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Hydrofoil stiffness & fuselage connections

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dave1986
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Hydrofoil stiffness & fuselage connections

Postby dave1986 » Sun Oct 13, 2019 8:56 am

I notice that 3 main connection types are used in the industry to join the front wing to the fuselage:

1) Moses type connection: Cylindrical shape fuselage with curved shape match the curve on top of the wing. Bolts through the wing to fuselage.
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2) Slingshot hoverglide type connection: "Mortise and tenon" type connection between wing and fuselage with bolts to hold.
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3) Axis type connection: Wide shovel shaped fuselage head. Wing recessed to match shovel shape. Bolts through the wing to fuselage.
SmartSelect_20191013-084153_Chrome.jpg

I believe that the Axis wide shovel shaped fuselage is much stiffer for big surf wings. But are there any other big pros and cons for each different connection type?

I'm particularly interested to know whether the less stiff Moses connection type is a big disadvantage for their largest surf wings (790 & 873) when compared with other brands such as Axis.
Last edited by dave1986 on Mon Oct 14, 2019 9:24 am, edited 1 time in total.

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Re: Hydrofoil fuselage connections

Postby tomtom » Sun Oct 13, 2019 9:16 am

No matter how it ride - bigger moses are almost laughably soft. You look at it and it move... But i think main culprit is the moses mast. If you have bigger problem on other place you wont discover relatively smaller details. And wing fuse connection is last place in order of importance. Because you must have everything else stiff to actually load wing fuse connection.

IMO importance is in this order.

1. Fuse stiffness both longitudinal and torsion
2. Mast fuse connection in regard to fuse torsional forces
3. Mast stiffness - both longitudinal and torsion /torsion is often overlooked and at least equally important/. - If you think about it longitudinal flex promote less input to your riding than torsional.
3. wing fuse connection /couse everything else is usually weak enough to no stress this/

Why i think this?

Couse - Moses somewhat works with very soft masts...

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Re: Hydrofoil fuselage connections

Postby Kamikuza » Sun Oct 13, 2019 10:20 am

Going between 900 and 750mm masts, I notice the additional twist and wobble and don’t like it a lot.

So for me a stiff mast is number 1, second would be solid connections to plate and fuse, and fuse to wing comes in last... but they’re all top priority, can’t do without them.

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Re: Hydrofoil fuselage connections

Postby dave1986 » Sun Oct 13, 2019 2:56 pm

Are Slingshot 90cm aluminium masts much stiffer than the Moses carbon 91cm masts?

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Re: Hydrofoil fuselage connections

Postby tomtom » Sun Oct 13, 2019 5:50 pm

yes, but oddly - moses carbon mast ride quite well. I dont think is straighforward - stiffer is better. Nothing is completely stiff. So everything somehow flexes and then i think matter where and how /how damped it is etc.../
Armstrong foils claim they make they masts flexing purposely and flexing on specific place. Also early French foil makers find out that sometimes flexing mast is better /some of them and for some riding style/. This whole thing is highly controversial.

I found that i can ride with soft moses mast without issues. But i cannot ride soft fuse. We try to make lighter carbon fuse for moses and it was quite less stiff in torque than original moses. This was very obviously bad. In contrast i tried moses with much stiffer neil pryde glide mast and improvement wasnt so obvious...

Point is there isnt any setup that is completely stiff. You always compare two setup which flex somehow.
Last edited by tomtom on Sun Oct 13, 2019 6:01 pm, edited 1 time in total.
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dave1986
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Re: Hydrofoil fuselage connections

Postby dave1986 » Sun Oct 13, 2019 5:52 pm

tomtom wrote:
Sun Oct 13, 2019 9:16 am
No matter how it ride - bigger moses are almost laughably soft. You look at it and it move... But i think main culprit is the moses mast. If you have bigger problem on other place you wont discover relatively smaller details. And wing fuse connection is last place in order of importance. Because you must have everything else stiff to actually load wing fuse connection.

IMO importance is in this order.

1. Fuse stiffness both longitudinal and torsion
2. Mast fuse connection in regard to fuse torsional forces
3. Mast stiffness - both longitudinal and torsion /torsion is often overlooked and at least equally important/. - If you think about it longitudinal flex promote less input to your riding than torsional.
3. wing fuse connection /couse everything else is usually weak enough to no stress this/

Why i think this?

Couse - Moses somewhat works with very soft masts...
I'm interested to know how you have you determined that the Moses masts are flexible and that it's not the other Moses components such as fuselage or connections that are causing the flex? For instance have you tried the Moses wings on a 91cm carbon mast back-to back with the same Moses setup on a 90cm Slingshot aluminium mast?

Moses have full control over the carbon layup and thickness and stiffness of their masts so I suppose they consider that their design to be the best compromise of stiffness vs hydrodynamics vs weight? Although I appreciate that this aspect is probably quite subjective.

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Re: Hydrofoil fuselage connections

Postby dave1986 » Sun Oct 13, 2019 5:55 pm

I appreciate that there will always be different materials at different price points for hydrofoils, but it will be interesting to see if the industry focusses on one particular standard construction and assembly type for any given material.

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Re: Hydrofoil fuselage connections

Postby tomtom » Sun Oct 13, 2019 6:12 pm

dave1986 wrote:
Sun Oct 13, 2019 5:52 pm
I'm interested to know how you have you determined that the Moses masts are flexible and that it's not the other Moses components such as fuselage or connections that are causing the flex? For instance have you tried the Moses wings on a 91cm carbon mast back-to back with the same Moses setup on a 90cm Slingshot aluminium mast?

By load /by hand/ and observing. Its very obvious what is flexing if you look.
Moses masts are quite soft - this is very known fact.
dave1986 wrote:
Sun Oct 13, 2019 5:52 pm
Moses have full control over the carbon layup and thickness and stiffness of their masts so I suppose they consider that their design to be the best compromise of stiffness vs hydrodynamics vs weight? Although I appreciate that this aspect is probably quite subjective.
Definately not - Moses freeride mast are not very thin. And they are very far from what is possible /stifness/ with carbon. But that means UHD carbon, much more of it, and more complicated production. Moses masts are very light and works quite well for reasonable money. Its good compromise but not SOTA.

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Re: Hydrofoil fuselage connections

Postby tomtom » Sun Oct 13, 2019 6:19 pm

I think Plummet construction Carbon with bamboo core is very WORTH exploring for manufacturer. It can be almost as good as solid carbon but lighter and much less expensive.
Good alu is almost always good but weight is nogo for me. Alu is very sensible for connections execution. Axis is example how to do it right. Carbon setups usualy dont have problem with connections, because they can use "Mortise and tenon" type of connections - which isnt possible with extruded alu.

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Re: Hydrofoil stiffness & fuselage connections

Postby stevez » Tue Oct 15, 2019 3:45 am

I'm in favour of connections that bolt together flat surfaces.
The Axis for example. This seems like a really good design, they're doing a lot of things right.
Bolting together curved surfaces like the Moses is not bad, but creates design and/or engineering challenges.

I'm also not that crazy about connections that plug or slot in like the gofoil for example. When I got mine it was super tight, but after a season it had definitely loosened quite a bit. These types of connections always develop some play over time.

I'm using the newer cloud 9 hybrid setup with a project cedrus mast. This is a ridiculously stiff setup with almost no flex anywhere, even without the full carbon wing.

You really feel the difference as a feeling of sure and predictable tracking and responsiveness. Just like a mountain bike, I can't see how anyone would want any flex anywhere on a foil.


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