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Do you need some rocker at tail of board

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RalfsB
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Re: Do you need some rocker at tail of board

Postby RalfsB » Fri Mar 29, 2019 5:06 pm

TomW wrote:
Wed Feb 13, 2019 6:42 pm
What I mean by tail rocker is not " tail kick," . It is the rocker from 1/3 up from tail to the tail. The foil is mounted on that curve.

"Made a 120cm with 20mm tail rocker works great."
I am planning to convert a kite surfboard to a foilboard. The surfboard, of course, has some rocker in the tail part. If I would attach the foil mount to the tail part as it is, the board would ride very much nose up. I am planning to create little "stringers/rails" that are parallel to the direction of the board and also are more in line with the surface of the board. They would be on the same level as board's bottom towards the middle of the board and would rise from the bottom towards the tail. In this way I can have foil to be more parallel to the surface of the board. I am thinking if it should be completely parallel with board's top surface or should I leave some angle, a bit of 'nose up'? How much is good and how much is too much? Any suggestions?

I wonder how much that 20mm rocker is in degrees?

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Re: Do you need some rocker at tail of board

Postby tomtom » Fri Mar 29, 2019 6:57 pm

Peter /Frank :D /, i think you are talking from Ketos point of view. Ketos foils are placed quite in center of board one of most forward position of all foils. Here tail rocker indeed wont matter. But other foils are much more in tail of board - some even on very tail of board and here tail rocker certainly have impact to board riding angle. Moses 633 is that case - its positioned ca. directly under back foot.

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Re: Do you need some rocker at tail of board

Postby TomW » Fri Mar 29, 2019 11:02 pm

RalfsB wrote:
Fri Mar 29, 2019 5:06 pm
TomW wrote:
Wed Feb 13, 2019 6:42 pm
What I mean by tail rocker is not " tail kick," . It is the rocker from 1/3 up from tail to the tail. The foil is mounted on that curve.

"Made a 120cm with 20mm tail rocker works great."
I am planning to convert a kite surfboard to a foilboard. The surfboard, of course, has some rocker in the tail part. If I would attach the foil mount to the tail part as it is, the board would ride very much nose up. I am planning to create little "stringers/rails" that are parallel to the direction of the board and also are more in line with the surface of the board. They would be on the same level as board's bottom towards the middle of the board and would rise from the bottom towards the tail. In this way I can have foil to be more parallel to the surface of the board. I am thinking if it should be completely parallel with board's top surface or should I leave some angle, a bit of 'nose up'? How much is good and how much is too much? Any suggestions?

I wonder how much that 20mm rocker is in degrees?
Ralf,

This is a difficult question. I suggest you place the board on your foil in your shop and use your eye to see how much you need to compensate for the tail rocker. Look from the side. I'd try to get the fuselage parallel with the area that you will stand on. With the nose up enough to give you 100 mm nose over that fuselage line.
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RalfsB
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Re: Do you need some rocker at tail of board

Postby RalfsB » Sat Mar 30, 2019 8:38 am

TomW wrote:
Fri Mar 29, 2019 11:02 pm
I suggest you place the board on your foil in your shop and use your eye to see how much you need to compensate for the tail rocker. Look from the side. I'd try to get the fuselage parallel with the area that you will stand on. With the nose up enough to give you 100 mm nose over that fuselage line.
Thank you Tom. My intuition says it should be something like this:
boardfoil.png
boardfoil.png (14.54 KiB) Viewed 247 times

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Re: Do you need some rocker at tail of board

Postby Peter_Frank » Sat Mar 30, 2019 9:27 am

The difficult thing is, if a new foil you can not know what angle the fuselage has.

It is not important, it is the most used riding angle, meaning the angle the front wing got compared to the mast, and the profile of the wing too.

Best thing would be if you got ANY board, or could borrow one, and ride the foil to get an idea of the angle, do you need the nose up or down to be balanced.

What most want to achieve, is that the board rides so both your feet are straight (or bend precisely the same) - otherwise it will be extremely tiring riding.

If you got a known well balanced foil (feet wise), but building a new board, the angle should be the same where your feet stands, to obtain balance.

Unless you got a really flat board at the nose, then you need to raise the nose a bit, to avoid nosediving too much.
This will unfortunately give you a very unpleasant riding stance, but needed on short really flat boards.

8) Peter
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Re: Do you need some rocker at tail of board

Postby TomW » Sat Mar 30, 2019 10:02 am

Ralf,
That looks about right. Not sure of the scale though.
You'll be able to put spacers under the front or rear of the plate to adjust afterwards.
I would recommend having the rear holes at least 250mm from the tail to reduce the amount of board that is swinging around and put the boards center of floatation centered under your weight. I'm assuming that you are a beginner and will be surface riding.
It's not going to be perfect, but it will get you going and learn enough to progress to a shorter Hydrofoiling freestyle board..
If you want to butcher the board, you could cut the tail off to make it 4-6 /140cm long. Then position the foil as above.
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RalfsB
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Re: Do you need some rocker at tail of board

Postby RalfsB » Sat Mar 30, 2019 10:57 am

Right now I am riding the Alpine foil with Alpine board (142cm); when I ride the board I think it is pointing up a bit, especially at slower speeds, but it is hard to tell the exact angle when you are riding. I just want to have another universal board that can be used both as a surfboard and as a foil board (for situations when I can take only one board). Length about 165cm (one of those cut-off-nose style) so that it still fits in a foil board length category and does not have too much swing weight.

Thank you for suggestions.

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Re: Do you need some rocker at tail of board

Postby Peter_Frank » Sun Mar 31, 2019 12:12 am

RalfsB wrote:
Sat Mar 30, 2019 10:57 am
Right now I am riding the Alpine foil with Alpine board (142cm); when I ride the board I think it is pointing up a bit, especially at slower speeds, but it is hard to tell the exact angle when you are riding. I just want to have another universal board that can be used both as a surfboard and as a foil board (for situations when I can take only one board). Length about 165cm (one of those cut-off-nose style) so that it still fits in a foil board length category and does not have too much swing weight.

Thank you for suggestions.

If it is a classic square waveboard with very little nose rocker (scoop) I think you have to go with a compromise, and lift the nose a bit so you stand with your front foot bent a little.
Otherwise it might nosedive too easy on touchdowns - just my experience.

It is worse with shorter boards though, so you might be okay with only small amount of nose lift, if board will be around 165 cm.

Boards with huge scoop/noserocker will be much better in this respect though.

8) Peter
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