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Vacuum bagging aluminum mast with carbon fiber

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atomic-chomik
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Vacuum bagging aluminum mast with carbon fiber

Postby atomic-chomik » Mon Feb 25, 2019 5:41 am

Anyone tried this to stiffen up the an aluminum mast by bagging a few few warps of CF? I know about the reaction, I'm pretty sure it could be mitigated with a base layer of regular glass and then followed by a couple wraps of carbon then a top layer (and thrown into a bag)? I would rough up the aluminum mast for mechanical bonding. I have fabricated a larger wing and the aluminum mast has too much flex. Any thoughts or experience anyone?

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Re: Vacuum bagging aluminum mast with carbon fiber

Postby downunder » Mon Feb 25, 2019 8:12 am

What's stopping you from buying carbon mast?

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Re: Vacuum bagging aluminum mast with carbon fiber

Postby revhed » Mon Feb 25, 2019 9:59 am

WHY?
Every HEAVY ALU STRUT, NOT mast, (DAMN IT) I have ever seen was heavy BUT stiff!
Aircraft companies using modern high tech materials do get good, great even bonding alu to epoxy, but NEVER, (have tried)
using normal easy to find products had a bond that lasts.
You will think so but just wait! Heat from sun, cold from H20, salt water, expansion, contraction, not to mention famous alu corrision!
I have used a now not legal here in France, "primer, glue" that still holds, doing it perfectly like sanded and CLEAN and ratios exact.
I will not mention product, really is shit to breathe even with good chemical mask!
SO,
Do not even try, unless you want to fail.
R H

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Re: Vacuum bagging aluminum mast with carbon fiber

Postby BWD » Mon Feb 25, 2019 3:51 pm

in salt water, carbon has to be meticulously separated from aluminum. A few makes have done this, with carbon wings and aluminum fuselage or carbon mast. But if any of the coatings or isolators used between parts break down, the mast will also break down.

I’ve never seen an aluminum mast wrapped in carbon. Horue makes masts that combine steel and carbon, very light, but also a little delicate.

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Re: Vacuum bagging aluminum mast with carbon fiber

Postby tmcfarla » Mon Feb 25, 2019 9:53 pm

I kind of doubt you’ll see much benefit, but consider laying down several layers of fiberglass between aluminum and carbon. Galvanic corrosion occurs amazingly quickly without insulation.

I can’t really discern any difference in flex between my aluminum and carbon masts.

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Re: Vacuum bagging aluminum mast with carbon fiber

Postby plummet » Tue Feb 26, 2019 10:09 am

Its very common to bond alluminium bosses in carbon frames for mountain biking. So yes its possible.
But if you have that skill what not make yourself a carbon mast. You could use the alloy mast as a plug for a mould.

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Re: Vacuum bagging aluminum mast with carbon fiber

Postby evan » Tue Feb 26, 2019 10:35 am

tmcfarla wrote:
Mon Feb 25, 2019 9:53 pm
I kind of doubt you’ll see much benefit, but consider laying down several layers of fiberglass between aluminum and carbon. Galvanic corrosion occurs amazingly quickly without insulation.

I can’t really discern any difference in flex between my aluminum and carbon masts.
Did you measure the profile thickness?

Stiffness has a cubed relationship with the thickness for the same material. So going from a 12 to 15mm mast doubles the Stiffness. (1.25*1.25*1.25=1.95)
That is why you see aluminum masts on slower foils as they can easily achieve a good Stiffness by making the masts a bit thicker and it is really hard to make a thin mast with low drag that is stiff enough.

Also there are huge differences in carbon types, the really expensive UHM carbon can be 2-4x as stiff as the cheaper off the shelf carbon. Mostly at the cost of strength and toughness.

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Re: Vacuum bagging aluminum mast with carbon fiber

Postby atomic-chomik » Wed Feb 27, 2019 5:35 am

I guess the motivating factor was the fact i have bent a couple of masts now. Have since bent them back but with the fatigued meta, it just went wonky again. I figured a wrap of carbon might fix em up, but the problems and cost seem not worth the experiment.

Ill buy a new mast. Thanks guys.

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Re: Vacuum bagging aluminum mast with carbon fiber

Postby evan » Wed Feb 27, 2019 8:37 am

Ah, you want to fix an existing mast or prevent a new one from breaking and strengthen it instead of adding Stiffness.

For increasing the strength you want to add material with the same Stiffness, if you add a stiff material to a flexible the stiff one ends up with all the load and you get a cascade failure where the flexible material gets loaded only after the stiff one breaks.
Imagine reinforcing a rubber band with a piece of rope, you are better off adding more rubber bands as otherwise only the rope gets loaded.

Glass is closer to aluminum in Stiffness, but better search for a aluminum mast with a thicker profile and more wall thickness if you want to avoid breaking them. Or was it corrosion on the inside that lead to the failure?

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Re: Vacuum bagging aluminum mast with carbon fiber

Postby tmcfarla » Wed Feb 27, 2019 10:24 am

evan wrote:
Tue Feb 26, 2019 10:35 am
tmcfarla wrote:
Mon Feb 25, 2019 9:53 pm
I kind of doubt you’ll see much benefit, but consider laying down several layers of fiberglass between aluminum and carbon. Galvanic corrosion occurs amazingly quickly without insulation.

I can’t really discern any difference in flex between my aluminum and carbon masts.
Did you measure the profile thickness?

Stiffness has a cubed relationship with the thickness for the same material. So going from a 12 to 15mm mast doubles the Stiffness. (1.25*1.25*1.25=1.95)
That is why you see aluminum masts on slower foils as they can easily achieve a good Stiffness by making the masts a bit thicker and it is really hard to make a thin mast with low drag that is stiff enough.

Also there are huge differences in carbon types, the really expensive UHM carbon can be 2-4x as stiff as the cheaper off the shelf carbon. Mostly at the cost of strength and toughness.
I didn’t measure the thickness, but they look to be about the same thickness, maybe carbon is very slightly thinner, but not much. Both seem plenty stiff and both are about the same weight. In both cases, most of the flex of the entire foil apppears to come from places other than the mast. My suspicion is that carbon doesn’t gain much in non-pro masts, but that carbon gains a lot in the fuselage/wings where stiffness is more important, cross sections are thinner, and where weight is more noticeable.

Fyi- Carbon is a 2018 Lift mast, aluminum is an older zeeko mast.


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