Citabria Wood spar
- Thread starter Flymiller
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Klaus M
Well-known member
You posted this while I answered your other post
Find the mechanic that is going to do your Annuals and ask them. Some are not comfortable with wood.
Find the mechanic that is going to do your Annuals and ask them. Some are not comfortable with wood.
Edgator
Member
Screws vs nails? New to the Forum and I haven't read Ron's take on the rib nails vs screws yet.
Back in the late 80's our Aero-club purchased a used a 7GCBC 150hp for our tail dagger/Acro division. One of the pre-flight requirements was to thump the trailing edge of the wings and listen for nails bouncing. I moved away but found out later that the spar was replaced because too many nails that were reinstalled had come loose again. The spar did not fail via cracks but because of loose rib nails. Is this typical?
Back in the late 80's our Aero-club purchased a used a 7GCBC 150hp for our tail dagger/Acro division. One of the pre-flight requirements was to thump the trailing edge of the wings and listen for nails bouncing. I moved away but found out later that the spar was replaced because too many nails that were reinstalled had come loose again. The spar did not fail via cracks but because of loose rib nails. Is this typical?
not typical at all but it happens.
Edgator
Member
Good to here,thanks
Desert7GCBC
Well-known member
Happy Thanksgiving!
Another option is ring-shank nails. When I recovered my wings in '90, there were a dozen or more loose nails rattling around in the wings and a few others partially backed out. Replacing all the nails with ring-shank nails solved the problem though it was quite time consuming. At that time, Wag-Aero stocked them.
Something that didn't enter my mind was that they would have to be removed without damaging the wing ribs if I was contemplating installing Millman spars. 33 years later, that sticky-wicket is on my mind
Another option is ring-shank nails. When I recovered my wings in '90, there were a dozen or more loose nails rattling around in the wings and a few others partially backed out. Replacing all the nails with ring-shank nails solved the problem though it was quite time consuming. At that time, Wag-Aero stocked them.
Something that didn't enter my mind was that they would have to be removed without damaging the wing ribs if I was contemplating installing Millman spars. 33 years later, that sticky-wicket is on my mind
there is info here explaining how to get the nails out without damaging the ribs. i can't go looking right now but it is in my Milman conversion thread
Edgator
Member
Nightmares? Ring shank nails, the engineering is obvious, think of barbless fish hooks vs standard barbed versions. Another thing is the wood used to make individual spars. I have no knowledge of "grading" spar wood (more growth rings better?) The Spruce Goose (no spruce LOL). Will a nail in one spar hold better than the same nail in another? Finish? Was the spar varnish of good quality, new or from last years open can? So many variables. However I would think that most of our wood spars are stronger than they need to be with weight vs strength a balancing act that was born out of trail and error starting with our early bicycle makers and the others that followed. Does a ring shank nail create multiple stress points upon entry vs a smooth shank? Think stop drilling in aluminum fractures. Who can figure the torque needed for a screw in a spar?
Two years ago I completed the Spar AD on a Cessna 177RG. The NDT firm I hired did work for NASA, Embry Riddle U, etc. They would not schedule a test until the spar was cleaned and polished (shiny). It took 3 weeks to clean and polish the spar ( 4 hours per day) Micrometer, sand. micrometer, repeat........ Who tests your wood spar and what is their knowledge and experience? Now another question.......who inspects your new metal spar etc. Here in Florida a good thing to discover is the goo, that greenish gummy fluid that you find oozing from the aluminum seams and on the hangar floor. Do the new era ACA owners apply Corrosion X to their metals?
Like someone here posted, metal spars can corrode and fatigue. How many YT videos have you seen of wood spared aircraft having their wings fold up under g loading? C130 CALFIRE, Ag Plane, more? I like wood but I do I buy a 40 year old GCBC with a12 year old factory metal spars because of the AD? Or do I stay with wood? You can bet I will examine a metal spar for surface corrosion but as far as fatigue/stress fractures..............you tell me.
What is a wood "Super Spar" ? Thanks for the link to Rainbow Flying Services, enjoyed watching Ron break spars.
Two years ago I completed the Spar AD on a Cessna 177RG. The NDT firm I hired did work for NASA, Embry Riddle U, etc. They would not schedule a test until the spar was cleaned and polished (shiny). It took 3 weeks to clean and polish the spar ( 4 hours per day) Micrometer, sand. micrometer, repeat........ Who tests your wood spar and what is their knowledge and experience? Now another question.......who inspects your new metal spar etc. Here in Florida a good thing to discover is the goo, that greenish gummy fluid that you find oozing from the aluminum seams and on the hangar floor. Do the new era ACA owners apply Corrosion X to their metals?
Like someone here posted, metal spars can corrode and fatigue. How many YT videos have you seen of wood spared aircraft having their wings fold up under g loading? C130 CALFIRE, Ag Plane, more? I like wood but I do I buy a 40 year old GCBC with a12 year old factory metal spars because of the AD? Or do I stay with wood? You can bet I will examine a metal spar for surface corrosion but as far as fatigue/stress fractures..............you tell me.
What is a wood "Super Spar" ? Thanks for the link to Rainbow Flying Services, enjoyed watching Ron break spars.
Bob Turner
Well-known member
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- Apr 4, 2018
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As a gentle suggestion - that could use a few paragraph breaks.
As a comment - the AD takes at least several hours, so if you have to pay shop rates the metal spar wings are better. It takes me a half hour just to get the plates off and back on.
Our local shop rates are $125/hr. A decent, careful inspection would be around $500 per year.
As a comment - the AD takes at least several hours, so if you have to pay shop rates the metal spar wings are better. It takes me a half hour just to get the plates off and back on.
Our local shop rates are $125/hr. A decent, careful inspection would be around $500 per year.
Edgator
Member
Advice taken, Sorry I like to bloviate. Amen to thorough inspections. ? out of 10 fail inspection.
Klaus M
Well-known member
@Edgator maybe you have more experience with aluminum then wood? Go with what your comfort level is. Many wood structure covered bridges have been standing for over 100 years with just a little routine maintenance. Also true with wood spars, just a good inspection regiment and hanger storage will deliver decades and hours of safe use.
Wood spars are not failing anyway near the rate you are reading or hearing in conversation. Most planes are stored out of the weather these days so the corrosion and deterioration rate have slow considerably. Once the average owner realized the replacement cost of their $25,000 aircraft, hangars have become cheaper and cheaper.
Stay in your personal comfort zone. Don't fly fabric covered aircraft if you feel safer in an aluminum aircraft. Figure out what kind of flying suits you best and fly the aircraft that fills that purpose. Wood aircraft have been safely doing aerobatics since the beginnings of aviation. 🛩
Wood spars are not failing anyway near the rate you are reading or hearing in conversation. Most planes are stored out of the weather these days so the corrosion and deterioration rate have slow considerably. Once the average owner realized the replacement cost of their $25,000 aircraft, hangars have become cheaper and cheaper.
Stay in your personal comfort zone. Don't fly fabric covered aircraft if you feel safer in an aluminum aircraft. Figure out what kind of flying suits you best and fly the aircraft that fills that purpose. Wood aircraft have been safely doing aerobatics since the beginnings of aviation. 🛩
Bob Turner
Well-known member
- Joined
- Apr 4, 2018
- Messages
- 3,749
I think he was just posing questions.
I have not heard of many Champs failing the required inspection. I think that folks replace spars at rebuild because they think wood just naturally deteriorates - but it doesn't. Keep the moisture content in the normal range with good varnish, don't hit anything with your wingtip, and a wood spar will outlast the rest of the aircraft by a bunch!
I am going to guess that a spar fails the inspection far less than one out of a hundred aircraft. I am unaware of any failures locally.
I have not heard of many Champs failing the required inspection. I think that folks replace spars at rebuild because they think wood just naturally deteriorates - but it doesn't. Keep the moisture content in the normal range with good varnish, don't hit anything with your wingtip, and a wood spar will outlast the rest of the aircraft by a bunch!
I am going to guess that a spar fails the inspection far less than one out of a hundred aircraft. I am unaware of any failures locally.