Treated wood could be as strong as CF?

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Lendo

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It sounds good and the Home Video was informative, it doesn't contain the resin and glue of Compreg or Laminated timber, so it may be lighter than Compreg and obviously it's tough, the rest is up to someone testing the finished product, I'm thinking in may be good in Propellers.
George
 

mcrae0104

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Southern Yellow Pine, for example, is stronger than steel, has a better fire rating than steel, and just looks better than steel.
Can you illustrate that with numbers and units?
Somehow I missed this thread earlier. I think what Yellowhammer might be getting at is the ratio of ultimate tensile strength to weight.

Steel: 61,000 psi (ultimate) / 7.8 (specific gravity) = 7,820
SYP: 12,800 psi (ultimate) / 0.52 (specific gravity) = 24,615
Note: specific gravity depends on moisture content and which source you look at; generally, strength of wood varies directly with density for a given MC. This is obviously a somewhat crude comparison.

This way of looking at things makes wood look like the clear choice, but the practicalities of minimum gauge, fabrication techniques, connection design, and the like tend to blur this seeming advantage (especially in things like spars, where space for the less-dense, though theoretically stronger-per-unit-weight wood is at a premium).

Without getting into burn tests and specific numbers, it is useful to observe that building codes recognize that "heavy timber" construction (members with a minimum nominal dimension of 4") fares quite well in fires, because the outer portion chars, protecting the remaining fibers, which continue to support loads. These structures can be exposed without fire protection, although building codes limit the allowable height and area of such buildings. Steel, on the other hand, rapidly loses strength at the elevated temperatures commonly seen in building fires (well below World Trade Center type scenarios). In recognition of this fact, unprotected steel structures are also limited in height and area, whereas those which are protected are allowed a greater height and area than heavy timber construction. It's hard to make a blanket statement, but for example, an assembly-occupancy (A-1) building would look like this under the 2012 International Building Code:

Unprotected wood stud construction (Type V-B): 1 story / 5,500 sf per story max
Unprotected steel (Type II-B): 2 stories / 8,500 sf max
Heavy timber (Type IV): 3 stories / 15,000 sf max
1-hr protected steel (Type II-A): 3 stories / 15,000 sf max
3-hr protected steel (Type I-A): unlimited height & area

For airplanes made of shockingly slender sticks and 1/16" and 1/8" plywood, obviously the charring protection does not apply, but we don't have the same concern that we do in buildings--namely, allowing time for occupants to egress before the building collapses under its own weight. I am not aware of any studies comparing the performance of aluminum or steel (obviously unprotected, except for the firewall) vs. wood in the case of in-flight fires, but I don't see any practical advantage either way--you're getting the plane on the ground, right now.

I'll let you be the judge as to which looks better, but you know what I'm building my airplane out of.
 

Vigilant1

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And, a discussion of fire characteristics brings us back to hangars. 😉
As mentioned, I insulated the hangar I am renting. Since I wouldn't own the improvements, cost was a concern. What I did (and which should not be construed as advice or meeting particular codes or standards elsewhere):
Walls: Original construction is steel girts and steel exterior sheeting. I used the tR8 fiberglass rolls with a white PSK facing as the insulation. This is widely available as insulation for metal buildings. I held it in place by trapping it between vertical fire resistant wood 2x4s screwed (on the flat) to the girts 24" OC. This has worked well.
Ceiling: I suspended fire resistant 2x4s 24" OC under the roof purlins and perpendicular to them (so the wood runs perpendicular to the eave and the peak). I used metal "hurricane strap" joist ties to suspend the wood under the purlins so there's a gap of a couple of inches. Then, I pulled the insulation over the wood, which supports it.
Taped all seams as I went.
It has worked well for 5 years. If I had it to do over, I'd strongly consider using rigid foam panels for the ceiling/roof. (I considered it in the planning stages, but didn't appreciate the hassle I'd encounter in wrestling the insulation over the wood supports). To meet fire codes (again, I'm no expert, check with local authorities etc, etc) you'd need to use special foam panels approved for interior exposure (e.g Thermax or similar). These are usually a special order item and more expensive than what you'd find at Home Depot. Compared to fiberglass batt, I think this approach would be a lot easier and will certainly hold up better if (WHEN) the exterior roof eventually leaks. I've been lucky so far.
Again, no gaurantees that what I did is right or smart.
 
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vhhjr

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I got some plyboo samples a while ago and was very impressed with the material. Not to sure as tohow one could use it in aircraft construction, but it looks like the strength to weight ratio would be very favorable:

Vince Homer

 
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