Kitfox 3 yamaha apex, Why not?

[Landcruisinmy93]

Educate me. I've been told that a model 3 1050 doesn't have enough gross. What does the airframe gross have to do with engine compatibility?

[avidflyer]

Heavy engine equals less available useable load. Kitfox 3 only starts off with 1050 gross weight.... Some of these planes end up being single seaters for all practical purposes. JImChuk

[Landcruisinmy93]

Heavy engine equals less available useable load. Kitfox 3 only starts off with 1050 gross weight.... Some of these planes end up being single seaters for all practical purposes. JImChuk

Jim! You're just everywhere sharing your wealth of knowledge. I understand the 3 has a low gross already but is weight the only consideration? I mean you have guys putting the apex in MKIV's with only a slightly higher gross, and in 1200 model 4's. Then you have some earlier models with O-200's, which, dry weight is about 25% heavier than an apex. Rotax 912's weight about the same with all the accessories etc... that's kind of why I was wondering why I've been told you can't run an Apex.i was thinking maybe it was way more power than the fuselage can handle.

[napierm]

My KF3 with a 582 worked out OK with W/B. Even so it would run out of elevator to give a good 3 point with flaps down. I learned to land w/o flaps if they weren't needed so I wouldn't bounce. Or push them up just at the right time.

With a 912 the battery has to go back to help the W/B even with the 912 mounted so far back there isn't much clearance between the carbs and the firewall. The Apex is heavier (I think) and isn't as compact so it sticks out farther. The fuse is too short to counter balance a heavy engine w/o weight in the tail.

Plus the KF 5-7 has a movable stab to help with trim. But not a KF 3 or 4. I'm putting a trim tab on the elevator but it is not as good as the movable stab. And that's with the larger elevator.

IMO a Phazer engine might be a better match for a KF3.




Jim! You're just everywhere sharing your wealth of knowledge. I understand the 3 has a low gross already but is weight the only consideration? I mean you have guys putting the apex in MKIV's with only a slightly higher gross, and in 1200 model 4's. Then you have some earlier models with O-200's, which, dry weight is about 25% heavier than an apex. Rotax 912's weight about the same with all the accessories etc... that's kind of why I was wondering why I've been told you can't run an Apex.i was thinking maybe it was way more power than the fuselage can handle.

[buckchop]

I have a good friend here in Fairbanks that installed an Apex on an Avid but im not sure which Avid it is. Nd im really thinking of building a single seat/wide body KF1 with a yammy of some size hahahahaaaaa, but im thinking of stretching the fuse 18” and using a KF4 tail.

[redbowen]

You should really look at the Yamaha Phazer as an option on a model 3. It is much more suitable for the CG.