Materials to build my elevator

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pilotstretch
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Materials to build my elevator

Post by pilotstretch » Sat Jul 20, 2019 8:37 pm

I just finished my test elevator and it turned out pretty good if i do say so myself, I now feel confident that i will be able to make two flyable elevators. I used hardware store nails regular birch plywood and Titebond original to put these together. I have three questions. Keep in mind I’m trying to be as frugal as possible but not unsafe, basically I’m not wanting to by “the best” just because its “the best”

1) I’m planing on getting a 1/2 pound of 20ga nails for nailing my gussets down. Is that enough? And are those going to be to long or to short?

2) What are your thoughts on plywood. Birch or mahogany? Do I need MIL-P-6070B plywood, is good quality wood store plywood good enough or will any old 3 ply do the job.

3) Titebond III, West System Epoxy Formula 209, or T-88? I’m aware that there might be some of you that say T-88 is the only way to go, I want to know your opinion on why WSE F209 or Titebond is inferior (I’m not here to argue but educate myself, so please add/link technical data/experience if you have any)

Thanks in advance,

Joshua
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ArthurD
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Re: Materials to build my elevator

Post by ArthurD » Sun Jul 21, 2019 12:35 am

I'm not sure about the nail quantity, I didn't use any. However I do know that you want to use brass, copper or stainless nails or at least galvanized.

Birch plywood should be fine, the main thing you need in the plywood is for it to be void free and I think most birch plywood is.

I don't think glue is where you want to skimp even if you're on a tight budget. I figure I'm going to have used two quarts of glue total so you're saving like $60 going with something other than T-88. What the specs do say about titebond is that it is only a little more than half the strength of T-88, it has a short open time and that's about all that they publish about it. You need a glue that isn't brittle when it's below freezing and doesn't weaken until about 150 degrees because you can get those temperature inside the wing on a hot sunny day.

Lorenzo
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Location: Tellico Plains, TN

Re: Materials to build my elevator

Post by Lorenzo » Sun Jul 21, 2019 2:29 pm

. . . What ArthurD said.

In any glue joint, the nails' only purpose is to serve as a clamp while the glue dries/sets. After that, the strength of the joint is carried by the glue/gusset. I used spring clamps and weights to do the job. Many steel nails in the structure might mess up your mag compass, not to mention the corrosion as it ages. Some pull their nails or staples after the glue has set.
If I was going to bypass aviation plywood, I think I would look for something 'marine' to be sure there are no voids. Your hardware store stuff can have voids.
I used T-88 throughout. It is easy to mix, and has plenty of working time. Once set, it is flexible, and stronger than the wood it joins. I only use a small amount at a time, so a $25 pint kit can last many months.

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taildrags
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Re: Materials to build my elevator

Post by taildrags » Sun Jul 21, 2019 6:10 pm

Ah, yes... the continuing glue discussion. Probably one of the most-discussed topics on this list and it's a good one, given the fact that the structural airframe of an Air Camper (and much of the non-structural part of it as well) is made up with glued wood joints. Gussets and joints generally also appear in this discussion, as they recently have over on the Matronics group regarding whether or not the wood members in a gusseted cluster all need to fit tightly into the angles or if they can just be squared-end sticks that the gussets then join together structurally. In any case, the glue part of the discussion is very interesting to me so I'll throw in a few cents here.

I've looked at the Titebond III and T-88 spec sheets and it's not possible to make a direct comparison of the stated strengths of these two materials in a wood joint because they apparently haven't been tested to the same metric. Looking at shear strength, the Titebond tech sheet shows a bond strength on hard maple under the ASTM D-905 testing protocol of 4,000 psi at room temperature. D-905 is a test for the strength properties of adhesive bonding of wood and similar materials in shear by compression loading. The T-88 spec sheet shows a lap-shear strength on maple under the ASTM D-1002 testing protocol of 1,800 psi. D-1002 is "Standard Test Method for Apparent Shear Strength of Single Lap-Joint Adhesively Bonded Metal Specimens by Tension Loading". So, I wouldn't infer from these numbers that Titebond III is twice as strong in shear as T-88 is because the testing protocols used to generate those strength values were different and were designed for different materials and loadings.

And who uses hard maple on their Air Camper frame? The hardest pieces of wood on the airframe are the ash crossmembers in the floor and all the rest of it is either spruce or fir (usually). Probably the only way to ever resolve this discussion would be to set up lab controls and prepare test specimens that are then tested to D-905 as being the most appropriate test for our application, but my guess is that the discussion wouldn't end there either ;o)

Oscar Zuniga
Medford, OR
Air Camper NX41CC, A75 power

pilotstretch
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Re: Materials to build my elevator

Post by pilotstretch » Wed Jul 24, 2019 3:48 pm

Thanks everyone for your input, the picture is starting to get a little more clear.

Brian Amato
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Re: Materials to build my elevator

Post by Brian Amato » Sat Jul 27, 2019 7:38 am

My two or three cents input on this and then I'll shut up and just lurk and read:
For years, my brother and I built boats using good ol' "Weldwood Brown Powder Glue" The description is: Weldwood® Plastic Resin Glue is a powdered, ureaformaldehyde wood glue activated by mixing with water. Forms a bond stronger than the wood itself. That's true. We always had wood failure before any glue failure. One of our boats is still in use after 30 years !
When I started building my Piet ribs, I read everything I could get my hands on about various glues and was attracted to Titebond-III. Waterproof, wont delaminate and super easy to use. Pop the top off the squeeze bottle, no mixing, squeeze it out onto the area you are about to join, fasten the gussets using what ever method you've decided on (I have the neatest little Senco stapler that shoots small, 1/4" crown staples, holds the gussets down perfectly, doesn't split the wood and saves a ton of time) and Bob's your uncle.
I built up three test partial ribs using Titebond-III, let them cure a couple days then broke them to destruction. In each case, I got wood failure and never glue failure. I soaked them....same story.
I made the mistake of telling this story on this forum and took so much flak for using something other than T-88 that I was shamed out of using it. I switched to T-88 and built all my ribs, and tail feathers. Never mind that Bernie built his airplanes using Caseine glue (an old time glue made from milk) and never had a problem.
I understand the FAA doesn't actually recognize T-88 as an "approved adhesive" but so many wood airplanes are out there having been built using the stuff that they don't say anything. What DID concern me is, after letting a rib cure for a week having used T-88, I set my little iron on top of one of the gussets (that little iron we use for sticking down Momocote on model airplanes and such...) and the T-88 softened so, that I was actually able to peel the gusset off. THAT got my attention. I don't think our airplanes are gong to get that hot but that got me to thinking.
I think the bottom line is, you could use Weldwood Brown Powder Glue and be fine, Titebond-III....lots of guys are building with it swear by the stuff. T-88....you'll get the blessing of the masses. Go forth and be fruitful.

pilotstretch
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Re: Materials to build my elevator

Post by pilotstretch » Sat Jul 27, 2019 11:35 pm

Brain,

Thanks, I really appreciate your thoughts.

Joshua

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