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Mast/baseplate joint amount of carbon needed

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seglarn98
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Mast/baseplate joint amount of carbon needed

Postby seglarn98 » Tue Mar 19, 2019 12:29 pm

Hi!

I’m just finshing up a hydrofoil build done with an old bladerider moth rudder set as wings and mainfoil. Made the stabilizer and fuse ourselves.

I’ve attached the mast to the baseplate with first epoxy/filler/carbon cutoffs to make a smooth curve, then I added 5 layers of unidirectional carbon and one twill 200g on each side, approx 10 cm up the foil.

Will it be strong enough?

Kind regards

seglarn98
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Re: Mast/baseplate joint amount of carbon needed

Postby seglarn98 » Tue Mar 19, 2019 12:39 pm

Here are some pictures;

The picture of the mast/basepalte joint is taken before adding the carbonlayers
Attachments
5A9E573D-7159-45C7-99DB-106176E727E0.jpeg
AF332D2D-14EF-4F50-B4E6-1B7C3ECA84D2.jpeg
50BB061F-3B30-453B-BBD3-81B08CE389CE.jpeg
3334244C-64E6-4245-ABB8-B868EC636CB3.jpeg

seglarn98
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Re: Mast/baseplate joint amount of carbon needed

Postby seglarn98 » Tue Mar 19, 2019 4:22 pm

Quite a bit of flex sideways in the mainfoil, fuselage doesn’t have enough torsional stiffness. Will it be rideable?

Almost 5 cm flex in the wingtip if I push it down hard, 82 cm wingspan
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E29EA115-064F-4FE0-ACCA-927FC6289864.jpeg

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Re: Mast/baseplate joint amount of carbon needed

Postby tomtom » Tue Mar 19, 2019 5:32 pm

about mast to the baseplate :

I will made it much thicker - thickness is most important for stiffness /cube relation/ - and here drag doest matter.
Imagine mast 2x as thick in point where it touch baseplate + some 3-5 cm - and then smooth everything

seglarn98
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Re: Mast/baseplate joint amount of carbon needed

Postby seglarn98 » Tue Mar 19, 2019 6:45 pm

tomtom wrote:
Tue Mar 19, 2019 5:32 pm
about mast to the baseplate :

I will made it much thicker - thickness is most important for stiffness /cube relation/ - and here drag doest matter.
Imagine mast 2x as thick in point where it touch baseplate + some 3-5 cm - and then smooth everything
Ok, its 3,5 cm wide right now should I put on some epoxy putty then and add some more carbon to get it wider? Feels very stiff at the moment, but I guess its stiff until it breaks?

What do you think about the mainfoil flex, should I add some more layers of twill for torsional stiffness?

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Re: Mast/baseplate joint amount of carbon needed

Postby tomtom » Tue Mar 19, 2019 6:57 pm

3.5cm is thick enough - it looks much less from picture
About mainfoil - For 82cm span it will be flexible no matter what - its combination bending of mast + torsional fuselage + bending front wing...

Production foils arent super stiff either - try it and will see...

seglarn98
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Re: Mast/baseplate joint amount of carbon needed

Postby seglarn98 » Tue Mar 19, 2019 7:14 pm

tomtom wrote:
Tue Mar 19, 2019 6:57 pm
3.5cm is thick enough - it looks much less from picture
About mainfoil - For 82cm span it will be flexible no matter what - its combination bending of mast + torsional fuselage + bending front wing...

Production foils arent super stiff either - try it and will see...
Ok, thanks for the input. I will add two layers of twill without building any distance instead of sanding down the peel ply finish. Mostly for feelgood I guess:)

Will try to put one or two layers of twill on the fuse, hopefully reduce the flex a bit. Is still a bit cold to go out and try it here in Stockholm, so I guess it’s fine to spend some time in the basement:)

It’s only 2,6 kg in total now, so I guess it’s fine to beef it up a little;)

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Re: Mast/baseplate joint amount of carbon needed

Postby kitexpert » Tue Mar 19, 2019 8:42 pm

If you want torsional stiffness you must put your fibers in an angle. If your fibers are straight no matter how many layers you add it won't help. I'd use biaxial or directional fiber tape rather than twill for torsional stiffening.

Your plate looks thin. Remember that you are standing on top of it and there will be a lot of bending forces. Because plate is almost all the time above water you don't have to worry some if it creates some drag. However some shaping should be done to avoid plate to act like a brake in water contact.

Your foil is so light weight you can add fiber to it without care, it will only be better.

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Re: Mast/baseplate joint amount of carbon needed

Postby tomtom » Tue Mar 19, 2019 8:46 pm

Best strategy for stiffness is always thickness. 2.6 total is super light!
did you mind share construction details - you probably have core inside when so light... ? Mainly about mast and fuse - profiles - technology...

Im going to make custom mast for moses - hoping for much stiffer than original... Not racing setup so i make it thicker...

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Re: Mast/baseplate joint amount of carbon needed

Postby bigcane » Tue Mar 19, 2019 8:47 pm

I think some big stiffness gains can be had by thickening up the fuse at the mast connection area with a ton of biax carbon. If you stand on the wings on the floor and flex the mast you will see a lot of flex originating in this area. I think this is the reason why the Mikes Labs and Chubanga fuses are quite big. Wobbly foils are ok- ish going upwind but brutal when trying to get back down to your launch spot


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