Weight and balance Hippert's plane

drrivah · 6 October 2009, 03:54 AM

NASM has a copy of the post-WW1 McCook Field analysis ofthe D.VII airframe.

Jeff Brooks · 6 October 2009, 04:19 AM

I have the report on the airframe, and there is nothing helpful on W&B, however there is a french report which goes in detail about W&B, I just can't read it.

buck toenges · 6 October 2009, 04:40 AM

Jeff,
Where can I find the french report? I know a french teacher who could help translate.
Buck

Jeff Brooks · 6 October 2009, 05:15 AM

Buck, email me, blkhrtsp@rochester.rr.com
when you are done translating it, please send a copy back to me.
Jeff

Jeff Brooks · 9 October 2009, 08:25 PM

Buck,
I haven't given up on ya ... I was deciphering the French report and Good news, I may have an answer you will like!

Here is the original report in metric weights & measure ...

Here I swapped the mm to inches and the Kg to lbs in red so it jives better with your posted numbers...
(the front number is both wheels combined)
Notice how much this plane weighs!! I don't think you are going to have any problems at all!

Here I added your datum line, and updated the arm to match your posted measurements in blue.

Note how far back the GC ends up. 25% with your datum is somewhere around 63.5" ... this one ends up around 67.98"
Looks like the ole Baldeagle was right ... Again!

buck toenges · 10 October 2009, 01:01 AM

Jeff,
I talked to Barney Peterson yesterday. He has a DVII with a ranger that has a 6" longer nose. I don't have all the information in front of me but he did say that his cg was 6.8" aft of the leading edge of the lower wing. It looks like the cg in your drawing is about in the center of the top wing. Can you tell me if the 6.8" inches is close to your mark?
Bald Eagle did tell me that WWI pursuit airplanes were designed to be tail heavy. He said it was to improve dog fighting abilities. He can chime in here and explain better then I.

buck toenges · 10 October 2009, 01:32 AM

Just looked back at the Rousseau report of the blue max DVII. They said the aft cg was 6.2" from leading edge of lower wing. They also stated that forward limit of cg was 2.2" from leading edge.

Jeff, do you have a measurement from prop hub to leading edge of lower wing?

By the way they said the length of the plane was 23' which is about 3" longer then "stock"

Jeff Brooks · 10 October 2009, 05:38 AM

Buck,
Despite where the datum appears on the drawing, I used your measurements to come up with the numbers. However, I was not sure where your 55" would end up in front of the plane. That blue dotted line might very well belong in front of the prop. I took your datum stated in your first post from the front wheels, and added the distance from the wheels to the leading edge to come up with 64.84"

I did not understand which plane you mean was longer? Byrons? Yours' or the measurements in my drawing? And longer where, relative to the wings?

The CG range stated in the Rousseau construction notes is 2.2" to 6'2" aft the leading edge of the bottom wing.
In the French report, the CG is only 3.14" aft the leading edge of the bottom wing, well within range.
Barney's plane is 6.8", which is 0.6" aft of the range given in the Rousseau notes.
Your plane is currently at 6.66" aft the leading edge of the bottom wing, which is 0.46" aft of the Rousseau range.

Having a plane with an aft CG does not make it better for dog fighting ... as Baldeagle said, "I wouldn't wanna spin it." When dog fighting, there are times when the pilot will need to stall or near stall the plane to create a tighter turning radius ... you can't do that with any confidence if you aren't sure if your plane can recover from the stall.

Jeff Brooks · 10 October 2009, 06:39 AM

John,
It would be great if you could get the CG dsta from the GWFM's DVII and post the details here. I wrote to Andy Parks, and hope he joins the conversation. I would love to capture all the data from as many DVIIs available to compare CG vs handling charactoristics.

jumpinjan · 10 October 2009, 07:28 AM

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