Go Back  RCU Forums > RC Airplanes > Beginners
 MY COMPLETED PT-40 MODS >

MY COMPLETED PT-40 MODS

Notices
Beginners Beginners in RC start here for help.

MY COMPLETED PT-40 MODS

Old 06-08-2008, 05:15 PM
  #1  
Thread Starter
 
Join Date: Aug 2007
Location: Pittsfield, MA
Posts: 1,610
Likes: 0
Received 0 Likes on 0 Posts
Default MY COMPLETED PT-40 MODS

As I stated in my other post I was redesigning my PT-40 trainer and this is what I've done:

1) Removed the old covering that I did not like
2) Added ailerons with dual servos
3) Added a bigger APS .46 with 3-line tank
4) Added exterior rear servos for the tail feathers
5) Made it into a tail dragger
6) Recovered with a better design

Let me know what you think.
Attached Thumbnails Click image for larger version

Name:	Om31759.jpg
Views:	22
Size:	140.0 KB
ID:	966496   Click image for larger version

Name:	Oj26625.jpg
Views:	19
Size:	132.6 KB
ID:	966497   Click image for larger version

Name:	Kp32886.jpg
Views:	17
Size:	138.6 KB
ID:	966498   Click image for larger version

Name:	Bv60475.jpg
Views:	22
Size:	124.2 KB
ID:	966499   Click image for larger version

Name:	Vg53169.jpg
Views:	24
Size:	100.4 KB
ID:	966500   Click image for larger version

Name:	Fw27940.jpg
Views:	17
Size:	85.6 KB
ID:	966501   Click image for larger version

Name:	Ig11719.jpg
Views:	16
Size:	102.0 KB
ID:	966502  
Old 06-08-2008, 05:16 PM
  #2  
Thread Starter
 
Join Date: Aug 2007
Location: Pittsfield, MA
Posts: 1,610
Likes: 0
Received 0 Likes on 0 Posts
Default RE: MY COMPLETED PT-40 MODS

Some more
Attached Thumbnails Click image for larger version

Name:	Lj22100.jpg
Views:	21
Size:	94.0 KB
ID:	966508   Click image for larger version

Name:	Xs59427.jpg
Views:	17
Size:	115.1 KB
ID:	966509   Click image for larger version

Name:	Gl18938.jpg
Views:	9
Size:	128.8 KB
ID:	966510   Click image for larger version

Name:	Ey70543.jpg
Views:	13
Size:	128.9 KB
ID:	966511   Click image for larger version

Name:	Nz28795.jpg
Views:	9
Size:	130.3 KB
ID:	966512   Click image for larger version

Name:	Pf60920.jpg
Views:	13
Size:	118.2 KB
ID:	966513  
Old 06-08-2008, 05:19 PM
  #3  
Thread Starter
 
Join Date: Aug 2007
Location: Pittsfield, MA
Posts: 1,610
Likes: 0
Received 0 Likes on 0 Posts
Default RE: MY COMPLETED PT-40 MODS

And some more
Attached Thumbnails Click image for larger version

Name:	Li21087.jpg
Views:	8
Size:	91.9 KB
ID:	966514   Click image for larger version

Name:	Zv66958.jpg
Views:	7
Size:	115.0 KB
ID:	966515   Click image for larger version

Name:	Ej14197.jpg
Views:	9
Size:	108.5 KB
ID:	966516   Click image for larger version

Name:	Uo35123.jpg
Views:	9
Size:	112.0 KB
ID:	966517   Click image for larger version

Name:	Dp84166.jpg
Views:	9
Size:	104.5 KB
ID:	966518   Click image for larger version

Name:	Ct17795.jpg
Views:	8
Size:	103.0 KB
ID:	966519   Click image for larger version

Name:	Km98459.jpg
Views:	13
Size:	67.4 KB
ID:	966520   Click image for larger version

Name:	On46855.jpg
Views:	17
Size:	77.5 KB
ID:	966521  

Old 06-08-2008, 05:21 PM
  #4  
Thread Starter
 
Join Date: Aug 2007
Location: Pittsfield, MA
Posts: 1,610
Likes: 0
Received 0 Likes on 0 Posts
Default RE: MY COMPLETED PT-40 MODS

Your opinion:

Please take a look at these two pics and tell me if the right thrust is too much.
Attached Thumbnails Click image for larger version

Name:	Vt56127.jpg
Views:	19
Size:	149.0 KB
ID:	966527   Click image for larger version

Name:	Mh18924.jpg
Views:	16
Size:	112.0 KB
ID:	966528  
Old 06-08-2008, 06:43 PM
  #5  
My Feedback: (1)
 
JohnBuckner's Avatar
 
Join Date: Dec 2001
Location: Kingman, AZ
Posts: 10,441
Likes: 0
Received 10 Likes on 10 Posts
Default RE: MY COMPLETED PT-40 MODS

I hate to say it but that looks like left thrust opposite of what you want with the prop pointing off to the left.
Old 06-08-2008, 06:45 PM
  #6  
Senior Member
 
Jester241's Avatar
 
Join Date: Aug 2007
Location: MCALISTERVILLE, PA
Posts: 683
Likes: 0
Received 0 Likes on 0 Posts
Default RE: MY COMPLETED PT-40 MODS

AWESOME!!!

...and I dont really even notice any right thrust,so I'd say it looks good to me

Thanks for the pics too
Old 06-08-2008, 07:32 PM
  #7  
Member
 
turdfergerson's Avatar
 
Join Date: May 2008
Location: Wichita, KS
Posts: 80
Likes: 0
Received 0 Likes on 0 Posts
Default RE: MY COMPLETED PT-40 MODS

That thing looks great! and no I dont think the thrust is going to be a problem.
Old 06-08-2008, 07:37 PM
  #8  
Senior Member
 
Join Date: Aug 2004
Location: Nowhere
Posts: 1,037
Likes: 0
Received 0 Likes on 0 Posts
Default RE: MY COMPLETED PT-40 MODS

Its realllllllly hard to tell about the trust.

However, that plane looks awesome. Good work my friend.
Old 06-08-2008, 07:48 PM
  #9  
Thread Starter
 
Join Date: Aug 2007
Location: Pittsfield, MA
Posts: 1,610
Likes: 0
Received 0 Likes on 0 Posts
Default RE: MY COMPLETED PT-40 MODS

ORIGINAL: JohnBuckner

I hate to say it but that looks like left thrust opposite of what you want with the prop pointing off to the left.
Yes, after posting these different angle pics below I can see the left thrust. How many washers do you think I will need on the left side of the mount? And would it be best with no thrust or a little right thrust?

I will need to cut away more of the engine compartment sides for the muffler and needle valve. Then I can finally check the CG.
Attached Thumbnails Click image for larger version

Name:	Hf10373.jpg
Views:	17
Size:	48.3 KB
ID:	966710   Click image for larger version

Name:	To44764.jpg
Views:	11
Size:	42.5 KB
ID:	966711   Click image for larger version

Name:	Af90549.jpg
Views:	11
Size:	48.3 KB
ID:	966712   Click image for larger version

Name:	Uo35627.jpg
Views:	8
Size:	49.3 KB
ID:	966713  
Old 06-08-2008, 08:33 PM
  #10  
My Feedback: (1)
 
JohnBuckner's Avatar
 
Join Date: Dec 2001
Location: Kingman, AZ
Posts: 10,441
Likes: 0
Received 10 Likes on 10 Posts
Default RE: MY COMPLETED PT-40 MODS

Visually from your photo there appears to be a slight amount of left thrust The left cowl cheek is closer to the prop than the right.

Granted it is not a hugh amount however what is important is you have 'no' right thrust. And with the changeover at the same time to a taildragger where right thrust would be most welcome to the ground handling at the point of rotation on takeoff this exacerbated by the fairly steep deck angle with that main gear.

This airplane is a prime candidate for about 3 degrees right thrust and thats remains my opinion.

John
Old 06-08-2008, 08:43 PM
  #11  
Thread Starter
 
Join Date: Aug 2007
Location: Pittsfield, MA
Posts: 1,610
Likes: 0
Received 0 Likes on 0 Posts
Default RE: MY COMPLETED PT-40 MODS

ORIGINAL: JohnBuckner

. . . takeoff this exacerbated by the fairly steep deck angle with that main gear.

Does that mean the landing gear is too big for this trainer? I truly hope not.

This airplane is a prime candidate for about 3 degrees right thrust and thats remains my opinion.

I agree 100%. How many washers on the left side of the mount would you say that'd be?
Old 06-08-2008, 08:58 PM
  #12  
My Feedback: (1)
 
JohnBuckner's Avatar
 
Join Date: Dec 2001
Location: Kingman, AZ
Posts: 10,441
Likes: 0
Received 10 Likes on 10 Posts
Default RE: MY COMPLETED PT-40 MODS

No its not to big but when you have a steep deck angle you have further to go when raising the tail on take off and its at this point there are a number of factors and during the first pull of the elevator for rotation that are trying hard to make the airplane swerve to the left. Its important to understand when these things are going to happen and its during this raising the tail that some will be doing their best to cause that swerve.

I can,t tell you how many washers. I would start with a piece of 1/8 ply long enough to go under both the left side bolts and about a half inch wide. And sand in a taper and drill it then install and check your angle just like those last pictures you posted over that building grid. If two much just sand down some and try agine.

John
Old 06-08-2008, 10:23 PM
  #13  
Thread Starter
 
Join Date: Aug 2007
Location: Pittsfield, MA
Posts: 1,610
Likes: 0
Received 0 Likes on 0 Posts
Default RE: MY COMPLETED PT-40 MODS


ORIGINAL: JohnBuckner

. . . drill it then install and check your angle just like those last pictures you posted over that building grid. If two much just sand down some and try agine.
Whereabouts should I sand the taper?
Old 06-08-2008, 10:50 PM
  #14  
My Feedback: (1)
 
JohnBuckner's Avatar
 
Join Date: Dec 2001
Location: Kingman, AZ
Posts: 10,441
Likes: 0
Received 10 Likes on 10 Posts
Default RE: MY COMPLETED PT-40 MODS

I don,t have any grafics capability but let me describe it. What we will endup with will be a ply plate may be two inchs or so long and somewhere around 3/8ths to a 1/2 wide with a firewall bolt hole on each end.

This plate is between the firewall and mount on the left side vertically between the two left firewall bolts. when installed the mount will be at a angle and by tapering the this spacer on its narrow side in other words the half inch side it will provide a relatively flat surface for the mount to rest on even though it is at an angle to the firewall. This is a bit more bother than washers but you will not have the problem of the mount always loosening as the washer digs into the wood with vibration.

Actually Ernst use to make commercial plastic ones even marked in degrees but I have no idea if they are still avalible. But it really takes only minutes to whack one out of ply. the easy way to do so is to saw out your eighth ply about 3/8 or 1/2 inch wide but make it around six inchs long even though it will end up around two inchs long.

You now have a handle to hold the stick on one end and the taper accross the narrow dimension is easy to do with thirty six or forty grit paper in a sanding block for a couple of inchs on the end. Then its just cut to length and sloppy bolt holes are added and assemble the thing. this is a lower maintenance method than the washers which gradually loose all the angle (right thrust) every time you retighten them.

John
Old 06-08-2008, 11:21 PM
  #15  
Thread Starter
 
Join Date: Aug 2007
Location: Pittsfield, MA
Posts: 1,610
Likes: 0
Received 0 Likes on 0 Posts
Default RE: MY COMPLETED PT-40 MODS

Cut one out and test fit so I can have an idea. Obviously too much of a right thrust but it's just a test fit.
Attached Thumbnails Click image for larger version

Name:	Mk26665.jpg
Views:	9
Size:	46.1 KB
ID:	966913   Click image for larger version

Name:	Yt62253.jpg
Views:	9
Size:	45.0 KB
ID:	966914  
Old 06-09-2008, 12:08 AM
  #16  
Thread Starter
 
Join Date: Aug 2007
Location: Pittsfield, MA
Posts: 1,610
Likes: 0
Received 0 Likes on 0 Posts
Default RE: MY COMPLETED PT-40 MODS

Sanded it down to a tiny bit over 1/16" thick but still seems a bit too much right thrust.

Question: The spinner and right mount is only about 1/4" away from the right cowl cheek while the left side cheek and mount is about 1/2" (see last photo). It will change a bit after more work but will that be a big factor in it's flight?
Attached Thumbnails Click image for larger version

Name:	Rm37907.jpg
Views:	14
Size:	53.0 KB
ID:	966948   Click image for larger version

Name:	Gm21827.jpg
Views:	9
Size:	44.5 KB
ID:	966949   Click image for larger version

Name:	Tn31529.jpg
Views:	8
Size:	43.2 KB
ID:	966950   Click image for larger version

Name:	Ay74261.jpg
Views:	10
Size:	60.3 KB
ID:	966951  
Old 06-09-2008, 08:54 AM
  #17  
 
Join Date: Jan 2002
Location: Johnstown, PA
Posts: 1,046
Received 0 Likes on 0 Posts
Default RE: MY COMPLETED PT-40 MODS

I've built several PT-40s over the years, but I don't recall what angle is recommended... knowing that could be helpful.

I tried to compute the thrust angle on your plane from the pictures, but the lighting may be off, which makes a lot of difference... measuring from the shadows of the prop tips and assuming the fuselage is lined up well on the fore-and aft line of the floor pattern, I got about 1.7 degrees... but measuring from the tips themselves I got about 4.5 degrees. Looking at the left side of the fuselage, though, it looks like the plane may be pointed a little to the right, which would make it look like more right thrust than it is.

In the end, you definitely seem to have some right thrust and you have rudder and you have ailerons I'd be more concerned with balance than with the amount of right thrust at this point. How's your CG holding up with that few ounces of servo added to the PT-40's big, long tail?
Old 06-09-2008, 09:52 AM
  #18  
Thread Starter
 
Join Date: Aug 2007
Location: Pittsfield, MA
Posts: 1,610
Likes: 0
Received 0 Likes on 0 Posts
Default RE: MY COMPLETED PT-40 MODS

Here is the finished project. Ended up using washers and this is what I got in the end. Looks like plenty of right thrust, and I don't know of anything thinner than washers so this is where it will stay. Thank you all for your input.

Now to do the CG and this baby is finished.
Attached Thumbnails Click image for larger version

Name:	Pn36473.jpg
Views:	9
Size:	128.7 KB
ID:	967221   Click image for larger version

Name:	Hc92685.jpg
Views:	10
Size:	102.0 KB
ID:	967222   Click image for larger version

Name:	Zx71034.jpg
Views:	7
Size:	124.6 KB
ID:	967223   Click image for larger version

Name:	Lg15602.jpg
Views:	13
Size:	144.3 KB
ID:	967224   Click image for larger version

Name:	Hm25027.jpg
Views:	11
Size:	111.9 KB
ID:	967225  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are On


Thread Tools
Search this Thread

Contact Us - Manage Preferences Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.