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Old May 25, 2012, 03:37 PM
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The various mods are all doing their stuff
All is good now, just a bit more rudder throw needed...
.
KFm4 propjet with better ailerons (5 min 32 sec)
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Old May 27, 2012, 04:35 AM
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I would recommend this being built with all doubled main layers.. so main wing, fins, ailerons, elevons, sub rudder, sides and the fuzz vertical shapes are all doubled.. so 12mm thick..
The outer step layer can remain as a single 6mm layer to the step.
I also recommend the insertion of a cloth hinge for all surfaces...
This is to be inserted as you laminate the two layers of the main wing shape together.. you should have cut off the ailerons and elevons prior to this..
Ailerons and elevons are then laminated onto the remaining section of the cloth hinge which protrudes from the main wing.. a similar build is made for the sub rudder
the illustration refers to 3mm depron layers , but for this big jet 6mm is to be used..
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Old May 27, 2012, 04:46 AM
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My prototype model was made using only a single 6mm depron layer for wing, control surfaces, fins, elevons the remainder was doubled up.. because of the power going through this a lot of vibrating of the wings surface was noticable.. So I then beefed it up on the center by adding an extra layer...
On the control surfaces I used full tape cover, even so, the stresses were slightly deforming the depron where the hinges are fitted, so I strengthened the area to spread the loads..

Better would have been to use a doubled 6mm depron layer right through.. then tape that over for even better strength..
All the beefing up ive done has increased the weight to 37oz ... 6.7 ozsqft.. and the thing still goes like a rocket, with no noticed slow flying differences
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Old May 28, 2012, 10:12 AM
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latest video..
.
Big'n propjet on the go (5 min 13 sec)

.
slower flight (3 min 40 sec)
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Old Jun 12, 2012, 06:15 PM
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My small F22 is now being given the sub rudders and a higher mounted motor.. I might also bung on a bigger motor to overpower it..
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Old Jun 12, 2012, 06:19 PM
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F-22 Project

Coming along nicely with some interesting modifications. Thanks for sharing this.
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Old Jun 14, 2012, 03:48 AM
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EDIT... the mods shown here and below are not worth doing they have reduced the performance a lot and rather than remodding it back I will be going down size for a lighter version

On the small one, I am making mods along the same build lines as the big model, but with a more open lower structure..
The first job was to strip the wing of its lower structures
, which were all too shallow for what I am doing
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Old Jun 14, 2012, 04:02 AM
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Because the motor is mounted much higher the small prop doesnt come far enough below the wing to produce a lot of air flow over the rudder.. I will be going with a bigger motor prop combo for flying... more power more fun..

At the moment I am covering up all the filled /repaired surfaces with tape ...
I will be adding another cross brace just before the slot, to act as a flattener for the grass, to keep the prop from cutting into it all the time on take off

Note the lower sides have been placed vertical and are 2" deep at the sub rudder fixing.. they go deeper to a point in front of the COG, where the wheels are placed and they go shallower to the front... Its all a TLAR cut
The lower sides are to work both as fins for high alpha flight and as side area when in knife edge position.
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Old Jun 15, 2012, 05:59 PM
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Its all modded now... a bigger motor setup is being used
AUW is 18.75 oz with better than a 2:1 power to weight
The wing is a 3 layer KFm4 all from 6mm depron

motor emax 2215/20...prop gws 9x5 cut down to 7 3/4x5... a Rhino 3 cell 20C 1300 lipo...30A ESC... 2 x emax metal geared servos on the elevons and an sg9 on the rudder...Hitec 35Mhz REC..
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Old Jun 18, 2012, 05:00 PM
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Ive had a fly today and, as it is , it is very poor.. some really weird behaviour that I am putting down to vertical areas... I think Ive got too much side and front area and with the original tail area its not going right..
Ive seen an rc powers video with the same fault/behaviour on one of his... the solution was to increase the tail fin area, so thats what I will do..
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Old Jun 22, 2012, 04:06 AM
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Ive now enlarged the fins.. doesnt look like an F22 so much but hopefully it wll be more stable
here is a video showing the problem.... at 40 secs in .. it looks like it span out.. I was only doing a gentle banking turn at moderate to low power
.
F22 stability problems (2 min 59 sec)
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Last edited by davereap; Jun 22, 2012 at 04:31 AM.
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Old Jun 26, 2012, 01:06 AM
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and here is my KFm4 F22 now with bigger fins.... now stable, but lacking in power as Ive underproped the motor
.
Bigger fins on my F22 have sorted the previous stability issue (4 min 11 sec)
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Old Jun 26, 2012, 08:42 PM
Standing Athwart History
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What a nifty build.
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