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Battery box and cabin heat hole size uh-oh

Draker

Draker

Well Known Member
Used the wrong knock-out punch and instead of 2", ended up with 2-3/8" lightening holes on the front of the battery box and a 2-3/8" cabin heat hole in the firewall before I realized my error. Rear holes in the battery box are 2". Battery box may just have to be scrapped but I want to save the firewall.







My plan to seal up the cabin heat hole is to rivet & pro seal two small horizontal strips of aluminum or stainless across the top and bottom of the hole inside the cabin, so I can get a good airtight seal for the cabin heat valve.

For the battery box, well I'm just going to shoot an E-mail to Vans to see if they believe the strength of the box is compromised, and plan on re-doing it.

Any other options I might not have thought of?
 
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Buy yourself a 1'x 1' piece of stainless from Aircraft spruce and use it to make a flat overlay for your firewall with a 2" hole where you want it. Cleco and pop rivet in place with stainless pop rivets and some sealant between the patch and the firewall.

I figure your patch will be 6" x 6" or thereabouts.

The battery box? I might start over there.
 
I recommend punching a correct size hole in a square or rectangular piece of stainless and riveting it over the entire heating hole. Put a good coat of your choice of fire seal between the stainless piece and the firewall. I believe you will get a much better seal that way. Make sure it won't interfere with your engine control cable locations.
 
Thanks, Kyle and Scott. Yes, you're right a single patch that covers the area under the head box with the correct size cut-out seems like an even better idea.
 
Ryan,

Put the patch on the inside. It will be covered by the center cover so it won?t be noticeable. On the forward side there will just be a little spot where the sealant is barely noticeable except for by you. Lol.

Also remember there is a cross piece that divides the heater area when you are placing your patch rivets.

Ray
 
Thanks, Ray, but I would think it's better to have the patch on the forward side of the firewall, to better seal against the heater box.
 
Can you turn the battery box around so the 2-3/8 holes are against the firewall instead?
 
Does the hole size in the battery box actually matter? IS there enough structure to support the weight of the battery in a 9-G turn with the larger holes?

9-G as the aircraft is rated at 6-G with an engineering safety factor of 1.5.

(The question I am asking is will the battery box support 9 times the weight of the battery when the holes are larger?)
 
Thanks, everyone, just an update: the stainless patch idea seems to have worked great:



VAF continues to be an amazing source of knowledge and experience!

Also, the mothership didn't really have an opinion on the battery box. They said the hole sizes were chosen arbitrarily, so it's unlikely to be a problem. Even so, the part is so inexpensive it seems like it wouldn't hurt to throw one in my next order and do it right.
 
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