Speed,Combat,Scale,Racing > Rat Racing and Team Racing

Landing gear wheel position on Rat Racers

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bob whitney:
Bob is correct  15 deg works for just about everything on pavement .on my stunters i move the wheels about 1 in forward for grass

back in the day we didnt know about 15 deg by moving the wheels up by the motor and extending the  tail skid to almost level we could get a pretty good hot (for the day) landing

Dennis Toth:
For flying of grass with these types of ships one of the concerns is having the prop and lines survive the landing. Yes I know APC props can take a lot of banging around but there are better prop choices that are less sturdy (wood, some thin glass). Our field is a grass soccer field with nicely mowed surface but still not like pavement. For Stunt 1 3/4" wheels get off and down nicely. I'm wondering with this style ship (rat, FOX35) does the more forward wheel position give a more survivable landing without the ship flipping end over end?

Best,   DennisT

Bob Heywood:
At the Chicago - Glenview NATS there was a very large, nicely cut grass lawn behind the work hangar. After hours there were C/L planes of every description being flown. I flew my Royal Rodent off the grass with the same set-up as pavement. We used K&B Racing Wheels in those days. No problems.

As a side note, the highlight of the evening was killer combat. 10 or more planes in the air at the same time. When one landed or crashed someone else went up. All evening 'till it got dark.

Just build the thing and fly it...

Trostle:

--- Quote from: Bob Heywood on August 27, 2021, 11:43:57 AM ---Dennis,

The correct reference is the wheel contact point on the ground relative to the aircraft CG. The default position for conventional gear is 15 deg ahead of the CG.

The attached scan is from the 1949 NAA rules for 190 cubic inch class racing airplanes (aka Goodyear racers)

--- End quote ---

Bob,

The drawing you showed is excellent.  Bill Netzeband showed similar drawings in several of his columns over the years and also in his 5-month long series on how to design and fly stunt ships in the mid 1950's.  That same 15o angle from the CG applies pretty much to all full size, conventional gear aircraft.  One thing to note is the 15o puts the point of contact of the wheels on the ground, not through the axles of the wheels.  Not that it makes that much difference for our models, but for relatively larger diameter wheels, it starts to make a difference.  Also what needs to be considered is the measurement is from the aircraft CG including consideration of its vertical CG.

Keith

Dennis Toth:
To Keith's point, for the small rat size ships that have gear for an 8" diameter prop you don't have much airplane weight that can settle the ship down once the wheels hit the ground. In stunt there is considerable airplane so the overturning moment is a little more controllable plus you have large wing area aft of the CG and significant control surface to stabilize the ship. With the rats hitting grass, should the same 15 deg angle hold or should it be a bit more forward?

Best,   DennisT

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