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Old May 05, 2005, 03:23 AM
Gloves are awkward
ipjodan's Avatar
Preston, UK
Joined Dec 2004
1,202 Posts
Flaps question

Hi there,

For a new challange ive added the landing gear in my brushless spit to practice ROG and landing, after some practice (and lots of repairs) im getting it, ive noticed this plane comes in hot, and as my runway is a single track road (next to my grass field which is to rough to land in) i need to be accurate. Can i install flaps on this plane to slow it a little on approch?, I have a 6 channel (non computer TX) and 6ch RX. Also can any one point me to a good set of wheels?

Thanks in advance

Joseph
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Old May 06, 2005, 11:59 AM
AMA 353531
rdeis's Avatar
United States, CO, Colorado Springs
Joined Aug 2003
6,564 Posts
Absolutely. I did a quick look for 3-views and don't see any full scale Spits that used flaps, but it's a simple matter to cut some out if you can work around the aileron torque rods.

If there's any taper to the flaps make sure they taper towards the tips.

Once they're in, practise deploying them at altitude to get used to how it flies, especially the new stall behavior.

With flaps deployed the airplane will want to hold a nose down attitude in level flight, you need to be ready wth a little down elevator to keep it from ballooning when you hit the flap switch. It feels funny to come in on final approach with the nose pointed at the ground, but if the fuse is level the wing is at a very high AOA with flaps deployed. (Exactly how high depends on flap size and how far you drop them)

Expect the glide path to be steeper and flight speed slower.

Note also that your stall speed is lower with the flaps deployed, so if you miss the approach after you've slowed down for final and decide to go around, sucking the flaps before you get back up to speed will stall the airplane.

Dynaflight has nice light wheels.
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Last edited by rdeis; May 06, 2005 at 12:15 PM.
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Old May 06, 2005, 12:15 PM
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United States, CO, Colorado Springs
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Next question will be "how big" and "how far to drop"

I don't have a very good answer, you might do a search and see if someone else has tried it. The soaring guys will have flaps as big as 30%-40% of the chord and drop them 90 degrees. I think that's very, very extreme and well beyond what you need.

I would make them use most or all of the wing span inboard of the ailerons, and use as much of the chord as is practical given the linkages and everything that are in your way. I would try to make them constant chord, but I think that's not going to happen with the Spit's curved TE. It's fine to let it taper a bit toward the tip, but not toward the root.

Play with different deployment settings at altitude and see what feels comfortable. The more they drop, the more you can slow down- but the steeper the nose-down attitude you need.

If I remember right, the rule of thumb is increasing lift dominates to 15* and increasing drag dominates after that. On landing the drag is helpful to slow you down, so I'd use 15* and 30* as starting points.

Also: Up to 15* can be helpful on takeoff to get you flying and climbing out to safe altitude sooner. With brushless power you may not care, but as long as you've got the flaps anyway... If your radio allows, use seperate landing and takeoff switch positions.
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Old May 07, 2005, 12:43 AM
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kensp's Avatar
Darwin Australia
Joined May 2002
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Quote:
Originally Posted by rdeis
Absolutely. I did a quick look for 3-views and don't see any full scale Spits that used flaps, but it's a simple matter to cut some out if you can work around the aileron torque rods.
Here is a drawing and photo showing the Spitfirs flaps. The Spitfire used split flaps so the top of the wing remains the same no mater if the flap position is up or down.

Ken
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Old May 07, 2005, 02:04 AM
Gloves are awkward
ipjodan's Avatar
Preston, UK
Joined Dec 2004
1,202 Posts
Thanks guys,

What the heck, i think i might just try it.

Joseph
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Old May 07, 2005, 09:37 AM
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United States, CO, Colorado Springs
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Quote:
Originally Posted by kensp
Here is a drawing and photo showing the Spitfirs flaps. The Spitfire used split flaps so the top of the wing remains the same no mater if the flap position is up or down.
Thanks, Ken! I didn't think it made much sense to see a carrier based airplane (supermarine) with no flaps.

Split flaps make more drag than lift, so I'd probably stick with a full flap for the model. Easier to build, too.
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