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HelicopterGasser Model RC HelicoptersOther › Carbon of Alu frame for gasser?
11-29-2007 06:34 PM  10 years agoPost 1
cdec

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Belgium

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Hi,

I'm thinng of making some custom frames.

Should I cut them in Alu of in Carbon? You see different brands use both o the materials,

What are the advantages of both materials, and more important, what are the disadvantages?

Chris

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11-29-2007 07:56 PM  10 years agoPost 2
lperagallo

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Westfield, Indiana, USA

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I'd look into G10 frames. These absorb vibration better then both materials and do not conduct electricity. They also are just as strong as carbon for the same weight.

Lou

Twin Bergen 44Magnums FBL Wren NW44s - Kero start

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11-30-2007 01:02 AM  10 years agoPost 3
oldfart

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Vancouver, Canada

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G-10 as strong as Carbon for the same weight???

What tests can you point me to that would confirm that???

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11-30-2007 01:10 AM  10 years agoPost 4
FCM

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Surrey, England

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I run G10 sideframes that I cut myself. G10 is actually a very dense material with a relative density of 1.8 so it is much heavier than graphite sheet of comparable thickness and will not be as stiff.

The good things about G10 are that it is non-conductive, heat resistant (especially the FR4 spec stuff)and has a dampening effect on vibrations. It is also very tough and difficult to crack. Nearly forgot - it's cheaper than graphite!

If designed carfully, G10 frames will not be much heavier than a set of graphite or alloy frames.

Hope this helps.

Paul.

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11-30-2007 05:12 PM  10 years agoPost 5
AceBird

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Utica, NY USA

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What tests can you point me to that would confirm that???
Oops! He didn’t mean to say that.

Cdec, carbon can be a bear to machine, it has been known to have RF issues and it is difficult to see failures if they occur.

Aluminum has all kinds of grades so it would depend on what grade you choose as to the negatives. Most commercial frames have a secondary process. Will you be using a secondary process or leaving the surface raw? I leave my aluminum parts raw.

The single most important thing after selecting your material type is the design. This will have much more affect on the results unless you plan on using the same design for all materials. If that is the case then aluminum will be the strongest. Actually steel will be the strongest by you didn’t give that as an option.

Ace
What could be more fun?

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11-30-2007 05:38 PM  10 years agoPost 6
cdec

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Belgium

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Ok, thx

Seems G10 is the best choice, then Aloy, and last carbon.

I wonder why there aren't any comercial gas helis made out of G10 (MA, Vario, Bergen,..)

The machining will be don by a workshop, so that's not an issue.

Thx all

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11-30-2007 05:48 PM  10 years agoPost 7
copperclad

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NY

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hi
Bergen frames are G10 , Maxum frames are listed as being G10 , dana
http://www.bergenrc.com/GasEB.php
http://www.realheli.com/page/maxum

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12-01-2007 02:02 AM  10 years agoPost 8
bellecrank

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Canada

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The "absorbs vibration" quality in G-10 is also a negative.

What allows it to absorb vibration is the fact that it is less rigid, so in order to insure the frames to not flex during maneuvers, in areas that are crucial for gear alignments, clutch to bell alignments, etc. they will require a rather complex inner structure of machined aluminum or other parts....again adding weight. Here the proper type of aluminum will be best.

Also, they "crush" easier, so bolts will wear into them and can loosen off in relatively short order, specially in any area where there is any heat. Here again aluminum is the best

They also have little (if any) value in dissipating heat...here again aluminum is the best.

IMHO, the biggest reasons for a manufacturer to use G-10 is a) easy to find b) easy to machine and c) the lowest priced material.

From a flight perspective, G-10's realtively heavy weight, its' lack of rigidity, and its crushability, would make it not desireable for me....specially in the torque, high vibration & high heat environment of a gasser heli.

Yes, it can be made to work (so did 4-wheel drum brakes), but IMHO, both C/F and aluminum would be better choices.

And best of all, would be the proper type of aluminum frame that is machined, uses no bends, and aligned properly during assembly to illiminate any pre-stressing, which eliminates any metal fatique issues of consequence....result...light....rigid....relatively low cost...and also a heat sink!!

So my choice, in order of priority, would be the proper type of aluminum, then Carbon Fiber and last would be G-10.

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12-01-2007 01:58 PM  10 years agoPost 9
AceBird

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Utica, NY USA

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Well some of what you say is true ...

select a choice of material and design accordingly. You could make a frame of wood if you wanted to.

Many people do not understanding prestressing metals. They get stronger when prestressed not weaker. If you build the frame with sheetmetal and bend some of the parts you have to know what you are doing and if you do know what you are doing you can blow away the competition. Same goes for welded construction. Some camera mounts have welded construction. That does not make them better or worse, it all depends.

Ace
What could be more fun?

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12-01-2007 02:10 PM  10 years agoPost 10
FCM

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Surrey, England

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What allows it to absorb vibration is the fact that it is less rigid,
I would attribute this property to the far higher density of G10 rather than it being less ridged.

Certainly G10 sheet for a given cross section is appreciably more flexible the graphite sheet. But it does not crush as easily as you might think. I have two helis with G10 sideframes and they are very strong and do not crush or loosen screws.

The really nice property and just about the only sideframe material with this, is that it is non-conductive. The only other frame material that has this is injection moulded GRN.

G10 is to all intents and purposes heat proof. You will not damage it by having hot engine parts cotacting against it. It is really tough, tougher than graphite but it may not be the best material for every helicopter application. If you do need great ridgidity and the lightest weight then I would say go for graphite frames.

G10 like graphite is not easy to machine. They are both good thermal insulators and you need the proper tooling to machine them. If you want ease of manufacture, aluminium alloy is by far the easiest to cut.

Paul.

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12-01-2007 04:11 PM  10 years agoPost 11
lperagallo

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Westfield, Indiana, USA

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bellcrank,

Hate to contradict you....but I have a Bergen Gasser and Turbine. I have no complex attachment set ups and I've never had a problem with any mechanical set ups with the gear train. The turbine is 18 pounds and I fly a bit aggressively doing loops, rolls, stall turns and fast flight. I haven't had any issues with the frames. If you want to talk about heat, let's. The turbine generates quite a bit of heat all be it mostly directed away from anything. But after shut down there is quite a bit of residual heat the surrounds the frames. Never had a problem. I also had an unfortunate situation where I had a bad auto and turned it on its side. There was a fire after a fuel line melted. While the fire took out fuel lines, wires, and a nice canopy paint job, there was no damage to the frames.

So I guess I'd have to say that G10 works pretty good. Oh and by the way, the Bergen Observer AP ship that weighs in around 38 pounds with gear and a twin cyclinder Zenoah flies quite well without anything more then G10.

Lou

Twin Bergen 44Magnums FBL Wren NW44s - Kero start

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