3/4 x 3/4" roof stringers.

[Arne]

I'm wondering what the minium size of a roof stringer could be. We recently had a demo of an r/c airplane. The new thinking is we way over build our r/c planes, and that makes them heavy.

After building my tear walls with 1/4" inside and out with 3/4" studs, I'm wondering why the ceiling could not be done the same way, especially if the roof had a slight curature to it.... the ply would be much stiffer, and other than snow load and road bounce, I'm thinking 3/4 sq. would be sufficient.

I see some use 3/4 x maybe 1-1/2, but the wheels are turning.....

If I did it, I'd use 6" spacing..... I'd need that because the outside roof will only be 1/8" ply..... But, the insul will be that bendy 3/8" foam doubled up to fill the whole void.

--

My trip to buy another h/f trailer is on hold till next week.... snow is coming tomorrow....

[Chuck Craven]

Roof stringers! My plan is for 1” x 1” angle iron, with a ¾ x 3/4” wood insert. The wood is for mounting the inside roof panels.
The aluminum out side roof panels will be bolted to the angle iron roof stringers, no plywood backer.
¾ inch square wood has about one fifth the strength of ¾” x 1 ½” wood. This is because there is almost no old growth wood left that has very tight-grain. Even White Oak to day is fast grown for the lumber industry. But if you can find some good tight-grain wood to make them out of, it sure would make for a light and strong roof system.
Chuck

[dwgriff1]

[quote="arnereil"]I'm wondering what the minium size of a roof stringer could be.

It seems that we are building Model T or Model A's here. Heavy frame and a ton of structure on top.

Plywood that can be held on edge is amazingly strong (witness the TJI's that go into modern floors), same for curved plywood, and torsion boxes.

Look at how airplanes are made. Go study the Belanca's of the 50's. They were all wood, and they were superb planes.

The metal small airplanes are made very light weight. My father's fabric covered plane was even lighter.

dave

[Arne]

A rose is a rose, but all plywood is not the same... I have some 1/16" aircraft ply with 6 plies.... the h/d crap in marginal 1/2" has 3.... huge strength difference.

I think I'll go with 3/4" x 1-1/8" stringers.... if there is a knot, I'll plate it with glued on 1/8" scraps. Making it 1-1/8 will be 3 thicknesses of 3/8 flex foam insul and make the roof less like a drum top. Cost difference will be minimal and strength increased.....

Having the void fully filled with foam will make a big difference in strength as well.

[dwgriff1]

[quote="arnereil"]A rose is a rose, but all plywood is not the same...

Why do you think they make a zillion grades? Each type has a place. Choose the kind to fill your needs, same with solid woods, and women.

dave

[len19070]

Arne
If your making a double Ply Roof/wall I see no reason why 3/4 ribs won't work. Once that plywood is bent it takes on new characteristics. With the roof panel bending around from the front at the frame, to the rear at the hinge, that bend gives it incredible strength. Go for it.

But, I really don't think that 3/4"X1 1/2 6" on centers is going to save you any weight. Infact I think it will add weight.

I generally use 5/4 (which is really 1") yellow pine stair treads ripped to 2" 12" on center. Which I'll bet is less weight than 3/4" 6" centers.

An 8' roof section would take 9 ribs @ 1X2 vs 17 ribs @ 3/4X1 1/2 6" on center is almost double the lumber.

Happy Trails

Len

[mbader]

I used 1" X 1" Oak stringers 12" on center.
1/8" ply on the inside, 2 layers of 1/8" ply on the outside.
It's solid.
Also with the 1" stringers you get 1" of insulation.

[Steve_Cox]

A rose is a rose, but all plywood is not the same...

Why do you think they make a zillion grades? Each type has a place. Choose the kind to fill your needs, same with solid woods, and women.

dave

Got to get me one of those CDX women. Have an A/C interior grade one, took her out in the weather too many times and she started to delaminate...

Steve

[Arne]

My brother talked to a house builder years back about the ply he used on houses... He said he used "2-soak" or "4-soak".... the number of rain storms it could take before delamination started.... never knew it appied to women, too..../g/.

[cracker39]

Arnereil, the 1800 lb trailer just went on sale for $299.99. Now, if you can just catch one of those 20% off coupons via email, you have a deal. I used one today that expires tomorrow. I bought their $290 industrial rabbit/jointer (i.e. planer) that was on sale for $200, and used the 20% off coupon. Got it for $160. A bench model would have cost me $180, and this is the full size floor model. I gotta stay away from that store. Thank goodness it's 20 miles away, not here where I live.

Got a deal at HD today too. I bought some of my shed materials and they had a 10% off if you applied for their credit card. Well, it turned out that I had an account with them. They canceled that account and opened a new one and I got the 10% off. But, I was told that I could open a commercial account too if I wanted to and get another 10% off the first purchase with that card. Since I did craft shows and may do them again, I had a business. So, I got two accounts now and get 10% off when I buy the rest of my materials. That will save me $60 or $70 on my shed. They also said there would be a free gift, but they didn't give me one. I gotta ask about that. Probably will be a carpenter's pencil.

[Arne]

I called the nearest h/f store and was told about the 299 price last week... was going up today, but snow was forecast,, never came, though... and have a 20% coupon, hope they renew that for next monday,when I hope to get up there......

sounds like h/d is treating you very well.....

[cracker39]

The $299.99 is good through Dec 26. Not sure about the coupon. I got two of them this week. One expired on the 4th and another on the 7th. They come at least once a month if you get their emails. I get both emails and paper sales ads. They honor both.

[Clancy Courtney]

If you are using a r/v type roof vent you may need to trim the interior garnish ring when used on a roof 1" thick. Probably not a big deal, just a consideration.
Clancy

[Arne]

ooops... when I said "going up today" meant to the store, not in price...

btw, for 9.95 I joined their 'club' for one year. Their big drill set which is usually on sale for 39.95 is 29.95 to club members.... and some other stuff equally cheaper..... for a buck a month, just the fun of looking is worth it....

If you want to look, the club member ship actually has an item #:

42800-0vga (that's a zero)

id is email and maiden name

[cracker39]

I'm afraid that if I joined their club, I'd spend even more there. I spend too much at HF now as it is. I've got to quit buying tools...it's addictive. Today, I ordered a Drill Doctor bit sharpener. I have so darned many old bits laying around that I think the sharpener will pay for itself eventually. When one or two bits get dull, it's usually cheaper to buy a new set than to replace individual bits. So, they keep piling up.

I hope their claims that the "QuadCut" makes old bits better than new is not just hype. We'll see when I try it.