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FAB Cracking on 10's?

lr172

Well Known Member
Curious if the 540's have problems with cracking of the FAB top plates. I know the 4 cylinders had issues and I doubled up the 063 plate and have had no issues on my 6A.

Do I need to do something on the 10 or does the stock setup hold up on these without issues? I haven't seen much on this in the 10 forum.

Thanks,

Larry
 
With 1500+ hours on my current RV-10 setup I have not seen any of the cracking that I have seen on the 4 cylinder aircraft.

Vic
 
I added a piece of light angle between the FAB and the engine case to reduce vibration fatigue.

Carl
46327-F04-D906-46-E5-B0-C3-6251-B433-F39-B.jpg
 
I have almost 1000 hours on mine with no cracking. I did reinforce the bottom with a piece fabricated from aluminum. The air cleaner was wearing into the fiberglass.
I think the key survival of the airbox is to make sure the snorkel in front has plenty of clearance and does not in any way contact the cowl from engine torque.
 
1500 hours on ours, no cracking.

The fibreglass part was binned at about 400 hours. Solution was to build a plate alloy air box. No more problems ever!
 
Related question: On my 0-320 powered RV-6, the filter is designed with a plate to seal the bottom of the filter, instead of using the airbox to seal the bottom of the filter.

Why is the O-320 the only setup to use this design? Seems to me it would prevent some of the cracking and wear issues associated with using the fiberglass airbox as the bottom seal of the filter.
 
Mine hasn't cracked but I just noticed the VA-192A air bypass inlet has actually started to separate from the bottom of the FAB. About half the rivets pulled through the fiberglass. It won't be difficult to fix but I was a little surprised when I noticed it.
 
Mine hasn't cracked but I just noticed the VA-192A air bypass inlet has actually started to separate from the bottom of the FAB. About half the rivets pulled through the fiberglass. It won't be difficult to fix but I was a little surprised when I noticed it.
Yep - and if you just make it like it was it will again fail.

Install a 0.032? aluminum plate on the bottom inside of the FAB - at least as big as the outside air filter edge. The fiberglass will be sandwiched between the alt engine air valve ring and this piece of aluminum. The real benefit however will be eliminating the air filter ablation of the bottom of the FAB.

Add some proseal between the plate and on the alt air valve ring rivets.

Carl
 
Yep - and if you just make it like it was it will again fail.

Install a 0.032” aluminum plate on the bottom inside of the FAB - at least as big as the outside air filter edge. The fiberglass will be sandwiched between the alt engine air valve ring and this piece of aluminum. The real benefit however will be eliminating the air filter ablation of the bottom of the FAB.

Add some proseal between the plate and on the alt air valve ring rivets.

Carl

Way ahead of ya -- I've already started fabricating an interior ring to do just that. Not sure I understand the air filter ablation issue though. I've never noticed any wear on the top or bottom of the filter or the inside of the FAB.
 
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Way ahead of ya -- I've already started fabricating an interior ring to do just that. Not sure I understand the air filter ablation issue though. I've never noticed any wear on the top or bottom of the filter or the inside of the FAB.

This is a common problem, most noted when the air filter goes conical and starts to bounce around. I added glass to fix this the first time around, then did the aluminum plate as just adding glass back does not fix the root problem. Photo is the fix on the RV-8A. The RV-10 has the same fix but a different, taller filter and modified FAB.
Filter-deformation.jpg

Here is the simple fix.
Airbox-mod-1-10-30-12.jpg

Airbox-mod-3-10-30-12.jpg

Carl
 
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This is a common problem, most noted when the air filter goes conical and starts to bounce around. I added glass to fix this the first time around, then did the aluminum plate as just adding glass back does not fix the root problem. Photo is the fix on the RV-8A. The RV-10 has the same fix but a different, taller filter and modified FAB.
Filter-deformation.jpg

Here is the simple fix.
Airbox-mod-1-10-30-12.jpg

Airbox-mod-3-10-30-12.jpg

Carl

Interesting. In 5 years of flying I have not experienced this issue.
 
I put a .063 plate in my FAB to keep from wearing through the fiberglass. At 200 hrs, I was doing my condition inspection and noticed that the aluminum plate is beginning to show significant signs of wear. I have the filter sandwiches down pretty good to prevent deformation and to ensure a tight seal.

Without the plate, I would already be replacing the box as the filter would easily wear through the glass. I?m sure I?ll be replacing the plate in the next year or two. But installing it was a good decision.
 
I put a .063 plate in my FAB to keep from wearing through the fiberglass. At 200 hrs, I was doing my condition inspection and noticed that the aluminum plate is beginning to show significant signs of wear. I have the filter sandwiches down pretty good to prevent deformation and to ensure a tight seal.

Without the plate, I would already be replacing the box as the filter would easily wear through the glass. I’m sure I’ll be replacing the plate in the next year or two. But installing it was a good decision.

I used packing tape on the bottom of the FAB on the 6. 600 hours and no wear. UHMW tape will also work. The wear is from contsant motion and not pressure. Eliminating friction is the key.

Larry
 
With packing tape inside the periphery of the filter, I'd be concerned for the possibility of tape fragments being scrubbed loose and ingested into the engine.

A possible risk?
 
I used packing tape on the bottom of the FAB on the 6. 600 hours and no wear. UHMW tape will also work. The wear is from contsant motion and not pressure. Eliminating friction is the key.

Larry
Aren't the clips riveted between the nut plates and the aluminum top plate of the FAB supposed to keep the filter from moving around? We just started working on the FAB, and the directions are really bad. All I see are drawings showing the clips, but they give no dimensions for those clips or anything. After checking out a bunch of builds which mentioned the wearing of the bottom of the FAB, we did fabricate a plate to put in the bottom, and were going to rivet it to the bottom using the same rivets that attach the alt air door air inlet, but if the metal plate will also have to be replaced eventually, I'm wondering what would be a better way to secure that bottom plate so it could be easily swapped out?
 
TryChick,

I'd agree the instructions were a bit hard to follow. Heck I almost left the clips out because I missed that part of the instructions. There is some angle that comes in the FAB kit that you cut for the clips, I think if you measure it to get 6 clips they end up being about an inch wide apiece. I just figured out to get 6 even pieces out of it and cut. They you are correct, they mount between the nutplate and top. I added another layer of glass and some kevlar on the bottom of my box, hoping that will be enough to keep any wear down.

Lynn


Aren't the clips riveted between the nut plates and the aluminum top plate of the FAB supposed to keep the filter from moving around? We just started working on the FAB, and the directions are really bad. All I see are drawings showing the clips, but they give no dimensions for those clips or anything. After checking out a bunch of builds which mentioned the wearing of the bottom of the FAB, we did fabricate a plate to put in the bottom, and were going to rivet it to the bottom using the same rivets that attach the alt air door air inlet, but if the metal plate will also have to be replaced eventually, I'm wondering what would be a better way to secure that bottom plate so it could be easily swapped out?


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