Hi,
I have done a lot of experimenting with flappers. Here my views on the issues.
For Gary's question: Why lock the flap at the tips.
1) To get height you need to stop flutter. Flutter starts at the tips, so locking the flap at the tips, helps flutter issues, less flutter translates into more height. If you say your getting to the ceiling already, then you need to make the wing thinner and lighter. All the data I have shows a lighter/thinner wing with locked flaps at the tips, will out perform a heavier/thicker wing with flaps all the way to the tips.
2) To get a great transition you want washout, again locking the flap at the tip achieves this.
3) I have not seen poorer sink rates with the flap locked at the tips.
Now my comments about Bill's questions:
1) How does flap stiffness affect incidence during the climb?
I think of the wing and wing incidence in two parts for a flapper. The front part of the wing that is rigid and the back part of the wing that is a flap. Now with stiffer flaps they don't lift as much during the launch which means you put less incidence in the front part of the wing.
2. WHEN do the flaps affect incidence during the climb?
Depending on the stiffness the flap start working or take affect as the speed of the launch slows down. Typically the flap starts working during the last 5ft of the launch.
3. What's the best way to set initial incidence?
Trial and error. The incidence needed for a flapper is dependent on the flap stiffness, so it is very hard to get the incidence right, until you launch the model about 10 times. I use a wing pylon, tape the wing to the fuse and bring a sanding block to adjust.
4. How does flap camber affect incidence during the climb and then during the glide?
Flap camber during launch has little affect, during the glide it helps a lot. Typically drop the flap about 1/4"; optimum setting is found by trail and error.
5. Connected to all the above: if you trim for a bunt (I normally do) then how does flap stiffness and camber affect when the bunt happens, how much bunt do you get and when does it stop?
I would try not to have a bunt during the launch. A bunt indicates your fuse is too weak and is bending. You can get the same model higher if you don't have a bunt. The shortest distance between to points is a straight line.
6. Can differential flap deflection or stiffness be used to get a better transition?
Yes, if your flying a left-left pattern the left flap should be stiffer.
So that my two cents on the subject.
Cheers,
Kurt
--- On Wed, 3/10/10, Bill Gowen <wdgowen_at_gmail.com> wrote:
From: Bill Gowen <wdgowen_at_gmail.com>
Subject: Re: [Indoor_Construction] Std. Catapult glider
To: Indoor_Construction_at_yahoogroups.com
Date: Wednesday, March 10, 2010, 6:38 PM
Rick
I would never put water on wood flaps. I don't think there is any way to keep them from warping. Even if you DON'T put water on them they will probably warp. This is my main reason for trying foam flaps.
For dry forming wood flaps you just squeeze them between thumb and finger and gently stretch in the direction you want them to go. As Stan says it may take minutes or hours.
Really thin wood flaps seem to expand after being attached to the more rigid front part of the wing. This produces bulges in the flaps that make it impossible to get the shape you want. When this happens I usually wind up cutting tiny chordwise slivers out of the flaps so they can be straightened out and then glue the edges back together with Duco.
For my new foam flaps I used some old Durobatics foam that came curved. I understand the newer stuff is flat. At any rate after you sand the stuff down to flap thickness you can manipulate it pretty much the same way as balsa. I used 5 minute epoxy to attach.
It takes a good bit of flap camber to get a good sink rate. I don't know how much is the right amount but I usually add camber as the day goes on and this usually helps.
There is a heck of a lot going on with flaps in the flight of low ceiling gliders. After a number of years of flying them I still don't understand much of it. Here are some of the questions:
1. How does flap stiffness affect incidence during the climb?
2. WHEN do the flaps affect incidence during the climb?
3. What's the best way to set initial incidence?
4. How does flap camber affect incidence during the climb and then during the glide?
5. Connected to all the above: if you trim for a bunt (I normally do) then how does flap stiffness and camber affect when the bunt happens, how much bunt do you get and when does it stop?
6. Can differential flap deflection or stiffness be used to get a better transition?
And on and on.........
----- Original Message -----
From: themaxout_at_aol. com
To: Indoor_Construction _at_yahoogroups. com
Sent: Wednesday, March 10, 2010 12:26 PM
Subject: Re: [Indoor_Constructio n] Std. Catapult glider
As long as we are talking about flaps on gliders....what is the preferred method to getting the curvature on them? On the std CLG I built for the PPCC I wet formed them...they were balsa, what is the method if using Depron?
Rick Pangell
Editor of "The Max-Out" Newsletter of
The Magnificent Mountain Men FF Club of Colorado
In a message dated 3/10/2010 9:47:57 A.M. Mountain Standard Time, wdgowen_at_gmail. com writes:
I've done it both ways and have had good and bad gliders built both ways. I think Stan's Slow Poker started this method. Drela's Upstart has full span flaps. Two of the talking points for the rigid tip are that it produces washout in the tips (relative to the rest of the wing) and helps control vibration of the flaps.
----- Original Message -----
From: Warthodson_at_aol. com
To: Indoor_Construction _at_yahoogroups. com ; freeflightml_at_ yahoogroups. com
Sent: Wednesday, March 10, 2010 9:07 AM
Subject: [Indoor_Constructio n] Std. Catapult glider
All the category 1 flapper type standard catapult glider drawings I have seen show the training edge flapper free to flex except at the wing tip where it is attached to a ridged wing tip section. This would seem to limit the ability of the flapper to flex. I am curious why this is? Wouldn't it be better to not restrain the flap at all?
Gary
Received on Wed Mar 10 2010 - 12:14:40 CET
This archive was generated by Yannick on Sat Dec 14 2019 - 19:13:46 CET