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        Discussion *** 26" Scythe mini/micro EPP suitcase wing ***

#1 Lee Mar 04, 2010 09:59 PM

*** 26" Scythe mini/micro EPP suitcase wing ***
 
11 Attachment(s)
http://www.crashtesthobby.com/index...._17_The-Scythe

[B][FONT="Arial Black"]The Scythe is a 26" micro wing we built at the request of flyers who wanted a mini/micro hand launch glider, slope soarer, or motorized flying wing. We decided to try to do all three with one plane. The kit comes with 2 planes in the box. We offer the double kit so you can try different things with each plane.

We have been pleased with the flying characteristics of this small plane. I think the biggest surprise is how well it glides even at 8-12 oz AUW. I designed it to fly like the big planes and it is much closer to their performance than I would have guessed it could be.

The Scythe is made of EPP foam and is tough and durable. The 26" EPP foam cores and elevons alone only weigh 1.3 oz making this a true micro plane candidate. How light can you build it???? Several flyers have been trying to get it smaller. I have one cut to 19" and have heard of one cut to a 16" span.

Scythe Setup Specifications:

Use a 30C 750-1300 mA 3S lipoly battery (3 oz)
The battery cut out 2" back from front of wing
The radio slot is back 4.0" and is 8" wide.
The center of gravity is back 5.5" from the nose of the plane.
The flat carbon spar is back 5" on the bottom of the wing.
The flying weight with battery is 6-12 oz.
Use a 12-20A ESC, the Turnigy 2230-1780 motor and MG90S servos.
I recently flew the Scythe with a 2812-1535 motor and it flew great.


Lee

www.crashtesthobby.com

808 #16camera on Scythe

Scythe Target Practice (3 min 32 sec)


Kevin's 6 oz Scythe

Scythe 6 oz 7-12 (1 min 34 sec)


Video of Steve flying a Scythe with his reaction.

1- Scythe 24" ( 4-10-10) (5 min 56 sec)


Here is a video of Scott flying the Scythe flying with 2S.

Scott's Scythe prototype 3-10 (2 min 42 sec)


This is Steve's 4 oz Scythe built as light as he could make it.

Steve's 4 oz Scythe testing. (8 min 51 sec)



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#2 Lee Mar 04, 2010 10:04 PM

#2 It may sound funny to start a thread for a new plane with what not to do as you are building your planes but there are some things to avoid:

Most Common Building Mistakes to Avoid

1. Plane is too heavy. Keep the planes light. A light plane needs less power for high performance and is less likely to break in an accident.
2. Didn't do each step in the right building order. I have heard builders say they got the steps out of order and had to undo to redo it right.
3. Plane is not balanced properly. Flying wings are sensitive to the center of gravity and fly poorly if they are tail heavy. You may have to make adjustments in the placement of your battery and radio or even add weight to get the the plane to balance on the recommended center of gravity.
4. There is slop in the linkages and hinges. Your linkages, hinges and servos all need to be tightly mounted and not flex at all under stress. Most flyers underestimate the forces on a plane in flight.
5. Too much or too little movement in the elevons. If the hinges are too tight the elevons won't go down far enough. Elevator stick should move the surfaces 1/4" and the aileron should also move the elevons 1/4". Combined full elevator and aileron will be 1/2".
6. Batteries get damaged. If your battery has an end or edge towards the front of the plane it may mushroom in an accident. In this plane you will need to lay the battery flat or Velcro it to the outside of the wing.
7. Plane is hard to see. If you can't see it you can't fly it. You need to be able to tell top from bottom of plane. Colors need to stand out in all weather conditions. We like to add a small amount of the colored packing tape, Ultracoat or my favorites are the 163 kinds of holographic tape from http://stores.ebay.com/Paper-Street-Plastics. Link to their 14 color sample packs. http://cgi.ebay.com/Glittering-Sequi...item1c0952f993
8. The plane is not strong enough resulting in flutter and control problems. We like to build reinforce and cover the wing before we go back and cut through the laminate to install the radio. There should be no empty space in the wing. The battery, servos, ESC and receiver should fill all cut out spaces tightly and become part of the solid core making the plane less likely to bend or flutter. Our method removes less foam so it is stronger, easier to build, protects the radio better and has fewer field repairs.
9. Radio problems with programing, weak batteries or weak servos. Get to know your radio. If your radio isn't working right you can't fly your plane. Batteries that are not powerful enough for the motors you are using will last only a few flights. Broken servos are not uncommon for new flyers.

Please give us feedback and try some different motors. This is where we need your help. When you try a any part please post here and tell us if it is the right size for the plane, the right power for the plane and how you installed it.

These building videos are for the Assassin. The planes are similar enough in design that they may help you build your planes

Assassin building instructions #1/3 - 9-09 (5 min 2 sec)


Assassin build 1.5 Tape 3-10 (4 min 8 sec)


Assassin build 1.5 hinge and radio 3-10 (6 min 59 sec)



Assassin bulding instructions #2/3 - 9-09 (4 min 23 sec)



Assassin building instructions #3/3 9-09 (2 min 46 sec)



How to preflight a RC flying wing 12-09 (4 min 22 sec)



Preflight of a flying wing #2 12-09 (4 min 17 sec)






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#3 Lee Mar 04, 2010 10:04 PM

19 Attachment(s)
#3 The instructions have been updated and can be found at

http://www.crashtesthobby.com/index.php?p=1_22_Scythe

Lee



#4 Lee Mar 04, 2010 10:05 PM

Reserved #4

#5 Lee Mar 04, 2010 10:05 PM

9 Attachment(s)
This is a prototype motor mount that is attached only with Velcro.


I like my little foam and Velcro mount. You could also glue this style of mount directly to the plane without the Velcro and it would be tough enough. I like this design because I can switch the motors between planes including trading the receiver and ESC in less than 5 minutes. Since I now have 4 Scythes I don't want to permanently commit a full radio and motor set up to each plane. The only part that will remain with each plane is the servos and linkages.


.

#6 Lee Mar 04, 2010 10:36 PM

Reserved #6

#7 microkites Mar 05, 2010 03:42 AM

Nice work Lee!

will see how they do

mk

#8 Atom1025 Mar 05, 2010 05:59 AM

Lee, curious if you have a "fool" proof way of cutting the roots, I have yet to find a reliable means that yield accuracy. Closest I have come is a chop saw but wing beds are needed to assure the foil is level.

Appears you prolly slice with a razor, unfortunately my hand eye coordination can not complete a true cut...... Usually by the time I am happy its 3" shorter then I planned :)

#9 Lee Mar 05, 2010 06:36 AM

Quote:

Originally Posted by Atom1025 (Post 14512736)
Lee, curious if you have a "fool" proof way of cutting the roots, I have yet to find a reliable means that yield accuracy. Closest I have come is a chop saw but wing beds are needed to assure the foil is level.

Appears you prolly slice with a razor, unfortunately my hand eye coordination can not complete a true cut...... Usually by the time I am happy its 3" shorter then I planned :)

Get your wife to cut the angle. :D Turn the heat up on your iron and melt the angle if you want. Don't try the heat thing on the elevons. Constant hand postion and straight even strokes with a very sharp blade work for me.

#10 nalby Mar 06, 2010 05:27 PM

OK Scythe ordered I'm planing on making it around
22-24" , I'm going to try a hc1811-2000 motor w/ either a 4040,4540, or5030 prop on 2s, turnigy plush 6a speedo,
2 x bluebird 303 3.7g servos ( it's what I have on hand lol )

all the electrics come in about 55 grams.


What do you think,too light too heavy not enough thrust with the
5x3 prop I should be getting around 112g of thrust

#11 nalby Mar 06, 2010 05:32 PM

Here's a Kesl Kfm4 wing I made 20" it's auw is 114grams ELE C10 2900Kv, 105grams of thrust 2s 360 I get 5-7 min flights

KESL20HD1 (2 min 54 sec)

#12 Lee Mar 06, 2010 06:16 PM

Quote:

Originally Posted by nalby (Post 14525199)
OK Scythe ordered I'm planing on making it around
22-24" , I'm going to try a hc1811-2000 motor w/ either a 4040,4540, or5030 prop on 2s, turnigy plush 6a speedo,
2 x bluebird 303 3.7g servos ( it's what I have on hand lol )

all the electrics come in about 55 grams.


What do you think,too light too heavy not enough thrust with the
5x3 prop I should be getting around 112g of thrust

You're a good person to have on board with the project. We need your input. Show us your motor mount set up. How did you make your motor mount strong and light?

I like the fins in the video on your micro plane. The Scythe will look good with something similar to them. I toe the fins in about 1/8" or more and they work better.

If you really want micro I cut this wing with a gentle taper and you could cut a wing down to 15" and get a double micro out of each plane. I would almost be willing to make a bet it couldn't be done but I have not seen planes that small that could perform.

One of our flyers prefers bamboo to flat carbon spars. We sent both in the kit for your to experiment with. When you get your planes you will find 4 wedge shaped foam pieces in the box. These are to use as you want for the motor mounts and they make good sanding blocks to clean the melt fibers off the wings. It was suggested to use a lighter weight string for the shock cord. I put 30# Spider wire braid in the kits. It is so thin and light it is almost hard to handle.

We mailed all of the Scythes that have been ordered so far. We even mailed a pair to Oslo Norway. I love this part of the test on a new plane. Thank you all for your participation.

#13 Lee Mar 06, 2010 06:28 PM

I was out flying the Grim Reaper this morning. It glides like a dream. The Scythe uses the same airfoil and rough lay out.

I'm building 4 Scythes. Each one is different testing different sweep and construction.

#14 nalby Mar 06, 2010 06:47 PM

1 Attachment(s)
The motor mount i'm using is a piece of 1/16 ply hot glued to the foam. I think i'm going to need something a little stonger for the
Scythe. lol what angle do you think I need ? a couple degree's up or down

#15 Lee Mar 06, 2010 08:41 PM

Quote:

Originally Posted by nalby (Post 14525719)
The motor mount i'm using is a piece of 1/16 ply hot glued to the foam. I think i'm going to need something a little stonger for the
Scythe. lol what angle do you think I need ? a couple degree's up or down

Your motor mount is a great idea. It's simple and light. It is what I was thinking.

I think the Scythe will need a couple of degrees of down thrust with the motor aimed at same direction as the angle of the bottom of wing. (I hope)

The carbon strip on the TE I assume is for wing strength. Our shock cord offers strength there too with the spar more in the middle of the plane.


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