CG Question
08-01-2004, 08:04 PM
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CG Question
Hey All,
I recently finished a Bucker Bu-133c Jungmeister (see below) from the MAN plans by Floyd Manly (Plan #5901) in .60 size. The problem is that the CG was not marked on the plans nor anywhere in the construction article. I thought I knew how to figure it out, but I guess I didn't get it right because the aircraft seemed extrememly tailheavy, porpoising and pointing skyward til stall. The results were not pretty. I plan on rebuilding the airplane, because I like the way it looks, but I ned some advice on where to start with the CG, especially if someone has built this bird and can give the benefit of their experience.
The wings are identical in planform, swept constant chord and offset with the top wing forward.
Lacking anyone with previous experience, if someone could supply the formula to find the MAC I would certainly appreciate it...
Thanx in advance.
Ed
I recently finished a Bucker Bu-133c Jungmeister (see below) from the MAN plans by Floyd Manly (Plan #5901) in .60 size. The problem is that the CG was not marked on the plans nor anywhere in the construction article. I thought I knew how to figure it out, but I guess I didn't get it right because the aircraft seemed extrememly tailheavy, porpoising and pointing skyward til stall. The results were not pretty. I plan on rebuilding the airplane, because I like the way it looks, but I ned some advice on where to start with the CG, especially if someone has built this bird and can give the benefit of their experience.
The wings are identical in planform, swept constant chord and offset with the top wing forward.
Lacking anyone with previous experience, if someone could supply the formula to find the MAC I would certainly appreciate it...
Thanx in advance.
Ed
08-02-2004, 12:03 PM
#3
RE: CG Question
ORIGINAL: Woodpile
Hey All,
I recently finished a Bucker Bu-133c Jungmeister (see below) from the MAN plans by Floyd Manly (Plan #5901) in .60 size. The problem is that the CG was not marked on the plans nor anywhere in the construction article. I thought I knew how to figure it out, but I guess I didn't get it right because the aircraft seemed extrememly tailheavy, porpoising and pointing skyward til stall. The results were not pretty. I plan on rebuilding the airplane, because I like the way it looks, but I ned some advice on where to start with the CG, especially if someone has built this bird and can give the benefit of their experience.
The wings are identical in planform, swept constant chord and offset with the top wing forward.
Lacking anyone with previous experience, if someone could supply the formula to find the MAC I would certainly appreciate it...
Thanx in advance.
Ed
Hey All,
I recently finished a Bucker Bu-133c Jungmeister (see below) from the MAN plans by Floyd Manly (Plan #5901) in .60 size. The problem is that the CG was not marked on the plans nor anywhere in the construction article. I thought I knew how to figure it out, but I guess I didn't get it right because the aircraft seemed extrememly tailheavy, porpoising and pointing skyward til stall. The results were not pretty. I plan on rebuilding the airplane, because I like the way it looks, but I ned some advice on where to start with the CG, especially if someone has built this bird and can give the benefit of their experience.
The wings are identical in planform, swept constant chord and offset with the top wing forward.
Lacking anyone with previous experience, if someone could supply the formula to find the MAC I would certainly appreciate it...
Thanx in advance.
Ed
The other thing which is CRITICAL, especially on a parasol wing or bi-plane is the incidence (angle of the wings and tail surfaces to the datum line). You don't want to know how I am aware of this.
08-02-2004, 04:54 PM
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RE: CG Question
Sorry, should have mentioned the incidence. It was as perfect as my Robarts meter could measure. I was sorta proud of the incidence, til I had a mid-air with the earth...
08-02-2004, 08:19 PM
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RE: CG Question
Hey Woodpile,
First, nice finishing job on the bipe. I bought an old Jungmeister that was sitting in someone's barn for 10 years. What is the wing span and fuselage length on yours? I am trying to gauge the size of my bipe. Where did you get the cowl? The bipe I bought had a Tartan single on it, 1.2, and I think it is way over powered. The engine weighs in at 2.7lbs so if your bipe is the same size as mine you may want to go with a larger/heavier engine instead of adding weight to the firewall (more power is always nice). How is Barnegat these days? I grew up in Toms River, I miss the shore but not the traffic.
First, nice finishing job on the bipe. I bought an old Jungmeister that was sitting in someone's barn for 10 years. What is the wing span and fuselage length on yours? I am trying to gauge the size of my bipe. Where did you get the cowl? The bipe I bought had a Tartan single on it, 1.2, and I think it is way over powered. The engine weighs in at 2.7lbs so if your bipe is the same size as mine you may want to go with a larger/heavier engine instead of adding weight to the firewall (more power is always nice). How is Barnegat these days? I grew up in Toms River, I miss the shore but not the traffic.
08-03-2004, 09:27 AM
#7
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RE: CG Question
Once you find MAC, this worked for my Jungmeister. Flew like it was on rails, right off the building board.
OK: Lets try to get the right photo up.
There it is: from Lennon on Bipes.
Les
OK: Lets try to get the right photo up.
There it is: from Lennon on Bipes.
Les
08-03-2004, 04:57 PM
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RE: CG Question
JRM,
Thanx for the compliment. I found a picture of the covering scheme on a fullscale Jungmeister still in airshow service in Germany and Austria. I liked it so I shamelessly copied it. Mine had a 54" span and was about 42" LOA. It weighed in at 6lbs, 10oz dry so the .60 I had on the front had the power. Just couldn't stop it from porpoising and nosing up. I made the cowl from a foam plug and West system fiberglass resin with a few nylons my wife donated to the cause. I love the shore, but still hate the traffic...
DB CHerry and Les,
Thanx fo the diagrams. I tried something similar to DB's picture but forgot to add a few numbers in. DOH! Oh Well... Live and (hear that balsa smash!) Learn...
Thanx for the compliment. I found a picture of the covering scheme on a fullscale Jungmeister still in airshow service in Germany and Austria. I liked it so I shamelessly copied it. Mine had a 54" span and was about 42" LOA. It weighed in at 6lbs, 10oz dry so the .60 I had on the front had the power. Just couldn't stop it from porpoising and nosing up. I made the cowl from a foam plug and West system fiberglass resin with a few nylons my wife donated to the cause. I love the shore, but still hate the traffic...
DB CHerry and Les,
Thanx fo the diagrams. I tried something similar to DB's picture but forgot to add a few numbers in. DOH! Oh Well... Live and (hear that balsa smash!) Learn...
