Thread Tools
Apr 21, 2006, 07:44 PM
Size Matters!
RocketRob's Avatar
Thread OP
Mini-Review

K&A Me 262 Schwalbe/Sturmvogel


Received today,
another casualty of Ken's spring sale

http://kamodels.com/

Well packaged, presheeted wings, lovely light glass.

Actually wasn't expecting this one quite so quickly, will make some room on the build table.
Last edited by RocketRob; Apr 21, 2006 at 07:50 PM.
Sign up now
to remove ads between posts
Apr 21, 2006, 08:36 PM
Pro Hoarder
turbonut's Avatar
Very cool Rob, please post lots of pics...I got mine about 2 weeks before the sale..That sucked....So I purchased three more planes for Ken Just because..What are you planning for fans and motors..I think wemo 505 for mine and retracts
Scott
Latest blog entry: In flight
Apr 22, 2006, 01:54 AM
Must... resist.... another one...

Monday I'll start my K&A build. 505 motor testing to follow.

Justin
Apr 22, 2006, 08:24 AM
Size Matters!
RocketRob's Avatar
Thread OP
Justin, Resistance is futile! Get going with that F86 and the 505!!!

Scott, I was thinking the 505's also with the neu 1105 2.5y on 3s.
This morning I was thinking about alfa fans and 4s mega 16/7-4. On initial examination, the nacelles look small for a 65mm fan??? Need to look closer, or it is an optical conclusion due to the short length...

retracts?
now you have me thinking as originally I wanted to build light, and still am favoring that approach but those light retracts are tempting and it should be a straightforward installation in this bird. Besides, retracts never add any time to a build

With the fans mounted outboard, I'm really looking forward to equipment layout and placement in that cavernous fuselage.....I won't feel like a gynacoligist working around a big uterous.
Apr 22, 2006, 08:31 AM
Size Matters!
RocketRob's Avatar
Thread OP
Presheeted wings.....Ken, you rock!

Jump ahead to #10 in the instruction manual - skip page 1!
Glue on leading edge, trailing edge and wing tips.
fondle nacelles.....
Last edited by RocketRob; Apr 22, 2006 at 09:55 AM.
Apr 22, 2006, 09:02 AM
Balsa Flies Better!
Hi All

I picked up one of these kits as well, although its not on the front of the build queue- I've got stuff on my bench at this point- and I'm not clearing anything off!

Couple of questions for the intake ducting gurus-

I'm looking at the nacelles for the Wemo 505 fan- I picked up both fans and liners from Ken. (He calls the liner what I'd call the fan housing- it's the tube the fan and stators get mounted in.) Anyhow, the ID of the 505 fan is a bit larger than the intake on the nacelle- I thought the intakes were supposed to be between 100-110% of FSA, which in practical terms for me is basically the fan housing ID. Also- the fan is going to be very snug getting it in there- it's going to take a bit of grinding to accomplish this trick.

Second issue- if the ducting liner just gets glued to the intake of the nacelle- this looks like a pretty sharp entry to me. Is this going to work? I always thought that a rounded entry lip helped a lot. I tried contacting Mr. Boogie for his molded entry lips- don't know if they are the right size for this fan, but maybe they can be grafted on. Haven't heard back from him yet. Are there any alternatives?

Three- given the restrictions on the intake- does it make sense to go to a smaller fan like the Wemo Micro? I keep hearing that these fans can take some 300 watts- what about going to a pair of them at 300 watts a side? I figure this airplane is going to need 600 watts or so total.


Sam
Apr 22, 2006, 10:07 AM
Size Matters!
RocketRob's Avatar
Thread OP
Sam,
In regards to the intake size vrs. the fan ID it relates to the Fan Swept Area, I think Herb describes it best......

https://www.rcgroups.com/forums/show...3&postcount=45

"Keep in mind that you want to match the F-86 intake area to the fan swept area (fsa), which is defined as the circular area of the fan minus the circular area of the fan hub. Even if the intake is a few percent below the fsa that is still not a problem from an airflow/efficeincy point of view. So, to answer your question, yes the fan looks like it has a bigger area but in fact it does not, as there's no airflow through the hub ."-Herb

Quote:
Also- the fan is going to be very snug getting it in there- it's going to take a bit of grinding to accomplish this trick.
Yes on second examination, I noticed this also.....guess a bit premature with my gynacoligist comment times two!

Intake shape/internal radius? Will let someone else take a stab at....
Last edited by RocketRob; Apr 22, 2006 at 10:13 AM.
Apr 22, 2006, 10:46 AM
EDF rules... :)
AirX's Avatar
Sam,

The first issue:

FSA is the only variable that matters in moving air thru the fan/duct system. FSA (Fan Swept Area) is calculated by the area of the shroud(fan cover) from the motor holder. The motor holder area is subtracted from the overall area because it is a solid area and the air cannot flow thru it. The duct itself is calculated from this one variable with 100% 120% of FSA for the inlet to 100% down to 90%FSA for the outlet. You may notice that the area's converge thru the system to create some work the fan must perform to accelerate the airflow thru the system and it is why fans do not unload when flying like prop models will. Now you will probably need to reform the other issues to fit.

Sencond issue:

I cannot measure the inlet diameter so I cannot calculate the area of the opening but if you will calculate the opening area and compare it to FSA as described in the first you will have your answer. On a tangent the inlet is not restricted by added a rounded entry as the catchment area is determined by the point where the airflow will split on the curve of the lip as air can accelerate and deccelerate with minimal energy losses(Low mass), the problem with sharp inlets is that it forces only the air flow that is covered by the area to enter and it is difficult to draw enough air volume in at low airspeeds where the rounded lip will expand the coaverage area. Go duct as there is minimal area for a plenum in that naccelle from the pictures I have seen. This is what makes EDF and DF difficult as you need to build the inside of the airplane as well as the outside.

Issue 3:

This has not been truly decided unless you go back and refigure the FSA. If you want to go Microfan, there are systems arround that will give you 300 watts thru it but without good duct your in the same shape you started.

Eric B.
Last edited by AirX; Apr 22, 2006 at 12:51 PM.
Apr 22, 2006, 11:33 AM
Balsa Flies Better!
Hi Eric and Rob-

Thanks for the responses-

Well, I did some measuring and some calculating- here's what I come up with-

1) The ID of the intake on the nacelle is about 55 mm.
2) The ID of the duct is 66 mm.
3) The diameter of the motor housing is about 30 mm.

My calculations- about 2700 sq mm for the FSA. The front intake on the nacelle is about 2300 sq. mm. Translation- this needs to be opened up.

The exit by the way is about 65 mm or so- that can use a little necking down, but that's easy.

Issues- opening up the nacelle 5 mm gets you to 2800 sq. mm for an intake, but there is no room for a lip. I have a sneaking suspicion lips are really important in the low speed regime.

Options-

Molded plastic nose from the Mig? Issues- I think the snoot of this nacelle needs to be pretty rugged, I'm very leary about plastic here.

Take the lip from a Wemo minifan (how many of us have these things lying around waiting for a use?) cut the diameter down some, and graft that to the nose of the nacelle. It's going to need a little surgery and glass to fill it in, but I don't think it should be too bad. Skinny down the interior ring of the MF ring so that it makes a smoother transition to the duct work- or just stick the liner on the MF ring cut down- don't bother with an intake liner and have the fan in the front of the duct. How bad is having the fan in the front versus further back? I'm assuming it doesn't really matter much.

Sam
Apr 22, 2006, 03:43 PM
Size Matters!
RocketRob's Avatar
Thread OP
Sam, I measured mine and came up with

ID of nacelle inlet 60-61mm
ID of nacelle exhaust 56mm
ID of 505 fan shroud 65mm

could you be confusing the inlet for the outlet? Or you have some flashing perhaps?

In my photo above the inlet is to the left.
The inlet is longer than the outlet - look at the wing saddle, leading edge.


good info Eric - Thanks!
Last edited by RocketRob; Apr 22, 2006 at 03:53 PM.
Apr 22, 2006, 03:53 PM
Balsa Flies Better!
OK, this Wemo minifan lip butchery isn't going to work on the 262. I've got another use for a shortened nacelle, so I'm not worried about it, but this is going to take more head scratching.

Sam
Apr 22, 2006, 03:56 PM
Balsa Flies Better!
Yes, Rob I could be that stupid....I was. I was looking at the moldings for the wing and made a dumb-dumb. Hmm, that puts a different complexion on things.

Sam
Apr 22, 2006, 09:39 PM
go fly! no crashes!
Synwpn's Avatar
man oh man. i've been eyeing this plane and trying to resist this sale! Tons of stuff in the build que, but this is another plane that I gots to have! must resist!!!!
Last edited by Synwpn; Apr 22, 2006 at 10:43 PM.
Apr 22, 2006, 09:56 PM
EDF rules... :)
AirX's Avatar
Thanks Rob, Herb had a lot of input in my knowledge base...

Eric B.
Apr 22, 2006, 09:59 PM
Size Matters!
RocketRob's Avatar
Thread OP
Did I mention how nice and light the balsa is?

I think I've decided....no gear

I'll try to keep this one light and see about gear on the next one


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Help! Messersmitt Me-262 Schwalbe drawing TomCZ Electric Ducted Fan Jet Talk 2 Jun 05, 2006 03:40 AM
ME-262 Schwalbe 78 inch span Heiner Skroblin Scale Kit/Scratch Built 0 Sep 23, 2004 06:35 AM
Anyone have Me-262 Schwalbe plans? The Max-Q Electric Ducted Fan Jet Talk 17 Jul 01, 2004 01:03 AM
New K&A Me-262 EDF Ken Williams Electric Ducted Fan Jet Talk 10 Feb 25, 2004 01:29 AM
Question K&A Me-262? Jeff Charlot Slope 7 Feb 17, 2004 03:39 PM