Yamaha 160 lb engine. 130 hp

[rv7charlie]

What chain drive are we talking about? Most of the Yamaha drives I've seen are gear; either custom boxes or adapters that mount one of the commonly available drives like the Rotax C.

Cruise rpm kinda depends on the a/c type/mission. A lot of the stuff flying the engine now is STOL, flexwing trikes, etc, and they're probably running 50%-60% rpm (& maybe half throttle) in cruise because the airframe hits an aerodynamic wall and there's no point in wasting fuel. But a slick cross-country a/c would run at 75% *power* up at altitude, and up around 8k feet, 75% power requires the same rpm (at wide open throttle) as full power at sea level.

Charlie

 

[way_up_noth]

I’m new to the Yamaha scene..got a few questions

-does the prop always windmill if the engine quits

-can you use the engine wire harness as is... or do you have to send it out to get clipped... is there a scematic somewhere so you can do your own clipping... the fellow that trims the harnesses charged $500 for the trim.. seems like a lot.. maybe I’m missing something... is he doing more then trimming?

-what trips the limp home mode of the ecu... is it only high coolent temp or other things to watch out for


Thanks

 

[Victor Bravo]

I would write a check for a A6M. I really like the lines of that plane.

WAR had a Zero if distant memory serves. I don't know how many were built, but I believe I saw they had at least one prototype. It would be almost impossible for it not to fly well, even at 60-70% scale, the proportions are just right.

 

[rv7charlie]

From what I've read about many of the little sub-scale fighter replicas from back in the 80'/90's, it's apparently *quite* possible for one to not fly well when scaled down. Supposedly, things like wing area shrinking faster than scaled span/chord seemed to bite them fairly often. 70% span/chord yields around 50% wing area.

 

[Pale Bear]

From what I've read about many of the little sub-scale fighter replicas from back in the 80'/90's, it's apparently *quite* possible for one to not fly well when scaled down. Supposedly, things like wing area shrinking faster than scaled span/chord seemed to bite them fairly often. 70% span/chord yields around 50% wing area.

So, .. what's the solution? Fatten the chord? Or, have a different airfoil?

 

[rv7charlie]

Wish I knew. I remember a few magazine articles about the issues & what drove them back then, around the time I started flying. Not much coverage in the media since then.

Some of the imitation WW1 stuff seems to do alright, but I suspect that's because they don't make any attempt to do pure scaled replicas. Different wing area, different airfoil, etc etc from a strictly scaled version. Starting lower on the speed spectrum probably helps, as well.

 

[Victor Bravo]

So, .. what's the solution? Fatten the chord? Or, have a different airfoil?

We have some fairly talented aerodynamic people on this forum, and I ain't one of them. But... I'm willing to bet any of those aero engineer folks a steak dinner that if you took the Dave Platt 1/5 scale R/C model of the Zero, and the actual Mistubishi A6M2 or A6M5 aircraft, and made a straight-line progression of all the proportions between them, if you took the dimensions on that linear comparison at 75% scale size, and built the 75% replica, and had the gross weight at 1500-1600 pounds, you would have a very good flying airrcaft.

The R/C model may (probably) have a slightly enlarged horizontal tail. That is one of the things that I am saying you would do... have a slightly enlarged tail, at 75% of the way between the model tail (X% enlarged) to the original aircraft (0% enlarged). If the model airfoil is X% thickness to chord ratio and the original full-size airplane is Y% t/c, then go 75% between X and Y and pick a good turbulent flow airfoil with that thickness, chosen for a cruise speed of 150-180 mph.

Who will take me up on that bet? Scott?

 

[Pale Bear]

Victor, yes .. I would guess so, too. Your mention of R/C, .. yeah, the opposite side of the scaling of things .. modellers have been doing some interesting things, of the past few years, taking advantage of lighter receivers, servos, and motors. This is interesting to me:

and, if you follow up on this guy, .. there's photos of the underside of the wings, which are basically just a top surface, with exposed ribs to hold the curved shape. Totally an under camber airfoil. I suppose he mentions his weight somewhere, .. and it's probably impressively low. It doesn't appear to be any enlarging or stretching of any of the surfaces, does there? There's also a 1/4 scale Corsair, and a DC3 model that fly, very very slow that are on Youtube, too.

So, if they can do it ..

PS, .. looking at that pic, of the video .. perhaps that rudder is a bit larger?

 

[TFF]

The indoor models take advantage of materials strengths and not deal with engine vibration using electric. That’s why they can be so light. Outdoor traditional models can not be that light. A Platt model enlarged would probably be close to building a WAR model. Traditional scale models with details have the same problem homebuilts do. Details add weight. They are flying on a much smaller Reynolds number, so unbricking a brick is the modelers job.
It was in one of my RC magazines when I was a kid that a modeler built a WAR Corsair. Very cool. Mission creep. Made flaps work when there were none, gear doors, gear got fancier, Lycoming kicking out the Continental. Weight added; wing loading went up. If I remember right the first flight was a scary pattern on the verge of stall until he got stuff sorted.

Airbrushed details or maybe a wrap instead of trying to make guns with bumps and panel lines.

 

[Pale Bear]

Until I saw this video, .. I've observed many indoor model videos that were flying about this speed .. but, they were half using their wings, and half hanging from the prop. But, this thing .. looks like alot fun.

If I had something like this, .. I'd give outdoors a try, on a very still evening.

 

[Pale Bear]

Apologies for the drift off topic, .. we were talking about an interesting engine, for a real plane.

 

[Bille Floyd]

Would the apex engine , be a fit for a Varieze ? Does anyone make
a pusher reduction for it ?

Bille

 

[rv7charlie]

A lot of the Yamahas are flying on pushers. I doubt that the drives care whether the prop is pulling or pushing, but you'd need to ask the individual drive maker. Some of the early versions used Rotax 'C' gearboxes mounted to an adapter, so obviously no issue with those (except feeding 130-150 HP into a drive made for way under 100 HP).

The bigger question for something like an EZ is whether a ratio is available that would accommodate the smaller diameter prop required. And the fact that they are still 'new'; they seem bulletproof, but no one will really know until someone flies one on a plane that requires continuous high power for hundreds of hours. You can bet that most of the stuff flying now is running around at 40-50% most of the time; the airframes are just too draggy to justify running at 75%.

Charlie

 

[Victor Bravo]

Well, there's a very highly optimized Vari-EZE at Santa Paula airport that pretty much re-wrote the whole record book on small aircraft efficiency. Klaus has moved on to working his magic on a larger and higher power Long-EZ, so maybe you could ask whether he's interested in trying the Apex engine on the original VE. He's pretty darn interested in efficiency, so if all of the fundamental technology improvements in the Apex engine actually will translate into an aviation use, Klaus will identify it and is capable of making it work.

 

[cblink.007]

-does the prop always windmill if the engine quits

I think we have been round and round on this, and the question has been answered in another thread.

 

[cblink.007]

Would the apex engine , be a fit for a Varieze ? Does anyone make
a pusher reduction for it ?

Bille

My group's aircraft design will use the Apex; and we are working with a chap who is doing a 3d scan and proper .stl format touching up for accurate fit checking and motor mount design. That being said, we still do not know to what extent we need to modify our cowling (originally designed for a Rotax 912ULS), but given that is a different profile than the O-200, I can all but count on a VariEze cowling needing to change to accomodate this plant!

 

[way_up_noth]

I think we have been round and round on this, and the question has been answered in another thread.

I’ll answer my own question.... I’ve educated myself since I posted that

With the most common gearbox for the Yamaha conversion...that contains the sprag clutch .... the prop will windmill at idle or if the engine quits

 

[cblink.007]

I’ll answer my own question.... I’ve educated myself since I posted that

With the most common gearbox for the Yamaha conversion...that contains the sprag clutch .... the prop will windmill at idle or if the engine quits

We will be running a sprag clutch with ours. Engine out best glide speed is still below the airspeed at which our desired prop would windmill to the point that range would be too adversely affected. But this drive, so far, absorbs TV the best until a better solution is found. We plan to run a full vibe spectrum analysis when we approach that point in our test plan...and try to devise a great solution!

 

[rbarnes]

My group's aircraft design will use the Apex; and we are working with a chap who is doing a 3d scan and proper .stl format touching up for accurate fit checking and motor mount design. That being said, we still do not know to what extent we need to modify our cowling (originally designed for a Rotax 912ULS), but given that is a different profile than the O-200, I can all but count on a VariEze cowling needing to change to accomodate this plant!

I'm itching to buy a Velocity SE and turn it into a mini-V-twin with a pair of 200hp Epex engines. Hmmm.....

 

[rv7charlie]

We will be running a sprag clutch with ours. Engine out best glide speed is still below the airspeed at which our desired prop would windmill to the point that range would be too adversely affected. But this drive, so far, absorbs TV the best until a better solution is found. We plan to run a full vibe spectrum analysis when we approach that point in our test plan...and try to devise a great solution!

Unless I'm sadly mistaken, a sprag clutch is an 'over-run' clutch. My understanding is that it disengages as soon as the driving force is removed, which will allow the prop to freely windmill. If you're flying a high-drag airframe, the extra drag from the freewheeling prop may get lost in the noise of airframe drag, but it would have a significant effect on a low drag airframe's glide performance.

Or I could be wrong about the sprag...

Charlie