Boomerang XL C o G ????
 

Boomy XL fitted with P160

Trimming C o G is stated as 350mm foward of trailing edge.

I'm miles off this even with two big lipo's and a 7.2 race nimh pack right up front. (accurate check as supported by wires 350mm forward of t/e from ceiling)

I bet it'll need 2lb of lead to reach this C o G.

All the gear's as far foward as poss, is this normal???

Where are others @ with bal point?

Cheers !!

Andy

RE: Boomerang XL C o G ????
 

I've built 2. One for me with a 120-SE, another with the 160.

Both built up without lead, however both are using Nimh right up the nose.

How far forward have you mounted your turbine??

Steve

RE: Boomerang XL C o G ????
 

Hello Steve

Turbine's as far forward as poss. I'm using a "cool power" US gallon container as a tank which is probably shorter than a 3 litre "Pop" bottle as suggested. Starter is virtualy touching rear of tank.
The install is all on the front plate (apart from pump which is back slightly). I've only tried with zero fuel at the moment (pun not intended!) will try full today.
How far back did you move after the "trimming flights", if at all?

Andy M (off to find the nearest church roof ;-))

RE: Boomerang XL C o G ????
 

http://www.mmfc.org.uk/may-07.pdf

Looks like I'm not the only one..

I've managed to drag the tank forward by about an inch along with the turbine, it's still miles out though.
Really don't want to add lead, but it's looking like I have no choice...

Andy M

RE: Boomerang XL C o G ????
 

something doesn't seem right...I have a 160 in mine, CG is fine with engine AFT!

I Did however, in anticipation of the problem, mount 3 4300 duralites waaaaaay up front. Two are just behind the very foremost bulkhead, and one is actually on the FORWARD side of that bulkhead under the radome which I made removeable. Also, and this was a massive pain in the butt, I mounted my fuel and smoke pumps in the nosegear wheel well.

RE: Boomerang XL C o G ????
 

Also have 2 4300 Dura's and a 3700 Nimh but above the wheel mounting.
Have moved the tank forward a touch and added about a pound of lead. This gets me
spot on at 350 foward from T/E. Looking at the tank position, balance point will move aft on fuel burn off, shouldn't be
too bad as there's not much lever arm there. (Will give more pitch authority for landing anyhow).

I guess the initial 350mm is pretty conservative anyhow. Where's everyone in the "real world"?

Thanks

Andy

RE: Boomerang XL C o G ????
 

Alan and others have stated that the specced CG is conservative. Others have posted real settings they've migrated to eventually in the XL thread.

RE: Boomerang XL C o G ????
 

My XL has a P-120 moved as far back as possible to get the CG where I like it. My CG is probably 1" AFT of Alan's suggested starting point, and I'd like to move it back another 1/4" or so but there is no way to do so without adding lead. I am using one 3600 mAH IB NiMH ECU pack and two 5 cell 2700 mAH SCR Ni-Cad RX packs, all mounted on the tray above the nosegear. I also mounted my fuel pump on the equipment tray at the very front (which turned out not to be necessary....)

Barry

RE: Boomerang XL C o G ????
 

Thanks Barry

Think it's me being over cautious... Is there such a thing???

Mine's spot on 350 from the t/e now. Were I to reduce that to 325 I could probably junk the lead. Better safe than sorry though.
(will probably not be far off that figure dry)

Thanks again

Andy

p.s. B4 I commit to aviation, any nasty suprises I should expect?

RE: Boomerang XL C o G ????
 

The last two boomerang xl i had with straight legs only just kept the nose wheel on the floor. If it sit on the floor with straight rear legs then it will fly ok. I added a small battery up front to get the c of g perfect for me.

RE: Boomerang XL C o G ????
 

I'm about a half inch to the rear of where the instructions stated. I was initially concerned about my CG being further back from the recommended setting in the instructions, but it was needless worry. It flys great. With the fuel tank situated mostly in front of the CG, and the subsequent CG shift from fuel burn, you would think the flying characteristics would be adversely affected. That is not the case, however, and the plane flys the same with 1/4 tank of fuel as it does with a full tank. So.... to sum it up, the airframe appears to have a wide CG tolerance and if you are in the ball park you will be fine. IMO:D

RE: Boomerang XL C o G ????
 

Andy, absolutely none at all. She flies like a charm, next to the Reaction 54 it is probably the most benign flying jet out there. Flies like a big pattern ship. Use the stock throws as a starting point, they are safe.

Biggest problem I have is developing bad habits on landing, as the Boomer is my "go to" daily jet...unlike most jets, even with an older (i.e. not the strongest) P120 and 70 degrees (as much as I could get) of flaps, I'm landing at idle thrust. Gotta watch it as most of the other jets I've flown want high AOA and some thrust on final when dirty. Do that with the Boomer and you'll just float on by.

Make sure you use some crow, I have 3/8" to 1/2", starting in at half flap, and that seems perfect. I have a very little (2%) up elevator mix at full flap. My approaches are made gear down with half flap, maybe 1/4 throttle, slightly nose high, I pull in full flap on the turn to final and work the AOA to determine touch down point...from the time I roll onto final, the throttle is basically at idle. get it right and you can drag the skids for 50' or so, and land in less than 75' with just a touch of braking. :D

Good luck and enjoy your test flight!

Barry

RE: Boomerang XL C o G ????
 

Thanks all... the big day approaches...

Barry you're not the first to tell me she's a floater! Looking at the videos on Al's hobbies website
the flaps are nearly @ 90^ when fully down! Luckily I have 300 yds to get her back down. Have dialed in some crow
but want to keep it mild to start with. Will check on the Jetcat forum the lowest safest idle revs for the 160 as well

Thanks again for all your help, it's much appreciated|!

Andy
Naseby England

RE: Boomerang XL C o G ????
 

Tanarg,

For what its worth, the XL is my second jet (after the Intro), it is powered with a Behotec JB165 turbine, and have adjusted CG as per Alan's recomendation i.e. at the former in front of turbine with gear down, UAT full and hatch off.
I also have crow braking using 45% flap and 23% up ailerons (have used a throw meter to fine tune throws)
For your guidance, our flying field is located on top of a hill at 4000 ft above sea level and runway is only 300 feet asphalt leaving no room for mistakes.
Needless to say that i had my doubts and fears before i actually flew the XL although i had read so much about this jet.
I was simply amazed by this jet since its first flight with its wonderfull caracteristics and easy maneuvering. I was able to use the crow braking on this same flight with great success. I simply engaged the mixing one lap before landing and i could feel the plane slowing down with no tendancy to move on either axes, no pitching, rolling whatsoever. With the setup i did, the XL came in like a charm very very slow and i was able to land in less the 100 feet!! and stop without brakes.

No worries, you will surely enjoy every minute and all your "fears" will be gone very soon.
Regards.
Dany

RE: Boomerang XL C o G ????
 

I recommend as near to 90degrees of landing flap as you can get.

m

RE: Boomerang XL C o G ????
 

Did it!!

Four flights today :-)) Jirst jet :-)))
All went great till the last bit of the last flight (Taxi in to be precise)...

Landed a treat (on grass) taxiing in when the aircraft came to an abrupt halt. Shut down to check it out and was
horrified to see the Jet A1 nose leg had fallen apart thus allowing the strut to dig in and bend back... It's damaged the underside aft of the bulkhead slightly. As I type, the internal epoxy mat reinforcement is going off... I'll fill and smooth the underside and with a bit of luck will be able to alter the paintwork pattern slighly and you'll never know.

The gear failed at the top mounting for the suspension arms. It's held to the strut with a small grub screw. Make sure it's tight! Have now fixed mine with a larger grub and bearing retainer!!

Annoying end to an otherwise enjoyable day!

Andy M

RE: Boomerang XL C o G ????
 

Congrats on the first flight! It truly is an awesome flying jet. To me, the Boomer is relaxing to fly versus some of the others I have had, such as my Skymaster Gripen. I'm so impressed with the Boomer XL that I just ordered the Baby Boomer. Anyways......another Boomer in the sky, good job!

RE: Boomerang XL C o G ????
 

Cheers Air dog

Didn't fancy the Elan then?

Andy M

RE: Boomerang XL C o G ????
 

I love the Elan, but I thought the Baby Boomer would be a better choice for my PST600......plus they are having a good sale of the Baby Boomer here in the States through Patricia Cardash..........I couldn't pass it up! One of my friends just bought the Elan and to me it is the culmination of advancement in Alan Cardash's design. Especially with the center section of the wing being fiberglass. Maybe the XL3, if there is an XL3 on the drawing board, will be designed that way.

RE: Boomerang XL C o G ????
 

Fair enough...

Have simmered down a bit now, half a bottle of decent Chilean helps...

Damage is not too bad. As a full size pilot I was never too happy with the design of the front strut
mount, (I know the shyte they can take) guess this is a good time to reinforce. (Had already done a partial job by bracing from the mounts to the decking, think I'll glass as well now)
I'm going to move the leg forwards by about half an inch as well. Most of the damage sustained was caused by rearwards flex into fuselage bottom.
Sooo p.ssed off it happened, I was going to fly the wings of her tomorrow!
Bit disapointed with the t/o perf. P160SE I would have thought she'd be ballistic! Maybe I need to increase front strut length?
Not happy with the cr.ppy wheel well inserts either, anyone got any ideas?
Just read the above and I sound negative... I'm not! Can't wait to get air under her wheels again! It's the noise... I think!
I was suprised by the power of the rudder by the way!
Mate rang me tonight and said he knows of a cheap Hanger 9 Extra, told him I'd sooner spend the cash on Avtur!

Andy M (Head in repair mode!)

RE: Boomerang XL C o G ????
 

Congrats on the succesful first test flight! My Jet A1 nose strut did exactly the same thing, but it was on concrete so it dragged for a bit until the nose gear mount broke. Easy fix, just some slight scrapes on the bottom of the nose....I also took apart and re-assembled my struts using Loctite. No problems in the last 50+ flights.

I have a wimpy older P120 (S/N in the 600 range) and I can get off with full fuel (almost 4 liters!) in less than 40' with no wind and in half that with 15 degrees of flap and a sight breeze...brakes on, full up, release brakes as motor spools up, nose will come up in 15' or so, ease off elevator as soon as the mains break ground. Grass will take a bit more distance but if the CG is right you should be able to do the same. :)

With a P160 you should be able to go vertical right after T/O....:D

Barry

PS - Re the rudder...yes it is strong...after burning off some fuel I can fly knife edge in both directions all day. It will spin like a top, better inverted than upright, something I have not enjoyed (or tried) with most of my other jets. Recovery is immediate. It will go flat inverted with some power on but so far has recovered quickly as soon as power is pulled. A fun manuever I have not been able to do with any other Jet so far.

RE: Boomerang XL C o G ????
 

The XL is great I have a jb 165 and over 90 flights on it the c/g is spot on with 13 c size nicads in the nose an 5oz of lead in the tail

RE: Boomerang XL C o G ????
 

Hmmmm,

Having read about needing to keep weight as far forward as poss I did so.

I am now about 2.5" too far in front of the CogG which itself is a little too conservative to start with??

Got 2 3800mah Nimh packs up front at about 11oz each. Guess I'll be swapping them out for 3700Lipos to save 10oz which should sort things out.

Anyone found their CofG suddenly came out waaaaaaaaaay forward??

Rgds,
Mark

RE: Boomerang XL C o G ????
 

Yup. planned all along to avoid lead in the nose. Mounted 3 duralites Waaaaaaaaaaay up front, along with my smoke pump. Was surprised when I was able to mount my Titan at the aft edge of the range. I was originally worried that I would need to mount the engine deep into the fuse.