J3 Cub Forum > Cub Discussions > Cub Talk > Asi

Help Support J3 Cub by donating using the link above or becoming a Supporting Member.
Reply
 
Thread Tools Display Modes
Old 08-10-2017, 04:41 PM   #11
jimrice
Supporting Member
J3_SUPPORTER.png
 
jimrice's Avatar
 
Join Date: Jul 2007
Posts: 3,987
Liked 715 Times on 495 Posts
Likes Given: 140

Default

Quote:
Originally Posted by OldblueJ3 View Post
Are both your ASI ports connected to tubing or just one? If it is only one, then it could be possible the the change in air pressure of your cabin relative to your air speed could effect the ASI readings.
My Cub has only a single tube from the ASI to the pitot. Don't know I've ever seen a Cub with a dedicated static port to feed the second opening. Static is typically at the instrument opening. That is why indicated airspeed changes by simply opeing or closing the doors.

When I was first flight testing mine after restoration, I found my pitot tube angle wasn't correct. I adjust the angle to a better head on angle and my ASI has been very true since. I've checked it with various GPS runs in different directions as well as some timed runs.


__________________
Jim Rice
Collierville, TN
1946 Piper J-3C-65 N7155H (Flying)
1994 Van's RV-4 N4WJ (Flying)
US Army Retired (still working to pay for flying)

EAA Member
AOPA Member
NRA LIFE Member
jimrice is offline  
 
Reply With Quote
Old 08-11-2017, 04:26 PM   #12
43-29080
Senior Member
J3_LIFETIMESUPPORTER.png
 
Join Date: Feb 2013
Location: West of the Pecos, Texas
Posts: 1,741
Liked 618 Times on 435 Posts
Likes Given: 398

Default

What engine, with which prop?


__________________
1943 Piper L-4A, AAF 43-29080, Sn. 10371, DOD 28MAY43
43-29080 is offline  
JimC Likes This 
Reply With Quote
Old 08-11-2017, 05:10 PM   #13
JimC
Supporting Member
J3_SUPPORTER.png
 
Join Date: Feb 2007
Posts: 10,841
Liked 989 Times on 783 Posts
Likes Given: 817

Default

I'll reinforce that - what engine, what prop?

Static port is the hole in the back side of the ASI.
JimC is offline  
 
Reply With Quote
Old 08-12-2017, 02:35 PM   #14
Gener
Senior Member
 
Join Date: Aug 2015
Posts: 272
Liked 125 Times on 79 Posts
Likes Given: 77

Default

An old thread discussed pitot tube angle.

http://www.j3-cub.com/forum/showthre...ght=pitot+tube
Gener is offline  
 
Reply With Quote
Old 08-12-2017, 05:05 PM   #15
boeingdriver
Senior Member
 
Join Date: Aug 2011
Posts: 100
Liked 17 Times on 6 Posts
Likes Given: 1

Default

A65, wood 70 pitch
boeingdriver is offline  
 
Reply With Quote
Old 08-13-2017, 05:23 AM   #16
OldblueJ3
Member
 
Join Date: Mar 2011
Posts: 48
Liked 12 Times on 9 Posts
Likes Given: 1

Default

Quote:
Originally Posted by Gener View Post
An old thread discussed pitot tube angle.

http://www.j3-cub.com/forum/showthre...ght=pitot+tube
Thanks for this history lesson (link), I did not know that you could point the Pitot tube to optimise your use of the ASI. Appreciate it.
OldblueJ3 is online now  
 
Reply With Quote
Old 08-13-2017, 02:10 PM   #17
boeingdriver
Senior Member
 
Join Date: Aug 2011
Posts: 100
Liked 17 Times on 6 Posts
Likes Given: 1

Default

Here are two pics looking left at pitot tube.
Will be able to get at it next week.
From the pic it looks like it is pointed down.
Name:  ImageUploadedByJ3 Cub1502633372.853676.jpg
Views: 99
Size:  90.8 KB
Name:  ImageUploadedByJ3 Cub1502633398.466759.jpg
Views: 98
Size:  90.8 KB
boeingdriver is offline  
 
Reply With Quote
Old 08-14-2017, 12:58 AM   #18
boeingdriver
Senior Member
 
Join Date: Aug 2011
Posts: 100
Liked 17 Times on 6 Posts
Likes Given: 1

Default

Looks like I posted same picture twice. Here is another....Name:  ImageUploadedByJ3 Cub1502672294.238857.jpg
Views: 86
Size:  92.4 KB
boeingdriver is offline  
 
Reply With Quote
Old 08-14-2017, 10:13 PM   #19
jimmy
Lifetime Supporting Member
J3_LIFETIMESUPPORTER.png
 
Join Date: Jul 2009
Posts: 2,260
Liked 282 Times on 219 Posts
Likes Given: 451

Default

The inclination of mine is 99*'s off the jury strut, yours is 97*'s best accuracy I can decern off your pic. Not much difference, see what some others are and you might tweak it. Grand kid pulled on mine once and I bent it back to old position with a kink. Seems It still gives some fair readings.
Attached Thumbnails
Click image for larger version

Name:	IMG_2585.jpg
Views:	70
Size:	128.1 KB
ID:	47937  
__________________
I rebuilt my cub in 94 from a duster basket case. Been flying and maintaining since and fly off an 1800' strip/pasture.
jimmy is offline  
 
Reply With Quote
Old 08-15-2017, 11:46 PM   #20
boeingdriver
Senior Member
 
Join Date: Aug 2011
Posts: 100
Liked 17 Times on 6 Posts
Likes Given: 1

Default

Quote:
Originally Posted by reileyr View Post
Great suggestion as a leak in the system is suspected. You can test yourself by taping a small balloon onto the pitot tube. Then blow into the line that connects to the ASI to inflate the balloon. Hold the line closed and see if balloon stays inflated. If it does, there is no leak. If the balloon deflates, there is a leaking line/connection that needs to be corrected.

This suggestion worked great. Found a leak. Replaced a black fuel tube with some medical like tubing that Ken from Keystone sent back with ASI. Even with a hose clamp there was air escaping...the ID of tubing was a little too big. Also the pitot tube was off by approximately 5*. Just did a flight in calm conditions and backed it up with gps. Air speeds were very close to gps. +\- 2mph.
Name:  ImageUploadedByJ3 Cub1502840630.888646.jpg
Views: 47
Size:  290.0 KB
Surprisingly with two young kids in the house I could not find a ballon. Rubber shop glove worked great.
Thanks for everyone's input.
Cheers


boeingdriver is offline  
3
People Like This 
Reply With Quote
Reply


Go Back   J3 Cub Forum > Cub Discussions > Cub Talk

Thread Tools
Display Modes

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

Forum Jump



Newest Threads