the box plus more with multiple holes in my plates. I always go back to factory settings on my Naish gear as standard).

Ride safe,

JB

PeterP
631 posts
11 Mar 2019 2:20PM
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Select to expand quote
JB said..
I always find these discussion interesting, as we are assuming that the foil flies parallel to its fuselage in the water. Which I think you will find is not the case. I also find a little tail rocker nice, Best to get a picture of you when you're flying. This is when you want your board running parallel with the water. To get the best control and most accurate feel, the only thing that matters is having your deck angle parallel in relation to the water during stable flight. I see so many boards looking really kooky and guys struggling to control them with their nose pointing down because they tried to level the fuselage with the deck with wedges. When you get loaded and need some front foot, it is so hard to find your sweet spot again if you already started with down tilt. The faster you go, and the more lift that is produced by the wing, the more the angle to keep control dips the nose.

Just my 2 cents,

Get photos of your board in stable flight. is it parallel with the water?

Y = trim is good.
N = something is not right (IMO)

Enjoy toying with things. (BTW, I have tried many wedges and track positions over the years. everything from 5mm down to 1mm and using the full 10" of the box plus more with multiple holes in my plates. I always go back to factory settings on my Naish gear as standard).

Ride safe,

JB


Completely agree - but one also has to bear in mind wing angle in relation to bottom of board, if it's too negative (LE of front wing pointing down) then getting up on foil becomes so much harder - board rocker and wing angle both need to be designed/aligned to achieve non-restricted liftoff while ensuring parallel flight.

peter_w
NSW, 65 posts
11 Mar 2019 5:53PM
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Thanks JB,

You have pretty much confirmed my suspicions, with your feedback regarding the shims. There are plenty of examples of flat rockered boards rocking other brands of foils, but not much with the Naish foils (at least that I can find). Surely there is quite a bit of variance between the AOA on the front wing (relative to the mast/fuselage) between the brands?

I have absolutely no issues with how the current board performs - and it definitely feels balanced and level to me whilst riding. I did experiment with the stabiliser angle a bit to try to get more lift, but that felt like I was riding around with the board doing wheelies (ie front foot high). In the end it seemed to be way better back in the approximately neutral position and just try to pump more speed into it.

PeterP, I have felt on occasion that the front wing angle has held me back from catching waves, but not too much lately - they only real way to confirm this would be to get some shims and play around with it like JB has. The smart approach would be to do this before making a new board...

To correct the 2.4? difference, I would need a wedge shim with a variance of approximately 6mm - does anyone know where I can find shims or sheets of tapered HDPE (or similar) to make some from?

Cheers Pete.

scubaste
WA, 168 posts
11 Mar 2019 4:06PM
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Select to expand quote
peter_w said..
Thanks JB,

You have pretty much confirmed my suspicions, with your feedback regarding the shims. There are plenty of examples of flat rockered boards rocking other brands of foils, but not much with the Naish foils (at least that I can find). Surely there is quite a bit of variance between the AOA on the front wing (relative to the mast/fuselage) between the brands?

I have absolutely no issues with how the current board performs - and it definitely feels balanced and level to me whilst riding. I did experiment with the stabiliser angle a bit to try to get more lift, but that felt like I was riding around with the board doing wheelies (ie front foot high). In the end it seemed to be way better back in the approximately neutral position and just try to pump more speed into it.

PeterP, I have felt on occasion that the front wing angle has held me back from catching waves, but not too much lately - they only real way to confirm this would be to get some shims and play around with it like JB has. The smart approach would be to do this before making a new board...

To correct the 2.4? difference, I would need a wedge shim with a variance of approximately 6mm - does anyone know where I can find shims or sheets of tapered HDPE (or similar) to make some from?

Cheers Pete.


Make it out of plywood and seal it in resin works for me.

toppleover
QLD, 1498 posts
11 Mar 2019 6:08PM
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Select to expand quote
Get photos of your board in stable flight. is it parallel with the water?

Y = trim is good.
N = something is not right (IMO)

Ride safe,

JB


Great tip, thanks.

JB
NSW, 1948 posts
Site Sponsor
11 Mar 2019 8:14PM
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I emailed the Naish Foil engineer in regards to this, and he came back with a few key things,

- Trim and flight angle will change between different weight riders at the same speed.

- The AoA will need to be varied to achieve the same amount of liftoff at a given speed for different weight riders.

- Flight trajectory will vary between different rider weights for given speeds.

So basically, what this means is there is no actual exact formula to get stable flight. It will vary for different weight riders at given speeds. This is interesting. I do notice this a lot with Prone foiling and foil placement in the track as I can ride the foil far more aggressive and forward than someone lighter than me. I guess the same is with SUP. Lighter guys may actually move their foil more aft in the tracks to allow for greater leverage over a higher given lift for the same speed. But what I do find is with the movement of the mount position you can definitely find the sweet spot where it all comes good without wedges on given foilboards (Naish).

But of coarse this all changes as a bigger rider uses a larger wing. The the lift is increased for the given speed and everything moves again.

I still think, test, ride, adjust (one thing at a time) and find that amazing neutral feeling.

Happy playing.

Ride safe,

JB

icharus
50 posts
11 Mar 2019 7:51PM
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Select to expand quote
JB said..
I always find these discussion interesting, as we are assuming that the foil flies parallel to its fuselage in the water. Which I think you will find is not the case. I also find a little tail rocker nice, Best to get a picture of you when you're flying. This is when you want your board running parallel with the water. To get the best control and most accurate feel, the only thing that matters is having your deck angle parallel in relation to the water during stable flight. I see so many boards looking really kooky and guys struggling to control them with their nose pointing down because they tried to level the fuselage with the deck with wedges. When you get loaded and need some front foot, it is so hard to find your sweet spot again if you already started with down tilt. The faster you go, and the more lift that is produced by the wing, the more the angle to keep control dips the nose.

Just my 2 cents,

Get photos of your board in stable flight. is it parallel with the water?

Y = trim is good.
N = something is not right (IMO)

Enjoy toying with things. (BTW, I have tried many wedges and track positions over the years. everything from 5mm down to 1mm and using the full 10" of the box plus more with multiple holes in my plates. I always go back to factory settings on my Naish gear as standard).

Ride safe,

JB


Not sure about this - without a shim I felt like my set up was like towing a bucket when paddling. so catching anything was hard. surely paddling performance is THE important thing. angled too far down or up will be disastrous. once you are up and flying - the angle of the deck isn't so important. ( within reason)

DWF
85 posts
11 Mar 2019 8:16PM
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When you mount a foil on a regular board (big rocker, end to end) you get into a situation where any movement on the deck fore and aft, or even simply bending over at the waist, can quickly upset the board trim and the foil angle of attack under the board. This is greatly reduced with a flatter rockered board. This makes it easier for most people.

Camarillo
138 posts
11 Mar 2019 8:46PM
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All Naish foil sups can also be used as a normal sup or am I missing something?
And of course these boards need rocker.
I would not be surprised if Naish comes with a dedicated foil sup next year with a tailkick behind the boxes for the plate and the rest of the bottom parallel to the deck....

Camarillo
138 posts
11 Mar 2019 8:50PM
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Select to expand quote
DWF said..
When you mount a foil on a regular board (big rocker, end to end) you get into a situation where any movement on the deck fore and aft, or even simply bending over at the waist, can quickly upset the board trim and the foil angle of attack under the board. This is greatly reduced with a flatter rockered board. This makes it easier for most people.


I didn't think of this before but it makes a lot of sense.

juandesooka
217 posts
11 Mar 2019 11:54PM
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Buddy has one of those digital degree measuring tools. Put it on the fuselage and then the midpoint of the board (where the board is flat on water surface), any difference in degrees means drag. Mine was 3 degrees, meaning while paddling for a wave I was fighting the foil trying to dive. We added 3mm of shims to the rear bolt, the difference in effortless glide while paddling was remarkable.

Once up on foil, you will naturally adjust to get it level. This will just cause your nose to be in the air more than normal. I've seen this lots kiting, with kite surf boards that are retrofitted with foils. But in kiting it doesn't matter too much (other than looking kinda goofy), since you aren't paddling, just slightly more energy from the kite to water start and you're off.

JB
NSW, 1948 posts
Site Sponsor
12 Mar 2019 1:53PM
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Important to also remember that the foil generate lift as soon as it starts moving foreward. This 3? you talk off is not really that dramatic.

Firstly, with no wedge. I do not have any trouble catching bumps. Not at all.

Secondly, parallel deck during flight is far more important for a comfortable flight. Remember, when you're good enough, you will be spending far more time up than down!

third, as mentioned, I've tried wedges and found only a negitive to their use. I can understand the thinking and theory behind it, but the reality in practice is different in my opinion (hense i do not use wedges).

obviously if you've done an aftermarket or foil mount on a non production heavily rockered board, then this may be different.

If I can find my wedges, I'll GPS some paddle speeds and liftoff speeds. Asside from being awkard in flight, I think the findings will surprise.

Test, try and repeat. Don't guess.

Ride safe,

JB

juandesooka
217 posts
12 Mar 2019 11:24AM
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Select to expand quote
JB said..
Important to also remember that the foil generate lift as soon as it starts moving foreward. This 3? you talk off is not really that dramatic.

Firstly, with no wedge. I do not have any trouble catching bumps. Not at all.

Secondly, parallel deck during flight is far more important for a comfortable flight. Remember, when you're good enough, you will be spending far more time up than down!

third, as mentioned, I've tried wedges and found only a negitive to their use. I can understand the thinking and theory behind it, but the reality in practice is different in my opinion (hense i do not use wedges).

obviously if you've done an aftermarket or foil mount on a non production heavily rockered board, then this may be different.

If I can find my wedges, I'll GPS some paddle speeds and liftoff speeds. Asside from being awkard in flight, I think the findings will surprise.

Test, try and repeat. Don't guess.

Ride safe,

JB


Aftermarket foil track installation: check. Though on a lightly rockered board. The measuring tool shows a 3-4mm height difference from front to back bolts.

In testing, trying, and repeating, I can assure you 3 degrees mattered a lot. The difference in paddling speed/glide was instantly noticeable. There is no difference in catching waves with a steeper drop or white water take off. The marginal difference in wave catching was that kinda-almost wave ... just-barely catching it vs not.

As for not guessing, also agree there, find someone with the degree measuring tool (most common with kiters who are serious about DIY'ing, especially race types). I'd definitely recommend experimenting with a wedge if your fuselage/board are not in balance. Costs near nothing to try, you can use a plastic scraper for fibreglassing with holes drilled in ... stack up as many as you need. Or even stainless washers.

[btw, if interested, the meter is one like this www.amazon.com/AccuRemote-Digital-Electronic-Magnetic-Protractor/dp/B006JR8XBG]

peter_w
NSW, 65 posts
Saturday , 18 May 2019 7:27PM
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Just to close this out for anyone looking in the future:

Managed to build the boardpretty close to plan(I was aiming for 91.7deg - ended up at 91.5deg according to this photo) [CNCd blank, not skill!]
This makes it about a degree steeper than the original board, and inline with the current batch of Naish boards (based on the images I have).




Ive had a few goes on this new board now and I feel that even this change is noticeable. I am pretty happy with how the board flies and paddles, although its not really fair to compare the paddling of the boards as Im pretty confident there are plenty of other variables effecting this more than the mast angle.

I am also glad I didn't change this more than I did as Im pretty confident that a completely perpendicular mast would be terrible with this foil.

Image below shows the old board laid over the new board - and the difference is not insubstantial even though it was only a degree:



Thanks again to JB for the input RE Naish foils.

Cheers, Pete

Seajuice
NSW, 400 posts
Saturday , 18 May 2019 10:47PM
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Hi Peter_w,
If you want to make some wedges. Just check my earlier post on making an epoxy wedge. Its simple.
In my opinion it is okay to try wedges to make the mast perpendicular to the deck & putting the mast far back towards the tail in the beginning stages of foiling. I believe this helps with paddle speed to catch waves. Then try different mast positions & finally reduce the thickness of the wedge to none at all on production boards to see whats the most comfortable. This can take up to a year to work out depending on how many sessions & ability of course.
In the end I believe its all body position, technique & confidence that gets you up on the foil early. Have fun.



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"Foil Board Tail Rocker ? (Naish L Surf Foil)" started by peter_w