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Sealing a 1" hole in firewall.

T

Tram

Well Known Member
Ok, so I've pulled the vacuum pump and all associated equipment and I'd like to seal the hole.

I'm thinking I have a few options:

A.) A stainless patch riveted into place
B.) A simple plug from the aviation aisle at Lowe's
C.) Reinstall the line splitter and AN cap it.

Any suggestions?
 
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I recently pulled my vacuum system and had to plug a hole a bit bigger than 1". I bought two oversize steel washers and sandwiched the firewall with them using a 5/16" bolt and a steel locknut; cheap and functional :D Rosie
 
A.

I just put 2 patches in my firewall from a rewire and vacuum pump removal. Put some Proseal or even high-temp RTV in between and rivet them on.
 
Rosie said:
I recently pulled my vacuum system and had to plug a hole a bit bigger than 1". I bought two oversize steel washers and sandwiched the firewall with them using a 5/16" bolt and a steel locknut; cheap and functional :D Rosie
Click to expand...

I agree with this, easy to do and bullet-proof.
 
Why not (B)? - with a suitable sealer of course.

The steel plug is just as fireproof as the thin SS you would patch with, and would look neater too....

It is also Vans solution on the -A model hole for the nose gear leg bolt hole.
 
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Rosie said:
I recently pulled my vacuum system and had to plug a hole a bit bigger than 1". I bought two oversize steel washers and sandwiched the firewall with them using a 5/16" bolt and a steel locknut; cheap and functional :D Rosie
Click to expand...

I bought the stuff to do the same but was worried the solution would find itself not centered at some time resulting in leaking fumes into the cockpit. How did you ensure it would remain centered over the hole besides tightening the bolt?

From Rosie: I used a permanent marker to mark the washer location and I put a couple of torque-seal stripes on it as well. Also, I used fender washers (way oversize) so even if it moved, the bolt would hit the firewall hole edge and the washers still cover the hole. I look at it every 50 hours when I change the oil (so far have 122 hrs with no movement)
 
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I've patched many holes in the -8's firewall and go with "B" whenever possible. You can peen the tabs over to make the installation permanent if you're worried about security. RTV seals out the fumes too. Nice, neat fix.

I'll rivet a patch only on the really big holes like where the heater box was.
 
DanH said:
Why is that?
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I'm no A&P, but this is what I've been getting:

Because with a riveted patch you are making more holes to plug one hole. The extra holes weaken the area.
The drilling of the holes leaves a chance to drill into existing wiring.
To use the right rivets you would be bucking them and be required to get a bucking bar behind the patch from inside the aircraft.
The plug will work just as well.
 
Sid Lambert said:
I bought the stuff to do the same but was worried the solution would find itself not centered at some time resulting in leaking fumes into the cockpit. How did you ensure it would remain centered over the hole besides tightening the bolt?
Click to expand...

you could also make a blank about the size of the hole, out of a similar thickness as the firewall, that you sandwich between the two large fender washers. That way nothing will be able to move unless the bolt loses tension. it could be al, it is only holding the bolt in place but if you have some ss or plain steel around that might be a better idea.
 
I've used the same technique as Rosie for years - works great, very simple - and generally, the washers are going to be thick enough that burn-through is NOT going to be an issue. The RV-1 will have "patches" of this nature when it flies again...lots of old holes no longer being used...

Paul
 
MSP-42 rivets in firewall

I'll add to this as I'm plugging several firewall holes right now. Using bolts and washers could add necessary weight if you're fixing more than one or two holes. Or, a couple of big ones in my case. So, I went researching for light-weight alternatives.

The recommended method from Van's was to use flat stainless steel sheet secured with MSP-42 rivets and pro-seal. The MSP-42 rivets have a much higher melting point than aluminum rivets and it will weight less overall.

Hope that helps.
 
I bought a plug, put it in, than slathered ProSeal over it.

And all the time I was doing it, I thought, "man, if there's a fire in my engine compartment, this hole might be the least of my worries."
 
Remember that plugs on the electrical aisle may be 'pot metal', & will melt at relatively low temps. Worth checking to be sure they're either steel or stainless.

Charlie
 
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