MJD

My Feedback: (1)

If this was a piped engine I'd be way less cavalier, but since the Toucan will fly on a fraction of the available power without trouble, why not just flight test? If I add IMC I have all the tools needed to deal with the mixture after unloading.

The behavior on the 3rd flight was promising - the rpm was down on the ground, but I left the mixture on the raggedy edge of rich counting on the unloading. It seemed to work - it got its legs in a few seconds and the engine took off and sang like a bird. This tells me there was no problem handling the pitch, and the airspeed looked and felt noticeably higher.

When I get a chance to fly the 3.9 x 4.75 against the 4.1 x 4.5 and track airspeed, that will provide some insight - a small reduction in disc area and a small increase in pitch. All else being relatively equal I hope this will point in the right direction. Maybe Santa will bring me a radar gun.

aspeed

The Profi project looks interesting. Is it piped? If you get everything sorted, I would guess the 200 MPH club t shirt would be in order, no probs.

MJD

My Feedback: (1)

It is pretty much the full Monty - a 2014 Profi F2A engine* with pipe. I have two pipes, one new and one used (identical). I'll work with the old pipe and use it to test stinger outlet ID versus staging, fussiness, overheating etc. The general plan I have after talking to folks like Bill Hughes (he seems to know how these work..!) is - due to the runtimes and heat buildup - to moderate the criticality of the setup with a slightly larger stinger outlet. The concensus is that with the freedom to dive and unload the engine and with the improved slipperiness, transition will be a lot easier than in CL. Plus.. it has the added benefit of IMC that ukies don't have.

Typical F2A flight prop is 2.9 - 3.0" radius x 6 pitch. We'll see about this later of course, gotta get out of the starting blocks yet, but there are pitches up to 7" available. This also might be an opportunity to take advantage of more pitch speed than CL. The D06 flies on 5" props normally.. and it will be light.. so i think it should be a willing and cooperative test bed.

I won't count any chicken before the eggs are laid, but it is my sincere belief that an F2A engine should be able to achieve and maybe top 220mph in an RC application. The best can do 208-210 on lines.. so following the "unchained" logic this is reasonable to expect. Whether or not I am able to do it is a whole other story! But I have only have this lifetime to find out, so why not get at it? Success for me starts with passing 200 on 2.5cc.


* the Junior is the more "production" F2A engine while the TOP 2014 is the limited production run for the worlds - 24 made as I was told. Mine is a hybrid - it has the 2014 TOP top end, in a Junior crankcase - the diff comes down to a regular rear bearing versus the full TOP which uses the crankcase as the inner race = EVEN MORE $$. It is believed I will get a good chunk of the TOP version performance from this special version. That will do fine!

MJD

My Feedback: (1)

It's also odd to think that it will fly at 5-6k rpm more than the .049.. egads.

Pond Skipper

Anything over 180mph that small RC is going to task your heart - lol better take some low dose aspirin an hour prior to flying!!!

Given the weight of the plane over CL and Sq.In of the wing:

4.75P
34k rpm 153 mph
36k / 162
38k / 171
40k / 180

3.5 x 5
36K / 171
3 x 6
36k / 205

MJD

My Feedback: (1)

Yeah but the electric guys fly these F5D models at 200 all the time, it must be easy..

No doubt this will be a baptism by fire when it finally launches.. but it ought to be a memorable day one way or the other! What else can you hope for?

MJD

My Feedback: (1)

In terms of the 1/2A, I am expecting to top out at 4.5" pitch with as little diameter/much rpm as will work. I will have to get the engine up to about 33k in the air on the 4.5" pitch to have a hope of reaching 150. May have to back down pitch and bring up rpm. We'll see come spring.

aspeed

Bill Hughes knows his stuff. Him, Carl Dodge, and Alex are on the US F2A team. I watched and timed them at Muncie and they just don't make mistakes. Normally there are planes falling out of dollies, shaft runs, planes shaking apart... They just fly, and whip them up to speed and go, pretty much anyway. That made me think, you may have a bit of trouble with hand launches, and broken single blade props kill planes without shutoffs. Just sayin. Control line planes do have an adjustment for inflight mixture control. You move the tank in or out so the centrifugal force richens it the correct amount. I needs to be landed of course. We used to have backplate pressure, and a centrifugal fuel switch back in the day. When they worked, they were great. When they didn't work, more prop money.

combatpigg

My Feedback: (3)

I think a launch from the back of a moving pick up truck is the way to get airborne with a single blade prop.
A 25 mph roll maybe...?

Pond Skipper

For RC a slide ramp bungee launch via foot pedal can't be beat - the RC jet and glider guys use them the most if no landing gear nor a good grip for hand launch or lack of arm throwing having enough speed per plane needs.

A single blade 5 x 6 loads like a 2B 2.5 x 6? As I understand it without the other blade in the way the incoming air is cleaner less induced drag / flutter.

33k with a 4.5 prop will only get you to 140.63 best possible.

MJD

My Feedback: (1)

Don't forget that the true pitch of the prop will be higher than the rated pitch. Rpm x pitch formula are okay for approximate potential top speed, but they don't factor in the zero lift angle of the prop airfoil.
In the end the empirical tests will tell the story.

On the .15 model.. IMHO launch will not be an issue. The power of an F2A .15 smoking and struggling along at 20-22k on the launch dolly is sufficient to get those models up to rotation speed fairly quickly. This model will be light with a very manageable wing loading. I anticipate it will fly away fine from a hand launch.. after all, how much power does it need to simply climb? If I can toss it hard enough for it to glide level. A TD .049 would probably haul one of these as briskly as an ACE Pacer. K.I.S.S. principle. Nobody uses launch rigs in F3 speed, and they are flying higher wing loading.

It's 217 sq in with a thin wing and flying weight of 31-32 oz in electric format.. meaning the glow version will come in lower, in the mid-upper 20's I think. wing loading ~ 18 oz/sq ft. No prob.

aspeed

Ya, if it is as light as yours, you should be OK.

MJD

My Feedback: (1)

And I'm not poo-pooing all the ideas flying around here, it's just that I don't think there's going to be a problem. I've thought a lot of this through and it seems like a good formula. The toucan is a good indicator.

There are guys overseas who have dropped NovaRossi .21's on these kinds of models - but what I have seen are fairly rough conversions - semi open engine, pipe sticking up on an angled header etc. One that I saw was clocked at 173mph. Yet.. there is an account from the F3 speed crowd of an F2A engine flying on a 1/2A pylon racer (I've seen no further description) and topping 210mph. I can believe it but I would sure like to see something about it.

aspeed

Video is always better than talk. I know I don't have the ability to fly RC that fast.

Pond Skipper

yea some nice passes on video will help tach it and I can point my radar gun at the screen and get a reading hehe

MJD

My Feedback: (1)

Here's the only 2.5cc speed model pic I know of from the German speed cup collections. I Love Jets mentioned speeds of around 170mph with a NovaRossi .15 running 5x5.5-ish size props.

Looks fun.

hllywdb

I'm guessing the helmets are a safety precaution in case they fall out of the back of the pickup durring the hand launch????

MJD

My Feedback: (1)

Must be. That's a small target to hit with a speed plane.

combatpigg

My Feedback: (3)

http://www.baltimoresun.com/news/mar...207-story.html

How about that...?

aspeed

There is a guy in our club here that has a huge biplane for launching gliders. That would be good for launching a speed plane. Kind of like the old X15 record holder.

MJD

My Feedback: (1)

By the time it gets up there the fuel will be gone.. not really sure I want an off-resonance expensive F2A engine gargling away for a minute while a carrier lifts it to altitude.

BUT - this is exactly what I need to do for the Demon.67 (maybe soon to be .80). It's a CS to hand launch (that's, uh, a "Challenging Subject"..).

combatpigg

My Feedback: (3)

What I have against my bungee style launcher is the time and cost to build it, the space it hogs when it's not in use and the chance of the sudden acceleration to lean out the engine.
My launcher takes up almost as much space in storage as a riding lawn mower.
Launching from a moving truck bed, the pitting can be done right there and I don't think it would take any longer to execute the release compared to standing on the ground.
My only question would be how the plane would react to weird air currents coming over the cab. Probably not much different from a slope soarer.
The other obvious concern is accidentally driving right over a plane that fails to launch. That would be a low moment in any one's "hobby career".
I'm fairly certain I've seen video of a speed plane being launched from a truck, but I'm not able to find it now.

aspeed

www.youtube.com/watch?v=qVVItE0tZFU Got time to waste. Too cold to fly.

MJD

My Feedback: (1)

ROFL.. love it.

combatpigg

My Feedback: (3)

I don't see how they knew for sure that the landing gear would clear the cab....outside of a "gut feeling" that it would work just fine.