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My Take on Keith Morgan’s PT-19 Trainer Babe_b10
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My Take on Keith Morgan’s PT-19 Trainer

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My Take on Keith Morgan’s PT-19 Trainer Empty My Take on Keith Morgan’s PT-19 Trainer

Post  batjac on Sat Feb 28, 2015 12:02 am

Well, I had to go ahead and build Keith’s PT-19 to try it out.  But, as I dither a lot, I could not decide what engine to use.  So, I cut out enough parts to build three planes. I went to the local sign store and asked to buy some yellow, but they only have white coroplast.   I only had a little blue coroplast in my scrap pile, just enough for a fuselage and tail surfaces, so blue and white it is for one.  I decided to make the fin/rudder the same color as the fuselage like the early Cox PT-19's did, rather than matching the wings like the later planes did.  The other two are all white.  Which is accurate, as Cox produced an all-white plane.  Since I couldn’t decide, I went with one plane powered by a Cox reedie, one by a front rotary, and one electric powered.  To make things easier, I decided to leave the landing gear off of the rotary valve plane.   Here are the parts I cut all stacked up and laid out:

My Take on Keith Morgan’s PT-19 Trainer DSCN2976_zpsztwtgxjc
My Take on Keith Morgan’s PT-19 Trainer DSCN2980_zpslivitowr


Keith did a great job of documenting how these’re put together (http://stunthanger.com/smf/index.php/topic,37584.0.html), so I won’t do a full build thread, as it would be redundant.  I’ll just point out the things I did differently.  First, Keith did a friction fit of his stabilators for his planes.  I like more secure attachment, so what I did was to glue the stab dowel in the left stabilator, and then drill two holes in the right stabilator for screws to keep the surfaces from rotating in flight. In the picture, there are holes drilled in both stab halves, but the left half is actually glued in place.  The two washers were put in a pair of pliers and bent to conform to the curve of the dowel through the coroplast.
My Take on Keith Morgan’s PT-19 Trainer DSCN2996_zpsqn6x2xgs
My Take on Keith Morgan’s PT-19 Trainer DSCN3000_zpsetkq812r


The next thing I did differently was the fuselage formers.  Keith used ½” and ¾” pine.  I didn’t use that because 1) I don’t have any pine, 2) I don’t feel like braving the mess in the garage to get to my drill press, and 3) That just seems like huge chunks of wood to use for the formers.  Instead, what I did was take some scrap 1/8” and 3/32” ply to make the formers.  I sandwiched the 3/32 between the 1/8 and left holes in the middle for the dowels.  Since I was planning on a little more power than a standard Babe Bee, I decided to make a former at the leading edge of the wing also, where Keith opted not to.
My Take on Keith Morgan’s PT-19 Trainer DSCN3027_zpscpoouw3m
My Take on Keith Morgan’s PT-19 Trainer DSCN3026_zpsctnytkul



But, these still seemed like overkill, so I tried using only enough 1/8” to bracket the dowel hole.

My Take on Keith Morgan’s PT-19 Trainer DSCN3021_zpsoyxgjyln

But, you know, Keith is a pretty smart guy.  So, I’ll leave the former at the front of the wing on the rotary powered plane, but not use it on the other two.

Another thing I did was to strengthen the area beneath the dowels in the coroplast.  With the rotary valve plane, I used some scrap 1/8” spruce sticks.  For the other two, I used bamboo skewers sanded to fit in the flutes of the coroplast.  To keep the screw holding the top of the firewall from tearing forward through the coroplast over time I also glued a piece of spruce stick forward of the screw hole above the firewall.

My Take on Keith Morgan’s PT-19 Trainer DSCN3011_zpsmk04l6j5
My Take on Keith Morgan’s PT-19 Trainer DSCN3138_zpsskdioonm



Keith has you hold the formers in place, and then stick a screwdriver through the plastic.  Here I am clamping the formers in place and making the holes for the dowels.  
My Take on Keith Morgan’s PT-19 Trainer DSCN3031_zpstnhlqppm
My Take on Keith Morgan’s PT-19 Trainer DSCN3033_zpsto8ejxk0


It wasn’t pretty afterwards.  For the second two planes I just measured and marked the hole locations, then drilled them out with the fuselages flat on a work surface.

Another thing I did on the glow powered planes was to cut the sides of the fuse such that the wing and the top of the fuselage were parallel.  I did the electric the way Keith’s plans show.  If I do another of these, I’ll stick to Keith’s plans, because when I cut the wing saddle parallel to the top of the fuse, it makes the engine point too far down to get the right thrust line.

Since the rotary valve plane would see more stress, I also put a carbon fiber tube spar in the wing to strengthen it.


I had to go out of town to see my mother-in-law in the hospital, so I decided to quickly finish one plane so I could take it with me.  When I first saw Keith’s planes, I thought they were perfect for travelling.  Just take them apart and they made a nice flat pack.  I put the plane in my carry-on bag.  It fit perfectly and took up minimal room.  The one thing I did do to make sure there was no problem at check-in, was to ensure the pushrod was no longer than 7 inches.  I checked TSA regs on what is allowable in a carry-on, and it states that you can take screwdrivers and sharp tools so long as they are less than 7” in length.  My pushrod is exactly 7 inches.  The plane had no markings, and was bare bones, but it was fine for the purpose.  Here’s how it would look flat packed for a trip:
My Take on Keith Morgan’s PT-19 Trainer Flat%20pack_zpstpckjmli


Unfortunately, when I went to fly the plane with Jim in Phoenix, the plane torque rolled in on the hand launch and lost line tension.  The results were non-optimal.
My Take on Keith Morgan’s PT-19 Trainer DSCN2995_zps13rkubmk


Oh, well.  I had a piece of dowel the right size, so I fixed it in a few minutes when I got home.  I’m thinking I’m going to make a set of landing gear for this one so it can R.O.G. and avoid the torque roll on launch.

But, on to the other two planes.  After a month of attending to other things, I got back to them.  The reedie plane went together quickly, and with no issues.  The electric plane took a little longer, but it went together rather straight forward also.  I ran out of 3/32 dowel, so I used carbon fiber tube for the dowels on the electric plane.  Here’s how the electronics are tucked away for the electric.
My Take on Keith Morgan’s PT-19 Trainer DSCN3133_zpsp8pn3bgr


The battery goes inside, positioned to set the c.g. in the proper location.  A 3S 800 just fits between the fuselage sides.

To finish the planes off, I printed out the graphics on plain heavy paper using my HP Photosmart printer.  Then I attached them to the planes.  I used the graphs that Keith includes with his plans for the blue and white plane.  For the all-white planes, I copied a set of fuselage side and tail surface stickers I have on an unused sheet.  For the wing, I took my white Cox PT-19, and put the wing in my scanner/printer.  I scanned and then cleaned up the wing graphic, then printed it out.  After getting the graphics on the planes, I shot three coats of flat clear Lustrekote to seal them.

Tip:  If you are using plain paper for your graphics, DO NOT use 3M 77 to adhere the graphics.  It was HIGHLY unsatisfactory.  


Here are the planes ready to go:
My Take on Keith Morgan’s PT-19 Trainer DSCN3093_zpskpvikdrr
My Take on Keith Morgan’s PT-19 Trainer DSCN3104_zpsvotmnzio


The Reedie weighs 7.65 ounces, and the rotary weighs 7.75 ounces.  Right about where Keith’s were at 7.8 ounces.  The reedie should fly fine.  The rotary should fly great with the extra oomph.  The electric?  Well, that one is the question.  It came out at 8.7 ounces without battery, 11 ounces with the 3S 800mAh battery.  The Cox version is about 10 ounces, so it’s not much heavier, and it does use a 7x4E prop.  So it may fly all right.  The glide I’m not too sure about.   We’ll see.

Mark
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Post  RknRusty on Sat Feb 28, 2015 2:07 am

Looks like good models. I use Testors inkjet decals sealed with Lustrekote clear. If it won't glide when the power cuts, then it's too nose heavy. It should glide pretty well.
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Post  rsv1cox on Sat Feb 28, 2015 8:04 am

Nicely put together and told. Do rules specify exposed bell cranks or was that out of necessity?
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Post  roddie on Sat Feb 28, 2015 8:12 am

Those look really nice Mark! We used to throw away SCADS of coroplast scrap when I worked at the sign company. We typically stocked 4' x 8' sheets of white, blue, red, grey and black. I should have saved some.. but I had saved a huge quantity of various-thickness foam-board scrap-sheets from work (years worth..) when I lived in my apartment. When Lynne and I moved 4 years ago.. I had to throw most of it away. It filled a 6 yard dumpster.. (with side-boards) Shocked
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My Take on Keith Morgan’s PT-19 Trainer Empty Re: My Take on Keith Morgan’s PT-19 Trainer

Post  Marleysky on Sat Feb 28, 2015 10:47 am

Those look fantastic! Ya beat me to it and with classic design stickers as well. I see you have also posted this on STUNT HANGER. I'm sure Keith will be pleased to know his design is being used. I received the PDF plan from him a while back, after reading your post and then signing up on SH.  I just haven't had the time to dig out the coroplast I've stored out behind the garage buried in snow.  Now I see what you've done, I'm getting fired up about getting one or two of my own folded up for flight!
Hey do you have a scan of the maple leaf on the Canadian version?  I do have some faded orange plastic that should work for that version. RC Plane


Last edited by Marleysky on Sat Feb 28, 2015 11:54 am; edited 1 time in total (Reason for editing : Saw post on SH)
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My Take on Keith Morgan’s PT-19 Trainer Empty Re: My Take on Keith Morgan’s PT-19 Trainer

Post  batjac on Sat Feb 28, 2015 1:52 pm

Marleysky wrote:Those look fantastic! Ya beat me to it and with classic design stickers as well. I see you have also posted this on STUNT HANGER.  I'm sure Keith will be pleased to know his design is being used. I received the PDF plan from him a while back, after reading your post and then signing up on SH.  I just haven't had the time to dig out the coroplast I've stored out behind the garage buried in snow.  Now I see what you've done, I'm getting fired up about getting one or two of my own folded up for flight!
Hey do you have a scan of the maple leaf on the Canadian version?  I do have some faded orange plastic that should work for that version. RC Plane

Thanks for the compliments, Guys.

I don't have a scan of the Maple Leaf. I only have what Keith sent me and what I scanned from my old plane. But, if you are a member or join the .049 Collectors group on Yahoo Groups, they have a bunch of scans of old sticker sets. They may have the Maple leaf.

The Redirecting Mark
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Post  batjac on Sat Feb 28, 2015 2:10 pm

RknRusty wrote: I use Testors inkjet decals sealed with Lustrekote clear.
Rusty

Yeah, but I'm pretty cheap. Those decals are like $1.50 a sheet at the local hobby shop. A sheet of heavy copier paper is 1.5¢ or thereabouts.

The Mizer Mark
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Post  getback on Sat Feb 28, 2015 5:05 pm

Nice looking group of PT's hope you can get us some videos be interesting to see how that elect. does . Doe they have a contest going on over at SH?
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Post  batjac on Sat Feb 28, 2015 5:43 pm

getback wrote:Nice looking group of PT's hope you can get us some videos be interesting to see how that elect. does . Doe they have a contest going on over at SH?

No contest over there.  Keith sent me his plans for his Sorta-Cox PT-19 and asked if it could be used for the Second International Cox PT-19 Fly It If You Got It Day.  He asked if I'd look at it and give it the stamp of approval.  So I built these to see how they fly.  Of course I'll take them for the SICPTFIIYGI Day, but I figured I'd best see how they fly.

The Certifier Mark
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My Take on Keith Morgan’s PT-19 Trainer Empty Maiden flight of Electric PT-19: Success and Failure

Post  batjac on Fri Mar 06, 2015 10:49 pm

Well, I got out to do the maiden flight on my electric powered PT-19.  It flies with:
An EMAX CF2822 Motor
A HobbyWing SkyWalker 20A esc
An electric 7x4E propeller
A GForce 3S 800 mAh battery
And a generic DSM2 receiver
A surplus transmitter from an eFlight Blade Force micro combat helicopter controls the plane speed.

Everything but the transmitter came from Value Hobby.

The success was that it flew great as a beginner’s plane.  Two flights were made on one pack for a total of 7 minutes.  On charge, it only took 440 mA to bring it back up to full charge, so I could have gotten a third flight with plenty of reserve left.  When I touched the motor after each flight, it was still at ambient temperature.  The battery was body temperature.  I would have made more flights, but the prop broke on the second grass landing.  This plane would do better landing on hard surfaces.  I’ll put on a prop saver tonight and hopefully get more flights in tomorrow.

The first flight went well.  It was trimmed out okay.  Flew a little right wing low, but not enough to mess with.  The speed control worked great.  Take off at full speed was nice and easy.  Throttling back made for smooth flight.  It flew well from half to full throttle.  It was controllable down to about a third throttle, but then it was getting light on the lines.  I only did roundy-roundy flight with some moderate wing-overs.  For the first flights I only put minimum throws in it.  It kept plenty of line tension with full throttle, so it should do good loops if the throw is increased.  Landing was okay.  I may need to move the battery back about a quarter of an inch to get an optimum glide.  The failure, and only irritating thing of the flight was that on landing, the left wheel broke.  The spokes snapped off.  I guess I’ll have to find light weight wheels with better spokes.

My Take on Keith Morgan’s PT-19 Trainer DSCN3156_zpsknpe4jtn

For the second flight, I let my son fly it.  He’s had 8 or 10 flights over the last two years, so I’d still consider him a novice.  Even with no wheel, the plane took off from my coroplast runway fine.  After take-off, I throttle back for him and let him fly it nice and slow at a pace he found comfortable.  Having the transmitter in my hand made it easy to control how fast he flew.  After he gets more handle time, I’ll let him do the throttle control.  My son flew it out for three minutes with no trouble, and then brought it in for a landing.  For some reason, I still can’t get my son to grasp the concept of the flare.  That’s where the broken prop came.  He liked it very much, and now wants me to convert his SIG Skyray that he doesn’t fly to electric. He likes the sound and smell of castor, but doesn’t like the mess or fiddling with an engine  :/

Here are the videos of today’s flights.  

First Flight:




Second Flight:




I think on my next mail order I will get a couple of smaller batteries and see how it flies weighing a little less.  Over all, I think it was a success.  But, the one thing I can say is, it just doesn’t sound like a real plane should.  And it most certainly doesn’t SMELL like a plane should.

So, in summary:  The plane actually does what it sets out to do.  Fly like the venerable Cox PT-19.  Smooth and easy so that any novice can learn to fly Control Line on it.

The Just Past Novice Mark
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Post  roddie on Sun Mar 08, 2015 10:02 am

I'm thoroughly impressed Mark! I'm glad to see the electric being tested first. I was very curious about that. It flies very smoothly.. and seems to have plenty of power. Did Keith's plans specify a "target weight" for the electric power system? Does he specifically recommend a motor in that approx. (KV) size range? I'm asking because this may help both of us. I bought a "Dynam" park-flyer package a while back, that I'm now wondering about the possibilities for this (or a similar) application.

The flight-pack consists of a 1300KV 2-3 cell motor (rated for 8 x 3.8/8 x 4 prop) an 18A speed speed-controller (and 3 micro-servos/horn pkg.) I bought the recommended (through a system review) 2S/800mAh LiPo pack.

I took some weights of the system this morning.

The 2S/800mAh 20C pack weight and dimensions..

My Take on Keith Morgan’s PT-19 Trainer 2s_80010
My Take on Keith Morgan’s PT-19 Trainer 2s_80011

You probably can't get away with this pack with your motor.. I'm guessing, but here's the weight of my system with batt/motor/ESC (less receiver..)

My Take on Keith Morgan’s PT-19 Trainer Dsc02524

My "Tactic" 6ch receiver weighs .29oz yielding a total e-flight system weight of just under 4oz. The Flight-pack and battery I purchased from "X-Heli" 3 years ago for $24.70/$7.80 respectively. I actually bought x2 batteries and a Thunder AC6 multi-charger on the same order.. which totaled $93.23 w/shipping.

Would this configured system be a possible candidate for Keith's design? The 2S/800 7.4V pack saves .85oz over your 3S/800 11.1V pack.. but there are of course other variables.
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Post  batjac on Sun Mar 08, 2015 6:28 pm

Roddie,

Keith only designed and built his planes for a Babe Bee.  I did the electric version on my own.  For the power system, I just looked at what I had on hand that would be suitable.  In no way did I try to optimize the setup.  There are so many different ways and combinations to do any particular size plane that I didn't even try.  I just grabbed a motor with enough wattage, a speed controller that would handle the max motor current, the smallest 3S battery I had, and a prop that was in the general range for the motor.

For your setup, the 1300 KV motor would max out at 9620 RPM, but if you look at the battery giving 7.0V for an average, then the prop RPM would only be 9100.  You'd need a pretty big prop to haul a small plane around.  I'm not sure how much thrust the 8x4 would give you, but I'd say it might fly the PT-19 as a basic trainer type plane.  Only one way to find out.

The Off the Shelf Mark
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My Take on Keith Morgan’s PT-19 Trainer Empty Re: My Take on Keith Morgan’s PT-19 Trainer

Post  roddie on Sun Mar 08, 2015 7:36 pm

batjac wrote:Roddie,

Keith only designed and built his planes for a Babe Bee.  I did the electric version on my own.  For the power system, I just looked at what I had on hand that would be suitable.  In no way did I try to optimize the setup.  There are so many different ways and combinations to do any particular size plane that I didn't even try.  I just grabbed a motor with enough wattage, a speed controller that would handle the max motor current, the smallest battery I had with high enough voltage, and a prop that was in the general range for the motor.

For your setup, the 1300 KV motor would max out at 9620 RPM, but if you look at the battery giving 7.0V for an average, then the prop RPM would only be 9100.  You'd need a pretty big prop to haul a small plane around.  I'm not sure how much thrust the 8x4 would give you, but I'd say it might fly the PT-19 as a basic trainer type plane.  Only one way to find out.

The Off the Shelf Mark

Yes.. you're right. Have you tach'd your motor with the 7 x 4.. or is there a theoretical # that you would arrive at; given certain components used? I'm obviously still learning about this. You seem to have a great combination there Mark. It would be interesting to place the battery far enough back to attempt a "Carrier"-type model, that could fly slow and nose-high. I think those models must use a lot of thrust and rudder offset to do that.
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Post  WingingIt74 on Sun Mar 08, 2015 8:12 pm

Very nice!
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Post  batjac on Mon Mar 09, 2015 12:05 am

roddie wrote:

Yes.. you're right. Have you tach'd your motor with the 7 x 4.. or is there a theoretical # that you would arrive at; given certain components used?

Nah. I started to pull out the tach and the watt meter, but then decided, "Eh.. It either flies or it doesn't." That's been my general attitude towards all my scratch builds, so why change now?

The Set In His Ways Mark
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Post  WingingIt74 on Mon Mar 09, 2015 7:35 am

The watt meter would be important to make sure you don't burn up your motor.
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