Aluminium square tube -v- spruce or other woods

[old man emu]

Seeing Betterbex's advertisement: Aluminium Frames | Recreational Flying got me wondering if, when building a wooden framed aircraft, would it be possible to substitute the wood with aluminium square tube.

 

Morgan aircraft seem to have sufficient strength when made from tubing. I wonder if their might be a weight advantage in using metal as opposed to wood. Also, aluminium square tube might be easier to obtain here than spruce etc.

 

OME

 

 

[Old Koreelah]

Good spruce has been getting hard to obtain, so many builders, including overseas, use Qld Hoop Pine. I believe it's at least as strong as Sitka Spruce.

 

Might be competitive with aircraft grade RHS alloy.

 

 

[bexrbetter]

Seeing Betterbex's advertisement: I wonder if their might be a weight advantage in using metal as opposed to wood.

Was humour of course, might have escaped some ...

 

I doubt you could build it lighter without a lot of engineering effort, time and expense including bespoke non-standard wall thicknesses.

 

Otherwise you are stuck with 'off the shelf' standard metal thicknesses where you always have to go to the next thicker size, and probably the same weight, if not slightly heavier. But you will get better consistency and easier to work with, although that opinion will differ depending on your background and tool ability.

 

 

[facthunter]

Wood is great stuff, (natures composite) but it's hard to grade reliably and determine the safe life of it and the glued joints. Careful selection and a good knowledge of the "faults" (like felling shakes, angled grain, how it's sawn etc are necessary) The original wooden fuselages with all the turnbuckles and tension wires are a riggers art form which we probably wont see much of except by real early enthusiast (of which I would like to be one) Square tube with riveted gussets can be a SIMPLE triangulated structure either based on a truncated square pyramid or a triangular pyramid. If you wanted better shape you would need extra bulkheads and some stringers with fabric cover turtledeck etc but then it's getting away from simple. I'm a round tube welded person but the other option is certainly easier to produce and worthy of consideration. That's pretty much a Morgan isn't it? Skyranger to a lesser extent. Just my thoughts. Nev

 

 

[diesel]

I will stay with wood. A new Robin DR 400 or 401 with the diesel has a 25 yr airframe guarantee. The origionals from 1950 still airworthy.

 

Robin is of course a Jodel airframe.

 

In 1934 Henri Mignet said aluminum is a treaturous metal. I believe him as I watch alloy aircraft corrode away while you sleep.

 

Chas

 

 

[bexrbetter]

I will stay with wood. A new Robin DR 400 or 401 with the diesel has a 25 yr airframe guarantee. The origionals from 1950 still airworthy.Robin is of course a Jodel airframe.

In 1934 Henri Mignet said aluminum is a treaturous metal. I believe him as I watch alloy aircraft corrode away while you sleep.

 

Chas

Chas, that just flies in the face of all the Cessnas still flying for example, among others.

 

1934 aluminiums are not the same as today's. 7000 series didn't even exist for example and every other base series have doubled or tripled in strength, life, etc. besides the many improved derivatives of each series.

 

Square tube with riveted gussets can be a SIMPLE triangulated structure either based on a truncated square pyramid or a triangular pyramid. That's pretty much a Morgan isn't it?

Yes, and interesting to the thread is that the Morgan is literally a wooden Rand KR2 metal'ised - one can compare the building processes of the 2.

 

 

[diesel]

Chas, that just flies in the face of ahe Cessnas still flying for example, among others.1934 aluminiums are not the same as today's. 7000 series didn't even exist for example and every other base series have doubled or tripled in strength, life, etc. besides the many improved derivatives of each series.

 

Yes, and interesting to the thread is that the Morgan is literally a wooden Rand KR2 metal'ised - one can compare the building processes of the 2.

As you said tongue in cheek.

It is true that wood outlived the metal cousins built to compete with new American machines.

 

A lot of dead cessnas now with corrosion.

 

Just keep building. A good aircraft will outlive its owner.

 

Chas

 

 

[facthunter]

Needs qualification. Mosquitoes flew apart in flight. Wacket trainer inflight wing spar failures. Ansons removed from service due wingspars glue problems. Some Percivals etc. This is all Australian experience. Much of the problem was glue and use in tropics. Well built and looked after wood is still a viable material for the one off and the hobby builder. There's an RV of wood that will soon be flying in australia. It's versatile and can be used in fairly complex shapes. Relatively cheap... Hard to grade consistently. Ply and a good glue may get around that to some extent. Don't let me put you off using wood. Just go into it properly and look after the finished plane. Nev

 

 

[diesel]

Yes the first Aussie mossie did flick its engines off on takeoff. I read the report.

 

Was not glue though.

 

Casine was either and still is very good, or bad.

 

Casa did not allow anything else to be used untill recent times.

 

Modern glues and well sealed timber should last forever and is reasonable to repair.

 

A look at why aerobatic aircraft have wooden wings is a good start.

 

Modern construction methods like alloy for mass production and boring look alikes.

 

Chas

 

 

[M61A1]

Most of the corroded Cessnas and such had no corrosion protection and lived outdoors in all conditions. Usually tied down in sun, rain and snow, with nothing more than a windscreen cover, if that. If you do that to a wood aeroplane, it won't last long.

 

The Champ, Citabria , Decathlon, and I fairly sure the Cub, all have aluminium spar upgrades available due t the wood coming apart, and most of the modern aerobatic aircraft use carbon fibre and glass.

 

Yes your modern adhesives will last as long as the timber is sealed, but it does need a bit of care, properly treated aluminium is very durable in very poor environmental conditions.

 

 

[facthunter]

I had a wood spar Citabria. (7 ECA) Loved it but I didn't lend it, although like all of them it has a "G" meter. You don't let people hangar rash your plane and you treat your spar with kid gloves. Later models are metal spars, and all aerobatic planes require a lot more inspections than non aero ones. A later Mosquito fell apart in flight, and I don't think there was just one. My wood work teacher at Univ of Technology NSW, Newcastle annex, built many parts for them and made a lot of money out of it. I thought CASEIN was banned for aircraft. It's probably attacked by some mould or fungus, I recall. We had two Wackets at Newcastle but they got grounded because of the wood spars before I got to them. A friend of mine in Sydney cancelled a booking on one and that plane fell apart in the air with someone else flying it, so that's a close call for him. Nev

 

 

[Marty_d]

As Nev said, if you're going to use wood, you need to know what you're doing. I agree there's some fantastic wooden aircraft out there but I certainly wouldn't buy one second hand.

 

Personally I don't have the necessary knowledge to build a plane out of wood (kitchens and laundries, yes, but not planes) - so I'll stick to the good old 6061-T6.

 

 

[diesel]

I could not find any aluminium

 

trees.In Europe the hardest working aircraft is the DR 400 and the new 401.

 

Pilots did not like the new metal ones and clubs wanted to carry on with the wooden ones.

 

Still in production its anything from a 120hp club trainer to a higher powered glider tug.

 

Top of the range 4 /5 seat long range tourer with 200 plus hp and csu.

 

In the alps the Jodel D140 is still the favoured aircraft for alti snow glacier work . A lot are 60 yrs old and still prestine. Tap up you tube.

 

Chas

 

 

[facthunter]

I agree about the second hand purchase situation. The Citabria had a new wood spar and upgrades with the monel barbed rivets attaching the metal ribs and a complete recover and rebuild. You need to know a plane's build quality and usage history as well as the design's suitability/quality. Nev

 

 

[old man emu]

I agree that working with wood is a pleasure, but working with a material that has uniform properties should make for a product whose quality is more predictable.

 

Apart from workability, I was interested in how the use of aluminium in place of wood for the fuselage frame would aid in reducing the dead weight of the airframe. Die Number UA8881 is a 25.4 mm square aluminium with 1.2 mm thick walls and weighing 0.301 Kg/m. How does that weight compare to a metre of wood typically used in an wooden airframe?

 

If I was joining wooden components using glues, I certainly would not contemplate using a glue that was seventy or more years behind current adhesive technology.

 

OME

 

 

[facthunter]

Without going deeply into it, I reckon it would be very close to the same weight as a wood truss but likely if there's a difference tending a bit heavier. Not enough to be a game changer. Depending on the actual design wood may be a little more brittle as you would use ply as bracing and it's not got a lot of give as a material performing that function. Under impact or over design forces the Al frame may distort a lot more without failure than wood. You would have to do a comparative analysis of the design behaviour in various situations to really know. Nev

 

 

[Old Koreelah]

...If I was joining wooden components using glues, I certainly would not contemplate using a glue that was seventy or more years behind current adhesive technology.OME

The really important bits of my Jodel were put together with resorcinol glue, which I believe was developed for the DH Mosquito. The rest is epoxy, a much easier glue to use, but it has its limitations, including going soft above 60C.

 

 

[diesel]

The really important bits of my Jodel were put together with resorcinol glue, which I believe was developed for the DH Mosquito. The rest is epoxy, a much easier glue to use, but it has its limitations, including going soft above 60C.

I just felt the area around my in wing radiator.

Its set in the leading edge similar to a mossie.

 

Been a hot nw day and engine temps were up there too. All seems ok.

 

Glues are not normally boiled although that was

 

part of the origional approval tests.

 

The biggest sacrifice was the parking up of the DH Hornets over there for so called weathering tests. Gee that would be a great homebuilt.

 

Chas

 

 

[Yenn]

Wood and aluminium are both good and require different joining methods, pick whichever suits you. Possibly the biggest kit maker, uses 2023T3 for most of his designs skins, which are load bearing and I don't know of any square section being used in spars. To change a design from one material to the other would be a major undertaking. For example to build an aluminium wing for my Corby would result in something much heavier than the spruce and ply original, which I can pick up with one hand.

 

 

[facthunter]

I don't think we were referring to spars, with the square section tube of Al. Nev

 

 

[spacesailor]

I have found that Good wood is very expensive, and hard to get a local supplier that has the size & grade needed, even short propeller lengths are problematic.

 

And they get upset when sorting through rack after rack for three or four good matching planks.

 

To make laminated wood spars would cost a lot more than alloy

 

spacesailor

 

 

[diesel]

The modern disposable world does not know what good wood is.

 

After the Christchurch earthquakes truckloads went down gullies. Nobody allowed near.

 

Canadian Oregon.

 

There are several species listed from war emergency.

 

Western Hemlock also from British Columbia is excellent at a small fraction of the cost.

 

Often sold as ladder grade.

 

Chas

 

 

[spacesailor]

Hi Diesel

 

Had a quick look for Western hemlock (Tsuga heterophylla),

 

But alas nothing stocked.

 

Were do you buy your stoke from?. as it's north American.

 

spacesailor

 

 

[diesel]

TE="spacesailor, post: 594935, member: 6426"]Hi Diesel

 

Had a quick look for Western hemlock (Tsuga heterophylla),

 

But alas nothing stocked.

 

Were do you buy your stoke from?. as it's north American.

 

spacesailor

 

Occasionally building suppliers bring it into nz.

 

Both for ladders or house finishing.

 

Beautifull to work with. Mine has 22 growth rings per inch. Stonger than spruce and lighter than oregon.

 

Chas

 

 

[spacesailor]

Woopsie

 

That should have read: stack not stoke,

 

slow reader perhaps

 

spacesailor