Weight and balance Hippert's plane

buck toenges · 4 October 2009, 04:52 PM

I can see about weighing the tail feathers later this week. I know the tail feathers are heavier then original. Roger showed me a Fokker rudder once and it was very light vs what we build using Cash's plans.
I am going to have to add weight up front. kinda want to know how much you guys think I will need to add.

Jeff, I don't know exactly what Tony, my ap, used as the datum line but I assume it was the front cowling. I will check with him. I didn't get a length distance to oil tank either. I also don't know exactly how big the gas tank is. I'll call Roger on that.

The real question is how close to the front of the fuselage I can fit weight. If you look at the pics I posted I plan to "hang" weight on the engine bearers.

Jeff,
You need some specific pics of the engine?

I'll be reading the weight and balance handbook this week.

Jeff Brooks · 4 October 2009, 05:14 PM

Yes please ... around the engine bearers and magnetos. the truss work around the bottom of the engine would be very helpful.

With a quick calculations, I think you might need as much as 390 to 400 pounds near where the streamline tube meets the engine bearers. Even less of course, if you can hang it closer to the prop.
Thanks Buck

jumpinjan · 4 October 2009, 06:06 PM

I could give a quick calculation (in a minute) on how much ballast is needed up front if Buck could provide a detailed chart of dimensions & weights of the total airplane (including the wing stagger, gap, wing area and leading edges location, cords, and so on).
If you can give me all the data, I can respond with the answer pretty quickly.
Jan

Jeff Brooks · 4 October 2009, 07:29 PM

Jan, I used the Kiger drawings to figure out the dimentions.

ulpilot · 5 October 2009, 04:13 AM

WEIGHT & BALANCE? WE DON'T NEED NO STINKING WEIGHT & BALANCE!

Jeff Brooks · 5 October 2009, 08:51 AM

Buck,

I was looking the photos of your plane, and I noticed the size of your tailwheel. I remember the GWFM had one heavy *ss tailwheel on theirs. I think I remember John telling me it was near 20 pounds. If you could take yours off, and weigh your tail wheel, that might provide more options.

I did some calculations, if you could reduce the weight in the tail by 18 pounds (over the tail wheel), it would correspond as a reduction in weight needed on the nose by as much as 89 lbs. If you remove your tailwheel, and add a skid, it will save you a lot of weight. I kow you will need it to fly on a paved runway, but you might consider hunting around for a lighter wheel.

Jeff

buck toenges · 5 October 2009, 09:56 AM

What is the cg range in the original DVII? Roger thinks it may be back farther then most suspect it to be. Does anybody (Achim) know what the range is? I am going to e-mail Gene Demarco in NZ to see what his weight and balance is with their blue max DVII. I will write and see if they added weight up front or moved the engine forward. How about other DVII running with Ranger engines? Jeff, were you going to place the engine more foward if you used that engine? Barny Peterson did push his ranger forward and it looked a bit odd.
Is there an e-mail address for Achim?

Jeff Brooks · 5 October 2009, 03:33 PM

Buck,
That is the holy grail of questions. Since I have been working on my plane, I have been asking other builders what they thought the GC range should be.

Most fly their planes extremly tail heavy, and increase the angle on the tailplane to gain additional lift in the tail. You can't spin the plane like you could with an original DVII with the GC aft like that!

I personally think you should be safe in the area between 23% through 25%. With 25% being the current industry standard. That would give you a range from 62.16" to 63.29" aft of your Datum.

The only way you can be sure, is to test fly your plane at different CG settings, and when your test pilot gets uncomfortable, make that your limit. And be sure to post your results for the rest of us! I bet the guys in holland have gotten this far!

Jeff Brooks · 5 October 2009, 05:30 PM

Buck,
Here is a link to the construction notes for the blue max DVII with the Gypsy engines (not inverted).
Fokker D.VII
The weight and balance info is on there, but you have to convert the datum to yours to be useful.
Also note how heavy this plane is.

baldeagle · 5 October 2009, 09:39 PM

When I was getting ready to test fly Brian Coughlin's first D.VIII we did a W&B and the empty CG was way aft of what any modern reference said was normal (don't remember exact numbers now) and worse with the pilot in. We found a McCook Field report on a D.VIII from the post-WW1 era, it gave weights on main wheels and tail skid when level empty, and the CG almost perfectly matched Brian's airplane, so I'm pretty sure they flew them at aft CGs, the question is how far aft is safe. I think Bleriots and Curtiss Pushers may have been as far aft as 50%. Good elevators on them.....

I wonder if McCook Field did a report on a D.VII

-