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Old Feb 16, 2009, 07:34 AM
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2.5 Kilo 72" Lancaster

Thinking about upgrading my *speed 300 with gearboxes* Lancaster to 4 of these

http://www.hobbycity.com/hobbycity/s...idProduct=6943

with large (scale) 3 bladed props, 20 amp ESC's and one 6000mAh 30C 3 cell Lipo for power.

What do you guys think? a reasonable combination? I'm looking for scale flight, not 3D........any suggestions on prop size, make etc ?

Any suggestions regarding motors, props would be welcome....would like to try scale 3 bladers if possible......

Thanks in advance.

Ray
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Old Feb 16, 2009, 10:12 AM
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Ray

I am going through the same process with my 62", 2.0Kg, Lancastrian.

What is your weight with all power items removed?
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Old Feb 16, 2009, 11:21 AM
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My concern would be the max. watts recommendation - only 48W! I would have thought you'd need at least 60W/lb... if not more to be on the safe side.. so that means 350W-500W total. Speed 300's would give you perhaps 80W each - that's 320W total - I can't see it flying at 200W (if we believe the Turnigy figure - heck, a 58g motor should surely be good for 150W+). GWS makes 3-blade 10x6 HD so I'd aim for something of that size, with at least 100W per motor. Something akin to Axi 2212/34's (740Kv) might do it... but that would be expensive!
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Old Feb 16, 2009, 11:30 AM
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Quote:
Originally Posted by peterangus
Ray

I am going through the same process with my 62", 2.0Kg, Lancastrian.

What is your weight with all power items removed?
Hi Pete, you mean this one :-)?????

http://www.peterangus.pwp.blueyonder.co.uk/lancast'n.htm ????..lovely model

I dunno exactly with the Lanc, take out all the motors/gearboxes which are about 60 grams each + 8 x 3600 NiHds = 500g , so we are looking at around 740 grams, so without that stuff the airframe is 1760 grams including servos, retracts and the like.......... about 63 ozs in old money...
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Old Feb 16, 2009, 11:38 AM
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Thanks guys.......I am a 18 carat dummy

see this post ,

http://www.rcgroups.com/forums/showthread.php?t=998868

posted by me !!!!!!!!!!!! I totally forgot about it........jeez senility is creeping in!!!! maybe another two of these would do the trick?............
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Old Feb 16, 2009, 01:32 PM
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Dr K

Look at this video.
http://www.rcgroups.com/forums/showthread.php?t=920998
************************************************** ******
Ray

First--choose the props.
Scale diameter will be about 8.5". Motor spacing?

Master do 7 x 4 and 8 x 6 3-blade.
GWS do 7 x 3.5, 8 x 4, and 9 x 5 3-blade. [9 x 5 could be trimmed]

What do you think?
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Old Feb 16, 2009, 02:01 PM
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Quote:
Originally Posted by peterangus
Dr K

Look at this video.
http://www.rcgroups.com/forums/showthread.php?t=920998
************************************************** ******
Ray

First--choose the props.
Scale diameter will be about 8.5". Motor spacing?

Master do 7 x 4 and 8 x 6 3-blade.
GWS do 7 x 3.5, 8 x 4, and 9 x 5 3-blade. [9 x 5 could be trimmed]

What do you think?
Hi Peter, the props size...rough scale of the Lancaster is about 1/17th (102 ft = 72").........I reckon the full size props on the Lanc are around 12 to 13 foot across. so that gives me nearly 9" props or there about.......distance between the nacelle centre lines is 9 1/2 inches and the inners are slightly forward of the outers........so maybe the 9 x 5 s would be ok ? or possibly these 9 x 7's ?

http://www.hobbycity.com/hobbycity/s..._propeller_9x7
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Old Feb 16, 2009, 08:35 PM
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I imagine you'll get more thrust out of 9x5 GWS HD 3-bladers, than from those cool-looking, but probably fairly inefficient MAS props (I must say I have only tested 6" and 7" MAS 3-bladers, but they are pretty poor).

In testing GWS HD 3-blade, tractor and pusher props, using a Suppo 2820/6 (~1040Kv), with the 9x5 GWS HD's I got over 1050g thrust @ 44mph from just ~19A/205W.
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Old Feb 16, 2009, 08:47 PM
homo ludens modellisticus
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Ray, maybe do a Lancaster thread overhere too?
http://www.modelbouwforum.nl/

Vriendelijke groeten Ron
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Old Feb 17, 2009, 02:15 AM
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deleted post ...opps sorry

Ray
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Old Feb 17, 2009, 02:17 AM
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Quote:
Originally Posted by Ron van Sommeren
Ray, maybe do a Lancaster thread overhere too?
http://www.modelbouwforum.nl/

Vriendelijke groeten Ron
Hi Ron, I wish I could write good Dutch and then I would !!!!!..maybe drop over and you can translate for me .It would be good to meet up I think sometime soon ...I can't seem to PM you..so drop me a line and we can sort something out..cheers for now....

Ray
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Old Feb 17, 2009, 06:18 AM
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Ray

What props currently fitted? And what prop rpm?

I had not seen those Turnigy bell motors. Useful range of Kvs. Garbage data as usual. Listed under "speed controllers"!!!
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Old Feb 17, 2009, 07:56 AM
homo ludens modellisticus
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Just write in English, we/they don't mind, you would not be the only one.

You'll find me e-mail address here Ray:
http://home.hetnet.nl/~ronvans/

Vriendelijke groeten Ron
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Old Feb 20, 2009, 10:32 AM
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Possible solution...........

well I have just tested one of these motors
http://www.rcgroups.com/forums/showthread.php?t=998868
with a three blade 8.5" (near scale size!) VarioProp set at around 7-8" pitch...and the figures I'm getting from a tired 4200 3 cell Lipo are looking promising......I get around 85-90 Watts at around 9-10 amps which means the Lipo is down to around app 10 volts......so with a decent Lipo I could be in with a chance........., I will be in the 340 -360 Watts bracket which is good I think..... I hope these figures are correct , I used the WattsUp meter for them. I will do the tests again to make sure......I'm never 100% confident in my measuring abilities :-)

I just received the low (600) Kv motors so will do some testing with those.
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Old Feb 20, 2009, 11:35 AM
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Ray

Since the Lanc seems to fly well on its current "geared can" set-up, the existing prop size and rpm would provide a good start point for an update.

In the absence of those numbers, I have done some speculative calcs. The attachment shows the Kvs required for some combinations of pitch, volts, and pitch speed. [There is an inbuilt assumption that the no-load speed is 1.4 times the operating speed. Necessary to ensure a good match between motor and prop.]

The indications are for a Kv well above 600.

Since you are predicating a prop size [roughly], pitch speed considerations come before power considerations. You will probably end up with a surplus of installed power.
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