Thorp Air Command - T18.net
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Retrofit Pitot Tube
http://thorp18.com/thorpforum/viewtopic.php?f=3&t=8052
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Author:  Jeff J [ Mon Jun 25, 2018 10:50 am ]
Post subject:  Re: Retrofit Pitot Tube

It looks like we lost the pictures in this thread right when I was getting serious about moving the pitot tube. Would you guys be willing to repost them?

Author:  Jeff J [ Tue Jun 26, 2018 7:28 am ]
Post subject:  Re: Retrofit Pitot Tube

Nevermind, I found a work around and downloaded the pictures.
viewtopic.php?f=29&t=8239

Author:  Jeff J [ Thu Jul 26, 2018 11:30 am ]
Post subject:  Re: Retrofit Pitot Tube

I finally installed a blade type pitot tube on the wing. I was pleasantly surprised at how easy removing the old pitot tube was. Disconnect the lines, remove 2 screws and lift it out of the fin. Since I have a T-18 with the original wing, I opted to install the blade behind the left aileron bellcrank. That puts it well outside the prop arc and kept me from needing to plumb anything to the outer wing. I connected the static line to a pair of ports located behind the cockpit per an article I found in the news letters. I checked the ASI against the GPS by taking an average of my ground speed over 4 passes and 4 different directions and was very happy with the results (average ground speed was 152.25 mph while ASI read ~152 during all 4 passes). I never checked the old system.

Author:  Binder [ Thu Jul 26, 2018 7:52 pm ]
Post subject:  Re: Retrofit Pitot Tube

Jeff J wrote:
I finally installed a blade type pitot tube on the wing. I was pleasantly surprised at how easy removing the old pitot tube was. Disconnect the lines, remove 2 screws and lift it out of the fin. Since I have a T-18 with the original wing, I opted to install the blade behind the left aileron bellcrank. That puts it well outside the prop arc and kept me from needing to plumb anything to the outer wing. I connected the static line to a pair of ports located behind the cockpit per an article I found in the news letters. I checked the ASI against the GPS by taking an average of my ground speed over 4 passes and 4 different directions and was very happy with the results (average ground speed was 152.25 mph while ASI read ~152 during all 4 passes). I never checked the old system.



I would like to see some pics on how you did it. That is what I would like to do in order to remove that weird prop wash to my pitot along with the loss of pitot due to high angle of attack on final. Anything below about 75mph my a/s is worthless.

Author:  Jeff J [ Fri Jul 27, 2018 5:41 pm ]
Post subject:  Re: Retrofit Pitot Tube

Look at Tony’s pictures for the bracket. He did a much better job than I did. I had to form mine over a bucking bar with a mallet and it shows how little experience I have working that way. I riveted the mount to the rib behind the left aileron bellcrank. I had to install an inspection panel (bought from Cubes) and remove the outer wing to do the work. I was able to remove and reinstall the outer wing unassisted. I had considered trying panel bond but the convenience didn’t out weigh the cost for me. It looked like it was going to be $100 for the small tube of epoxy with the application gun plus no one local carries it. All of rivets for the job cost less than ten cents and I have hundreds on hand.

Image

Image

Author:  Binder [ Sun Jul 29, 2018 9:43 am ]
Post subject:  Re: Retrofit Pitot Tube

I remember Tony’s pictures but I can’t get them to work. They are x’ed out on the site.

Author:  Jeff J [ Sun Jul 29, 2018 4:56 pm ]
Post subject:  Re: Retrofit Pitot Tube

This should work:
https://postimg.cc/image/bnua663c5/

Author:  Binder [ Mon Jul 30, 2018 5:46 pm ]
Post subject:  Re: Retrofit Pitot Tube

thank you! I just saw your thread on the .cc change on the images.

Author:  Jeff J [ Tue Jul 31, 2018 3:44 pm ]
Post subject:  Re: Retrofit Pitot Tube

Here are shots of the new static ports:

Attachments:
87840677-D95A-4AC8-AB5C-AFDBB2AB7D50.jpeg
87840677-D95A-4AC8-AB5C-AFDBB2AB7D50.jpeg [ 1.42 MiB | Viewed 7235 times ]
CA05F50E-4F6D-47B2-B20A-76E776292353.jpeg
CA05F50E-4F6D-47B2-B20A-76E776292353.jpeg [ 1.02 MiB | Viewed 7235 times ]
7923ACEC-7B9E-4B7C-8505-A5FD49CBE3CB.jpeg
7923ACEC-7B9E-4B7C-8505-A5FD49CBE3CB.jpeg [ 962.26 KiB | Viewed 7235 times ]

Author:  James Grahn [ Wed Aug 01, 2018 9:39 am ]
Post subject:  Re: Retrofit Pitot Tube

Jeff,
Nice work. I'm sure you know this, but make sure the static line rises inside the fuselage so you don't get water stuck in it.
Cubes

Author:  Jeff J [ Wed Aug 01, 2018 10:23 am ]
Post subject:  Re: Retrofit Pitot Tube

Good eye! The way I have it now, water can collect between the 2 ports but not gravity flow forward so the left side "should" always be clear. However, I have access to some salvaged Cessnas and I thought I might eventually raid them for their static line sumps but I like your idea better. It is easier to do and I don't have to wade through poison ivy and/or briars to do it. Thanks

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