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new Arf Boomerang 14lb thrust

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new Arf Boomerang 14lb thrust

Old 02-28-2005, 03:37 AM
  #51  
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Default RE: new Arf Boomerang 14lb thrust

Dave

The booms come with wire skids in case you touch them on landing / takeoff. There is still a bit of clearance with the model in a good takeoff attitude. At our field the runway drops away at the end of the tarmac and we tend to let turbine models fly straight off the end a bit like a carrier take off! When landing you can actually fly finals below the level of the runway and then pop up and drop the model onto the runway. sounds scary but it works! Got to finish the model may fly p.m. today if the weather holds up.

John Agnew
Old 02-28-2005, 06:32 AM
  #52  
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Default RE: new Arf Boomerang 14lb thrust


ORIGINAL: john agnew

Dave

The booms come with wire skids in case you touch them on landing / takeoff. There is still a bit of clearance with the model in a good takeoff attitude. At our field the runway drops away at the end of the tarmac and we tend to let turbine models fly straight off the end a bit like a carrier take off! When landing you can actually fly finals below the level of the runway and then pop up and drop the model onto the runway. sounds scary but it works! Got to finish the model may fly p.m. today if the weather holds up.

John Agnew
John,
Great! Alan seems to have thought of everything except hardware.

Dave
Old 02-28-2005, 07:57 AM
  #53  
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Default RE: new Arf Boomerang 14lb thrust

Guys

Now for the bad news! To achieve the suggested CG of 150 mm back from the leading edge I will have to add 1 1/2 lbs of lead to the nose, this is not good! Alternatively by my calculation a 25 % CG would be 187.5mm back from the LE . The root chord is 450mm the tip 250mm giving an average of 350mm at mid span 25% 0f this is 87.5mm plus the difference between the mean chord and LE is 100mm giving 187.5mm.
This can be achieved with only12oz of lead giving a dry weight of 14lb 8oz with a full hopper tank.

Would any one like to confirm my CG calculation before the model is flown? I cetainly feel that 150mm is too conservative if my calcs. are correct.

To be fair to Allan he suggests moving the CG rearwards after initial flights without giving a specific figure.

John Agnew
Old 02-28-2005, 08:56 AM
  #54  
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Default RE: new Arf Boomerang 14lb thrust


ORIGINAL: john agnew

Guys

Now for the bad news! To achieve the suggested CG of 150 mm back from the leading edge I will have to add 1 1/2 lbs of lead to the nose, this is not good! Alternatively by my calculation a 25 % CG would be 187.5mm back from the LE . The root chord is 450mm the tip 250mm giving an average of 350mm at mid span 25% 0f this is 87.5mm plus the difference between the mean chord and LE is 100mm giving 187.5mm.
This can be achieved with only12oz of lead giving a dry weight of 14lb 8oz with a full hopper tank.

Would any one like to confirm my CG calculation before the model is flown? I cetainly feel that 150mm is too conservative if my calcs. are correct.

To be fair to Allan he suggests moving the CG rearwards after initial flights without giving a specific figure.

John Agnew
Bummers! AND this is with a manual start W54? WOW! what kind of weight is needed for an auto start P60????
Alan tells me the plane in the video is box stock with retracts and weighs in at 14#. Maybe Alan can shed some light on this? How about some pictures of the insides of the plane shown on the video? I understand it is powered with a P60?

Dave Rigotti
Old 02-28-2005, 09:57 AM
  #55  
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Default RE: new Arf Boomerang 14lb thrust

Dave Hi,
The prototype model is indeed powered by a P-60. I know Alan did have some weight in there to get the CG forward but I certainly don't remember it anywhere near 1.5lbs. I also know that I l flew it with the weight in and it was too nose heavy so Alan removed some on subsequent flight which made handling a lot better for me. I am sorry that I don't have exact figures as I was just flying Alan's model.
Normally Alan would be straight on here to help but I know he is now in the US clearing the us delivery of the intro's and prepping for Florida Jets. I will see him On Thursday in Florida so if he hasn't answered by then, which I am sure he will I will tell him to get on here and help you guys out.
Old 02-28-2005, 10:22 AM
  #56  
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Default RE: new Arf Boomerang 14lb thrust

Guys

The model is now 100% complete. Final weight 14lbs 10oz CG at 175mm behind LE, 12oz lead right up in nose (In noseleg compartment)

You may not need as much noseweight with a P60 as it has a heavier ecu battery than the manual start Wren 54 and you can also mount the solenoids and ecu at the front. My model has a 6 ounce Graupner hopper which is always full mounted right behind F1 under the radio tray.
You can see this in the gear install photos. I still don't believe this model can be built at 14lbs unless you use very light servos.

Sorry no flying today as it's crap weather here, hope to get out sometime thia week. A picture of the finished model and one with my Savex size L39 for comparison. I don't know why Allan used to call this the Baby Boomerang as it ain't no baby!
This is a large model and should be vey easy to see in the air.

Any more queries regarding the model don't hesitate to ask.

John Agnew
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Old 02-28-2005, 11:19 AM
  #57  
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Default RE: new Arf Boomerang 14lb thrust

Great looking model....Didn't realise that it was that comparable in size to the Savex L39! Intro looks to be a great little package, I'd like to hear how well it goes with a 44.

Dave
Old 02-28-2005, 11:47 AM
  #58  
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Default RE: new Arf Boomerang 14lb thrust

Dave

I think my photo is slightly misleading. It was meant too show how much bigger than the L39 the Intro is!

I did think of putting my 44 into the Intro. I think it would be possible to get the weight down to about 12lbs dry if you did this.

The problem with the CG is the long tail moment which probably makes the model so nice to fly. With a 44 you could use light servos in the tail and reduce the amount of weight required up front.

I still think the ideal model size for a trainer for the 44 would be about 65" span weight 9/10lbs, mini servos and light retracts or fixed gear.

Unless someone comes up with a suitable model I may build my own.

John Agnew
Old 02-28-2005, 11:52 AM
  #59  
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Default RE: new Arf Boomerang 14lb thrust


ORIGINAL: john agnew
I think my photo is slightly misleading. It was meant too show how much bigger than the L39 the Intro is!


If you want to knock up a trainer for the MW44 that's cool looking. I'll 'av one
Old 02-28-2005, 11:58 AM
  #60  
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Default RE: new Arf Boomerang 14lb thrust

Dave

This is my IAD Serpent which flew great at 17lbs with a Ram 500. I put my 44 in it when I was waiting for my L39. Took some battreies etc out and got the weight down to 12lbs or so. It flew very well with limitations on the vertical. A 65" version of it would be perfect for the 44.

Now tell me which is the beter lookiong model?

John Agnew
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Old 02-28-2005, 12:05 PM
  #61  
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Default RE: new Arf Boomerang 14lb thrust

I can't answer that! I look forward to seeing your flight report and video?

Cheers
Dave
Old 02-28-2005, 12:24 PM
  #62  
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Default RE: new Arf Boomerang 14lb thrust

i no its of topic but my mate flys the iad serpent with a kj66 in it 3litters of fuel it a nice model
Old 02-28-2005, 03:11 PM
  #63  
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Default RE: new Arf Boomerang 14lb thrust

Centre of gravity

For anyone building the Intro. I have confirmed that a 25% CG is in fact 187.5mm back from the leading edge as I previously stated and this should still be a safe point. Maybe Allan will confirm when he gets a chance. Little or no nose weight should be required to achieve this CG depending on gear install / turbine / batteries.

John Agnew
Old 02-28-2005, 03:31 PM
  #64  
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Default RE: new Arf Boomerang 14lb thrust


ORIGINAL: john agnew

Centre of gravity

For anyone building the Intro. I have confirmed that a 25% CG is in fact 187.5mm back from the leading edge as I previously stated and this should still be a safe point. Maybe Allan will confirm when he gets a chance. Little or no nose weight should be required to achieve this CG depending on gear install / turbine / batteries.

John Agnew
John,
Sounding better! The straight trailing edge puts the CG "looking" too far aft. 25% of MAC should be a nice safe place to start. Thanks for the updates!

Dave Rigotti
Old 03-01-2005, 04:46 AM
  #65  
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Default RE: new Arf Boomerang 14lb thrust

Guys

It's the first of March! The lucky people are at Florida Jets, its snowing in Glasgow and the forecast for the next ten days is s**t.Now we know why there are so many people of Scottish descent in the US, they just got tired of the weather!

I don't think the Intro is going to maiden anytime soon!

John Agnew
Old 03-01-2005, 05:03 AM
  #66  
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Default RE: new Arf Boomerang 14lb thrust

John,

Put skis on the bloody thing, that would be a first!!!!

Gazzer
Old 03-01-2005, 03:03 PM
  #67  
john agnew
 
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Default RE: new Arf Boomerang 14lb thrust

Guys

I believe there may be a window in the weather tomorrow p.m. Still cold but sunny and 10mph winds, not promising but I am really keen to fly this bird. Keep 'em crossed.

John
Old 03-01-2005, 03:08 PM
  #68  
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Default RE: new Arf Boomerang 14lb thrust

john,
I KNOW how you feel! i have a bruce Tharpe Reaction 54 ready to go...except the weather....
Keepin' 'em crossed!

Dave Rigotti
Old 03-01-2005, 03:37 PM
  #69  
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Default RE: new Arf Boomerang 14lb thrust

A few pictures from Abingdon Dec 2004.
Including Alan and friends!
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Old 03-01-2005, 04:35 PM
  #70  
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Default RE: new Arf Boomerang 14lb thrust

Thanks for the pictures!

Dave Rigotti
Old 03-02-2005, 03:36 AM
  #71  
john agnew
 
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Default RE: new Arf Boomerang 14lb thrust

Guys

I like the colour scheme on the two centre birds. The cammo scheme looks good too!

We have sunny skies 40 o F and forecast 10knot wind,
it's looking possible.

John
Old 03-02-2005, 07:31 AM
  #72  
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Default RE: new Arf Boomerang 14lb thrust

I seem to recall that Alan Cardash mentioned that he designed the BI to be able to take a 2L fuel bottle. From the more recent pics, I see that 2l plastic bottles were used as a fuel tank. Does anybody know where to source the cap with fittings for the bottle?

I have a couple of empty prosynth 2L fuel bottles available and would like to carry the extra 500ml that these would allow (vs the dubro 50oz).

Are there any cons to using a UAT, the pics all seem to have aircraft with UATs fitted!

Thanks
Old 03-02-2005, 07:34 AM
  #73  
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Default RE: new Arf Boomerang 14lb thrust

Actually, looking at Eric's pictures it looks like a bung has been fitted to the standard bottle cap. I assume that the fuel system is not pressurised on the up stream side of the pump, which would make this a fairly easy assembly.

Am I correct ?
Old 03-02-2005, 07:39 AM
  #74  
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Default RE: new Arf Boomerang 14lb thrust

Rory,

Dave Wilshere, at motors and rotors sells some great fuel cap fittings, will convert most bottles to a suitable fuel system!!!


Gazzer
Old 03-02-2005, 11:56 AM
  #75  
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Default RE: new Arf Boomerang 14lb thrust

Guys

"Look upon my works ye mighty and despair"

The intro has flown! Here is the story. Departed home in sunshine 39oF light wind, drove through heavy snow shower on way to field thinking I must be mad! Arrived at field to find one other idiot, sun comes out, tarmac runway is wet 1/2" of snow on grass, decide to fly.

Assemble model, takes 5 minutes, wing locks now adjusted and working smoothly,fuel up, Wren starts immediately at first attempt, carry out range checks, refuel and carry her out to tarmac, decide on down wind takeoff to avoid climb out over trees in case we get a sudden silence!
Max rpm set at 150k which I think is about 12 / 12 1/2 lbs thrust. Start takeoff run at idle, model accelerates quickly and tracks straight, pull in about 50% elevator and model lifts off smoothly after about 40 / 45 yards.

Maintain shallow climb out to allow model to gain speed, trim looks ok at this time, commence shallow bank / climb to right and fly upwind leg, bring throttle back to about 60% and make 180o turn back downwind. Model seems very stable in both pitch and roll, start to fly racetracks at about 150 feet one click of right trim and one of down and model is flying hands off, need about 60% forward stick to maintain nice cruise speed ( remember there is about 2/3lbs thrust still to come) Try slow roll, nicely responsive to aileron (all throws as instructions) come down to about 30 feet for full throttle pass, very stable, flies like pattern model. couple of rolls, just a dab of down to keep her level, climb to 150 feet and slow down into wind, again very stable, no sign of wing drop, come round again at about 30% power and drop flap, nose lifts a little more than I like so reduce flap to about 1/2 this is better. Believe it or not the timer is now telling me 6 minutes are up!

Reduce height to about 50 feet and try landing approach, off power at about 10 feet and we are slightly too fast over threshold , keep her level and apply full power, climb away with no drama , round again off power slightly earlier and grease her in right on the numbers ( Yes I know there are no numbers on the grass!) Halway along the langding roll the right main leg collapses, model slows to a halt no apparent damage, but flying is over for today.Remove nappy!

Back home check the leg and find the laminated plywood block has split along a lamination, needs longer screws, no damage to gear mounts.

To sum up

The Intro is very easy to fly and seems very stable at my CG 175mm back from LE.The model is easy to see and orientate in the air.
It is quick to assemble at the field. It is slightly slower than I anticipated but I will reserve judgement until I turn up the rpm/s to max.
Landing is a breeze, I am sure that I hit a hole in the grass as we have had cows on the grass during the winter when the ground is soft
and I think this caused the gear leg to break the mount.
This is a perfect beginners model and also good for the days when we don't want to fly a more demanding job.

The Wren 54 Mk3 is a lovely piece of work. I didn't even think about it when it was in the air.

I am looking forward to my next flight already and can now relax a bit now the hard part is over.

Unfortunately I forgot my camera so you will just have to take my word that all the above is true!

John


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