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Experiments and Builds
#1

As I am a builder at heart, I thought I'd start a new topic for discussion of your latest designs, experiments and scratch builds.
This is not athread for discussing mods to ARFs or overclocking your funjet but for new designs or inovative builds with interesting materials or designs from first principles using traditional techniques.

Drew

Code:
---------------------------------------------------------------------
Built-up
Balsa:                            Commercial:           Depron:
Great Planes PT-20 (modified)     HK Hawk 80            Index 3
Indoor Thingy                     Skyartec Cessna 182  
Katana X lite (in construction)   UM SU-26              12"WS Shoestring (Plantraco)
                                  HK Extra 260
and a Fox chuck glider converted to RC
---------------------------------------------------------------------
Reply
#2

To start things off, I'll rop some pictures and a vid of my experiment with SPAD. This is based on the FNS 0.15 design. However, this is based on the use of Canadian square PVC downpipe. I've substituted a 16mm Ally channel for the fuse and made experimental motor mount to suit a slavages EMax motor.

The first pseudo-maiden proved that
1. the prop was way too small
2. the wheels were way to small

I measured the thrust of the 7x5 prop by standing the model vertically on kitchen scales (in the lounge room) and gunning the motor. I got about 400g of thrust against an 820g model. A 10x4.7 prop gave almost 800g thrust but the motor was getting warm with the load.

Regardless, my next try will be a quick hop wit hthe 10" prop as I don't have any 9" props about and I get pretty twitchy impatient at this point of building somenthing Wink


Attached Files
.jpg PB271859-10.jpg Size: 58.17 KB  Downloads: 313

Drew

Code:
---------------------------------------------------------------------
Built-up
Balsa:                            Commercial:           Depron:
Great Planes PT-20 (modified)     HK Hawk 80            Index 3
Indoor Thingy                     Skyartec Cessna 182  
Katana X lite (in construction)   UM SU-26              12"WS Shoestring (Plantraco)
                                  HK Extra 260
and a Fox chuck glider converted to RC
---------------------------------------------------------------------
Reply
#3

Hi Drew

Great little Build, Nice.

P.s I too use the digital weight scales for thrust testing as it gives a great guide, I also have a digital fish scales that work OK as well on the tail of plane.

I Too Like Custom Building, But So Far on Existing ARF etc not Scratch Build.
But I am Keen to Do Some In the near future as i have a couple of really out there designs with some unusuall concepts on paper.

Steve Smile

What Do You Mean Theres a Throttle Curve ?, Its Either all the way up or all the way down Tongue_smile
Reply
#4

For some reason, the vid didn't seem to upload (Aha! .AVI file). Here's trying again.

[youtube]http://www.youtube.com/watch?v=R5xelyDaV5Q[/youtube]

If you look carefully, you will notice the dodgy prototype use of a drill bit for the front wing dowel and bamboo skewer for the rear wing dowell. I did this to add more frontat weight and also because I didn't have anythng else handy on the bench Smile. This will obviously need to be corrected before any serious flying.

Drew

Code:
---------------------------------------------------------------------
Built-up
Balsa:                            Commercial:           Depron:
Great Planes PT-20 (modified)     HK Hawk 80            Index 3
Indoor Thingy                     Skyartec Cessna 182  
Katana X lite (in construction)   UM SU-26              12"WS Shoestring (Plantraco)
                                  HK Extra 260
and a Fox chuck glider converted to RC
---------------------------------------------------------------------
Reply
#5

good video drew but we need some keen eyesight to see the drill bit and skewer. Biggrin
Good to see someone with engineering skills.

Paul

Jet Teng L39(Breitling)
Scratchbuilt F14 Tomcat(Pukin Dogs)
Vector X
Eflite F86 Sabre(Taz Tiger)
Qantas Airbus A380(Nancy-Bird Walton)
Boeing 737-800
ProEDF F16
Falcon 120(Gas Turbine)
Fly Fly F100 Super Sabre
Pheonix Tiger 6
VQ Models P61 Night Fighter
CY Models FW190

Reply
#6

There is plenty of info online regarding building & design of RC aircraft;
this link is particularly useful:
http://adamone.rchomepage.com/cg_calc.htm
for calculating the numbers for your plane to make it fly correctly -
Centre of Gravity, Neutral Point, Aerodynamic Centre & such things.
I found it usefull for calculating the C of G of my Glider.
As it has swept wings, the location is not so obvious (with straight wings C of G is roughly 25% of the Chord from the leading edge).
I used this calculator and my Glider subsequently flies well balanced.

John Jelovic
Planks: Lark, California 28, Skyartec Cessna 182, Skyfun, Extra-300S EPP 3D, Stinger 64 EDF, Rare Bear 1400mm,
Durafly P51 Mustang, Edge 540T 3D.
Helis: Blade mCPX, Blade 450X, HK450GT V2Belt, Gaui 550 Hurricane.
Spektrum DX9, DX7se & DX4e
Reply
#7

I use X-plane for my aeronautical musings, Its come in handy for obvious reasons:
   

And not so obvious Wink
   

Maximum kudos to the first member to turn his aircon into this:
   
Reply
#8

being a drug free club im not sure any of our members could produce such craft kieran Biggrin

Jet Teng BAE Hawk 2010 Demo Team
Sapac Blue Arrows Hawk
ESM Texan II / 35cc Gasser
PRO-EDF Composite F16
HK 450 Heli
Seagull PC-9
Parkzone Habu
Falcon 120 (Prepping for Kingtech K100 turbine )
Spektrum DX6i



Reply
#9

I've consulted the plastic surgein and am currently talking to the weight loss experts (robair) but here's my baby all marked up and ready to go under the knife.
(any last minute comments/ suggestions?)


Attached Files Thumbnail(s)
       

Drew

Code:
---------------------------------------------------------------------
Built-up
Balsa:                            Commercial:           Depron:
Great Planes PT-20 (modified)     HK Hawk 80            Index 3
Indoor Thingy                     Skyartec Cessna 182  
Katana X lite (in construction)   UM SU-26              12"WS Shoestring (Plantraco)
                                  HK Extra 260
and a Fox chuck glider converted to RC
---------------------------------------------------------------------
Reply
#10

Kieran dropped by with my white covering on sunday night so it was out with the knife last night. I chopped all the holes, making those on the fuse a bit bigger and rounding all the corners to keep maximum strength.

Original flying weight without the battery = 1760g
I've subtracted 66g of balsa from behind the balance point. 46g came from the stabiliser and tail fin! = 1694g

The result is that the balance point has moved about 40mm forward on the wing. this should allow me to drop a couple of batteries.
I'm hoping I can drop 4x the weight from the nose to let the balance point move back to 30% chord = 1694g - 4x66g = 1430g. That's an 18% weight loss but I'm still nowhere near the biggest loser! Frown.

I did notice a dent near the tail which occurred about 3 sessions ago is now structurally relevant so I'll stick a little beam back in there to re-join that corner.
My next step is to drill holes in all the beams in the stabiliser and tail fin. I'd like to get to 100g cut out of the fram but I'm afraid that I'll start hurting strength before I get there.







Attached Files Thumbnail(s)
           

Drew

Code:
---------------------------------------------------------------------
Built-up
Balsa:                            Commercial:           Depron:
Great Planes PT-20 (modified)     HK Hawk 80            Index 3
Indoor Thingy                     Skyartec Cessna 182  
Katana X lite (in construction)   UM SU-26              12"WS Shoestring (Plantraco)
                                  HK Extra 260
and a Fox chuck glider converted to RC
---------------------------------------------------------------------
Reply
#11

Gday Drew

Nice one however you have only just begun, now you need to drill a zillion holes in what's left.
Have a look at my photos on the easy sport rebuild thread to see what I mean.

Cheers
Rob B
Reply
#12

I got another 6g at the tail by drilling 120 holes.
Here it is, all ready for re-covering, back to her naked glory and with the minor fuse repair.

Now, without the ballast and battery, it weighs 1440g. Hopefully, I won't need to put too much ballast back on the nose to get a decent COG back.





Attached Files Thumbnail(s)
       

Drew

Code:
---------------------------------------------------------------------
Built-up
Balsa:                            Commercial:           Depron:
Great Planes PT-20 (modified)     HK Hawk 80            Index 3
Indoor Thingy                     Skyartec Cessna 182  
Katana X lite (in construction)   UM SU-26              12"WS Shoestring (Plantraco)
                                  HK Extra 260
and a Fox chuck glider converted to RC
---------------------------------------------------------------------
Reply
#13

Here's my PT-20 all covered up and re-assembled.

Except for the collet which holds the nose wheel Frown. After I cleaned the bench, threw out all the covering off cuts and hung the plane back up in the shed, I discovered the collett which holds the nose wheel on the floor near the bench!!! I had better make sure I replace this before the re-maiden in a couple of weeks. Eek


In the end, the balance you see is with no extra ballast. That's a saving of 167+72g = 339g, almost 20% of the original model weight.

The AUW (including the battery) is now 1,584g. That's enough for me to put 2x3s2200's in series for 6s performance at the original weight Icon_evil - somehow, I'm not sure the speedy/motor/airframe could take that.

Now... how do I engineer some field time? ...

Drew

Code:
---------------------------------------------------------------------
Built-up
Balsa:                            Commercial:           Depron:
Great Planes PT-20 (modified)     HK Hawk 80            Index 3
Indoor Thingy                     Skyartec Cessna 182  
Katana X lite (in construction)   UM SU-26              12"WS Shoestring (Plantraco)
                                  HK Extra 260
and a Fox chuck glider converted to RC
---------------------------------------------------------------------
Reply
#14

    Hang in there young Luke Skywalker (AKA Drew), eventually experience & creativity will come together reaping great rewards. - Yoda 50_50
Reply
#15

I had the raptor down at the filed today and discovered 3s is essential - probably a bit more grunt would be great too.

Here's a couple of pics of its earlier "landings".


Attached Files Thumbnail(s)
           

Drew

Code:
---------------------------------------------------------------------
Built-up
Balsa:                            Commercial:           Depron:
Great Planes PT-20 (modified)     HK Hawk 80            Index 3
Indoor Thingy                     Skyartec Cessna 182  
Katana X lite (in construction)   UM SU-26              12"WS Shoestring (Plantraco)
                                  HK Extra 260
and a Fox chuck glider converted to RC
---------------------------------------------------------------------
Reply
#16

After having the F22 at the field the other day, I've swapped the 2805 to a 2822 and a 7" prop. This makes a heap of difference but a control rod came unglued on one of the elevons and the result was a similar landing to that pictured above Frown.

The good not is that this signboard stuff seems indestructable! No airframe damage at all Redface.

More super glue/ araldite and stiffer control rods required.
After several nose-ins and meetings with the wall, the front end of my Index 3 waslooking severley inadequate. I've cut it off, grafted on a new on and added a bit of carbon to stiffen the wing.

Took it out today with the new Turnigy 2204-14T and 8x4.3 prop on a 6A speedy (all Steves recommendations - thanks!) and the power is awesome! I flew out my 500mAh pack after my son was asking "how long before you land dad?". Leet Most of the time, I flew around at 1/3 throttle which is less than 2A.

The pitch balance is quite nice although laterally it likes to roll right. I was using the rubber bands included with the motor (doubled over) and when I went WOT for a tight loop or a U-turn with the rudder, the prop flew off!! With the balance just right, hard up elevator gave a nice elevator glide to the ground with no panic, no grief.

I think my skill level is still soccer pitch rather than basketball court but I'll keep squeezing in practiec as I can.

FYI: The 2204-14T produces about 300g thrust on 8A @ WOT.

Drew

Code:
---------------------------------------------------------------------
Built-up
Balsa:                            Commercial:           Depron:
Great Planes PT-20 (modified)     HK Hawk 80            Index 3
Indoor Thingy                     Skyartec Cessna 182  
Katana X lite (in construction)   UM SU-26              12"WS Shoestring (Plantraco)
                                  HK Extra 260
and a Fox chuck glider converted to RC
---------------------------------------------------------------------
Reply
#17

There's an indoor pattern flying session tomorrow so I figured it was time to finish my new Index 3. Nothing spectacular but my first go at pull-pull controls on elevator and rudder.


Attached Files Thumbnail(s)
           

Drew

Code:
---------------------------------------------------------------------
Built-up
Balsa:                            Commercial:           Depron:
Great Planes PT-20 (modified)     HK Hawk 80            Index 3
Indoor Thingy                     Skyartec Cessna 182  
Katana X lite (in construction)   UM SU-26              12"WS Shoestring (Plantraco)
                                  HK Extra 260
and a Fox chuck glider converted to RC
---------------------------------------------------------------------
Reply
#18

Very Nice Drew, Nice Build.

I Think I may Get a bundle of Depron Sheet sizes next Time a Order Is Done.

I Enjoy Building Myself.

Steve Smile

What Do You Mean Theres a Throttle Curve ?, Its Either all the way up or all the way down Tongue_smile
Reply
#19

Steve,

Thanks. The proof of the build will be in the flying. I've had a tentative hover in the lounge room and it feels like it'll be ok.

If there's interest for 12 or so sheets, I'll fill up the pack and happily order more. I have more ideas than time or materials these days and the foamy build methods make experimenting with prototypes so easy Smile.

Drew

Code:
---------------------------------------------------------------------
Built-up
Balsa:                            Commercial:           Depron:
Great Planes PT-20 (modified)     HK Hawk 80            Index 3
Indoor Thingy                     Skyartec Cessna 182  
Katana X lite (in construction)   UM SU-26              12"WS Shoestring (Plantraco)
                                  HK Extra 260
and a Fox chuck glider converted to RC
---------------------------------------------------------------------
Reply
#20

My plane just went for a swim.... pictures @ 11 Wink

Drew

Code:
---------------------------------------------------------------------
Built-up
Balsa:                            Commercial:           Depron:
Great Planes PT-20 (modified)     HK Hawk 80            Index 3
Indoor Thingy                     Skyartec Cessna 182  
Katana X lite (in construction)   UM SU-26              12"WS Shoestring (Plantraco)
                                  HK Extra 260
and a Fox chuck glider converted to RC
---------------------------------------------------------------------
Reply


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