|Martin McIntosh||06/08/2017 17:42:24|
2281 forum posts
If you would allow me to pick your brains, I wish to build a 90mm version based on your design.
You said somewhere back on here that a 5-10% increase in size may be required but in order to keep the fuselage in the same proportion it would need to be 28% larger to accommodate the fan. The new span would be around 54". The `quoted` thrust of my 11 blade 10s fan is 5kg as against an equivalent 70mm one which is 2.1kg, an increase of 250%. What do you reckon?
The HK 90mm one has disappeared from their website. Cannot remember the span but I seem to remember that it was less than 54" and probably not very scale.
Thanks in anticipation,
|Tim Hickey||10/08/2017 16:51:34|
3 forum posts
I know this thread has been dormant for a while but I have decided to take the plunge into the world of edf.
Your Hawk (42" looks amazing and having read your article in the mag I think the ROG version would work at our flying strip. If you get a chance please can you look at the edf spec below and advise if looks ok. Its similar to the Dr. Mad thrust you specified but being new to edf your thoughts would be appreciated.
Dr Mad Thrust 70mm 8 blade 2200kv, 1900w (6s), weight 313kg, max amp 86A, max thrust 2.8kg
Do you think a Lipo with a capacity of more than 4000mah would work given any additional weight.
and finally...honest..what sort of flying times would you expect to achieve with a 4000mah Lipo as a starter.
I would also like to make some sort of retract doors.
Should this model work I would hope to move on to your 50" version later in the year.
I appreciate you taking the time to read this and thanks for everything you put into our hobby..
|Martin McIntosh||10/08/2017 19:27:36|
2281 forum posts
I think that we are on the same wavelength here.
I have decided to do a 90mm fan version at +28% and have actually started to produce it despite no response from TN. This works out fine for the HK retracts and EDF to fit in. The retract units supplied for the former HK Hawk which is no longer listed are for a rearward retracting nose wheel but I can get round this by using two! micro steering servos. Got a Dr. Madthrust 90mm 1000kv 10s fan so the batteries are going to be a fair weight. Tried the set up yesterday with a 120A YEP ESC and it started to smoke at just 20A so they are getting it back. The fan has been tested with another ESC and is fine, drawing 40A on a 5s pack.
I have ground down some wheels to maximise the diameter of the retract unit`s capability.
I may put this on a separate build blog entitled `90mm EDF Hawk`.
|Piers Bowlan||11/08/2017 05:26:59|
1133 forum posts
Hi Martin, Did you not see Tony's 90mm prototype EDF Hawk thread here. 50in span for 8s EDF, although Tony thought 6s would be viable too with my Lander five blade 90mm fan. What span is yours, about 54in? Tony's plan available in October RCM&E.
Edited By Piers Bowlan on 11/08/2017 05:31:38
|Martin McIntosh||11/08/2017 09:27:14|
2281 forum posts
Thanks for that, I had not seen it.
Mine will be 53.75" span so 6.88:1 scale. The 28% increase was the minimum to get the fan in without cheating on the fus width.
I see that Tony is also using the YEP 120A esc so they must work. My replacement is already on its way so good service from HK for a change. May try to prise a canopy from TN/SLEC because it should be near enough the right size and would save me a lot of work.
|geoffrehy Frost||14/02/2018 17:32:04|
|1 forum posts|
What was the exact paint and film colour you used?
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