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-   -   a couple printed ideas (https://vansairforce.net/community/showthread.php?t=147771)

Captain Avgas 04-24-2017 10:46 PM

Quote:

Originally Posted by Steve Melton (Post 1167829)
a brass tube (C260) section fits nicely into this fuel drain fairing and protects the alum drain boss from the set screw turning and provides a secure fit but is it a source of galvanic corrosion?

Hi Steve, the 3D printing thing is really fascinating and I'm sure many VansAirforce members are watching the developments in this area with great interest.

In answer to your question I think that there would be considerable galvanic reaction between the brass tube and the aluminium fuel drain flange. These two metals are a long way apart in the Galvanic Series. I recommend you use an aluminium tube instead of the brass.

AlexPeterson 04-25-2017 08:37 AM

The drain valve is brass, and the flange into which it threads is aluminum, so these two materials are already in intimate contact on every RV. For galvanic corrosion to occur, it needs the presence of an electrolyte, such as contaminated water (salt, dirt, etc.). And, it needs to be wet a cumulatively long time for problems to happen. Additionally, isn't the aluminum boss, onto which the split brass tube clamps, typically painted?

Nice work on the fairing!

Snowflake 04-25-2017 08:49 AM

Quote:

Originally Posted by Steve Melton (Post 1167998)
Why would the sump boss be installed in the inside of the tank and allow trapping water? That's not in the direction of goodness.

That was my thought as well. Still, one less potential customer for the fairing, unless it's sold with adhesive rather than a screw mount.

Quote:

One time I needed to drain my tank away from the home base because of low octane fuel contamination. It was nice to be able to remove the JD fairing easily. I wanted the same with these plastic fairings. So far I have not used any adhesive on the fairing and they have been secure.
I wouldn't use a liquid-style adhesive, but i've been thinking one of the 3M "command adhesive" style that can be removed by stretching it might work well. Either that or 3M double-sided body molding tape like they use to hold protective door strips and manufacturer's emblems on cars.

Quote:

yep, I looked but the right size was only avail in brass. help me find similar in alum.
Wouldn't a shorter strip of flat aluminium bent to fit work just as well, say half an inch long or so by whatever height you need? You can model a recess for it in the plastic. You could even model a couple of slots to fold the ends into as well, so it would be retained during installation.

Captain Avgas 04-25-2017 11:26 AM

Quote:

Originally Posted by AlexPeterson (Post 1168306)
The drain valve is brass, and the flange into which it threads is aluminum, so these two materials are already in intimate contact on every RV.

The fuel drain valves supplied by Vans are cad plated steel. At least mine were.

AlexPeterson 04-25-2017 12:57 PM

Quote:

Originally Posted by Captain Avgas (Post 1168365)
The fuel drain valves supplied by Vans are cad plated steel. At least mine were.

Ah, yes, you are correct.

Steve Melton 04-25-2017 08:10 PM

I'm going to find a sleeve in alum.

RV-4 04-25-2017 09:34 PM

FUEL DRAIN FAIRINGS
 
Hi Steve

Will it be possible to have a copy of your file ( specially the one you used for your friend's RV-4 )??

''I did a check fit on a neighbor's RV-4 that has a significant proseal build up around the flange to wing skin and the fairing would not fit flush. I will make a custom enlarged flange recess area for his. ''

Thanks

Bruno
rv4@videotron.ca

Steve Melton 04-26-2017 06:16 AM

Quote:

Originally Posted by RV-4 (Post 1168527)
Hi Steve

Will it be possible to have a copy of your file ( specially the one you used for your friend's RV-4 )??

''I did a check fit on a neighbor's RV-4 that has a significant proseal build up around the flange to wing skin and the fairing would not fit flush. I will make a custom enlarged flange recess area for his. ''

Thanks

Bruno
rv4@videotron.ca

Bruno, I gave my neighbor an oversized fairing for a fit check but I don't think he ever got around to checking it because he has been busy. I sent you a copy of the both the regular and oversized fairing. The oversized fairing should allow for the proseal buildup. Blue skies. Steve

jthocker 04-26-2017 05:39 PM

Quote:

Originally Posted by Steve Melton (Post 1168569)
Bruno, I gave my neighbor an oversized fairing for a fit check but I don't think he ever got around to checking it because he has been busy. I sent you a copy of the both the regular and oversized fairing. The oversized fairing should allow for the proseal buildup. Blue skies. Steve

Is that me?

Steve Melton 04-26-2017 07:07 PM

nope, that's my RV4 neighbor. your bullet nose test print has started as of 30 minutes ago. modeling effort in Solidworks, 5 minutes.




not too bad. this test was to understand if this 1mm thick bullet nose would print without any internal support. it's workable. this piece cost = $0.57 plastic. but will they withstand 200 mph?




9.5" tall x 3.5" diameter x 1mm thick. no internal support. ABS material.



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