RickVB

My Feedback: (24)

OK, last pass, I give up. One, I stand corrected, the Quadra/US classes of 40 sized engines are rated down around 3hp.

Two, you should know that speed calculations done in ThrustHP are purely theoretical, based on pitch and RPMs only, and will not reflect the resulting max speed of a given airframe driven by that prop. Without getting real technical, *that* involves all the aerodynamics of the airframe, which is born on by thrust as much a max theoretical speed in most cases.

Finally, stress on an airframe is a combination of speed, vibration, and thrust/drag effects, not just speed. So you're comparing apples to oranges there.

As a parting shot, I'd just point out that the AMA has standards for both underpowering *and* overpowering, which many manufacturers support, probably for a good reason.

RickVB

My Feedback: (24)

Oh, I have to add one more point of disclosure. I never use anything above 10% nitro in any of my engines, so I guess that would account for some of the difference in performance I've seen.

locomotive

My Feedback: (7)

My Tcraft will be a multi role ship. Glider tug, Float plane, camera platform. And I have a throttle on my Tx.. so.... I am definately going with the Brison 2.4.... not for speed... for pulling power.

RCAddiction

My Feedback: (87)

Hey, Rick, don't bail, it is just getting fun

Seriously, you are right about ThrustHP. It is purely theoretical, and is plain wrong on HP. But I've found it useful to make good comparisions. It's been scarily accurate in predicting rpms on a prop change, if I already have a baseline with the same brand of prop on that engine.

Also you are correct on the airframe stress. If I am adding 4 lbs more thrust (pulling on the nose of the plane) and dragging behind a draggy shape at the same speed, I am likely inducing more structural stress at that speed. But flutter won't increase if the plane's speed does not increase.

I do disagree on the flutter is the flying speed is not increased. However, flutter avoidance is why I am using HS-605's on 6 volts and we should always be careful to set up servos to get good mechanical advantage. And my aircraft is still fairly slow. It's propped for thrust, not for speed.

AMA has standards for power? I'd be interested in knowing more about them/where to find them.

RickVB

My Feedback: (24)

Alright, one last time. I misspoke, technically, since it's an IMAA recommendation I was recalling. (Technically, the IMAA is a SIG of the AMA, so in a way it's an AMA rec. ) And since the rec is:

Generally, it is recommended that no attempt should be made to fly a radio controlled model aircraft with a gasoline engine in which the model aircraft weight would exceed 12 pounds per cubic inch of engine displacement (under powered), or be less than 5 pounds per cubic inch of engine displacement (overpowered). Example: Using a 3 cu. in. engine, a model would likely be under powered at an aircraft weight greater than 36 pounds. With the same engine, an aircraft weighing less than 15 pounds would likely be overpowered.

(IMAA Safety Code Section 8.2 paragraph 8)

the gas engine range for a 15 lb. plane would be 1.25 to 3 cu. in. (21 to 50 cc), you can go ahead an dump your 40cc in and be within the recommendation. Of course, if you do that with the PAM Gee Bee, you void the warranty...

RCAddiction

My Feedback: (87)

Hey, that's neat. Thanks, Rick.

So, now, with my 18lb+ plane, with a range of 1.5 to 3.6 cu in, I don't seem quite so crazy :spinnyeye with my 2.7 BME. Right in the middle. No wonder it flies just perfect!

locomotive

My Feedback: (7)

Ok..... how about a DA50 on a Tcraft????

RickVB

My Feedback: (24)

<Ack> :drowning:

RCAddiction

My Feedback: (87)

Yes, I have to agree with Rick. I don't know that the BME44 is the limit, but the DA50 is a bit of a monster, powerwise, for this plane. It's a wonderful engine, but you'd need to pin the firewalls, reinforce a lot of stuff, at a minimum, I'd think.

Also, the prop would start to be getting kind of big.....

bentgear

No, locomotive, go ahead and use a DA 150. Don't you think the heads sticking out the sides would add a nice touch..........

Ed M.

Flyboy Dave

My Feedback: (21)

....would look real sharp hanging out the sides....

....64.5 ozs., ....(perfect)....leave the big 2-strokes
in the weed whacker.... ....(flame suit on)

locomotive

My Feedback: (7)

The DA50 was a joke guys... geeeeeeze

bentgear

locomotive, I think we were joking along with you. I was laughing so hard I'm surprised anybody could even make out what I was tyring to say because of the spelling.
Ed M.

RickVB

My Feedback: (24)

Yeah, and while we're at it, I'm sure it could use come N motor JATOs to help with those short fields...

(Hah, got ya Ed, now your typos are preserved for all time... )

bla bla

Any way, back down on earth....
Zenoah 23 or 26 what ever it is!
Flew one yet again this week (not mine) and it's simply wonderful, a very happy airframe, motor, aerodynamic combination. Thoughs that say it'll under powered simply haven't any experience flying aerobatics with this type of aeroplane.
Yep, it won't pull out of hover... why would anybody be doing this in the first place...Isn't that what other aeroplane are for? But as far as scale aerobatics are concerned it's way over powered. Scale aerobatics, sounds boring? It's a great deal more complicated, demanding and takes a great deal of skill to accomplish... far more than it takes to hover an aeroplane or pull of a bender or a wall. All very silly names for pretty basic, low skill aerobatics.

ptebbe

My Feedback: (27)

bla bla,

bla bla bla

Why install a G26 when a 40cc gas (FPE) is the SAME weight! I like to have that extra power on hand, if I need it. And I can stil fly in a scale fashion if I choose.

PT

bentgear

Maybe so the extra power will not be there and it forces you to plan the maneuvers to use what you have, much like the real airplane.
Not taking sides on this discussion, sorta straddling the fence and hoping that the wire don't catch on nothing.
Ed M.

RCAddiction

My Feedback: (87)

Well, Ed, if the extra power is not there, and I run into trouble, I will shortly thereafter run into the ground.

I'd rather not follow the logic of "forcing myself" to plan maneuvers. I can plan them just fine. Also, not all maneuvers are planned. Ever have someone lose control of their plane, or have a jerk who owns the sky swoop in front of you and need to pull out the way in a hurry, or someone decide to take off while you are doing an announced landing?

I'd much prefer to get out of an "oops" (cause by me or others) by having the reserve power available, thanks.

That's why there's Chocolate AND Vanilla. Not everybody likes the same thing.

GoeKeli

My Feedback: (18)

What about the G45 on the TC? I got one that runs really great and starts on the 4th flip. Hmmm. 2.8 and it will weight what? 17lbs?

Joe

RCAddiction

My Feedback: (87)

Joe,

The only concern I'd have is weight and trying to balance that heavier engine. As it is, with the light BME44, I have the main (heavy) sub-C 5 cell 1800 mah battery at the far rear of the radio compartment. It's velcro strip wrapped around the back former that supports the servo tray. Of course, I also have a 1400 AA sized ignition battery against the interior of the firewall, as far from the radio as possible.

You might need to make a hatch for a battery. Caution, the plane is built very lightly in the back so you would need to build some structure to support it.

Also, the landing gear would take a bit of a harder hit with the heavier nose. I built spring coil struts to help support the main gear and it helps absorb the shock.

GoeKeli

My Feedback: (18)

Thanks Lee,
I might need to move the elevator and rudder servos to the rear too. Hmmm. The weight people are getting with added smoke and smoke oil with G26 setups are not far from what a G45 would be with no extras. Just distributed differently. Lee, can you see any way to get the servos in the aft?

Joe

RCAddiction

My Feedback: (87)

Joe,

I just took at look at mine to double-check.

I'm sure you could mount the servos in the tail to help with the weight if you needed to. Would be hard to do pull-pull, but straight, short 4-40 pushrods should be do-able.

The sides of the fuselage, starting from the servo compartment, and heading back to the tail is all lightweight stringer construction.

However, these sides becomes solid ply top to bottom, starting from the leading edge of the horizontal stab and all the way back to the tailwheel from that point. So, the stab is supported by solid ply. You could mount servos there, but it would weaken the ply from the holes. Probably some 1/8" ply pieces glued vertically on the interior side of the servo cut-out would help offset the lost strength. You'd likely add those anyhow to give the servo screws something solid to bite into.

bentgear

Dang, that DA 150 with the heads sticking out the sides idea is starting to look better and better. ;-)
Ed M.

GoeKeli

My Feedback: (18)

Thanks Lee.
HAHAHA Ed! I'm gonna wait for the 4 cylinder!

Joe

TD1

Hi guys, I have been reading all the post, and I have a 3w 42 that needs a home. The 3w is quiet a bit heavy and I was wondering if this engine is to heavy for this plane?
Initially I though in getting a Cub, but I don't know of anyone that makes a cub for a 3w 42. Any help is welcome