by stearmoth » Wed Jun 29, 2016 5:52 am
Hi all,
That clarifies a few uncertainities to me! I recall, that Jeff Shoemake told me that he set the thrust line about 9" below the centerline of the the top longeron, but never had the oportunity to see Jeff's plans update for the Rotec. When Doug wrote it is 6" I thought Jeff made it as low as we have it, but this is not correct.
As I wrote before, we are very happy with the engine's position in every aspect. We have the original gear lengt as per initial plans (I heard Jeff increased this as well later on), but we have the huge, large 25" dia Bedix wheels and therefore we don't have any problems with floor prop clearance (our prop dia is close to 80.7").
So,if you want to set the engine lower than we did, bee sure to have enough prop clearance for the prop you will install!
We have set our stab slightly at a negative angle (close to 0,1°) for neutral trim, however we are slightly nose heavy (which is much better than tail heavy, but in no way we could place the engine closer to the firewall!) I will measure the tail incidence and publish it here.
So, if you can lower the engine more than we did (and your prop clearance is o.k.), then it might have an effect to the tail incidence for neutral trim for cruising speed.
One thing you must consider when you are setting the vertical position of the radial engine: Visibility! The Classic fuselage lofting is made for a good streamlining for a cowled Lyc. engine. When installing a radial, then the thrust line must be set lower than for a Lyc., othervise it affects the forward visibility and looks strange in my objection! We raised the top decking that much, that it is almost as high as the pilot's back fuselage decking. We closely followed Mehlin's cockpit decking design. Of course, our forward visiblity is not as good as on John Kerr's Hatz (top decking is as per plans), but ours meets our taste for a bit a boplane fighter look...
I think you can do it eighter way, what suits you best. John Kerr's Hatz flies as well as ours and makes looooots of fuuuunnnn!
By the way: we have figured out a true cruising speed of 95 to 100 mph!
Kind regards
Hans & Sam, H.C.#78, Switzerland
Hi all,
That clarifies a few uncertainities to me! I recall, that Jeff Shoemake told me that he set the thrust line about 9" below the centerline of the the top longeron, but never had the oportunity to see Jeff's plans update for the Rotec. When Doug wrote it is 6" I thought Jeff made it as low as we have it, but this is not correct.
As I wrote before, we are very happy with the engine's position in every aspect. We have the original gear lengt as per initial plans (I heard Jeff increased this as well later on), but we have the huge, large 25" dia Bedix wheels and therefore we don't have any problems with floor prop clearance (our prop dia is close to 80.7").
So,if you want to set the engine lower than we did, bee sure to have enough prop clearance for the prop you will install!
We have set our stab slightly at a negative angle (close to 0,1°) for neutral trim, however we are slightly nose heavy (which is much better than tail heavy, but in no way we could place the engine closer to the firewall!) I will measure the tail incidence and publish it here.
So, if you can lower the engine more than we did (and your prop clearance is o.k.), then it might have an effect to the tail incidence for neutral trim for cruising speed.
One thing you must consider when you are setting the vertical position of the radial engine: Visibility! The Classic fuselage lofting is made for a good streamlining for a cowled Lyc. engine. When installing a radial, then the thrust line must be set lower than for a Lyc., othervise it affects the forward visibility and looks strange in my objection! We raised the top decking that much, that it is almost as high as the pilot's back fuselage decking. We closely followed Mehlin's cockpit decking design. Of course, our forward visiblity is not as good as on John Kerr's Hatz (top decking is as per plans), but ours meets our taste for a bit a boplane fighter look...
I think you can do it eighter way, what suits you best. John Kerr's Hatz flies as well as ours and makes looooots of fuuuunnnn!
By the way: we have figured out a true cruising speed of 95 to 100 mph!
Kind regards
Hans & Sam, H.C.#78, Switzerland