Questions/Photos from ACA HQ?

[Bartman]

Folks,

I'm going to be heading back to Wisconsin soon to pick up my newly refurbished 8KCAB fuselage frame. While there, what photos would you like to see and what questions would you like to see answered?

Naturally, I'll be stocking on bare fuselage details as I get working on populating my frame with all of the various doo-dads that go in prior to fabric, but think about what you're working on or what you've been thinking about and I'll try to get some answers for you.

Bart

 

[Bob Turner]

Currently refinishing floorboards. Check out what their current attachment philosophy is? I am moving to #8 Tinnermans and flat head stainless type B screws.

Also thinking about finish. Leaning toward gloss black with clear polyurethane top coat. One suggestion was "bedliner."

I was going to do new boards out of Baltic Birch, but the originals are not cracked, and my favorite lumberyard got bought by Wallymart, and probably deals in more common stuff now. Plus, there are probably little tiny Covids in there.

 

[Bob Turner]

Oh - and we have had problems with belly fabric getting beat to death. See what their current thinking is on attachment to those cross members under the cockpit area?

 

[BB57]

I have a 1967 KCAB. It has the old style cowl (obviously) and uses a piece of black rubber tubing that is about 4 1/2" in diameter and about 3 1/2" long to connect the air induction fitting in the cowl to the air induction fitting on the air intake on the engine. It is an absolute bear to get the cowling on while lining the tubing up to fit over the intake on the air box. The thing is, once they are connected there is virtually no gap between them and no room for a second clamp.

I'd love to see what they are doing now and find out if ACA come up with something better for these older aircraft. A 3/4" thick rubber gasket would press fit between the two and make re-installing the cowling something less than a 3 man, 1/2 hour job.

 

[Bartman]

Oh - and we have had problems with belly fabric getting beat to death. See what their current thinking is on attachment to those cross members under the cockpit area?

I can answer that one, metal belly skins. it's a popular upgrade lately

 

[Bob Turner]

I have scat tube from the air box to the cowl inlet. It is clamped to the box, and I just stick my fingers in there and roll it over the cowl lip. Seems to stay there. Easy. Usually oily, which helps.

 

[Bartman]

I have a 1967 KCAB. It has the old style cowl (obviously) and uses a piece of black rubber tubing that is about 4 1/2" in diameter and about 3 1/2" long to connect the air induction fitting in the cowl to the air induction fitting on the air intake on the engine. It is an absolute bear to get the cowling on while lining the tubing up to fit over the intake on the air box. The thing is, once they are connected there is virtually no gap between them and no room for a second clamp.

I'd love to see what they are doing now and find out if ACA come up with something better for these older aircraft. A 3/4" thick rubber gasket would press fit between the two and make re-installing the cowling something less than a 3 man, 1/2 hour job.

Mine is the same way, a semi flexible, thin walled rubber sleeve that needs to be lined up as the cowl is raised into position but mine slides on pretty easily.

 

[BB57]

I took it up for a test flight today. I'm getting 105 mph IAS at 2200 rpm at 1500 ft MSL leaned 100 degrees ROP. That's 15 mph faster than before we removed and replaced the cowl. The air box was obviously blocked and reducing manifold pressure. I thought the ASI was inaccurate at the upper end of the range before we discovered this.

 

[Joesf]

I have scat tube from the air box to the cowl inlet. It is clamped to the box, and I just stick my fingers in there and roll it over the cowl lip. Seems to stay there. Easy. Usually oily, which helps.

I used to do it that way too until I read somewhere years back of the unclamped cowl portion coming undone in flight and collapsing depriving air and causing an engine failure. The front clamp is important. A zip tie after installation will suffice.

 

[Bob Turner]

I can barely get my fingers in there. Cannot imagine how one gets a clamp in. Your scenario seems a stretch, since there is positive pressure to keep the scat from being sucked in, except perhaps when taxiing. But I am open to ideas about how to install a clamp.

 

[Joesf]

Hi Bob,
I believe the issue was a partial obstruction on the air filter which caused the boot to be sucked in. May have been ice.

We attach the boot to the cowl with a zip tie
Then the boot is worked around the other end at the Air intake and zip tied again.

It’s been a while since I’ve even thought about this. It’s only because I used to do exactly what you were doing that I made the comment
. The way you were doing it is a heck of a lot easier though. It just takes a little time getting the sleeve around the neck of the air in take, Not much time a few minutes.

Give American Champion a call they may remember the incident

regards joe

 

[BB57]

I used to do it that way too until I read somewhere years back of the unclamped cowl portion coming undone in flight and collapsing depriving air and causing an engine failure. The front clamp is important. A zip tie after installation will suffice.

I like the zip tie idea in lieu of a second clamp (which I can't see how it would possibly fit). I have some large zip ties that would work well for this.

The benefits of securing it on both ends would be preventing it being sucked in during low power operation as well as preventing unfiltered air leaking into the induction system.

Induction leaks (in non turbo charged or supercharged aircraft) are worst at idle, when the manifold pressure is low. For example, in a power off descent you might have an manifold as low as 12", compared to 29" ambient pressure. That's 17" of Hg, or about 8.3 psi pressure differential pushing in on that induction tubing and trying to suck air past that insecured lip.

 

[Bob Turner]

Manifold pressure is not measured at the intake. It is measured after the throttle body. Maybe if your air filter got really dirty . . .

Let me know how to get a zip tie in there. Also how to get it cut when it is time to uncowl. Safer is better. Maybe if I use the back support on the creepie crawley . . .

 

[Bartman]

I take a lot of pride from being able to get a zip tie in with one hand just about anywhere, blind, while juggling three chainsaws with my other hand. Honest, I've done it. But in that cowl isn't somewhere where I'd imagine it's humanly possible! Challenge accepted! lol