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Aug 30, 2012, 04:51 PM
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vtdiy's Avatar
Cool! subbed. I saw flying boxcars as a kid in Louisiana. I think I remember that toy, too. Love twin boomers for flying.
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Aug 31, 2012, 05:42 AM
AMA 986339 FCC KB5LAM/4
davidterrell80's Avatar
Thanks for joining in. I would have had the power system completely mocked up on the test stand last night but I couldn't find a servo connector Y to join the two speed controllers at the receiver. As I sit here, I also realize that I haven't reprogrammed the second ESC to 2S.

So, I'll be making a stop at the local hobby shop and, hopefully, will have pictures to share tonight that show the power system with two props turning.

Then, it will be time to make and mount the firewalls; stuff the power system in the airframe; ground test the motors; paint and install the cowlings; touch up the body paint in a few areas; and, think about finding some tall grass to test fly over.
Aug 31, 2012, 07:39 AM
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vtdiy's Avatar
I hadn't really looked carefully before, but maybe it's the pix, it just looks like the vert stabs are kind of small.

There's a lot of frontal area in the main pod, so I hope there is enough stab area to counteract it for good stability. I think you could increase the size of those without too much pain if you wanted at this point. Might make it easier to fly.
Aug 31, 2012, 03:49 PM
AMA 986339 FCC KB5LAM/4
davidterrell80's Avatar
The toy's vstabs are way too small.

So, I gave the flying version a tail volume coefficient equal to the HZ Champ, so I think they'll be enough; especially as they will be in the slipstream of the props.

I was worried about the wing loading, so I made the bottom of the fuselage a bit flatter than the toy, for additional lifting surface. I also believe the amount of fuse below the center of lift will provide plenty of effective dihedral.

I've run the design through the spreadsheets I developed during my rubber FF days, when I still worked at Bell Helicopter... before 9/11 changed my career arc... I miss being an engineer... WAH!... and it should be fine. If there is still some dutch roll, I'll add more.

Here's the motor test data:

One E-Flite Park 180
Continuous Current 2.6A w/ 3.2A burst limit

E-flite 10A ESC programmed for 2S use

I have unmodified clearance for a 4.75 inch dia prop. Any more, and I'll be making a slot in the fuselage to accommodate them.

I looked a three props, running 2S@100%:
Baseline: 6030x2 ran 3.2A and 25.1W
Candidate 1: 4530x2 ran 2.3A and 17.4W
Candidate 2: 4025x2 ran 1.6A and 12.7W

I wish I could find a 4530x3... it would probably be perfect. GWS makes a 4540x2 but the LHS didn't have any. If it needs some more low-end power, I'll find some.

So, I cobbled the entire powersystem together and ran her up. The wattmeter readings are in the photo... 4A and 30W... and this after a few minutes of running.

So, I'm going to grab a bit'o'dinner and go cut and mount my firewalls.
Last edited by davidterrell80; Aug 31, 2012 at 04:14 PM.
Aug 31, 2012, 04:07 PM
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vtdiy's Avatar
okay, hats off to you!
Sep 01, 2012, 09:00 AM
AMA 986339 FCC KB5LAM/4
davidterrell80's Avatar
She lives!

Last night, I made and installed the firewalls. This morning, I mounted the motors and fed the power systems components into the fuselage. I dressed her with propellers, and hooked up the 800mAh 2S and everything works! The big battery even fits under the hatch.

Of course the battery is dead in my camera and it will be another half-hour before I can take photos.

The current weight (all up flying, minus battery, wheels and cowls) is 219 g... not bad, considering my post #7 pre-construction estimate was 204g. Well that's still 7 percent out and, I'll probably be 10% out when I done... anyway; I stood her on her tail, on the scale, and at WOT it appears the thrust to weight ratio is in the vicinity of 0.7 with this prop.

As she sits, I need to finish, paint and mount the cowlings; put wheels on her; touch up the paint; wait for the end of the rain; and, find some open space & tall grass.

It was most gratifying when I first advanced the throttle, to see her begin to ski across the table on her nubbin' knees.
Last edited by davidterrell80; Sep 01, 2012 at 01:06 PM.
Sep 02, 2012, 09:36 AM
AMA 986339 FCC KB5LAM/4
davidterrell80's Avatar
I went out this morning for test flights... I had one.

I learned several things.

1. I need twice the down thrust.
2. I need to double and triple check the CG.
3. It's amazingly crashworthy.
4. I should have waited until after flight testing to add the wheels.

That said, when I got it leveled for a moment and used repeated short surges of power to keep her speed up, there were signs that give me great hope of her being a good flyer.

Adjustments and minor repairs this evening, after religious obligations are satisfied.

Sep 04, 2012, 05:49 AM
AMA 986339 FCC KB5LAM/4
davidterrell80's Avatar
Repairs and modifications are complete.

I've added down thrust; making the total about 5 degrees. I've also added some more right thrust. I'm not counter-rotating the motors as I was concerned turning one prop about might reduce the efficiency of one of the motors.

When I precisely measured the CoG, I found I needed to move the battery forward another centimeter, to get it exactly where I'd planned it.

I will leave the wheels off, until things look better.

Sep 05, 2012, 08:13 PM
AMA 986339 FCC KB5LAM/4
davidterrell80's Avatar
On final inspection, I found one more thing to do.... the elevator pushrod was loose in the control horn.

I did take a couple hours and make a box for her.

I need to get the expanding foam and make the cradle, in the box; but, the bubble packing will get me to and from the flying field for a while.
Sep 06, 2012, 12:32 PM
Registered User
cracksmeup's Avatar
Sounds like you are getting a handle on it Dave,i hope the next try goes well. If it does not go well you could always bury it in the box but do me a favor put a cat in there first. I still have two planes sitting in my closet that i did not give up on yet but the aggravation is still there.I will dig one out and do the new mods on it to see if i can get them to fly sooner or later . joe
Sep 06, 2012, 07:28 PM
Registered User
maurice076's Avatar
O.k. I went through the whole thread and I didn't see the part where the CAT ate the new wing.Whats up with that Joe?..Great looking fattie there Dave I'm sure your next attempt will be better.Scott.
Sep 06, 2012, 08:48 PM
AMA 986339 FCC KB5LAM/4
davidterrell80's Avatar
Oh, I'm just waiting for the weather to change, so I can go out and have test session #2. The checklists (yes, multiple) are complete and she's ready to fly.
Sep 07, 2012, 08:22 AM
Registered User
cracksmeup's Avatar
Originally Posted by maurice076
O.k. I went through the whole thread and I didn't see the part where the CAT ate the new wing.Whats up with that Joe?..Great looking fattie there Dave I'm sure your next attempt will be better.Scott.
Iam a dog person but we have neighbors that had their dog attack their own cat and they asked my girlfriend could keep their cat here for a little while. That was 6 years ago and the cat is still here and has taken a liking to me. I will never get use to having a sneeky cat around but iam getting better at it.
Sep 07, 2012, 09:52 AM
Addicted to building...
Freddie B's Avatar
Our kitty is now like 10 pounds. He pulls pieces out of the carpet if I shut a door because he has to be near ME all the time. I don't even like him because he is such an . He expects me to give him treats everytime I go in the kitchen. Maybe he thinks he is on of my Grandkids??? Only hairy. LOL.


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