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Boomerang Sprint Build Thread!

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Old 03-20-2011, 07:42 PM
  #1701
Jaime_Arenas
 
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Default RE: Boomerang Sprint Build Thread!

Hi folks,

I just received my Sprint a few days ago and I've started the process of putting it together. I have a specific questions about the sprint and a general questions about fuel systems. The Sprint has a couple of wire skids hanging on the the end of the booms that I assume are there to protect the rudders from ground strikes. Are the skids suppose to be free to rotate? Mine do and have already caused some minor damage to the booms just forward of their mounting point.

My question about fuel systems is this: should I install barbed fittings to the brass tubing used in the fuel tank? I know that the fuel lines have to be safety-wired to any hard line in the system, but does a Kero fuel system require the extra step of soldering the barbs onto the hard fuel lines? I use barbed fitting on my Gas planes and wanted to know if the practice is necessary or recommended on Kero fuel systems.


Thanks,
Jaime
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Old 03-20-2011, 11:08 PM
  #1702
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Default RE: Boomerang Sprint Build Thread!

Hey Jamie
Congrats on your new Sprint.. I am sure you will love the way it flies.
To try and help with your questions....
1) Yes the wire skids are supposed to rotate. It's rare that they should o so and cause damage in transit, but hopefully the marks they have made should disappear with a bit os attention with a heat gun. We did try fixing them solid on early kits, but found they could break out. The loose way seems to be more forgiving and last longer.
2) You do not have to used barbed tubes in the fuel line.. Just like you do not have to used lock wire. However. In my opinion its an option worth taking. The barbed tank tubing, is by far the best way to get a really snug fit on the lines, and its also the best way to counter any expansion, or loss of flexibility in the fuel tubing used.
Regards Al
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Old 03-21-2011, 05:12 AM
  #1703
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Default RE: Boomerang Sprint Build Thread!

Chris

In reply to your question about balancing, see post #1184. That's how I balanced mine.

Jack
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Old 03-21-2011, 05:22 AM
  #1704
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Default RE: Boomerang Sprint Build Thread!

Jamie

I always have an "oh s**t" moment when I begin to hook up my fuel lines and realize I didn't install any barbs. So, I rough up the tubing and put a layer of JB Weld on the ends of the tubes and shape it like a donut. When set, the fuel tubing slides right over them. Then put on the tie wire. Very secure. I've even used Hysol for this with good results.

Jack
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Old 03-21-2011, 02:56 PM
  #1705
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Default RE: Boomerang Sprint Build Thread!

Thanks Al and Jack. Adding the barbed ends to the hard lines is on the check list now.

I think the wire skids on my kit simply need to be bent out a bit to avoid rubbing on the lower surface of the boom. Unfortunately on one side I will have to peel back the covering and patch up the balsa before I iron down the covering. No big deal the job should be done in 10 minutes or so.


Jaime
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Old 03-22-2011, 09:54 AM
  #1706
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Default RE: Boomerang Sprint Build Thread!

HI GUYS

Just thought I would share this photo a buddy of mine took last weekend of my Sprint on finals, full flap and crow deployed. Zero WIND and the start of the SUMMER Sun.

Regards

Mick
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Old 03-28-2011, 01:25 PM
  #1707
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Default RE: Boomerang Sprint Build Thread!

I did a bit of vinyl cutting over the weekend.... Had a bit of fun with the tail of my Sprint....
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Old 03-28-2011, 02:24 PM
  #1708
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Default RE: Boomerang Sprint Build Thread!

That is great and so original but where's the mouse???
......and what do I have to do to get a pair to put on mine?????
Alan
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Old 03-29-2011, 02:15 AM
  #1709
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Default RE: Boomerang Sprint Build Thread!


Quote:
ORIGINAL: skaap2k

I did a bit of vinyl cutting over the weekend.... Had a bit of fun with the tail of my Sprint....
You should'nt have been playing about with stickers on the best weekend we have had this year, you should have been at Offaly Jets you missed a fantastic weekend we clocked up 70 jet flights between us.
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Old 03-29-2011, 02:23 AM
  #1710
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Default RE: Boomerang Sprint Build Thread!

I know!
I got caught up this Saturday - and only ended up fixing the boomerang on Sunday morning!! I got 3 flights in, turns out the clunk in my tank is completely clogged up and we got away very very lightly with no incidents, but my UAT was practically empty on the last flight!
PS - look what arrived....
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Old 03-29-2011, 02:46 AM
  #1711
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Default RE: Boomerang Sprint Build Thread!

PS - Alan, I sent you an email
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Old 03-29-2011, 03:07 AM
  #1712
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Default RE: Boomerang Sprint Build Thread!

That is even worst! you still went flying but not with us, not impressed!
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Old 03-29-2011, 09:01 AM
  #1713
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Default RE: Boomerang Sprint Build Thread!

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
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Old 03-29-2011, 10:50 AM
  #1714
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Default RE: Boomerang Sprint Build Thread!

Sounds spot on to me, any aeroplane will start to climb when power is increased as the lift increases with the square of the speed, likewise when power is reduced it will drop. If the pitch up and down is a lot then it is a thrust line issue.

If you need a lot of down elevator when inverted then it is nose heavy.
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Old 03-29-2011, 11:27 AM
  #1715
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Default RE: Boomerang Sprint Build Thread!

add a mix in your radio throttle to elevator..only do very small amounts.. mine was oposite. at full throttle mine would nose down a little. programed a mix and problem solved... or you can adjust the engine.. thats a pain in the butt..easy fix is the mix...take care
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Old 03-29-2011, 02:09 PM
  #1716
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Default RE: Boomerang Sprint Build Thread!

Thrust line should be level with the top of the fus with the canopy removed, easy fix, as Xflyer says if you need loads of down in inverted then its nose heavy.

Mike
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Old 03-29-2011, 02:28 PM
  #1717
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Default RE: Boomerang Sprint Build Thread!

I put a new engine in my Sprint after the original had a bearing go and burned it up. It was going to cost me more to fix it than it was worth. The new engine was running great on the ground until the first flight. I flew it for 6 minutes and when I was about to touch down on the runway I could hear the engine shutting down. I called the distributor and told himof the problem but he said to fire it up again. The next time I started it it flamed up and cooked the stab even though I was using a start tube. It even dripped fuel out of the exhaust pipe and into the back of the fuselage and caught the wood on fire. We put it out with an extinguisher and I called distributor again and told him what happened. He said it might have been flooded so try it again. I took the stab off and tried it again with the same results but at least this time the stab wasn't hurt anymore! I packed the airplane up and took it home.

I called distributor again and he said to send it to him. When he got it he fired it up and said it was still flooded on the first start but once it cleared out it started and ran fine 6 or 7 more times. It is on it's way back to me and a friend of mine has a test stand that we are going to fire it up on a few times before it gets put back in the Sprint.

I said all of this to ask a question. Has anybody ever had an uncommanded shut-down that caused a flooded condition? Will the pump keep running or is the ECU supposed to shut the pump off when the engine shuts down? I don't know what caused the shut down, I still had half tank of fuel and UAT was still full. Maybe an air bubble in the lines? And how can I keep it from happening again. I am running a ball shut off valve between the solenoid and engine that is always shut off during fueling. Anyway the distributor in question has been excellent and this is not a bash thread about anybody or anything. I am still pretty new to turbines and want to keep something like this from happening again.

Thanks,
Chris
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Old 03-29-2011, 02:29 PM
  #1718
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Default RE: Boomerang Sprint Build Thread!

I always talking about a thrust issue.. plane was nose heavy.. the engine set level but always had a problem at full throttle to nose down slightly.. was nothing crazy but wasw noticable...I just mixed in some up elevator with full throttle and fixed problem perfectly...maybe it increased a little drag but who cares its a boomer...I did have one of the first sprints out so maybe it was off a little..
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Old 03-29-2011, 03:51 PM
  #1719
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Default RE: Boomerang Sprint Build Thread!

you will have to let me what turbine your using.. if you dont want to say you can pm me... but yes the fuel pump will shut off once the engine is shut down...
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Old 03-29-2011, 04:13 PM
  #1720
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Default RE: Boomerang Sprint Build Thread!

That is to say the fuel pump SHOULD shut off once the engine is shut down. But...., that ain't the way it always works. The TEMS ECU cost me an airframe once cause it freaked out, at Mississippi Afterburner ('03, I think) and continued to pour fuel as fast as it could into the combustion chamber. It is not supposed to happen that way, but that does not mean it won't!!!!
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Old 03-29-2011, 10:59 PM
  #1721
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Default RE: Boomerang Sprint Build Thread!

Hi,

In my case it's the same throughout the flight, fully loaded with fuel or empty.
I don't think it's nose heavy. I added 35 g of lead on the tail just to check, and there was no change.
Of course it was lighter on the elevator, but did't solve the piching problem with throttle.

On my Intro i had to raise the aft part on my turbine, to avoid it from piching down when increasing speed.
And it was not noseheavy for sure. I did slow flybyes with tails touching.

A throttle to Elevator mix is a solution... after I have tryed all other options. I like to have it set up mechanical 100 %

Brgds
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Old 03-30-2011, 06:57 AM
  #1722
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Default RE: Boomerang Sprint Build Thread!

Sounds like you have a tailplane incidence problem, if I remember you said you fly with down elevator trim, try packing up the front of the tailplane by a washer or so.

Mike
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Old 04-05-2011, 11:27 AM
  #1723
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Default RE: Boomerang Sprint Build Thread!

We have been asked to do quite a few turnkey builds recently so I thought I would share a few pictures of a turnkey Sprint build I have put together for a customer in the past few days. He is coming over from India next week to take delivery so just need to get it maidened and dialed in...


First pics, out of the box, servo hatches film cut out and ironed down, ailerons, elevator and flap attached

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Old 04-05-2011, 11:32 AM
  #1724
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Default RE: Boomerang Sprint Build Thread!

Next...

More control surfaces attached, main retract units installed, wheel wells trimmed and tested for fit. Film cut away to glue wing centre section and start of work on front retract
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Old 04-05-2011, 11:38 AM
  #1725
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Default RE: Boomerang Sprint Build Thread!

Nose wheel bay covered in a few coats of grey primer - good if you are operating off grass as despite there being a cover to go over this area bits of grass inevitably get flicked up into this area.

A couple of spacers to make the chosen nose retract unit sit at the right height on the rails.

Wing centre section now secured with a combination of supplied locating dowels, bolts and aeropoxy. Beginning to look like a Sprint..

I always give the whole install bay inside the fuselage a coat or two of finishing resin to seal against any fuel spills and for general longevity of the airframe. The equipment board gets some special treatment of between 4 and 6 coats of gradually thinned finishing resin, sanded through the grades between each coat and then primed ready for a "shiny" paint finish
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