Bruce Fenstermacher wrote:....I might have missed it but I don't believe any of these instructions address this felt seal. Has anyone made one? I imagine it's about 1/4" thick and so I have to find thicker felt to use to cut one out. Anyone have one of these felt seals that can post a picture of it so we can get an idea what we are trying to reproduce?
Perhaps you missed the downloadable "doc" file I attached to the first post in this thread, where I described the process?
Here's the pertinent section:
"...The lower seal will simply be cut about 1” wide by about 7 inches long. Shorten it as necessary when you wrap it around the tube. Make certain it completely surrounds the tube in order to make a complete seal. Then glue it in place with 3M brand 1300L adhesive or suitable substitute. ... After the adhesive is thoroughly dry hold the vent up to it’s receptacle tube and compare the felt thickness to the inside diameter of the receiving tube. You will probably have to remove some material to “thin” it down slightly, in order to get it to slide into the wing-root tube. This is easy to do with a wire wheel but can also be done with a hand-held wire brush. Don’t remove any more than absolutely necessary or the vent will not work properly. You want a fairly tight fit so the vent will remain closed by friction in flight against air pressure. It should be tight enough to require “wiggling” it into the wing-root tube. Remember to slightly depress the plungers to assist inserting the vent back into place...."
Of course, you could always simply order the seal from Cessna, PN 0413163-5, (supercedes to 0413163-43, for only $34.60 EACH ...plus tax and shipping.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention. An originality nut (mostly) for the right reasons.
Thanks George, I did see that as well as the .doc file but it is not the seal I'm talking about. I shouldn't have started a new paragraph when I asked my question.
There is another felt seal. It is found in the open end of the outer tube in the groove. It is not attached to the inner tube which slides in it.
So both style tubes have two seals, the 1" glued to the inner tube and the one on the open. In addition the B model vent tube has a third seal under the cap that seals the cap to the outer tube.
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Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
Shopping for felt sheet 1/4 thick to cut donut seals out of. Grainger has it but in order to get the best material I need to know something about the grade and density I might want. I can't afford to buy one of each.
Anyone have a good feeling for felt grades F1, F3, F3 or other and then there are different densities of each. What would work?
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Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
The felt I used (and depicted in my photos) came from TRUE VALUE Hardware, several feet in a roll, sold in a bag, 1-1/4" X 3/16" X 17 ft. for $3.49. They'll take a credit card and let you pay it off in installments.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention. An originality nut (mostly) for the right reasons.
To make it seal properly, cut the felt on a point opposite on the ends so that when brought together they will overlap beside each other to make a positive seal. If you don't do this it might have a canyon opening to flow through unless you very carefully cut the butt edges.
John
John Hess
Past President 2018-2021 President 2016-2018, TIC170A Vice President 2014-2016, TIC170A Director 2005-2014, TIC170A N3833V Flying for Fun '67 XLH 900 Harley Sportster EAA Chapter 390 Pres since 2006 K3KNT
n3833v wrote:To make it seal properly, cut the felt on a point opposite on the ends so that when brought together they will overlap beside each other to make a positive seal. If you don't do this it might have a canyon opening to flow through unless you very carefully cut the butt edges.
John
With all the other places for air to leak thru a 170, is sealing the vent such a critical thing?
I was thinking for the front opening seal I needed a sheet of felt so I could cut a continues donut. I was thinking this front seal was not glued in but stayed in place in the groove. I've not found sheet felt in the 1/4" thickness that I believe I need. It is so hard to reproduce something when you haven't seen the original to see how it was done in the first place.
I didn't have a visual of the material you started with George but seeing the bag makes the source material clear. And it is a much better source of felt than the craft store sheet felt I was using for the 1" inside seal
As the material George used is 3/16" thick maybe I'll break the bank and get a bag of it and try to cut a strip and glue it together forming a donut suitable for the front seal.
John you have an excellent point about overlapping the seam. I'd already thought of and did it for the inside 1" wide seal. I will do the same with the test donut seal, not to make a better seal at the join but to create more surface area for the joint. Stay tuned.
CAUTION - My forum posts may be worth what you paid for them!
Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
bagarre wrote:With all the other places for air to leak thru a 170, is sealing the vent such a critical thing?
This is an excellent point David. What you don't realize however because you don't have this vent in your '52 is that the 1" seal in the back really only acts as a guide and drag to hold the vent in place. The front seal under the cap seals the vent. Since the older style has no cap and seal it relies entirely on the inside opening seal to cut off air flow. This weekend I flew for the first time with my new felt 1" seals inside and was shocked that even with the vent closed there was a pretty large high volume flow of cold air rushing in the cabin. Of course this problem is exacerbated with the speed of my GREEN plane.
Leroy, my plane partner, wasn't worried cause he's going to cover the inlet with Duct Tape like he has for the last 35 years. I on the other hand have been bitten by the challenge to make these vents work as well as they did from the factory. (Even though I doubt Cessna took the speed of the Green paint into consideration. )
CAUTION - My forum posts may be worth what you paid for them!
Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
Bruce, good luck with the sealing project on your air vents. Maybe you can get them to seal up good and tight, but I sort of doubt it owing to the fact that your plane is GREEN! You may just have to throttle back to RED airplane speed to keep out that cold air
bagarre wrote:With all the other places for air to leak thru a 170, is sealing the vent such a critical thing?
This is an excellent point David. What you don't realize however because you don't have this vent in your '52 is that the 1" seal in the back really only acts as a guide and drag to hold the vent in place. The front seal under the cap seals the vent. Since the older style has no cap and seal it relies entirely on the inside opening seal to cut off air flow. This weekend I flew for the first time with my new felt 1" seals inside and was shocked that even with the vent closed there was a pretty large high volume flow of cold air rushing in the cabin. Of course this problem is exacerbated with the speed of my GREEN plane.
I looked right past that portion of the thread.
Yes, in that case, the seals would be more critical.
From the looks, they could be retro fitted easy enough tho.
It's not the speed of the green plane that's causing the air to slip past the vent-tubes.....DOH! It's the speed of the AIR attempting to fill the VACUUM inside a green plane. (RED planes have RAM-AIR-PRESSURE.)
By the way, Bruce, ...it's a shame you didn't do the vent tubes prior to the windshield...you could have found a use for all that extra 16-feet of felt.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention. An originality nut (mostly) for the right reasons.
After realizing the difference between the early vent tube set up and the B model vent tube setup with the cap that seals the tube when shut, I went about trying to figure out how to manufacture a new felt seal for the inside end of the tube around the inside sliding tube. This seal is the only thing that seals the vent tube when it is closed on the early set up. And now one has suggested a solution likely because they had the later B model style and made a seal for under the cap which works nicely.
After several attempts at different solutions for this seal I was about to go public with my solution. But one thing bothered me. I knew the B model end cap was a better deal. I didn't want to try to find B model caps. I wanted to make my own and of course I didn't want to spend a dime to do it.
And there it was. An empty Bud beer can just laying on it's side on my work table from my beer can Stirling engine build. And it had a nearly perfect dome bottom. But the beer can shape is a bit small and after working with three of them to try to make them better I saw a small lubricant spray can that was the perfect size. Now what needs lubrication around the house cause this can needs to be empty.
I cut the bottom out of the can by cutting it around the bottom in the sides and then slowing cut the sides down as close to the crimp as possible. What was left of the sides I then bent outward so I could use a file to file then flat and dull. I brushed the tin with a scotch brite to finish the dulling process as well as dull the shiny surface to match the original vent tube. Drille a 1/8" hole in the center and it's done. You will have to drill a larger hole for the side with the OAT. Not shown in the pictures is the felt seal I will glue up under the cap like the B model version. One other adjustment you will want to make is to the felt seal on the inside of the tube. It has been shown here about 1" wide and glued to the end of the tube. By making this about 3/4" wide and glueing it about 3/16" from the edge allows the inside tube to slip further into the outer tube closing it tightly. In fact the seal under the cap is probably not needed.
This is a Desenex foot 3.6 oz foot powder can shown which is the right size. I've also found small spray paint cans to be usable.
Looks like Cessna made it.
New Cap installed slightly open.jpg (83.19 KiB) Viewed 10948 times
Original Cessna setup. New cap installed and shut.
Original vent prior to B model.jpg (89.88 KiB) Viewed 10945 times
CAUTION - My forum posts may be worth what you paid for them!
Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
Soft sponge rubber makes the best vent seal. I realize that some of our purists might lose sleep worrying that the FUZZ might find out about the unauthorized material substitution.
Bruce,
Nice work on the vent tube caps! Installing them on a green aircraft may be problematic though as they will constantly blow open during cruise. Cessna came up with a fix for this on their C-210 with SL-210-7. The "fix applies to all Cessna single engine airplanes."
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