Cox PT-19 weight?

WingingIt74 wrote:How much does one weigh?

I got 9.9 ounces with mine that has the plastic backplate, not like the classic ones that were sold with a complete Babe Bee. This includes a tailwheel, so stock, they may be a bit lighter.

Also, my Stuka came in at 10.5 oz. with it's bomb weighing an additional .3 oz.

My Wen Mac Aracobra came in at a whopping 14.4 oz. ...minus a couple of the plastic gear-strut fairings. No surprise that it flys somewhat like a dump truck !

Kim wrote:No surprise that it flys somewhat like a dump truck !

Love it!! I used to fly Caribous, which were affectionately known as "Gravel Trucks".

I've noticed mine has a left handed spring and
Prop on anyone know why?

John Goddard wrote:I've noticed mine has a left handed spring and
Prop on anyone know why?

JB:



Well because you Brits seem to do things differently.

John Goddard wrote:I've noticed mine has a left handed spring and
Prop on anyone know why?

It seems like I saw a couple of PT's over the years that had that set-up. The idea is to help insure line tension by having the engine torque toward the outside of the circle. Don't know for sure if they came from the factory that way.

Sorry for the thread revival. I was searching for weights of models and stumbled on this thread.

Kim wrote:

John Goddard wrote:I've noticed mine has a left handed spring and
Prop on anyone know why?

It seems like I saw a couple of PT's over the years that had that set-up. The idea is to help insure line tension by having the engine torque toward the outside of the circle. Don't know for sure if they came from the factory that way.

I cannot say for certain, but I have a theory why some of the plastic rtf's may have had engines that turned the "wrong" way.

In full scale aircraft, there is something called P Factor (http://en.wikipedia.org/wiki/P-factor). It has to do with the thrust produced by each side of a propeller/engine when flying at different angles of attack (AOA). When a plane is flying at a high AOA (when heavy, slow flight, or climbing), the descending prop blade produces more thrust than the ascending blade. A standard engine turns clockwise when viewed from the pilot's seat, so when flying at high AOA (again, climbing or heavy), there is more thrust on the right side (from the pilot's prospective) than the left side.

So, figuring the plastic rtf's were VERY heavy, they likely flew at a high AOA. To keep the lines tight, using an engine that turned counter clockwise would cause the plane to yaw right or outside the circle just as if the thrust angle were pointed outward. The difference would be that in a clockwise engine with an offset, the engine would need to correct for the P factor BEFORE working to keep the lines tight. A counter rotating or counterclockwise engine would NOT need to counter P factor (the P factor would help keep the lines tight), so less offset would be required.

Now, on the PT-19, one could move the firewall to give the engine a downward thrust angle (relative to the wings). The plane flew slower with more downward thrust, and it had the added benefit of REDUCING the P factor (the wings were at a high AOA, but the engine pointing downward meant the LEFT prop blade was producing more thrust). So, the downward angle helped to keep the lines tight even at lower speeds.

So what does this all mean?

If one wants to absolutely maximize performance, a counterclockwise engine is the way to go: more effective thrust (less wasted thrust from offset) from the same engine.

Unless of course you fly in the UK (the wrong way around the circle, just like driving on the wrong side of the road), then a standard engine is fine.