KMP CL-215 Fowler Flaps

parkcityskier · Oct 16, 2009, 04:56 PM

The KMP CL-215 is a great flying airplane but the flap configuration is not very effective in doing its job. I am modifying my version with Fowler flaps. As part of the modification, the flaps will be one wing bay longer in length while the ailerons give up one bay. The ailerons are more than adequate. In addition, due to the flap profile, it adds 1.25 inches to its chord. The total wing chord remains the same.
The flaps build fast. I am using 6mm Depron for ribs, 1/8" ply for the flap portion of the hinges, and 1/64" ply skins. The wing portion of the modification involves removing the rear spar where the standard flaps are hinged to, and cutting back the wing ribs to match the contour of the new flap leading edge. The wing portion of the hinges are made from 1/16" ply with a 1/8" spacer between them. The flap portion of the hinge is positioned between the two wing pieces and pinned with a short piece of CF rod to complete the hinge.
Pictures show 0, 15, and 30 degree flap positions.[IMG]Flap 0, Flap 15, Flap 30[/IMG]

ashdec87 · Oct 17, 2009, 01:07 PM

just so you know scale goes to 40 degrees. looks good tho!

parkcityskier · Oct 17, 2009, 03:20 PM

Thanks, Ash, I will probably consider using 40 deg, also, but at the moment my transmitter won't handle that many positions and 15 and 30 will probably be what I will be using the most. I have a new transmitter on order, however, that will allow all three positions and with that I think that I will have the ultimate CL-215.
I scratch built a similar sized CL-215 25 years ago and, as I recall, with 40 deg of flaps the airplane would just about stop in the air. Great for steep approaches, though.

ashdec87 · Oct 17, 2009, 03:58 PM

Ya my transmitter is kinda the same. But i'm gonna have 15 and 40..figure I can add extra power if needed, but I want to be able to make a steep decent..

parkcityskier · Oct 17, 2009, 05:39 PM

Yes, 15 will help with the takeoff and 40 will definitely get it going downhill. Don't try the landing power off, however. Let me know how they work out for you.

marnochs · Oct 18, 2009, 11:01 PM

I think the flap setting for the full size 215/415 are 25/15/10/5 degrees

Full size flight test report from FlightGlobal (1995)
http://www.flightglobal.com/pdfarchi...0-%202925.html

ashdec87 · Oct 19, 2009, 12:00 PM

I read on another site where they used 40 degrees for a really steep approach, it was also a flight report...

pappy69 · Oct 22, 2009, 06:12 AM

marnochs is right

10 / 15 / 25 are the positions of the flaps for 415.

the plane doesn't have a 40 deg position!!

ashdec87 · Oct 22, 2009, 10:32 AM

lol hm interesting. I could have sworn the article said 40 degrees...maybe they were talking about the outside temp

wallis_100 · Oct 26, 2009, 04:18 AM

10, 15, 25 degrees sounds most likely.
For these flaps, anything much beyond 20 degrees starts to add a fair bit of drag! Fowler flaps, were originally designed to allow a large lift increment at low speeds

without excessive drag.

I fly them on my IP twin otter, and only have 1 setting (15 degrees) which allows me to slow her down quite dramatically.
This setting doesn't produce a great deal of drag, so for steep approached, greater deflection is a good idea.

According to research i found last summer whilst doing a dissertaion on high lift devices, much above 40 degrees, these flaps start to lose some of their lifting ability (the flow starts to seperate, despite the slot) but they double in drag production.

scott

parkcityskier · Nov 01, 2009, 09:29 AM

Good comments to clear up the confusion. By definition, the maximum lift over drag for a fowler flap occurs at just about 25 degrees, hence Canadair's decision to use this amount of deflection for its maximum. As a veteran pilot of six years of full scale fire fighting aircraft of various types, I appreciated the ability to get the maximum of drag available for steep descents but the pullout was difficult without a reduction in that drag. For model aircraft, with no loss of life involved, use of extreme flap deflections can be fun, with less penalties for any errors in judgement.

ashdec87 · Nov 01, 2009, 02:06 PM

ya, that extra drag might actually be a nice thing when trying to set down in a tight spot or something.

marnochs · Nov 03, 2009, 10:21 AM

parkcityskier,

Was looking at my MR Aerodesign CL-415 wing plans and found the flaps are about 22-23" long and the ailerons are about 13". That pretty much takes the flaps to the aileron servo control horn connections ( 2 bay extension ).
I'm going to be extending my flaps over the winter also. I need to recover the wings anyway, the covering material that comes on the plane loosens up frequently.

parkcityskier · Nov 03, 2009, 07:17 PM

Marnochs,
It sounds like you're thinking the same as I am. I have found that the ailerons, as they are, are more than adequate so I would rather have more flap and cutting the ailerons back to where things get complicated with the servo pushrod makes it a good point to stop. This will be very close to the scale location, too, so it will look better. I will be rebuilding my flaps as Fowler flaps. They look better and, despite what some people think about the value of doing it, they do work better, with the scale of these larger models such as the CL-215 and 415.
I found covering that is an almost exact match for the stock yellow. Unfortunately, the literature is gone but it's a product made in Germany and sold here, if you haven't found a good match for your mods.

Oct 16, 2009, 04:56 PM	#1
parkcityskier Registered User Join Date: Aug 2001 Location: Park City, UT, USA Posts: 25	KMP CL-215 Fowler Flaps The KMP CL-215 is a great flying airplane but the flap configuration is not very effective in doing its job. I am modifying my version with Fowler flaps. As part of the modification, the flaps will be one wing bay longer in length while the ailerons give up one bay. The ailerons are more than adequate. In addition, due to the flap profile, it adds 1.25 inches to its chord. The total wing chord remains the same. The flaps build fast. I am using 6mm Depron for ribs, 1/8" ply for the flap portion of the hinges, and 1/64" ply skins. The wing portion of the modification involves removing the rear spar where the standard flaps are hinged to, and cutting back the wing ribs to match the contour of the new flap leading edge. The wing portion of the hinges are made from 1/16" ply with a 1/8" spacer between them. The flap portion of the hinge is positioned between the two wing pieces and pinned with a short piece of CF rod to complete the hinge. Pictures show 0, 15, and 30 degree flap positions.[IMG]Flap 0, Flap 15, Flap 30[/IMG] Attached Thumbnails 29.3 KB · Views: 95 34.7 KB · Views: 59 34.6 KB · Views: 71

Oct 18, 2009, 11:01 PM	#6
marnochs Registered User Join Date: Dec 2006 Location: Canyon Country, California Posts: 36	I think the flap setting for the full size 215/415 are 25/15/10/5 degrees Full size flight test report from FlightGlobal (1995) http://www.flightglobal.com/pdfarchi...0-%202925.html Last edited by marnochs; Oct 18, 2009 at 11:21 PM.

Nov 03, 2009, 10:21 AM	#13
marnochs Registered User Join Date: Dec 2006 Location: Canyon Country, California Posts: 36	flap length parkcityskier, Was looking at my MR Aerodesign CL-415 wing plans and found the flaps are about 22-23" long and the ailerons are about 13". That pretty much takes the flaps to the aileron servo control horn connections ( 2 bay extension ). I'm going to be extending my flaps over the winter also. I need to recover the wings anyway, the covering material that comes on the plane loosens up frequently.

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Oct 17, 2009, 01:07 PM	#2
ashdec87 Registered User Join Date: Feb 2004 Location: Chicago suburbanite Posts: 5,396	just so you know scale goes to 40 degrees. looks good tho!

Oct 17, 2009, 03:20 PM	#3
parkcityskier Registered User Join Date: Aug 2001 Location: Park City, UT, USA Posts: 25	Thanks, Ash, I will probably consider using 40 deg, also, but at the moment my transmitter won't handle that many positions and 15 and 30 will probably be what I will be using the most. I have a new transmitter on order, however, that will allow all three positions and with that I think that I will have the ultimate CL-215. I scratch built a similar sized CL-215 25 years ago and, as I recall, with 40 deg of flaps the airplane would just about stop in the air. Great for steep approaches, though.

Oct 17, 2009, 03:58 PM	#4
ashdec87 Registered User Join Date: Feb 2004 Location: Chicago suburbanite Posts: 5,396	Ya my transmitter is kinda the same. But i'm gonna have 15 and 40..figure I can add extra power if needed, but I want to be able to make a steep decent..

Oct 17, 2009, 05:39 PM	#5
parkcityskier Registered User Join Date: Aug 2001 Location: Park City, UT, USA Posts: 25	Yes, 15 will help with the takeoff and 40 will definitely get it going downhill. Don't try the landing power off, however. Let me know how they work out for you.

Oct 19, 2009, 12:00 PM	#7
ashdec87 Registered User Join Date: Feb 2004 Location: Chicago suburbanite Posts: 5,396	I read on another site where they used 40 degrees for a really steep approach, it was also a flight report...

Oct 22, 2009, 06:12 AM	#8
pappy69 Thanos Papantonopoulos Join Date: May 2007 Location: Thessaloniki, Greece Posts: 299	marnochs is right 10 / 15 / 25 are the positions of the flaps for 415. the plane doesn't have a 40 deg position!!

Oct 22, 2009, 10:32 AM	#9
ashdec87 Registered User Join Date: Feb 2004 Location: Chicago suburbanite Posts: 5,396	lol hm interesting. I could have sworn the article said 40 degrees...maybe they were talking about the outside temp

Oct 26, 2009, 04:18 AM	#10
wallis_100 build like there is no 2moz Join Date: Apr 2009 Location: Southampton Posts: 99	10, 15, 25 degrees sounds most likely. For these flaps, anything much beyond 20 degrees starts to add a fair bit of drag! Fowler flaps, were originally designed to allow a large lift increment at low speeds without excessive drag. I fly them on my IP twin otter, and only have 1 setting (15 degrees) which allows me to slow her down quite dramatically. This setting doesn't produce a great deal of drag, so for steep approached, greater deflection is a good idea. According to research i found last summer whilst doing a dissertaion on high lift devices, much above 40 degrees, these flaps start to lose some of their lifting ability (the flow starts to seperate, despite the slot) but they double in drag production. scott

Nov 01, 2009, 09:29 AM	#11
parkcityskier Registered User Join Date: Aug 2001 Location: Park City, UT, USA Posts: 25	Good comments to clear up the confusion. By definition, the maximum lift over drag for a fowler flap occurs at just about 25 degrees, hence Canadair's decision to use this amount of deflection for its maximum. As a veteran pilot of six years of full scale fire fighting aircraft of various types, I appreciated the ability to get the maximum of drag available for steep descents but the pullout was difficult without a reduction in that drag. For model aircraft, with no loss of life involved, use of extreme flap deflections can be fun, with less penalties for any errors in judgement.

Nov 01, 2009, 02:06 PM	#12
ashdec87 Registered User Join Date: Feb 2004 Location: Chicago suburbanite Posts: 5,396	ya, that extra drag might actually be a nice thing when trying to set down in a tight spot or something.

Nov 03, 2009, 07:17 PM	#14
parkcityskier Registered User Join Date: Aug 2001 Location: Park City, UT, USA Posts: 25	Marnochs, It sounds like you're thinking the same as I am. I have found that the ailerons, as they are, are more than adequate so I would rather have more flap and cutting the ailerons back to where things get complicated with the servo pushrod makes it a good point to stop. This will be very close to the scale location, too, so it will look better. I will be rebuilding my flaps as Fowler flaps. They look better and, despite what some people think about the value of doing it, they do work better, with the scale of these larger models such as the CL-215 and 415. I found covering that is an almost exact match for the stock yellow. Unfortunately, the literature is gone but it's a product made in Germany and sold here, if you haven't found a good match for your mods.