Paul Williams
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Everything posted by Paul Williams
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Yeh, next door neighbour is a land rover nut. I have just done a load of static prop testing and have come to the conclusion it is not a true reflextion of what goes on in flight, read prop testing, I was seriously worried bench testing my twister edf when it bubbled up a li-po after 4minutes at 70%. In the air it runs like a dream barely warming its conponenants and my worrying was unfounded. I dont think a true conclusion can be drawn without field tests. Unless you know different. Still its better than watching TV or doing the garden. Are yo going to Cosford tomorrow? Hope the weather stays good
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Following Tim's advice on pre-testing before flying any thing eletric I cobbled together a test rig versatile enough to test most things. I purchased numerous props of differing sizes and makes and set about coming up with the best combination for current and thrust. I did find that although the testing is paramount for ensuring you don't burn out your electrics the differing props and thrust obtained was not making sense. I found the best power to current ratio was obtained using a master screw nylon which is intended for glow engine use. This leads me to believe the light thin props for electric must be changing contour under load. This is probably due to holding the model stationary while testing. I cant of course measure slip so as to the best prop to use I guess the only true test is to fly it.
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some one said a picture paints a thousand words.
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Enough I have run out of headache pills, the fan dia for my hawk is 89mm what lenth and exit dia should I fabricate the tube? Just the 2 dimentions would be great. Thank you thank you thank you
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Jim, where you ever in one of those camp places where they did experiments on people? I love your sense of humour takes a lot to make me smile first thing in the morning, but I would defy you to put a little any control in whilst rolling this jet. You would need reactions quicker than a Pentium 6. I can hear your reply as I type "slow it down old boy" but then it would not be a jet would it. tally ho Biggles.
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Jim, you wise old bird, your advice is gratefully accepted and I bow to your vast knowledge. I have only one problem with it I don't have a rudder!!!!! ha ha
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The July Grand Prize Draw
Paul Williams replied to David Ashby - Moderator's topic in All Things Model Flying
count me in and thanks great idea -
I pinched timbo's design ( sorry mate you will get your reward in another life as for most things) and left out the lever bit, I mounted a cradle on top where his fan was and simply sat what ever plane I have on it. The measurement is by a simple digital pull mounted horizontally. Bingo. A versatile machine that cost 7 quid plus a few screws to make. I can mount fans motors or the whole model, which is great for a quick prop change then test. Mount the digital pull so the pivot arm is slightly past 12 o clock set the tear and fire up. I have not stopped using it since.
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Landing the edf jet has always been a heart in mouth expearience, it comes in lke a dark and soon eats up 100m landing strip this is not made easier with nearby trees preventing a gradual hieght loss. I had a play yesterday and set up the flap switch to give 10 degree down on ailerons with 5 degree up on elevator. Much better result I can drop to quarter throttle or less and not stall. Do you ever stop learning?
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Timbo, did you try different length tubing attached to the fan rear? I am holding off building the hawk until I get some information on how this will fare. I was going to get some cardboard tube and try differing lengths and cone shapes. Perhaps even set in some ribs to create swirl. The twister is fantastic as my confidence grows flying it I am really impressed with its performance I flew it yesterday on full aileron movement the roll rate is ballistic around three full turns per sec. The point being the internal shape of the exit airflow is quite different to the hawk. I wonder if its makes a big difference to the power output. One other thing I quite fancy building a larger scale version with twin fan, have you seen any fans that run in opposite direction? I was thinking of counter acting the torque. Why are most edf models under 1m wing span?
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If you had the rig and scales on a board you could turn the lot 90 degrees and calibrate with a known wieght. Just a thought.
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I am building a puppeteer Sopwith Pup and although not ready yet I was thinking ahead to covering it. I recently saw one done with a material which looked like a fabric not the usual solarfilm stuff. Any ideas what this could be and where to purchase from.
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Thanks Simon, it was also a proper pilot that suggested I use rudder then counteract this using wing control, I did try that but found it difficult to stay on the flight path so to speak.
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Ah the wit I knew I went on here for something, Eric you are right and since posting this its not stopped raining or that awful thing work has got in the way of play time. Its all about practice I am sure. I like the idea of nose up an find stall point rarther than the more elaberate methods mentioned eariler. Thanks for your time fella.
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I would not know how to do the calcs for CG, just guessed it mate. I will try your test method as soon as weather permits. The engine is set at the usual down and right. thanks
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flying field near Tesco Hanforth
Paul Williams replied to Paul Williams's topic in All Things Model Flying
FOUND IT. Smithy Model Air Club thanks for your help guys -
Oh no I like flying fast gets the old adrenalin going, I just have a problem stopping before I run out of field.
