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Old Sep 22, 2005, 11:51 AM
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Ben Buckle Falcon

Greetings all,

I have been hankering to build a falcon for many years and have finally ordered a set of plans from Colin Buckle. I have had these delivered to a UK address where I can pick them up during a visit in Nov.

My intention is to power it with an Axi 4130/16, looking at 16 Nimh 3300's turning a 15x8 inch prop to start with.

Until I can get my hands on the plans, I have no idea of the wing area to guesstimate the wing loading and power requirements. I phoned Colin and he indicated that the AUW with an OS 60 was somewhere in the region of 10 lbs, but couldn't tell me the wing area.

If any of you gentlemen or ladies out there have built the Falcon, I would appreciate any info (especially if you have dropped in an electric motor), with regards to AUW, bare airframe weight, build problems, etc.

Thanks

Tim
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Old Sep 22, 2005, 05:00 PM
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cant help apart from i rebuilt an ohlsson sideport sparky for a chap last year and he is building a falcon for it. if you could find out how much power it puts out you could possibly work out an equivalent power for your electric.
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Old Oct 15, 2005, 06:30 PM
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That would be the "old" OS60, open rocker version, which was sweating hard to put out 1/2 HP. Take heart from Peter Miller's comment that "FS-60s are the most common power unit for KK Falcons, a large 8ft span vintage model which tends to be heavier than average". A 12x6 flew them beautifully; such a prop absorbs about 500W at 9K, and the resulting pitch speed of about 55 mph would be more than enough for a Falcon loaded at a "high" figure of 20ozs/sq.ft. The Falcon sports 1210 sq.in. wing area.
I'm sure with 16 cells this clean airframe would be fine on 400W (say 20A in the air) - remember the originals flew on Anderson Spitfires with heavy spark ignition at these power and weight loadings. In fact you would be pretty near bang on the button to find out "what were they like to fly..."

Good luck
C
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Old Oct 17, 2005, 07:28 AM
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Gentlemen,

Thanks for the replies. With that wing area, it certainly gives me good idea what I will need to do with regards to getting the weight down to an acceptable wing loading.

Ideally I would like to see sub 16 oz/ft2. My powerpack as chosen will weigh in around 1.5 kg +/-. That gives me something in the region of 2.3 kg for the fully covered (minus powerpack) airframe - should be do-able.

I saw a small article somewhere discussing the wing joiners-these being hardwood and ply of considerable proportions. I have not yet got my hands on the plans (got to wait two more weeks), But I have strong feeling that all large uses of hardwoods as spars and similar will be replaced with CF tubes and alternative lightweight structure.

Either way, this is going to be one of this winter's projects and should be great fun.

cheers

Tim
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Old Oct 29, 2005, 01:52 PM
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With regard to a "power" query from another modeller for this aeroplane, I just checked over some of the "old" performance figures - and the pre-Surpass OS FS60 mentioned by the modeller with a Shereshaw "Cumulus" turns a 12x6 at 9,600 static- and lordie, how we forget!

The Enya 60 III used by Phil Kraft to win the World R/C Champs would have spun that 12x6 at only about 10,300 static - the potent Veco 61 maybe 10,800.

Maybe our modern power options are encouragingly high, so we can fit electric systems with confidence.
C
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Old Oct 30, 2005, 03:42 AM
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Quote:
Originally Posted by Chas
With regard to a "power" query from another modeller for this aeroplane, I just checked over some of the "old" performance figures - and the pre-Surpass OS FS60 mentioned by the modeller with a Shereshaw "Cumulus" turns a 12x6 at 9,600 static- and lordie, how we forget!

The Enya 60 III used by Phil Kraft to win the World R/C Champs would have spun that 12x6 at only about 10,300 static - the potent Veco 61 maybe 10,800.

Maybe our modern power options are encouragingly high, so we can fit electric systems with confidence.
C
Those prop figures and RPM figures equate to about 500-600W electric, foir what its worth..4120/14 will do that on 5sLIPO
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Old Nov 01, 2005, 09:40 AM
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Yes Vint that sounds spot-on. The snorting, potent ten si-si engines of the seventies were only putting out about a horsepower, and they were starting to weigh a pound and a half without silencers!

B/L and Lipo are starting to equal them not only in terms of power, but also in all-up power system weight, and in duration.

Yippeee!
C
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Old Nov 05, 2005, 05:58 AM
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Looking at what the prop is doing to deliver 500-600 W (i.e 9-10 k with a 12x6) from IC, maybe we do not need the equivalent power in to get a respectable flying result from electric, when using bigger props.

My 4130/16 will probably pull something in the region of 28 amps on 16 cells when spinning a 15x8 at around 6 k. The full grunt would only be used (if at all) on ROG and sauntering around the sky at half speed is the goal. At the reduced rpm's, surely the 15x8 is significantly more efficient than the OS whirling its thin profile 12x6 at around 7 k?

At approx 3 k on the 4130/16, current draw should be down to around 12-15A. I am very sure it would fly on 1/4 throttle and with a total power in of around 120-150W (assuming I can keep the AUW around my targeted 3.5 kg)

Going with Lipo's would definitely reduce the required cruising power, but I have decided not to go down that route. I do have a 4S3P Saphion pack destined for another project that I will probably give a go as well.

Cheers

Tim
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Old Nov 05, 2005, 12:06 PM
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At the reduced rpm's, surely the 15x8 is significantly more efficient than the OS whirling its thin profile 12x6 at around 7 k?

Yep!

And your pitch speed of about 48 mph is fine for the Falcon at those loadings (but see other posts regarding my lunacy ).

You have 440W to play with, and as noted before, these flew well with heavy spark gear and Anderson Spitfires on less power, less efficiently used. It all looks F.A.B. Tim, prepare for launch!

Surly and bonded
Chas
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Old Nov 05, 2005, 06:31 PM
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Not a Falcon, but while living in the UK in the '90's I built and flew regularly a 9 ft span version of the Trenton Terror. I'd been fairly casual about weight and it sat at about 9 lbs. I used an OS .70 Surpass to fly it and I don't think I ever used more than 2/3rds throttle even on short take-off. Certainly in flight the motor was barely used above idle to maintain height and on 1/4 throttle it climbed. Although a confirmed electric flier now I still keep my old "open rocker" OS .60 and that flew numerous OT's about the size of the Falcon most notably the Ben Shereshaw Cloud Cruiser which is reputed to be the origin for the Falcon and once again very, very, rarely was full throttle ever used.
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Old Nov 07, 2005, 01:16 PM
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F.A. B. Haven't seen that in a while.

I'm watching this thread with great interest as I too have the Falcon Plans plus plans for another 9 footer. I've been trying to decide on what power to use as well.

Spectrum is green.
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Old Nov 07, 2005, 05:45 PM
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Ian,
The very similar build/weight/size/drag Super Buccaneer went very well indeed on my Astro 40G and twenty cells. I think I used a 16x8 but the gear never got hot, at what I suppose was about 25 A static - so we're talking maybe 500W tops. I never got it weighed but it must have been, hmmm, substantial - I'd guess 10 lbs TOW.

Stolen from my loft. Every day, in every way, I'm getting better and better....

Certainly, m'lady.

Chas
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Old Nov 27, 2005, 02:44 PM
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Well, managed to squeeze some time in this weekend and get a new 16 cell pack bedded in. In this case I am using Puffin Hi-flow 3300 Nimhs.

I fired up the 4130/16 and ran the pack for 30 seconds at 10 amps before continuing the test. Jeti 70-3P opto controller used on hard timing, APCE 15x8 prop.

27.9 amps, 17.9 volts, 6300 rpm, 499 watts
21.2 amps, 19 volts, 5800 rpm, 402 watts
15 amps, 19.6 volts, 5200 rpm, 294 watts
10.8 amps, 20.2 volts, 4800 rpm, 218 watts
7.2 amps, 20.5 volts, 4200 rpm, 147 watts

Although a 4120/18 might be a lighter option, to swing the same prop at similar rpm's would certainly draw a lot more current and limit flight time. I believe that this 4130/16-cell setup will allow a fairly good flight time at a nice low current draw cruise, turning the prop at 4000-4500 rpm.

Certainly judging by the wind flow during the test, 6300 rpm with this prop will haul the Falcon into the sky with a vengeance.

cheers

Tim
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Last edited by Tim Trick; Nov 28, 2005 at 10:27 AM. Reason: typo
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Old Nov 27, 2005, 06:22 PM
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Look forward to some flight reports..

Its nice to see electric technology at fairly sesnible prices pushing towards giant scale dimensions.

A 600W pack of LIPOS is probably possible for not much over $100, if you shop around...
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Old Nov 28, 2005, 07:38 AM
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Quote:
Originally Posted by vintage1
Look forward to some flight reports..


A 600W pack of LIPOS is probably possible for not much over $100, if you shop around...

Sounds like you're looking forward to snapping up all those gently-used- Ni-Cads on e-Bay!

Chaf
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