Brodhead Pietenpol Association

Hi everyone

I’m helping my EAA chapter tackle a “mostly done” Pietenpol project. Joined BPA and bought the Weight and Balance manual. This evening was our first work night in the chapter hangar. I have questions.

The project was built for a Corvair, and we are *hoping* to use a Donated C-65-8. We do have a Corvair if it comes to that. It apparently has the longer fuselage - First thing we did this evening was measure things. After reading the weight and balance manual, I was fairly shocked to find the center of the axles on this project are between 7” and 7 1/2” behind the leading edge of the wing as currently set. This was aircraft level, and a plumb hung from the L.E.

I read the weight and balance manual. It clearly states the axles are intended to be 0.5” behind the leading edge.

Before I start thinking about how we can completely re-do the gear....am I missing something? I have photos and data, but no experience and I’m the first to admit it.

Thanks
Robbie

Robbie; there's quite a bit of difference in reworking a split-style, welded-steel landing gear with spring struts (or bungees) and reworking a straight-axle, "Jenny style" landing gear with wooden gear legs. Which style of gear does the project have on it? In the steel tube landing gear case you'd be talking welding and metal fabricating work, in the other case you'd be looking at shaping a new set of wooden gear legs. Different people on this list have stronger skills on one or the other, and I'd also venture to say that some on this list have assisted in rebuilding wiped-out gear from a groundloop or other incident and can offer some suggestions on changing the axle geometry.

Oscar Zuniga
Medford, OR
Air Camper NX41CC, A75 power

Robbie: also, look at this picture of Chris Rusch's Piet, which has wooden vee legs and large spoked wheels. The plane isn't quite in the level attitude, but notice where the axle centers are relative to wing leading edge, but also notice that the cabanes are swept back a bit. In fact, the cabanes on my airplane are swept back almost 4 inches, which if you had to swing the wing back to adjust the CG on the project plane an equal amount, could reduce the far-aft axle position from 7-1/2" aft of LE to only 3-1/2". It still wouldn't be ideal and should be considered for a rework, but may not be as bad as it looks.
-Oscar

I just looked at my plans for the short fuselage. The axles are 9.5" behind the wing leading edge, with vertical cabanes. That would be for no brakes. N34KP is built this way.

Edit time. I dug out N34KP's weight and balance. The actual axle position on 34KP is .25" forward of the location shown on the plans, 16.75" aft of the lower firewall, instead of 17". So N34KP's axles are 9.25" aft of the leading edge. Once again with straight cabanes and no brakes.

Robbie,
How far back from verticle are the cabane struts slanted?

Earl

Hi

I had homework to do before replying.

The fuselage is a long version from what we can tell. Attached are the photos I have to at least partially answer what the current configuration is.

As I mentioned in my post, the weight and balance manual emphasized the position of the gear being just aft of the L.E. So this is what caught our attention immediately.

I have to go measure things to give specifics on that. I’ll try to do that tomorrow.

Assuming I measured this accurately, it appears to be 27” on center

We believe the fuselage is at or close to 172” long. This is from a measurement and the builders hand drawn notes.

Since we are planning an A-65 engine instead of the Corvair, our big questions are the location of the axles (again, we are referring to the weight and balance manual which we bought from BPA) and the amount the engine mount must be extended.

These are the notes we found in the materials that came with the airplane.

We worked on the Pietenpol again last night and continue to scratch our heads about the location of the gear and axle.

If I interpret the weight and balance guide properly, we have a challenge on our hands with the location of the gear.

Our question is on a long fuselage Pietenpol (built for a Corvair) is the axle still supposed to be 0.5” behind the wing leading edge?

We will be putting a Continental on the aircraft with an extended engine mount.

Robbie,

Yes, per Bernard, the axle should be about 1/2" behind the leading edge. It should be near the front of the leading edge no matter what engine you are using.

Why are you extending the motor mount and not moving the wing back?
You get a greater change in the CG moving the wing as opposed to moving the engine, and the wing fittings are designed for that very purpose

Earl

Hi Earl

Thank you for the response! I had read the weight and balance manual and found the 1/2” reference. That’s what prompted the questions.

We do plan to move the wing back now that we have a better understanding of the specifics.

The fuselage was built for a Corvair. Our understanding was for a Continental we would need to extend the motor mount. This came from the person kind enough to weld the mount for us, and our reading the weight and balance manual.

I sincerely appreciate the reply, and any information we get is very important to us. We are on a mission to do this right.

Split gear and long fuselage. How far should the center of the axle be from the firewall? I have a mock-up and I'm looking at about 19".

After review at the West Coast Piet site, I decided anything in the 15" area will work. After adjusting my "V" mock up, it looks like my axle will be about 14.75" behind firewall.

John C