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Old Jul 02, 2007, 06:00 PM
FlyingPenQuinn
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Maryland, USA
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Question
How does intake port design affect EDF performance

Forgive the newbie question, but it is specific to EDF. In the distant future I plan to build a Martin P6M Seamaster. The scale model will have 4 EDF's topside of the wing (or maybe just 2). Due to the shape of the scale design the intake ports are rather small. My question is this:

How does intake port design affect EDF performance and build considerations?

I've seen other EDF designs on the forum that appear to have similar characteristics - one, even, with a very long intake port with the EDF apparently at the end of the "cowling". (I'm a noob, so please excuse any incorrect terminology). Thanks to all for responses.

Quinn
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Old Jul 02, 2007, 06:14 PM
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If you want opinions there are plenty in the Cermark F16 thread! There is lots of science and at the end of the day the limitation will be whatever the scale design will let you do. From what I know, anything down to 70% fsa (Fan Swept Area) with a good rounded lip will not give you any problems. Place the fans in the duct to suit access and CG, because the control of the air coming in is just as important of the air going out.

Its easier to build a light outlet duct as the EDF is trying to inflate it, so not so strong is no problem. Inlets not so. not familier with the full size, why not post a pic?
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Old Jul 02, 2007, 06:32 PM
go fly! no crashes!
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Its a neat flyingboat (vs seaplane? not sure which fits better). There was one done as a GDF (i think?) unit before.

http://www.aviation-history.com/martin/p6m.html

ah. found a thread(somewhat) in waterplanes forum.
http://www.rcgroups.com/forums/showt...&highlight=p6m

Lovely jet. I'd think 4 Wemotec 50mm fans perhaps?
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Old Jul 02, 2007, 07:00 PM
smug in granny panties
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also dont pass up the idea of a smaller fan with better fsa being a better alternative. Even at same power levels multiple motors have a better inherent efficiency.


Barry
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Old Jul 02, 2007, 10:08 PM
FlyingPenQuinn
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Maryland, USA
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Quote:
Originally Posted by Synwpn
Its a neat flyingboat (vs seaplane? not sure which fits better). There was one done as a GDF (i think?) unit before.
......ah. found a thread(somewhat) in waterplanes forum.
http://www.rcgroups.com/forums/showt...&highlight=p6m
Lovely jet. I'd think 4 Wemotec 50mm fans perhaps?
Yup, that's David Plummer's scratch build. Total weight came to 15+ lbs. (about 7 kilos). He successfully taxied, but I never heard if it flew or not. I'm thinking it was too heavy. Agreed, it is a gorgeous model.

My plan is to come in under 9 lbs (4 kg) at around 1/16 scale (ws 100"), or there-abouts. David's intake ports appear to be out of scale - about twice the opening from scale design drawings I have. This is why I am asking the question. Knowing zilch about EDF, I'm trying to get a head start on design features. I figure I have a GREAT deal to learn about EDF and the science that goes with it. The responses so far are a good start - thanks to all.

BTW, Flying Boat is the correct term. Seaplanes do not have hulls, only floats. The P6M Seamaster truely was a water born version of the B-52.

Quinn
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Last edited by QuinnH; Jul 02, 2007 at 10:39 PM.
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Old Jul 02, 2007, 11:50 PM
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Looks like a job for a couple of wm400's. Have a look at the Slingshot 70mm thread, some photos there. the longer case design lends itself to what I see in the picture and it (in theory, but never seen anything to disprove it) works better with a restricted inlet.
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Old Jul 03, 2007, 04:30 AM
Claus at Area 52
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whistling Watts is correct you should be able to have two wm 400 on 500watts to do the job. Depending a little on how big the scale exhaust is one could consider twin outlet .

Claus
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Old Jul 03, 2007, 05:02 AM
Claus at Area 52
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the top drawing is for "standard installation" here shown for a 80 mm fan but the same factors go for 70mm fans as well.
notice that we operate with two differnt terms around the intake.
Inlet area .. the tube size at the inlet
Catch area.. the area outlined from the middle of the intake rounding.

on faster models a catch area of 100% and down to 90% of fsa will work on higher levels of power.

For normal model i would look for 100- 120% fsa inlet area and a Radius 6 rounding.
Claus
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