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Mast Building Method

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GrantL
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Re: Mast Building Method

Postby GrantL » Sat Jan 14, 2017 9:40 pm

I understand what you are trying to achieve.
But solid carbon rods will only help reduce the bending moment over the mast length. Also laying the rods into a core (wood) , you will have a lot of shear between the two dissimilar materials.

My thoughts on rapping.
I have attempted this many years ago on a bike frame.
I found it was extremely hard to get the core profile correct, meaning after wrapping it always end up oversize and profile lost.
Sanding is the only solution to maintain what original shape you started with. The only problem with sanding is you remove all of those fibres.
Just my experience.

But your question how much is enough.
If you use 300 gsm uni carbon and 600gsm double bias +-45deg lay up this.
3x uni first
2x double bias.
Last layer of laminate, 150gsm twill. The twill is only a protection layer.
This would be a start, but personally it will not be stiff enough in torsion.

The question is how are you going to do the laminate.
I can give you some ideas if you are interested.

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Re: Mast Building Method

Postby TomW » Sat Jan 14, 2017 11:26 pm

Hi Grant,

I'm also building a strut, 70 cm long. So far, I've built a 7 layer Abachi veneer Core and shaped it, with compensation for a 3mm wall thickness of CF.

I've already purchased biax in 300 gsm and twill 450 gsm. I also have some 15mm wide Cf tow tape I could add. Sounds like I should of purchased Uni d too.
My plan was to vbag on 4 layers of biax and 3 strips of Cf tow each side, clean it up and then bag on 2 -3 layers twill.
Then I will attach strut to a plate and v-Bag on more twill.

Any recommendations welcome

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downunder
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Re: Mast Building Method

Postby downunder » Sun Jan 15, 2017 1:20 am

I am on the same boat, any suggestions are well appreciated.

If we go with 70/30% are the numbers right? Coz Uni 300g is 1/2 of Biax 600g, hence 3x300=900, 2x600=1200
Maybe swapping 300g uni for 600g, that sounds better?

But with 300/600g we need to remember that 5 layers of 200g makes it about 1mm thickness. The weight variations significantly change the profile thinness, as we know.


Tom, to answer "5kg, 80cm out test" - the core is very fragile atm, I do not want to break it :)

Cheers

D.

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Re: Mast Building Method

Postby GrantL » Sun Jan 15, 2017 2:13 am

TomW wrote:Hi Grant,

I'm also building a strut, 70 cm long. So far, I've built a 7 layer Abachi veneer Core and shaped it, with compensation for a 3mm wall thickness of CF.

I've already purchased biax in 300 gsm and twill 450 gsm. I also have some 15mm wide Cf tow tape I could add. Sounds like I should of purchased Uni d too.
My plan was to vbag on 4 layers of biax and 3 strips of Cf tow each side, clean it up and then bag on 2 -3 layers twill.
Then I will attach strut to a plate and v-Bag on more twill.

Any recommendations welcome
Hi Tom.
Firstly when you say biaxisal is it two layers sown together (150 @ 45deg and 150 @ - 45).if that is the case then perfect. 45deg - + will have the most effect on torsional load on mast.
The twill if laid 0deg on the mast (so weave square to mast) will only be active in 0 direction. The fiber running parallel to the profile will add no strength at all. What you could do is carefully distort the cloth so the fibre is running say +/-30deg. That would give you more strength in the 0deg direction (length ways).
I can't comment on the tow rope, but the tensile strength of it might be least that normal high modulus carbon. The more threads /sqinch the stronger the cloth normally is.
But I guess you could still use it for what you want.

Tom I have started a post on the process of infusion I used to make a foil got some pics of the process I used. Have only started writing so got lots to add yet if you are interested.
I am sure your layup will work, it really depends on how strong you want to make it.

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Re: Mast Building Method

Postby GrantL » Sun Jan 15, 2017 2:40 am

downunder wrote:I am on the same boat, any suggestions are well appreciated.

If we go with 70/30% are the numbers right? Coz Uni 300g is 1/2 of Biax 600g, hence 3x300=900, 2x600=1200
Maybe swapping 300g uni for 600g, that sounds better?

But with 300/600g we need to remember that 5 layers of 200g makes it about 1mm thickness. The weight variations significantly change the profile thinness, as we know.


Tom, to answer "5kg, 80cm out test" - the core is very fragile atm, I do not want to break it :)

Cheers

D.
Hi down under.
Sorry I was properly a little vague with my numbers.
1/.300uni x 3
2/.600 double bias x1 (300@+45deg sown to 300@-45deg)
3/.300uni x 3
Etc....
This gives you a ratio of 25/75. You can just add another double bias to adjust the ratio as the layers build up. It is all dependant on the laminate you use. But if you stick to the 70 /30 ratio you can go wrong.

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Re: Mast Building Method

Postby TomW » Sun Jan 15, 2017 10:52 am

Thanks Grant. I do what I can. Considering I'm building a 70 cm strut, I figured all the Uni D might be overkill, but reading and thinking more about it, I understand. That's a lot of Uni in the lamination.
It would have only been another 20 £ for the Uni D, regret not getting it. Shipping is costly.
And Downunder brings up the skin thickness. If I have a lamination of :
4x 300g biax, 4x 450g twill - in vacuum bag, how thick will the skin be? I don't have anymore CF.
I might want to add some glass to my Core just to add some thickness.

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Re: Mast Building Method

Postby TomW » Sun Jan 15, 2017 10:53 am

Found a lamination thickness calculator

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Re: Mast Building Method

Postby TomW » Sun Jan 15, 2017 4:32 pm

Using this : https://www.saertex.com/en/products/material-calculator

And some different variables it looks like 3000g fiber in 8 layers will give me at least 3 mm.

Am I correct in assuming that if I put twill on 90/0 to strut, the twill at 450g and therefore has 225 g running in correct direction?
That gives me 4x 225 g running in correct direction. Yes, the twill fibers are not non-crimp due to weave.
It seems like I have a decent layup. : 4x 300g biax, 4x 450 g twill each side.
I will alternate biax and twill, ending with twill last, and add final 4oz glass layer as protective / cosmetic layer.

Want to do lamination next weekend.

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Re: Mast Building Method

Postby TomW » Sat Jan 28, 2017 10:59 pm

I put the strut in the vbag with 4x300g biax and 4x 400g twill. Cf thickness is 4mm.
I wrapped the LE and it became very rounded and needed a lot of grinding. Might have been better doing flat join at LE. Shape is now done by eye and feel. Have no idea if it's right, I'm ust going by how it looks.
Will be laminating onto fillet up onto strut and base plate both sides.
This photo is before I shaped it...
2017-01-28 11.39.14.jpg
2017-01-28 13.11.55.jpg
2017-01-28 15.02.22.jpg
2017-01-28 15.01.59.jpg

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downunder
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Re: Mast Building Method

Postby downunder » Mon Jan 30, 2017 4:59 am

Whow, Tom,

that is a bit overkill, 4x300g biax and 4x 400g twill...I think, can't be 100% sure.

That must be stiff as concrete :) Let us know please! Thx for the flat join at LE tip.

Cheers


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