Sboatcaptain

Alberto,
I havent had a chance to get much done over the weekend, or monday......been doing the Honey-do's around the house....Hopefully I will get some more done tommorow afternoon, and will post a few pics of my progress...
Take your time with the Monokote...
I did get a chance to go to the local Hobby shop, and picked up some servos, and a new transmitter and receiver....along with some other things i will be needing.
Have to finish a painting project in my wife's craft room, and put down some flooring, so wont be getting much done during the day....gonna have to work in the evenings...
Jerry

ululi1970

I finally had some time to start the covering. After reading some ~2008 posts about problems with Monokote I was a bit nervous. I did some practice on some scrap balsa and initially I was having trouble getting rid of wrinkles, until I realized that problem was insufficient heat.
The technique I am using is the tack first at lowish temp and then shrink at high. It turns out that out of the box with the cotton cover on my hobbico iron was not hot enough: solution was getting rid of the cotton cover and tweaking the dial settings. For the latter, I removed the
knob, which is mounted on a brass post. Inside the brass post, there is a small screw. Turning is counterclockwise seems to increase the temperature range, though if you turn it too much then it won't turn off. Modified, the temperature at the base of the iron
read with an infrared thermometer is ~ 370F. With the iron modified, I was able to do a decent job both on the solid stab, as well as over the ribs (well, at least decent enough for a newbie). Surprisingly, so far I even managed to avoid burns . I also experimented with
using a heat gun to shrink, but the one I have does not provide enough heat at low, and burned a hole while practicing at high, so I quickly shelved it. The iron seems to work well.


At this point, I am waiting for some red to finish the job. Apparently, there has been a shortage in the area. Alas, I will be traveling in the next 10 days so I won't be able to work on it for some time.

Here's some pics, showing bottom (blue) and top (white), left side done, right side ready for the iron. I am planning to use red for the leading edge, as well as bottom of the fuselage and half sides and some trim here and there. White
the rest...

Zor

Your model is coming along fine ululi1970.

Keep us posted at your convenience.

A hobby is for leisure times and enjoyment.

I am following along with great interest.

Zor

KMR1

Hi A & J,
I built the PT-60, and converted it to a tail dragger. Don't really know why, except the steering is critical for me and my construction methods.
I bought a super-tiger .51 for it and found it weighed quite a bit less than GP's recommended motor. Result is a lot of lead in the nose. (8oz.) I even cut a lot out of the tail surface to try and lessen the lead up front. 8 pounder. I think trainer means built to survive if you compare it to a 4*40. I'm itchen to try it again as I find gassers more challenging by far.
Ken

ululi1970

Hi Ken,
do you pics showing your modified PT-60? I am curious how you did it...
Alberto

Zor

Hello Ken,

A trainer means "built to survive" if it is "built to survive".
That means if strong covering is used and ifthe structureis properly glued.

Concerning the weight you had to put in the front, you may consider any possibility of moving the engine forward and removing some of the added 8 oz.

Zor

KMR1

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Not sure if this has worked.
A couple of pictures; the old gals' beak has been smashed, the main gear are under the leading edge.

Zor

KMR1,

I do not see anything obviously "smashed" in the pictures.

The landing gear under the leading edge of the wings or slightly ahead of the leading edge is quite normal for a taildragger.

I would serously consider moving the wing back and removing the extra 1/2 lb of weight behind the prop.

It would not be very difficult to reshape the wing saddle.

Zor

ululi1970

Zor,
I am a little confused. Wouldn't moving the wing back shift the CG further aft requiring more weights upfront?

Alberto

KMR1

Zor,
Good point. Alberto moving the wing back increases the length of the lever the lead is part of. I'll have to see how far back it will have to go.
Looks doable. thanks.
Ken

Zor

As KMR1 just explained, what you need is more weight up front WITHOUT the 8 oz of lead.

The fact of moving the wing toward the tail by itself does move the CG backward since the mass of the wings themselves is moving back.

The amount of motion would not be much and it is easy to remove the wings attachments, just sit the fuselage (all the rest of the model a bit ahead on the wings, use masking tape temporarily to make the checks, and define how far back the wing saddle has to be altered.

In reshaping the wing saddle care has to be taken to maintain the decalage angle from stabilizer to main wing chord assuming that this angle was correct to start with.

Zor

Sboatcaptain

Hey All,
Sorry about not posting in a while, but had lots of things to do around the house before I could get to work on my build! The honey do's never end! lol I did manage to get the covering done on the fuse, mounted the engine, gas tank and afew other odds and ends before having to head back to my ship....

I will finish up the wings when I get home next time....

Meanwhile I have brought a Herr P-51 Mustang on board with me to keep me busy....looks like a nice little plane.

Jerry

ululi1970

Well,
after some time off, I did manage to finish the covering (see attached pics). Hopefully this weekend I will be able to break in the engine and finish installing the control surfaces. I am a little nervous about glueing them together...

Alberto

Zor

Coming along nice Alberto,

I do not glue control surfaces. I always find a way fo screw (bolt) them on.

It makes them easier to repair if needed by taking them off.
It also allows for adjusting the decalage angle as I wish.

Zor

ululi1970

As usual, still messing up the lingo. I meant the hinges of ailerons , elevator and rudder .
Though the idea of using screws for the stab is a good one.

ululi1970

Well, I CAed the nylon hinges of elev and rudder, but I am a little worried. After applying CA, the hinges became considerably stiffer. Is it normal? Or did I mess up something, like too much glue... Haven't done the ailerons yet...
On the plus side, I fired the engine for the first time today. It started with just a click of the starter, and I went through the break-in sequence as per instructions (WOT, alternating enriching and leaning out every minute or so for 10 minutes). This Norvel engines is a little strange. In all the other engines I had, the head is a solid piece. ON this one, the head has a ~ 3/4'' aluminum plug, into which the glow plug is screwed in.
The big plug has six holes (see pic), which I had assumed were just to fit the teeth of the tools used to remove it. However, at high RMPs the bottom of these holes drops a bit, and oil seeps out. Looks like there is a diaphragm that moves in response to some conditions. Wonder what is the purpose...

Alberto

ululi1970

Well, after a few weeks, I finally managed to finish it! It came to 4.6 lb. Ended up a little nose heavy, so I had to fit the battery aft of the servo tray, as opposed to under the tank, but I guess that it means being easy to replace.
Over the weekend I will head to a nearby field and see if I can find some experienced flier for the maiden voyage. Overall it was very fun to build it and can't wait to see it take it to the skies.
Thanks to everybody who contributed ideas and/or support.

Alberto

ululi1970

Today I headed out to the field and a local pilot took it for its maiden voyage. To my relief, everything went well. Here's a link to a short video showing take off. Landing was just as smooth. Overall, it flew well (according to the pilot), but it is now a bit too tail heavy.
I will have to move the battery forward a little. Not too difficult.


http://www.youtube.com/watch?v=wkpjc2ezhFc

Needless to say, builder is very pleased too!


Alberto

gene6029

Congrads on your maiden! Hope you have many more sucessfull flights....Gene

Zor

Alberto,

Beautiful flight.

Soon to enjoy all by yourself.

Congratulations on a nice model.

Zor

ululi1970

A little post-scriptum...
I was lucky to find a field nearby with a great instructor. I soloed after about ~ 1 hour of stick time at the end of July. The plane handled very well. It is smooth and predictable.
There were other people out there learning to fly with the same instructor. Most of them flew cubs or EPO warbirds. Comparing notes, I was glad to have my PT-20.
Those fellows always seem to struggle with their crafts...
The plane took well a few less-than-perfect landings, including a dead-stick in ~10 mph wind... Relative to EPOs, the front landing gear is quite strong...
Now I am practicing simple sport aerobatics (loops, rolls, Immelmans...), which
the PT-20 seems to take well.

I am already thinking about the next one. Probably a low-wing tail dragger.

Still curious to hear from Jerry.

Cheers to all
Alberto

carrellh

I'm glad you're enjoying your plane. This is a fun hobby. Your plane has enough mass to handle some wind and turbulence where the foam planes might be grounded.

The PT series are really good planes. I think the fact that the fuselage is all balsa (rather than lite ply) makes them super tough without being overly heavy.

The blue PT-60 was my first kit. I had an ARF trainer before it and the ARF did not survive my slow learning curve. My PT took a lot of abuse before I finally killed it.

The white PT was built by my brother. It had no dihedral and a few other mods. Even with a totally flat wing it was plenty stable as a trainer.

For your second build,
Bruce Tharpe Engineering Venture 60 www.btemodels.com BTE is a one man operation so each kit goes in and out of availability. Only available from BTE

Sig Four-Star 40 or 60, Mid Star 40, or Astro Hog www.sigmfg.com or http://www.gravesrc.com/category_s/105.htm (Graves stocks a lot of their stuff)
The Astro Hog is an old style "builders kit" but it is a super plane. One comment about the biuld is 'be sure your chainsaw is sharp before you get started.'

Great Planes Goldberg Tiger 60 http://www3.omnimodels.com/cgi-bin/w...I=GPMA0968&P=0 free shipping
Great Planes Goldberg Tiger 2 (40 size) http://www3.omnimodels.com/cgi-bin/w...I=GPMA0966&P=0 free shipping

This is not a complete list. My favorite is the Astro Hog (probably because it is the one I have). The instructors at my club mostly recommend the Four Stars because they are considered quick builds and usually are available at the hobby shop or online. The one who built a Venture 60 commented that it was the nicest and best cut kit that he had seen in 40 years of building.

ululi1970

Thanks for the suggestions!
I found somebody not too far from where I live selling a Tiger 2 (modded to tail dragger). I may go for that. I actually like a lot
the Sig Something Extra (really beautiful lines), but that may be too much of a step forward.

Also, I was thinking about getting rid of the dihedral on the PT-20, but not sure how to proceed. Should I just cut the wing in two and reglue it...
Other fun option would be to put floats (the field is next to a lake)...

Alberto

carrellh

The Somethin Extra could be OK, especially if your instructor would be willing to help you through a few flights. It will be VERY responsive compared to the PT. I thought my Big Stik 60 was an absolute beast for the first few flights (on buddy box) but got used to it pretty quickly.

If I decided to flatten the PT wing, I'd probably:
remove the center sheeting from the top of the wing
cut the wing in half
sand the ends square with each wing half flat on the table
make straight joiners (1/8 aircraft plywood) for leading edge, main spar, and trailing edge
join the halves just like the original build
resheet the top

Since the wing does not have "root ribs" like a lot of models, I think it needs the joiners (but I could be wrong).