# wing rib gussets

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#### Hot Wings

##### Grumpy Cynic
Log Member
But they are not as strong as plywood for their weight. While your method works, I'm sure it was heavier than it needed to be.
The Aeronca paper gussets are probably denser than the more traditional wood gussets (especially if you soak the paper with something like West) and therefor probably do have less strength to weight ratio. But they are thinner than the wood and the old ribs weigh just a bit less than replacements made with wood. The weight differance is insignificant and a good cleaning under the seat would remove as much weight from the plane :nervous:

I don't think you can beat the time or cost factor with any other material. For your particular interest the strength to weight ratio is most important and will suggest the use of other material.

#### gicummo

##### Member
Just to show you:
If I buy it there (aircraft spruce), 6 sheets of 1/16 cost U$S 44, and now, as an international order it will cost me 88.25, plus 20 for a bank transfer; when it arrive here I have to pay at least half the final price in taxes, etc.. total cost U$S 150 at least for 6 sheets of plywood... too much.
Anyway, fiberglass will be ok, it take me 20 minutes build a sheet, I am going to make some home tests and tell/show you later how it wok,
ohoh!!! Huston I have a problem!!!! How can I make a comparasion test if I do not have 1/16 plywood? .

Let's beguin again... hello everybody... Ihave a problem ( I can't stop lough) :gig::gig::gig::gig:

#### Rienk

##### Well-Known Member
ohoh!!! Huston I have a problem!!!! How can I make a comparasion test if I do not have 1/16 plywood? .

Let's beguin again... hello everybody... Ihave a problem ( I can't stop lough) :gig::gig::gig::gig:

Reminds me of the old song... "There's a hole in my Bucket, Aunt Liza!"

(my kids love that song... replace with any 'modern' chore, and they can thoroughly relate)

#### Autodidact

##### Well-Known Member
You're going to be building lots of ribs anyway, make a test rib with the gusset material and maybe pine or something less expensive than spruce, set it up (upside down) on saw horses and hang weights from it. If the weaker material is strong enough (pine is only a little weaker than spruce), then you should be good to go.

EDIT: I take that back, use the same material as the "flight" rib. I hate wasting "good" stuff, but it is necessary for safety.

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#### Hot Wings

##### Grumpy Cynic
Log Member
! Huston I have a problem!!!! How can I make a comparasion test if I do not have 1/16 plywood? .
You don't need a comparison test, just a test. Who cares how strong the joint might be with the unobtainable material if the material you are substituting has adequate strength and durability? onder:

If the stick the rib is made from brakes before the joint fails the gusset is doing it's job.

#### gicummo

##### Member
Uau!! so deep is the epoxy join into the wood?.. I am building the ribs with douglas fir... it is a strong wood.... ok, let's see.

#### HumanPoweredDesigner

##### Well-Known Member
The Aeronca paper gussets are probably denser than the more traditional wood gussets (especially if you soak the paper with something like West) and therefor probably do have less strength to weight ratio. But they are thinner than the wood and the old ribs weigh just a bit less than replacements made with wood. The weight differance is insignificant and a good cleaning under the seat would remove as much weight from the plane :nervous:

I don't think you can beat the time or cost factor with any other material. For your particular interest the strength to weight ratio is most important and will suggest the use of other material.
True. Yours are cheap, easy, and work for you. But paper gussets are only strong in tension. Plywood works both in tension and compression, and thus work on twice the surface area for any given force. The plywood can handle a higher maximum load. Well, with the paper you can just solid fill the whole rib with a sheet. That would have lots of surface area. I did that in one of my test towers, and it held a lot.

And paper tensile strength is low. 1"x0.003" can hold 5 pounds. That is 1500 psi. Low compared to wood's 13,000 psi at the same density. I don't know your exact structural loads. Maybe ribs don't need much at all and light weight is more important than strength to weight. Probably depends if it is fabric wing or structural skin.

#### Autodidact

##### Well-Known Member
A comment made by HumanPoweredDesigner in this thread - How do you keep spar gussets from sheering off? - implies that the gussets on his tower sheared off because the compression caps deformed a greater amount than the gussets did causing them to shear off. The fiberglas gussets could also have a problem like this if their modulus of elasticity is much greater than the wood. A static test might not show a problem, but repeated strain close to the limit might cause a fatigue failure. I think your best course of action is the aforementioned veneers glued up for a good "homebrewed" plywood, or just bite the bullet and get som real plywood. Maybe there is another avenue of importation than directly from the US: Europe, Brazil, Argentina? You could become an importer of aircraft grade plywood and make some extra money, after all, you've identified a need!