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Old Mar 29, 2013, 10:03 AM
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Build Log
First liner - HK Geronimo / flyfly 2.0m

This will be a detailed build log of the Geronimo 2m powered glider.

I want to show others building this airframe my techniques and mods, while hopefully I can get advice from some of the high performance veterans on the setup.

I will be including lots of photos of the build then eventual flight videos. Then start changing the power system components for more speed.

This is a super cheap airframe out of china, fiberglass molded fuse, and built up balsa sheeted wings that are covered. Although low tech it should be able to hold up at some extreme G's, the wing joiner is a 10mm solid carbon rod, this slips in side fiber glass tubes in the wings.

I think this plane is for someone who wants to try out hotliners but has a limited budget or just wants a cheap plane to try out before spending some more on a quality ship.

You do need some build experience though, as its assembly is questionable and not plug and play. You need to be comfortable with epoxy, making mods etc.

The covering is all tight and nicely done, I like the colors. Bottom sid is white. The molding of the fuse is nice but it has some alignment issues that I will be fixing.

The fuse is HUGE, so I can run any battery I want. 6s 5000mah is possible in two 3s pacs.

My first mod will be to make the V-tail removable for transportation.

I ordered the PNP 2m versions from hobby88 who sell just flyflyhobby products direct. It comes in a 2.6m and 3.0 version also. Its also available from hobbyking and some other places. Not really plug and play though, it has all the servos, a esc, motor and folding prop but they are not installed. I paid about $210 delivered
http://www.hobby88.com/shop/product_...roducts_id=408
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Old Mar 29, 2013, 10:12 AM
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I suspect you may need to prepare yourself for the fact that those wings may not be able to handle 6 cell power...

Chris
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Old Mar 29, 2013, 10:30 AM
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True, thats the maximum thats possible. I will build up to that in increments. I think they would fold just outside of the joiner spar.
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Old Mar 29, 2013, 10:35 AM
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Im also worried about the nose ripping off with too much power so I need to renforce the motor mount and nose area.

At what RPM do folding props explode? Plastic vs carbon? At a certain rpm you have to ditch the folding prop for a small speed prop right?
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Old Mar 29, 2013, 11:08 AM
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The V-tail is designed to be controlled by two 20gram servos that are mounted just under the canopy in a ply former. The kit includes music wire pushrods. This might be an alright setup but I dont like it for several reasons. So Im going to try a different setup for the servos.

Firstly the ply servo tray was poorly glued in, one side was cracked and it pulled out by hand quite easily. If you plan to use this pull it out and re-glue it. Second thing I dont like is the push rods dont include any kind of guide down the fuse, they will flex massively so you must make some guide system. Teflon tubes glued to the inside of the fuse is probably the way to go. But this is a huge pain in the azz so I plan to skip this whole setup all together.

I already checked the CG 80mm from leading edge, it seems a bit nose heavy. After ripping out the servo tray I was blown away by how free and open the fuse would be. So given these facts I plan to mount the v-tail servos in the tail right under the control surfaces. Using some micro 11gr instead of the 20 gramers. This will help CG, and give nice short linkages. Also I dont have the pain of making the push rod guides. Its going to require some cutting and hacking and will give slightly more drag.

Installing servo extensions is so much easier than doing the push rod guides.

Since I dont have the pushrods I removed the standard control horns / rods. They also caused some binding, which reduced the down throw.
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Old Mar 29, 2013, 12:30 PM
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Quote:
Originally Posted by lrdesigns View Post
.........
At what RPM do folding props explode? Plastic vs carbon? .....?
I suggest you look at the maximum rpm for Aeronaut props to get an idea of what a good plastic prop will do-:
http://www.aero-naut.de/en/products/...ropellers.html

It will be a lot higher for a good carbon prop, but you also need to consider the acceleration and braking forces as well as max rpm. What sort of power levels are you planning on.

Quote:
Originally Posted by lrdesigns View Post
.........At a certain rpm you have to ditch the folding prop for a small speed prop right?
Not necessarily. It depends on what you are trying to achieve and which particular props you are talking about. There are small folding speed props.

Dick
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Old Mar 30, 2013, 12:56 AM
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Incidence angle?

Thanks for that Dick. I think I would prefer large folding props, for the sound and static thrust.

Does anyone know what the correct incdence settings are for a plane like this? Im assuming 0 deg from wing to tail, (for minium drag) zeroed to an imaginary line from the motor axel to the rear center of the fuse?

I just picked up this sweet robart incidence meter at the LHS.
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Old Apr 01, 2013, 07:31 AM
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@dickw
Quote:
It will be a lot higher for a good carbon prop, but you also need to consider the acceleration and braking forces as well as max rpm. What sort of power levels are you planning on.
22v X 100 amps so max around 2000w - I will start at 250w-500w Then probably buy a new motor for between 1000-2000w

More than 2000W and all the parts starting getting really expensive and enough power to break things easily.

As I plan for bigger motors later Im going to shorten the nose for CG and larger diameter, reinforce the fuse and build a thicker motor mount.

I like the looks of this 40-25 525kv scorpion motor http://www.scorpionsystem.com/catalo...s40/S-4025-10/
At 22volts the RPM should be 11,000 - what would be a good folder at this RPM?
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Old Apr 01, 2013, 08:01 AM
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Was not happy with the straitness of the wings so I decided to reset the spar. The plan was to drill it out the sleeve then re-glass a new one inside while positioning the wings perfectly strait.

Also I needed a hole to get the glass inside the fuse. So I hacked a hole in the top. I will re-enforce this are later with carbon toe.

I plan to keep the hole as an acces to the wing securing mechanism. Which Im thinking will be two hooks pulled together by a zip tie
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Old Apr 01, 2013, 12:11 PM
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Quote:
Originally Posted by lrdesigns View Post
@dickw

22v X 100 amps so max around 2000w - I will start at 250w-500w Then probably buy a new motor for between 1000-2000w.........

I like the looks of this 40-25 525kv scorpion motor http://www.scorpionsystem.com/catalo...s40/S-4025-10/
At 22volts the RPM should be 11,000 - what would be a good folder at this RPM?
Since you are tlaking about 22v I assume you would be using 6s Lipo?
I don't have any experience of that motor myself, but I ran the data through MotoCalc and it sugested that a 15x10 folder will give you about 100 amps static with a max rpm of close to 11,000 in flight.

The Aeronaut 15x10 has a max rpm of 9,000 so you should really be looking at carbon props at that power level.
http://www.soaringusa.com/product.ph...cat=60&page=11
plus spinner
http://www.soaringusa.com/product.ph...&cat=58&page=8

You would definitely be wise to start off with the lower powers you suggested and see how you get on with that.

Dick
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Old Apr 04, 2013, 12:28 AM
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Servo layout and wiring begins. Decided not to use the cheap 9g analog kit servos and using some on hand 11g digital servos. Also cheap servos but they are a lot more durable and accurate. They also have thicker spline shafts.

Committed to cutting servo holes in the tail. More draggy than internally installed but it gives me more internal fuse space and nice simple short linkages.
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Old Apr 04, 2013, 08:14 PM
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Looks to me that you are building Wonder Woman's Invisible Jet.

Seems that a light blue plane with white wings will all but disappear against a blue and white sky.
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Old Apr 05, 2013, 12:48 AM
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invisible color

Quote:
Originally Posted by bigblueswope View Post
Looks to me that you are building Wonder Woman's Invisible Jet.

Seems that a light blue plane with white wings will all but disappear against a blue and white sky.
We never get blue skies where I live so it don't bother me. I'm going to put red strips on the underside to help orientation.
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Old Apr 05, 2013, 12:55 AM
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Zero incidence

I have finally got the wings set. Both set to zero degrees incidence, to each other and to the fuse center line.

The V-tail seat was widely crooked. So it was some extra setting here. But now its going to fit like a glove.

I have noticed some difference between this flyfly version and the hobbyking version. The HK one has the wings top mount on the fuse, and this one side mounts.
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Old Apr 10, 2013, 12:55 AM
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V-tail and servos

Epoxy dried on the V-tail saddle. Installed the servos and made a long wire harness.

Quite happy with the supper short linkages. The servos stick out a lot more than I had imagined. I wanted the arms at a 90 deg angle to the control surfaces so this made them stick out more.

After getting everything hooked up I started testing and doing the radio mixing. This is where I had some problems, one of the servos would intimately oscillate at high speed. This made me and then get depressed. Because I assumed the problem was in my wire harness which took ages to make and would be difficult to find the exact location of an issue, or a faulty servo, which I took a short cut and hot glued in. Did not want to have to take it out. So I stoped working on it for 48hrs and worked on low stress depron F22 for a bit.

Then did some more testing with the radio to try to figure out the issue. It was strange, sometimes the left servo would do it, sometimes the right. But it was hard to replicate. Shaking the wire harness did nothing. The oscillation was sort of like if the servo was turned on / off / on / off really fast. Checked if my receiver was loosing power, seemed not. On this behaviour I thought it was power related. So I took out the 1 cell lipo I was using to power the receiver and checked the voltage 3.6v

Changed it for BEC power and the problem was magically gone. Very relieved it was so simple to fix and not due to my soldering skills. Live and learn.
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