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Boomerang Sprint Build Thread!

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Old 04-05-2011, 11:44 AM
  #1726
Colin Gontier
 
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Default RE: Boomerang Sprint Build Thread!

Equipment board given a top coat. Turbine and air system ancillaries going in - all very straightforward..
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Old 04-05-2011, 11:48 AM
  #1727
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Default RE: Boomerang Sprint Build Thread!

And now the finished product !

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Old 04-05-2011, 11:58 AM
  #1728
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Default RE: Boomerang Sprint Build Thread!


Quote:
ORIGINAL: Aviator-No

Hi,

I have a few questions....?
My Sprint fly hands of straight at half throttle.
If I increase the speed it rises it's nose a bit, and lower the nose when decreasing the speed.
I have the Elevator trimmed a bit down to make it fly straight at half speed.
Upside down it dives a lot.
CG is almost spot on (5 mm aft of carbon rod)
The turbine is is raised in front a few mm.

Do I have thrustline problem or wing and stabilizer incidence issue?


Brgds
Svein-Roe

What turbine do you use? The Boomerang set up means on turbines with higher exhaust velocity, the faster moving air under the tail produces lift on the underside of the tail, drawing it down and making it pitch up.
Changing the turbine angle (down at the back) gets the exhaust away from the tail surface. Do this and re trim at 2/3rds power. Then try inverted also at 2/3rds power.
The high tail you will always get at least a small trim change, you can mix it (throttle to Elevator) but normally a good compromise is possible.


Dw
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Old 04-05-2011, 03:01 PM
  #1729
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Default RE: Boomerang Sprint Build Thread!

Dave, thanks for that explanation. I never knew why, but all of my Boomerangs have needed at least a thick washer under the front of the turbine mount. My new Sprint needed a bit more (see picture). Plus, I have about 3 mm of down trim on the elevator. Maybe because I'm using a P-120 turned down.

Jack Needham
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Old 04-05-2011, 06:08 PM
  #1730
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Default RE: Boomerang Sprint Build Thread!

Hi Dave,

Im running a Simjet 2250 pushing 10 kg on my fishweight :-)

I have a small washer under the front. I have did try to ad another, but it's not possible since the starter is touching the bar under the canopy/hatch. I need to modify it or remove it.

Svein-Roe
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Old 04-06-2011, 03:32 AM
  #1731
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Default RE: Boomerang Sprint Build Thread!


Quote:
ORIGINAL: gontflyer

And now the finished product !

Not finished yet it has no pilot, and will never look finished until it has one!
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Old 04-06-2011, 04:43 AM
  #1732
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Default RE: Boomerang Sprint Build Thread!

Pilots crash airplanes....
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Old 04-06-2011, 07:20 AM
  #1733
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Default RE: Boomerang Sprint Build Thread!


Quote:
ORIGINAL: Xairflyer


Quote:
ORIGINAL: gontflyer

And now the finished product !

Not finished yet it has no pilot, and will never look finished until it has one!
And a full scale cockpit, pitot tube, anti stall warning tab and a drain point for the fuel tanks to check for water, where do you stop. All of our models are drones so they don't need a pilot unless they are trying to be something they are not, Oh hang on they are.

Mike
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Old 04-06-2011, 10:04 AM
  #1734
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Default RE: Boomerang Sprint Build Thread!

Why have a canopy then, the very fact it is there is because it is meant to be the cockpit of the aeroplane where the pilot fly's it from.

If you are not going to actually make it what it is there for, then better to not have one at all and black it out like you done on your recover, much better looking than a blank cockpit which just looks bad and unfinished!
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Old 04-06-2011, 10:10 AM
  #1735
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Default RE: Boomerang Sprint Build Thread!

We will have to agree to disagree on this I think, IMO it make no difference at all, I just think sprayed out glazing looks better, unless you want to show off the workmanship inside.

Mike
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Old 04-06-2011, 11:36 AM
  #1736
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Default RE: Boomerang Sprint Build Thread!

Interesting side discussion here: For me, on my 'warbirds' - jets and props - I have pilots and cockpits. On sport airplanes, scale or not, they are either pilotless or the canopy is 'silvered' out. Don't really have an explanation for it...seems to just have evolved that way over time.
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Old 04-08-2011, 06:00 PM
  #1737
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Default RE: Boomerang Sprint Build Thread!

I was talking to a friend of mine that has a lot more turbine exp. than I do about my issue with the engine being flooded and having a hot start that I posted about on previous page. He told me what I did wrong because it has happened to him before. I started the engine on propane and had the manual shut off valve for the fuel in the closed position. When it was switching over to fuel I could tell that it wasn't sounding right. I reached down and opened the valve and all heck broke loose!

I guess the pump being under pressure and suddenly being released must have filled the engine full of fuel and caused all the trouble. Has anybody else ever pulled this dumb stunt besides me?

Chris
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Old 04-08-2011, 06:18 PM
  #1738
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Default RE: Boomerang Sprint Build Thread!

Oh he'll yes. I burned the a_s off an Isobar once doing that!!!!
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Old 04-08-2011, 06:27 PM
  #1739
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Default RE: Boomerang Sprint Build Thread!

Good, I'm glad that I am not the only one that has happened to! Sorry about your airplane though! I guarantee that I will not do that again! It was pretty scarry watching all those flames shoot out and up!

Chris
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Old 04-09-2011, 08:44 AM
  #1740
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Default RE: Boomerang Sprint Build Thread!

Another advantage of Kero start, that whole senario can not happen, tap not on it can't start at all therefore no flames if you forget to turn it on.

Mike
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Old 04-09-2011, 01:08 PM
  #1741
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Default RE: Boomerang Sprint Build Thread!

Hello Everyone,

I'm looking for information on the depth of the holes in the center section which receive the aluminum dowels. I found the same question back on page 18, but I did not see a response. On my kit the wing dowels only go in about 10mm and that just doesn't seem like enough depth.

Thanks,
Jaime
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Old 04-09-2011, 02:11 PM
  #1742
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Default RE: Boomerang Sprint Build Thread!

They have to at least go deep enough in the center section that the screws can tighten down on them to hold the wing on. There are four screws in the top of the wing that you have to cut out the hole openings in the monocoat and then install the screws from the top. They will hold the wing in place during flight after you tighten the screws down on the aluminum rods. The aluminum rods screw into each of the wing panels.

Chris
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Old 04-09-2011, 02:29 PM
  #1743
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Default RE: Boomerang Sprint Build Thread!

Also I had to sand down all the aluminum rods to make them slide into the holes. My carbon fibre tube also wouldn't fit so I had to take a dowel with sandpaper glued to it and sand the inside of the center section until the tube would slide in the center section.

Chris
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Old 04-09-2011, 08:29 PM
  #1744
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Default RE: Boomerang Sprint Build Thread!

Chris,

I meant the other dowels; the two dowels that you're suppose to glue to the front of the center section.


Jaime
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Old 04-09-2011, 11:08 PM
  #1745
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Default RE: Boomerang Sprint Build Thread!

Jaime

You might want to drill deeper holes for the front wing dowels. A good guide for the depth is to make sure the notched part of the dowel is contained inside the wing section (to take the epoxy used to secure it). Make sure you use the same size drill as the dowel.

Also ensure you leave enough of the dowels outside of the wing so they fit well in the plastic sleeves. Do a dry fit to the fuselage before you glue it all up to make sure you are satisfied that it's all good.

Regards

Colin
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Old 04-10-2011, 08:52 AM
  #1746
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Default RE: Boomerang Sprint Build Thread!


Quote:
ORIGINAL: Jaime_Arenas

Chris,

I meant the other dowels; the two dowels that you're suppose to glue to the front of the center section.


Jaime
Is this something that is on the latest kits? I have't any dowels on my sprint....
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Old 04-11-2011, 01:18 AM
  #1747
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Default RE: Boomerang Sprint Build Thread!

If you strip the covering properly on wing and fuselage wingseat and follow the instructions re gluing the wing on, once the initial epoxy glue has set, you can get inside the fuselage and add plenty more glue between the wing leading edge and the former it butts up against, and one or two small balsa fillets (1/4" square or so) along the each side of the fuselage if you want to be extra sure. This is how I have all our demo planes built.

I felt that the alloy pins were not necessary so I instructed the factory to delete them some time back, but it looks as though they have decided unilaterally to leave them in.
Bearing that in mind, 10 mm is plenty if they are well glued in place. As I said, I personally don't use them at all and it has caused no problems so far!
Do not use them to make the centre wing removable. That would require a re-think altogether considering the aerobatic tricks and allied stresses associated with high G manoeuvres, particularly negative, so that is an absolutely definite no-no!
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Old 04-22-2011, 06:01 AM
  #1748
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Default RE: Boomerang Sprint Build Thread!

I have a set of DreamworksRC trailing link Sprint struts for sale at a good price, if anyone is looking for some:

http://www.rcuniverse.com/market/item.cfm?itemID=738289


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Old 05-06-2011, 02:31 AM
  #1749
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Default RE: Boomerang Sprint Build Thread!

Hi guys, Im new here
I just ordered a Boomerang Sprint with a Jetcat P-80SE from Als Hobbies while I was over in the UK on holiday which will be sent back to NZ.
I'm 15 years old and been flying since I was about 9. While I was in the UK I went to Paul Heckles school of model flying and had a few good hours flying some of their aircraft. Unfortunately all of their Boomerangs were getting overhauled so I just had to spend the day flying their aerobatic machines. I learnt a lot while I was with them and they fully recommended the Boomerang Sprint as a first jet because of how it flys so here I am.
At the moment Als Hobbies are waiting for the Jetcat which will take 2 days to arrive and also the retracts which will take 10 days. 
I will take time to build it (yea right) to make sure this plane doesn't go up in flames on the first flight. I've looked through this forum and picked up many helpful tips since this is my first turbine. Ive also got my father and a friend (who has a degree in engineering of some sort) who is fascinated by RC aircraft and surely will help me assemble the model.   
I'll update you guys when she arrives. By the way it is in the red sports scheme, The P-80 is using kero start and I'm using jettronic valves for retracts and brakes since these are my first retracts. Yes I know!! First turbine and retracts and I'm 15 years old!!
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Old 05-06-2011, 03:03 AM
  #1750
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Default RE: Boomerang Sprint Build Thread!

Good luck with it, and don't be afraid to ask questions even if you think it is something minor, we all have to start somewhere.
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