This is a "Fowler" flap!!!(and a 737 flap)
05-19-2003, 10:55 PM
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06-28-2003, 09:27 PM
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This is a "Fowler" flap!!!(and a 737 flap)
Probably not, getting the sequensing right would be a real headache, making sure the fore flap and aft flap extend and retract with respect to the midflap would just be too hard. You need to see how Boeing have done it, it's not pretty. They have sorted it out somewhat on the 737-6, 7, 8, and 900 by doing away with the foreflap and a new arrangment to actuate the aft flap,
07-25-2003, 03:46 PM
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This is a "Fowler" flap!!!(and a 737 flap)
I am building a Fowler Flap right now. It is a double slotted flap with a non moving Fore-flap like that on some of the corporate jets. It actually resembles the flap on the old Bristol Britannia Turbo- prop.
There have been numerous obstacles to overcome. Here are but a few. Size of flap in percentile to chord length. Track operation and the ultimate question as to mechanical movement of the flap as no servo has enough throw to move it the required distance.
I solved the problem of movement by deciding on using a screw jack system operated by a electric motor with a noise supressor on it. It is located in the center of the flap. Graupner car universal joints(really expensive buggers) connect the motor to 4 custom made 90 degree gear boxes . Power is then converted at the output end with universal joints housing 4 - 8/32 titanium rolled thread all rod which are threaded into a swivel receptacle mount on each side of the flap. Track hardware is secured inboard of the flap cove.
In traditional fashion much of the fowlers movement in the beginning of it's travel is increasing the chord length providing more lift then drag. Further movement exposes the gap and allows high energy air to flow through the slot re-energizing the boundary layer air which is de-accelerating and beginning to seperate. While further movement becomes more drag than lift. The track design must reflect and complement all of the above.
Special Flap- track vacuform covers were made to hide the track hardware. Flap has 2 limit switches while moving out and two limit switches moving to the clean configuration. Each of the switches are on either side of the wing. If one switch were to fail the other will turn the system off. This is important as the flap moving in the down postion can move off the track and thus off the wing. OUCH!!
The flap speed is slow as the screw (all-rod) acts as a gear reduction of speed. Good torque doing it this way...Not good if you have to get it up in a hurry. Flap position is completely variable and will have to be operated on/off up/down. Specific flap degree postions will not be obtainable on the radio. It will be where I want to put it. I suppose I could have all kinds of relays etc. to create this but I'm trying to keep the weight down. Suprisingly, by using composite materials, it's not all that heavy.
One potential problem is contamination. If any particles of dirt get into the all- rod it could bind the flap with disasterous results. So I'm opting to clean assembly after each flight and to not use grease or lubricants on the moving parts as dirt will connect itself easily. Things can also disconnect , break etc. Lot of mechancal monkey motion goin on here, but the results and the challenge to build this is very rewarding and whatever happens...happens.
Even though the flap system is heavier than a simple drop flap, remember the coefficent of lift goes way up in a fowler as the chord is increased dramatically not to mention all that high energy air accelerating threw the slot to keep the air from rolling off the back of the flap.
Interesting side note here is that many people believe the more flap the better. Fowler yes ... Drop flap no. One guy that flys jets at our field found out the hardway by putting in too much flap in his Bandit. The result was flap stall. As you drop the flap deeper and deeper you are asking the air to travel a greater distance. As it is the air is loosing it's velocity toward the trailing edge and it is more prone to seperation.Remember too that as you increase the angle of attack the air seperation point at the leading edge now moves below the leading edge. The stagnation point where this occurs has the effect of slowing the air speed at the opposite end at the trailing edge as it has to travel even further. So if you have too much flap and air is beginning to seperate from it and you increase the angle of attack , say in the flare, boom!!! You can without notice all of a sudden stall the aircraft. Point of all this. I think more models out there should have moving fowlers, somewhat simpler from what I am doing, but effective in the same way. Even though the Reynolds numbers are lower... Air is still Air and the benefits of this design are obviously duly noted in many articles and books. Dean
There have been numerous obstacles to overcome. Here are but a few. Size of flap in percentile to chord length. Track operation and the ultimate question as to mechanical movement of the flap as no servo has enough throw to move it the required distance.
I solved the problem of movement by deciding on using a screw jack system operated by a electric motor with a noise supressor on it. It is located in the center of the flap. Graupner car universal joints(really expensive buggers) connect the motor to 4 custom made 90 degree gear boxes . Power is then converted at the output end with universal joints housing 4 - 8/32 titanium rolled thread all rod which are threaded into a swivel receptacle mount on each side of the flap. Track hardware is secured inboard of the flap cove.
In traditional fashion much of the fowlers movement in the beginning of it's travel is increasing the chord length providing more lift then drag. Further movement exposes the gap and allows high energy air to flow through the slot re-energizing the boundary layer air which is de-accelerating and beginning to seperate. While further movement becomes more drag than lift. The track design must reflect and complement all of the above.
Special Flap- track vacuform covers were made to hide the track hardware. Flap has 2 limit switches while moving out and two limit switches moving to the clean configuration. Each of the switches are on either side of the wing. If one switch were to fail the other will turn the system off. This is important as the flap moving in the down postion can move off the track and thus off the wing. OUCH!!
The flap speed is slow as the screw (all-rod) acts as a gear reduction of speed. Good torque doing it this way...Not good if you have to get it up in a hurry. Flap position is completely variable and will have to be operated on/off up/down. Specific flap degree postions will not be obtainable on the radio. It will be where I want to put it. I suppose I could have all kinds of relays etc. to create this but I'm trying to keep the weight down. Suprisingly, by using composite materials, it's not all that heavy.
One potential problem is contamination. If any particles of dirt get into the all- rod it could bind the flap with disasterous results. So I'm opting to clean assembly after each flight and to not use grease or lubricants on the moving parts as dirt will connect itself easily. Things can also disconnect , break etc. Lot of mechancal monkey motion goin on here, but the results and the challenge to build this is very rewarding and whatever happens...happens.
Even though the flap system is heavier than a simple drop flap, remember the coefficent of lift goes way up in a fowler as the chord is increased dramatically not to mention all that high energy air accelerating threw the slot to keep the air from rolling off the back of the flap.
Interesting side note here is that many people believe the more flap the better. Fowler yes ... Drop flap no. One guy that flys jets at our field found out the hardway by putting in too much flap in his Bandit. The result was flap stall. As you drop the flap deeper and deeper you are asking the air to travel a greater distance. As it is the air is loosing it's velocity toward the trailing edge and it is more prone to seperation.Remember too that as you increase the angle of attack the air seperation point at the leading edge now moves below the leading edge. The stagnation point where this occurs has the effect of slowing the air speed at the opposite end at the trailing edge as it has to travel even further. So if you have too much flap and air is beginning to seperate from it and you increase the angle of attack , say in the flare, boom!!! You can without notice all of a sudden stall the aircraft. Point of all this. I think more models out there should have moving fowlers, somewhat simpler from what I am doing, but effective in the same way. Even though the Reynolds numbers are lower... Air is still Air and the benefits of this design are obviously duly noted in many articles and books. Dean
07-25-2003, 06:40 PM
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Science!
Hi Dean,
I'm one of the others here who is interested in slotted Fowler flaps. When you feel it's appropriate, I would love to see some photos and/or drawings of what you're doing, as I'm sure others here would.
I'm attempting to accomplish my version of the flaps using servos and linkages, rather than the jackscrew method, but am always interested in seeing how others do things.
Please keep us informed, as you have time.
I'm one of the others here who is interested in slotted Fowler flaps. When you feel it's appropriate, I would love to see some photos and/or drawings of what you're doing, as I'm sure others here would.
I'm attempting to accomplish my version of the flaps using servos and linkages, rather than the jackscrew method, but am always interested in seeing how others do things.
Please keep us informed, as you have time.
07-25-2003, 09:06 PM
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This is a "Fowler" flap!!!(and a 737 flap)
I am thinking that the jackscrew method may benefit from having the nut portion slotted to allow any debris to fall off and away from the threaded rod, similar to a die but maybe just one of the slots, facing down.
07-25-2003, 09:36 PM
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This is a "Fowler" flap!!!(and a 737 flap)
I've installed slotted flaps on a few airplanes, always using offset hinge line for motion.
I've been considering how to do the flaps on a tracked system for an giant A-10 I will be building, maybe next year. I'd love to see specifics on how folks are building tracks & avoiding jams. There is big potential for jaming of the flap tracks if the flaps get a little sideways during deployment or if junk gets in the works.
I also was thinking about the jackscrew system, but just using a servo divorced from it's pot to drive the screw. Here's an exaple of that being used to pivot a turbine engine on a VTOL model:
http://www.corpcomp.com/weeks1/Rig/Moter_moves.html
FWIW- I think use of titanium on model hardware is more trend than science. It just isn't a big benefit vs the cost increase; discuss...
I've been considering how to do the flaps on a tracked system for an giant A-10 I will be building, maybe next year. I'd love to see specifics on how folks are building tracks & avoiding jams. There is big potential for jaming of the flap tracks if the flaps get a little sideways during deployment or if junk gets in the works.
I also was thinking about the jackscrew system, but just using a servo divorced from it's pot to drive the screw. Here's an exaple of that being used to pivot a turbine engine on a VTOL model:
http://www.corpcomp.com/weeks1/Rig/Moter_moves.html
FWIW- I think use of titanium on model hardware is more trend than science. It just isn't a big benefit vs the cost increase; discuss...
07-25-2003, 10:45 PM
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Yep
Me too!
I'd like to have a correct, tracked, jackscrew system for the King Air, rather than fake it with offset hinges, (done that plenty) if it can be done reliably and strongly.
Maybe we as a group can figure out a good way to do this that will help a lot on our scale projects.
Here are some drawings of real Fowler flap mechanisms that you may have seen. (patent drawings, and some nice (Russian) drawings I recently found.)
I'd like to have a correct, tracked, jackscrew system for the King Air, rather than fake it with offset hinges, (done that plenty) if it can be done reliably and strongly.
Maybe we as a group can figure out a good way to do this that will help a lot on our scale projects.
Here are some drawings of real Fowler flap mechanisms that you may have seen. (patent drawings, and some nice (Russian) drawings I recently found.)
07-25-2003, 10:46 PM
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This is a "Fowler" flap!!!(and a 737 flap)
Been there done that!The problem with using a servo is the reduction is already present in the unit. The motor I'm using turns 16,000 rpm and the rolled all rod reduces this alot. Using a servo may be ok, but your wife, kids and buddies at the airfield will all be home asleep 
before that flap passes 30 degrees. Dean
before that flap passes 30 degrees. Dean
07-25-2003, 11:06 PM
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This is a "Fowler" flap!!!(and a 737 flap)
Originally posted by dean apostal
Been there done that!The problem with using a servo is the reduction is already present in the unit. The motor I'm using turns 16,000 rpm and the rolled all rod reduces this alot. Using a servo may be ok, but your wife, kids and buddies at the airfield will all be home asleep before that flap passes 30 degrees. Dean
Been there done that!The problem with using a servo is the reduction is already present in the unit. The motor I'm using turns 16,000 rpm and the rolled all rod reduces this alot. Using a servo may be ok, but your wife, kids and buddies at the airfield will all be home asleep
before that flap passes 30 degrees. Dean
Seriously, it would take longer than a direct-connect servo, and that's fine with me. Kinda scale, even. Choosing thread pitch, etc can be used to adjust speed to some extent.
I get the feeling though- especially since I would want two pushrods per surface to avoid jamming - that just putting 2 smaller servos per flap segment with normal pushrod setup will be the most effective control method for what I need.
07-26-2003, 04:33 AM
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So, how about some parts?
Dean,
Would you consider letting us know where you got some of the parts, such as the threaded rod and limit switches? I assume that if we use gearboxes, we'll each have to figure that out on our own, if yours are custom made.
I'd like to start constructing some (outside the plane) prototype mechanisms, and get as many of the bugs worked out as possible before sticking it on a wing.
Thanks!
Would you consider letting us know where you got some of the parts, such as the threaded rod and limit switches? I assume that if we use gearboxes, we'll each have to figure that out on our own, if yours are custom made.
I'd like to start constructing some (outside the plane) prototype mechanisms, and get as many of the bugs worked out as possible before sticking it on a wing.
Thanks!
07-26-2003, 02:27 PM
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This is a "Fowler" flap!!!(and a 737 flap)
Yes that would be fine...lets make sure that when everything is hooked up it actually works. Alot of work, theory and was it you that said sanding? My life is measuring! Gear boxes were first made in metal and then a mold was made and the samples are urethane, light and strong.Enclosed is one of my early mechanical flaps. Plane is trying to be DC-9 50 series. It has leadfing edge Droop not slat and spoiler set at trailing edge. Outboard augmentation spoiler rolls with aileron(ala Boeing not Douglas) well boys... this forum won't allow me to attach a 295 DPI photo of my plane...What a joke!!! If anyone wants to see a photo of it let me know a address I can send it to.Dean
07-26-2003, 10:39 PM
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Flaps, Slats, Spoilers
Cool, Dean.
I'll go a step further. If several of us here are going to seriously investigate this, I'll host the photos myself. Just email them to me, and I'll create a page and provide the link so we can all have a look.
If you send your name and other details with the info, I'll properly credit each image, too.
Thanks.
I'll go a step further. If several of us here are going to seriously investigate this, I'll host the photos myself. Just email them to me, and I'll create a page and provide the link so we can all have a look.
If you send your name and other details with the info, I'll properly credit each image, too.
Thanks.
07-27-2003, 12:56 AM
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This is a "Fowler" flap!!!(and a 737 flap)
Hello. have you ever seen the worm gear drive of a Nitro .049" Cox "Meyer's Manx" dune buggy? There's a drive system that eats debris at high RPMs!!!
07-27-2003, 03:59 AM
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Here's the web site for RCU "Flap people"
Hi everybody,
I've created a web site where we can collect info on high lift devices, including Fowler flaps, slats, leading edge flaps, spoilers, etc..
The site is at http://homepage.mac.com/mikejames/rc...ite/index.html
Send any articles and images you like to my email address, and I will post them on the site and credit your for the contribution. Have fun!
- Mike James
I've created a web site where we can collect info on high lift devices, including Fowler flaps, slats, leading edge flaps, spoilers, etc..
The site is at http://homepage.mac.com/mikejames/rc...ite/index.html
Send any articles and images you like to my email address, and I will post them on the site and credit your for the contribution. Have fun!
- Mike James
07-27-2003, 09:52 PM
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fowler
Here's a sketch of what I'm using for a warbird. Two mid-cord carriers slide on tracks in the "roof" of the wing. Two pins (not shown), on the flap leading edge ends, slide in guide slots in the adjacent ribs.
07-28-2003, 01:33 AM
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Thanks!
toy264,
Thanks for contributing. I've added your image and comments to the "RC Linkages" of our new high lift site, at
http://homepage.mac.com/mikejames/rc...ite/index.html
All RCU participants are invited to add their ideas. We can build up a pretty good reference library fast. Take a look where this site has gone already, and I only built it yesterday. (!)
Thanks again to all. Keep 'em coming.
Thanks for contributing. I've added your image and comments to the "RC Linkages" of our new high lift site, at
http://homepage.mac.com/mikejames/rc...ite/index.html
All RCU participants are invited to add their ideas. We can build up a pretty good reference library fast. Take a look where this site has gone already, and I only built it yesterday. (!)
Thanks again to all. Keep 'em coming.
03-13-2011, 08:45 AM
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RE: Thanks!
Hey Mike James,
where did you get that second picture of that flap mechanism in Post # 10? I'm doing a school project on that exact flap mechanism and I'd like to know what website it is from to see if there's any other information on it.
I'd really appreciate your help
Thanks in advance,
Sean
where did you get that second picture of that flap mechanism in Post # 10? I'm doing a school project on that exact flap mechanism and I'd like to know what website it is from to see if there's any other information on it.
I'd really appreciate your help
Thanks in advance,
Sean
03-13-2011, 05:20 PM
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RE: This is a "Fowler" flap!!!(and a 737 flap)
Mike James' website was moved from the old link shown in that 8 year old post some years back. Try PM'ing him directly to see if he has the old drawings or pics still available.