Colin Gardner doing a great job of flying his Merlin 160 powered Firebird in a very blustery UK.

http://www.youtube.com/watch?v=nOfN-M281aI

Rob.

Wow, that looks great with the Merlin 160, I have a Merlin 160MKII here, any idea on the top speed on Colin's plane? I'm trying to decide on getting a bigger engine right away or just putting one of the engines I have in it right now. I have options, 44lbs thrust, 38lbs thrust, 32lbs thrust (not really an option LOL)
Of course bigger is better, but the big engine is on my Kingcat, I'd change that for the Firebird though

Just keep in mind that the FireBird only has 150oz of fuel capacity. With the larger Turbines and high speed flight you will have a short flight. I think 35 -40 lb thrust range is good for this airframe. You will have no problem hitting 300mph on 38- 40lbs. Also if you have never flown an airplane that fast you better make sure you have good eyes.. It gets out there really, really fast......

Dennis

This is my Kingcat, I wanna go fast :P
http://www.youtube.com/watch?v=2RZbaMSUCVo

Then If fast is what you really want then you are on your way. The Firebird is the perfect airframe for you! It really doesent matter what Turbine you choose, it will be faster then your King Kat. When I get mine will have the AMT/NL Titan at 88lbs of thrust. I am looking for 400mph...... Can you imagine :-)


Dennis

My Kingcat was radar'd at 284mph, definitely wanna hit the big 300, isn't it funny, it wasn't that long ago that people were excited about 200mph!

Do You have a suitable runway?? the firebierd needs some room to slow down on landings.
V..

About 5000' of asphalt
I was flying a CAI Raptor last year as well, it lands pretty fast and takes a while to slow down too, the runway is about 5000' I believe by 80' or so wide I think.

There is only one choice...... AMT NL OLYMPUS HP!!!!
I just have one in my UL. If you hear this turbine running you know it will give you confidence.
The parts used and the reliability is second to non.

Unfortunately the Olympus HP is pushing $8000 in Canada, not gonna be using one of them I'm afraid, I do have a couple options though

I have no idea of top speed but it's certainly one of the fastest jets I've seen. The problem is (at least with the Merlin) it never reaches terminal velocity. One big thing to consider is drag and engine diameter, JMP have gone to a lot of trouble to design a lovely smooth jet to minimise drag wherever possible but a fatter engine with lower exhaust velocity would negate a lot of that work.

I also think it would be a struggle fitting a Titan in there, let alone the weight, limited endurance and human facters.

Rob.

I have an incredible G Booster 160+, high exhaust gas velocity, putting out about 44lbs of thrust, I think I might put that in there, it's on my Kingcat right now, but I could always put the Merlin I have on the Kingcat

Fatter engines do not necessarily have lower exhaust velocities. The velocities of all engines are around 600-700mph so the issue is really moot.
Fatter engines usually have better fuel economy - means smaller tanks - more room for engine

It blows my mind to think that manufacturers go for slimmer motors with more thrust per weight (of the engine) instead of maximizing efficiency. People tend love to buy those high T/W engines and then negate the whole thing by putting in much more fuel! Better to have 200 more grams of motor than carry 1000 in fuel IMHO.

+1

Of course I can't know which engines u were referring to, but the Wren SS, Rabbit, and Merlin 90 all make lots of push for their radius/weight AND are very effient w/ regard to specific fuel consumption, yes?

You get into diminishing returns with bigger block engines in a FB........excess thrust over drag vs speed is not a linear function but approaches a square function due to induced and parasitic drag as well as cooling drag(turbulence in our intake ducts, bypasses, and tailpipes).....so to double speed, you need not 2X the power but 4X the power.......add to that the extra power needed because of increased weight, which is also a square function, and you reach a terminal velocity which is hard to exceed, no matter how big a block you put in. Plus the big blocks suck more gas. But what the big blocks give you is exceptional Hill Climb ability.....the old power to weight thing. My BVM Phantom at 27 lbs dry with a 35 lb Titan is an Unlimited Banshee in the climb, whereas my BVM F-100D at 38 pounds dry with a 37 lb Pegasus runs out of gas half-way up the same hill.....

Talked to Tom today.....he is now flying with some crow in the ailerons, 40 deg flap, and, of course, the bigger rudder for increased stability in the down and dirty configuration. But it still stalls at an airspeed in the high 40's, so chop and glide 75 yds out like a Boomerang is not suggested for landing.....best to fly it with some power on until mains are about to touch.

I'm leaning towards my Booster, it's the same size as a P120, pushing out 44lbs of thrust. Same weight as a P120 as well. The fuel consumption is only about 10% more than the PST1300R that it replaced on my Kingcat, So that's about 3lbs lighter than the Olympus, I think it will work well. I thought about a P200, but again, much heavier and higher fuel burn. I guess I'll start with the Booster and if/when I decided I want more power I can upgrade

Besides the Multiplex Rhino for the stab, what servo's are guys using in this? I would assume 8611s are more than enough considering I don't even think we had 8411's when the kit was first available? Flaps? 2721's? Thanks in advance!!!

Really nice servo spreadsheet, click on all and see 1800 servos compared. Click on a tab and sort up/down..............Let me know what you like, The ACE servos really look impressive to me.............

enjoy

www.servodatabase.com

JR 8711's for ailerons, flaps, rudder.....JR 9411 for Nose Gear steering.......JR 351's for retract valve and door valves......JR 821 on the UP-6 brake valve......

I use digitals on flaps the last couple of years.....just be careful setting them up with an ammeter to be sure they are not stalled when fully up or down....

Right now I have it set up using the plastic HD servo arms that come with the 8711's, but I may switch to SWB metal arms with ball joints.......Using a 300 oz servo with metal output splines and plastic arms seems a bit risky....

When the rudder fluttered big time on my UltraBandit last year, all the servo arms stripped out, not just the rudder ->R.I.P UB.....[] so I am a little paranoid.....

Hi Tom,
I will of course ask Tom Cook about servo's as well, but I would think you can get away with less than 8711's and still have a huge margin for safety? The Firebird design has been around longer than even the 8611's have, with the Multiplex Rhino Digi 4 servo for the stab being a 250oz servo, surely you don't need more than that for the other surfaces? I have some 8611's right now, and a couple of 2721's. With 2721's being used on Kingcat and Super Bandit flaps, are they enough for a Firebird? I don't want to underpower any surfaces at all, but at the same time, if I can use the servo's I have, that would be cool. I don't have any 8711's and would prefer not to buy them anyway, I don't see any servo specs on JMP's website so that's why I'm asking, Tom called me (but I missed the call) to find out what servo's I will be using for the servo mounts, just wondering what the consensus is
Jeremy

Understand your situation Jeremy......use what you have. I still am a big fan of 8411's, in fact, I just upgraded the old, old 2721's on my BVM Phantom and F-100D to 8411's on the flaps. I did have an 8611A a while back that was bad right out of the box. That spooked me, as it was going into my UB.....ever since then been going with 8711's.

That MP Rhino is awesome. The internal gear train, motor and the special arm that Tom offers could pull a freight train......250 oz.in is more than enough holding power for the all flying tail.....

Any size will fit, as you set his zero-flex mounts up for whatever servo mounting hole distances you end up with. Those zero-flex mounts are the best anyone has to offer.

I still am a bit twitchy about the plastic servo arms on the 8711's and may convert those to SWB aluminum arms with 4-40 ball joints, at least on the rudder......

Jeremy,

I would agree with your rationale and think that you should be fine with the 8611 set-up. The 8711's are just pumped up 8611's anyways. (Use the same top case and gear set) I would however, use aluminum arms everywhere. I can't believe that any of the manufacturers of servos with torque over 200 oz-in even ship a plastic arm with the servo.

PaulD

I talked with Tom today and I am using 8611's on everything except the stab and nose gear steering, I will use an 8411 on the nose gear and the MP on the stab.
I was going to use the aluminum arms until I talked with Tom, he recommends against them. He prefers the heavy duty nylon arm that JR supplies with the 8611's and 8711's (not the flimsy typical nylon ones that come with the smaller servo's, but the large heavy duty nylon arm). The reasoning behind this is that using the aluminum arms with a ball link puts an un-necessary twisting load on the servo arm, this transfers to the output shaft of the servo. His recommendation is to use clevises on the servo arms and horns.
I think I'll go with that, to be honest, I can't say I have ever broken a servo arm, even in a really bad crash. Truth is, Tom mentioned to me that he is still using 8231's on his Ailerons in his original Firebird, that's only 90oz of torque, that being said, just because you can use a 300oz servo, doesn't mean that the load on the arm will be more than the 90oz servo can handle. Having seen Tom fly his Firebird, I don't have any concerns, he flies it hard
Jeremy

Food for thought..

There is little/no vibration to deal with on a turbine aircraft. Using a clevis (assuming one you can lock closed) is probably your best bet. I would NOT recommend using nylon arms though. I still for the life of me don't understand why JR includes them with the servos like this. There's no way they can handle the torque the servo can generate. Furthermore, all it will take is a bump on the control surface from moving the airplane, assembly, what have you, and that nylon arm can shatter/strip teeth. They're great for relatively high sustained loads, but VERY poor when it comes to shock loads. I've broken more than a few on giant scale aerobatic airplanes just from assembly.

My suggestion would be to run 8611's with metal arms, using a locking clevis that is silver-soldered onto the pushrod. DO NOT rely on the threads on a piece of 4-40 rod to handle the flight loads of this airplane. While the threads on the pushrod are fine, the clevis itself would be likely to spread open in the threaded section.