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Pitot tube - whats with the goop

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kookaburra

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I've been slowly converting the RV7a I bought from here to be a good IFR machine. Next up, Pitot Heat.

I have a Dynon Pitot Tube with AoA and I decided to start poking around to T-shirt size my next project and to my surprise when I opened to access hole I found quite a lump of goop on the fittings. I was hoping this would be a "quick" swap out and re-use the old fittings, but now it's looking like a lot of goop to clean and hope I can still reuse the ones here. I think the goop is some fire resistant Permatex.

What's the reason for having it over the fittings? Is this potentially masking a leak? Is this what it's supposed to look like?

Also what's people's opinions on bending the aluminium tubes vs having a right angle connector and no bend.
 
What a mess! I would cut the gooped portions of tubing out & insert new sections with in line couplers. Check if there are any builders close to you that might have some left over tubing & Dynon/Garmin slip fittings laying around.
 
Stein air will sell you new tubing and couplers to fix that however you see fit.

Regarding your other question, the pitot is just measuring pressure (not flow), so as far as how it will read, it doesn't matter if you bend the lines or put in elbows. However, you need a certain minimum length of aluminum tube coming off the pitot before the transition so you don't melt the nylon tube with the pitot heater. Garmin says that number is 8". I imagine that dynon says something similar.
 
Probably just a crude way of trying to seal the connections. Not required if you do it correctly with the proper fittings. I just put a bend in the tubing to eliminate a possible source for a leak by adding another fitting. I only use fittings when absolutely necessary. Just my personal preference. Not that difficult to install the Dynon heated pitot without a 90* elbow. I did it on both my 7 and 4. Your biggest issue will be running the wire since I don't see a wiring conduit.
 
kookaburra said:
I've been slowly converting the RV7a I bought from here to be a good IFR machine. Next up, Pitot Heat.

I have a Dynon Pitot Tube with AoA and I decided to start poking around to T-shirt size my next project and to my surprise when I opened to access hole I found quite a lump of goop on the fittings. I was hoping this would be a "quick" swap out and re-use the old fittings, but now it's looking like a lot of goop to clean and hope I can still reuse the ones here. I think the goop is some fire resistant Permatex.

What's the reason for having it over the fittings? Is this potentially masking a leak? Is this what it's supposed to look like?

Also what's people's opinions on bending the aluminium tubes vs having a right angle connector and no bend.
Click to expand...
That “goop” in your photos is proseal. Not much sense in doing that. Waste of time and effort, and unnecessary. Messy and difficult to clean up. As been suggested, cut out those messy fittings and redo with new tubing and fittings.
 
Looks like red RTV in an effort to stop or avoid potential air leaks. Possibly a "jerry-rigged" connection from aluminum to flexible line. Ugly aesthetic but I'd leave it unless you're ready to correct more than a sloppy installation....
 
A nice, clean and airtight way of making a transition from aluminum to Nylon tubing is to use a generous length of heat shrink tube
The one with glue would be preferred and pitot heat is not an issue.
Of course that is if you cannot get yourself to pay the price for a proper fitting. (available from Stein and others)
 
Thanks everyone!

lol yes it does look like he wiped his fingers on it. Since it’s in between the two access panels it’s quite hard to cut off the goop but looks like that’s the only way to get it out.

Yeah not having a wire conduit does suck a little. I had my arms all scraped up from routing a coax cable for the wing tip antenna. The pitot heat being thinner would be a little easier.

I might have some fittings but since I’m new to this I don’t know if they’re the right ones . The previous owner gave me a bin with a bunch of parts. I’ll post it here once I get home and hopefully by then I get this cleaned up.
 
In the future if you’re going to use RTV (silicone), cleanup with mineral spirits (or Stoddard solvent) makes it easy as long as you clean up your misses before it cures. It dissolves the silicone and wipes right off nicely. Works on your hands/fingers too.
 
Update: I finally scraped all the goop off. Mostly just took a lot of nails and persistence. It was quite hard to get any solvent or knife in there. I can barely reach in with 1 arm through the access panel. I think just to be safe, the plane will be grounded for now in case there's a leak that was being sealed by the goop until I get the new dynon heated pitot with AoA gets installed and tested. Not perfect but my fingers are tired of scraping.

1728274022616.png1728274119738.png1728274150929.png

I ?might? be able to re-use those couplers. It turns out my parts bin may not have all / the right pieces...not exactly sure what these are for
1728274583071.png
I did see that Stein's sells this (https://www.steinair.com/product/fitting-straight-pitot-union-connector-1-4-to-3-16-adapter/) which seems to be a way of fitting the pitot directly the plastic tubes instead of doing this. Has anyone used the stein's fitting?
1728274831651.png



I did notice quite a bit of corrosion on the Pitot Mast. I could probably sand it off and re-paint, or should I just replace the entire thing? It looks to be secured only by 4 screws, so I'm guessing it's an older version of the blue mast? What mast do folks recommend? Also since I'm making a big shopping list from ACS anyway, where do you guys get those nut-plates?
PXL_20241006_214047617.jpg1728274049529.png


>> Those are red flags. Inspect the rest of the RV carefully.
I agree, definitely red flags, but I did buy the plane (not builder) and got a prebuy from reputable VAF members, and I think both of them did a great job. It was also built by a multi-RV builder and a reputable DAR. Sadly, I don't know enough about the plane to tell what's off but am very willing to learn and hope that I can learn more and do a thorough inspection in December for my CI. Fingers-crossed this is just a one-off.
 

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Also, I just want to saw a BIG thank you to everyone and the VAF community! Y'all are all incredibly helpful. I've always wanted to build so I'll have all these knowledge and skills to fix a plane but not having a garage + 2 year time commitment kept me from doing that so I bought one instead but kept feeling like I'm regretting not building due to my lack of knowledge. This is single-handedly the BEST forum and most helpful community! You guys what sets apart Van's aircraft from other experimentals 🤗
 
I can't remember the exact parts but I believe this is correct. Maybe one of the experts will chime in.
Nipple (AN816-3D)
Coupler (P-515)
You will need the nuts (AN818-3D) and sleeves (An819-3D) for the flare fitting and it may be a good idea to cut off the flares and re-flare them.
SteinAir has a photo
IMG_7157-3-Complete.jpg
 
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wirejock said:
I can't remember the exact parts but I believe this is correct. Maybe one of the experts will chime in.
Nipple (AN816-3D)
Coupler (P-515)
You will need the nuts (AN818-3D) and sleeves (An819-3D) for the flare fitting and it may be a good idea to cut off the flares and re-flare them.
SteinAir has a photo
View attachment 71744
Click to expand...
Yep - what Larry said.

If you get the pitot kit from Dynon that goes with your pitot tube, these fittings will be included.

Carl
 
kookaburra said:
Update: I finally scraped all the goop off. Mostly just took a lot of nails and persistence. It was quite hard to get any solvent or knife in there. I can barely reach in with 1 arm through the access panel. I think just to be safe, the plane will be grounded for now in case there's a leak that was being sealed by the goop until I get the new dynon heated pitot with AoA gets installed and tested. Not perfect but my fingers are tired of scraping.

View attachment 71713View attachment 71715View attachment 71716

I ?might? be able to re-use those couplers. It turns out my parts bin may not have all / the right pieces...not exactly sure what these are for
View attachment 71718
I did see that Stein's sells this (https://www.steinair.com/product/fitting-straight-pitot-union-connector-1-4-to-3-16-adapter/) which seems to be a way of fitting the pitot directly the plastic tubes instead of doing this. Has anyone used the stein's fitting?
View attachment 71719



I did notice quite a bit of corrosion on the Pitot Mast. I could probably sand it off and re-paint, or should I just replace the entire thing? It looks to be secured only by 4 screws, so I'm guessing it's an older version of the blue mast? What mast do folks recommend? Also since I'm making a big shopping list from ACS anyway, where do you guys get those nut-plates?
View attachment 71712View attachment 71714


>> Those are red flags. Inspect the rest of the RV carefully.
I agree, definitely red flags, but I did buy the plane (not builder) and got a prebuy from reputable VAF members, and I think both of them did a great job. It was also built by a multi-RV builder and a reputable DAR. Sadly, I don't know enough about the plane to tell what's off but am very willing to learn and hope that I can learn more and do a thorough inspection in December for my CI. Fingers-crossed this is just a one-off.
Click to expand...
I purchased the fittings that you show above for my Dynon Heated Pitot. Due to the weight on the aluminum tubing and need for proper strain relief to keep the aluminum from moving around and work hardening, I chose to slip one piece of Tygon tubing over the plastic and aluminum joint, then some heat shrink with the integrated glue to ensure an air tight connection.

Has worked well for 800 hours and 11 years.
 
wirejock said:
n819-3D) fo
Click to expand...

climberrn said:
I purchased the fittings that you show above for my Dynon Heated Pitot. Due to the weight on the aluminum tubing and need for proper strain relief to keep the aluminum from moving around and work hardening, I chose to slip one piece of Tygon tubing over the plastic and aluminum joint, then some heat shrink with the integrated glue to ensure an air tight connection.

Has worked well for 800 hours and 11 years.
Click to expand...

Good point! I'm guessing that's what the red RTV was for since there's no other strain relief that I see.
Doing some googling on build blogs, it looks like there's a few approaches to strain relief. The most common one I see looks to be a bracket that supports the weight of the couplers. That's a little hard to do with so little room to work with since I'm retrofitting a new pitot.

Is yours heated? Will Tygon tubing be able to good with a heated pitot?
 
kookaburra said:
Good point! I'm guessing that's what the red RTV was for since there's no other strain relief that I see.
Doing some googling on build blogs, it looks like there's a few approaches to strain relief. The most common one I see looks to be a bracket that supports the weight of the couplers. That's a little hard to do with so little room to work with since I'm retrofitting a new pitot.

Is yours heated? Will Tygon tubing be able to good with a heated pitot?
Click to expand...
My $.02.
The red RTV was used because the builder didn't make a good flare or made a wrong flare and it leaked. Possibly didn't use the correct flare tool for AN fittings.
You may want a second look at the entire airplane.
 
kookaburra said:
Good point! I'm guessing that's what the red RTV was for since there's no other strain relief that I see.
Doing some googling on build blogs, it looks like there's a few approaches to strain relief. The most common one I see looks to be a bracket that supports the weight of the couplers. That's a little hard to do with so little room to work with since I'm retrofitting a new pitot.

Is yours heated? Will Tygon tubing be able to good with a heated pitot?
Click to expand...
The Tygon is 8-12”?? Away from the tube, so I’m sure there is no heat left in the tubing by that point. The aluminum fittings are nice, but i did not want to build a bracket in the tight area when I felt the other approach was adequate. The Tygon tubing claims temperatures up to 200c.

As for the corrosion on the mast, that is a lot of structure for a light weight part. I’d sand blast, primer, and paint. If i remember right, the new one I bought was starting to rust out of the box.
 
Judging by the weldments, this _miiight_ be the old style SafeAir pitot mast that was prone to cracking, although the color is throwing me off cuz its not gold.

I haven't removed the pitot due to stripped & painted over screws. I'll be working on that in the next few days and post an update.
 
kookaburra said:
Judging by the weldments, this _miiight_ be the old style SafeAir pitot mast that was prone to cracking, although the color is throwing me off cuz its not gold.

I haven't removed the pitot due to stripped & painted over screws. I'll be working on that in the next few days and post an update.
Click to expand...
The safeair pitot mast that had weld issues was a gold anodized aluminum mast. I had one many years ago.
Yours looks to me to be a steel one judging from the internal and external corrosion - which should hopefully clean up easy enough.
Good luck with your upgrades. As others have said, definitely have a close look over this bird. Dare I say it - maybe another fresh set of RV experienced eyes.
There’s evidence to suggest some corner cutting/poor quality control practices going on here. Hopefully it’s not widespread.
Cheers
 
I don't know about this mast on RVs (I have one, but it's chromed or polished, don't recall what exactly they did when I bought it ages ago), but I was told that painting the mast is not a good idea as the pitot heat will conduct to the mast and could discolor or burn the paint.
 
gasman said:
A close inspection would be a good thing.....
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Will definitely get it inspected. Got a mechanic who specializes in RVs that's going to be doing a CI in December and I can ask for a more thorough inspection than usual, if it can wait til then. Not sure if there's availability for a CI in the next month or so, locally - unless there are any experienced RV eyes that are local to the bay area who can help and I can take off the panels and such. The plane's prop is getting re-pitched anyway so it won't be flying until end of month, at least.
 
Finally got the old pitot tube out and cleaned out all the goop. I had to drill out the screws.

My next question is do you need to remove the bolt to the aileron bell crank to be able to remove the mast?

IMG_1029.jpeg
 
kookaburra said:
Finally got the old pitot tube out and cleaned out all the goop. I had to drill out the screws.

My next question is do you need to remove the bolt to the aileron bell crank to be able to remove the mast?

View attachment 72072
Click to expand...
Ya’ gotta do what ya’ gotta do! There are so many ways that folks install pitot tubes and masts that rarely are two RV’s alike, so it’s hard to generalize. In your case, you might have to unbolt the pushrod at both ends to get it out of the way _ or you might have room to swing it - you wont know until you get into it. Worst case is t pull the wingtip to slide it outboard and out of the way.
 
Ironflight said:
Ya’ gotta do what ya’ gotta do! There are so many ways that folks install pitot tubes and masts that rarely are two RV’s alike, so it’s hard to generalize. In your case, you might have to unbolt the pushrod at both ends to get it out of the way _ or you might have room to swing it - you wont know until you get into it. Worst case is t pull the wingtip to slide it outboard and out of the way.
Click to expand...
Hopefully the wingtip is not riveted on!
 
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