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Mast/baseplate joint amount of carbon needed

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seglarn98
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Re: Mast/baseplate joint amount of carbon needed

Postby seglarn98 » Tue Mar 19, 2019 11:12 pm

tomtom wrote:
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...
Hi! We didn’t do anything spectacular, the reason it is light is because the bladerider rudder and elevator was light. Haven’t had a look inside the mainfoil/rudder, so don’t know what mach2 did there.

The mast/vertical was made with two plastic bags inside that the pumped up in a mould. I know that mach2 have moved on to use some kind of foam nowadays to be able to make it thinner/stiffer. The cord is 12 cm, so quite wide. Thickest point probably 14 mm, maybe 13.

The stuff we did ourselves is made with carbon and some glass for thickness through and through on baseplate/stabilizer. Nothing special there, probably used way too much resin.

Fuselage is made with 6 layers of 4mm plywood, close to three cm high. At the moment only one layer of carbon on the outside, except for two extra layers of uni going out from the mast position. 6 layers of carbon on each side of the inside of where the mast attaches.

Plan is probably to add some thin and long strips of uni from mast attachement going in an x shape to where the mainfoil attaches, then two layers of twill over everything to get more torsional stiffnes, does that sound reasonable?

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Re: Mast/baseplate joint amount of carbon needed

Postby seglarn98 » Tue Mar 19, 2019 11:18 pm

kitexpert wrote:
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.
Thanks for the input.

Maybe I could use strips of uni that i pull from one side to the other going forward of the mast position. Maybe even go around the fuse when going towards the stabiliser. Try to get it angled at 40 degrees. Will put one/two layers of twill over it afterwards to make it look nice.

I don’t have any biax/tape unfortunately.

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Re: Mast/baseplate joint amount of carbon needed

Postby seglarn98 » Wed Mar 20, 2019 9:58 am

bigcane wrote:
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
I’ll try to lay strips of uni down in a diagonal pattern going out from the mast joint. Don’t have any biax, but I guess uni should be ok as long as i angle it right and work carefully, hopefully my handlaid strips arent too bumpy

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Re: Mast/baseplate joint amount of carbon needed

Postby tomtom » Wed Mar 20, 2019 10:26 am

thanks for info!

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Re: Mast/baseplate joint amount of carbon needed

Postby kitexpert » Thu Mar 21, 2019 6:22 pm

Uni tape (which can be also cut from cloth) is good for torsional stiffening. You can wrap it around fuse and mast to 45 degree angle like you would do with any tape. Best is to put two (or four etc.) layers crossing each other. Some unevenness will hide itself under top layers and it is possible to smooth it by sanding.

IMO all carbon sanding should be done wet.

I once did about 8mm thick laminated plate from carbon and glass fiber. I didn't put any diagonal fibers in it. When I cut about 30x7cm pieces from it they were extremely stiff for straight bending but for torsion it was like hard rubber. I could easily twist it tens of degrees by hands.

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Re: Mast/baseplate joint amount of carbon needed

Postby downunder » Fri Mar 22, 2019 5:33 am

seglarn98 wrote:
Tue Mar 19, 2019 11:12 pm
tomtom wrote:
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...
Hi! We didn’t do anything spectacular, the reason it is light is because the bladerider rudder and elevator was light. Haven’t had a look inside the mainfoil/rudder, so don’t know what mach2 did there.

The mast/vertical was made with two plastic bags inside that the pumped up in a mould. I know that mach2 have moved on to use some kind of foam nowadays to be able to make it thinner/stiffer. The cord is 12 cm, so quite wide. Thickest point probably 14 mm, maybe 13.

The stuff we did ourselves is made with carbon and some glass for thickness through and through on baseplate/stabilizer. Nothing special there, probably used way too much resin.

Fuselage is made with 6 layers of 4mm plywood, close to three cm high. At the moment only one layer of carbon on the outside, except for two extra layers of uni going out from the mast position. 6 layers of carbon on each side of the inside of where the mast attaches.

Plan is probably to add some thin and long strips of uni from mast attachement going in an x shape to where the mainfoil attaches, then two layers of twill over everything to get more torsional stiffnes, does that sound reasonable?
That in bold is nowhere near enough around the mast and wings, imo. If u used 200g carbon. Even if bigger weight, it totally depends how was wrapped, since the torsion here is huge (think hitting the sand!). I wrapped my fuse in 45/45 two layers, plus UNI all the way, and number of layers diff angles around the mast. Duno, 7? 8?

Easy to test. Bend it as Beckham :) Holding the wing put the stress on fuselage. How much does it bend?

Uni would be extremely difficult to apply on fuselage, because your fuse profile is changing. Easier on rounded profile but even than if profile is changing, impossible task.

"6 layers of carbon on each side of the inside of where the mast attaches." - on which angles?

Good luck

PS
In the case someone is wondering, what I'm building
IMG_0295.JPG
IMG_0321.JPG

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Re: Mast/baseplate joint amount of carbon needed

Postby downunder » Fri Mar 22, 2019 5:58 am

seglarn98 wrote:
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?
Well,

the thickness does not really matter for the mast/plate. What matters the most is the angle. As I see it your carbon angle mast/plate is almost 90, and that will break no matter of the thickness (well, maybe not if is high modulus carbon).

With that angle you would be better off with no plate at all, but a tuttle box.

How to fix it? Slap epoxy putty and make 45 degree angle all around, than slap carbon on that to overlap and bond with mast/plate.

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Re: Mast/baseplate joint amount of carbon needed

Postby grandeand » Wed Apr 24, 2019 10:21 am

I tore the attack plate of my silent moses.
I have created a reinforcement collar with bi-directional carbon 200 gr.
15 layers on the right, 15 on the left and front and back. put under vacuum.
this is the result.
I put the layers to climb. I haven't tried it yet, I hope it holds up.
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