Exhaust reroute tip

sea1dww · Post by **sea1dww** » Tue Jun 20, 2006 10:55 pm

I have just installed the Benham exhausts on my '54B. The installation was painless and I like the way the pipes push the sound below me instead of around me.

At the time of the installation I wasn't prepared to have the holes in the cowling patched, as I have a lot of other sheet metal work to have done. I was concerned about proper air flow and cylinder cooling, so leaving those holes in the cowling open wasn't an option. I needed to find a way to plug those holes without a full blown patch.

In the course of hanging out at the aviation parts store I happened upon some concave aluminum inspection hole covers with spring steel fasteners (intended for rag wings). These measured about 4 3/4" and my exhaust holes are 4 1/4".

To my surprise they fit perfectly inside the rivet ring and were held solidly in place by the spring steel backing. I test flew the aircraft for an hour in all normal conditions (including multiple landings and also at full cruise speed). They never moved the least little bit and the concave shape fits snugly against the cowl.

Its only a temporary fix until I can get all the sheetmetal work on the cowling done, but at a cost of $9.00 it'll do for now.

Just thought I'd share, and at the same time ask if anyone can think of a reason this might not be acceptable.

Dave

Post by **GAHorn** » Wed Jun 21, 2006 4:03 am

It's waaaay too simple and not expensive enough to get FAA approval for the mod.

Great thing-king!

cessna170bdriver · Post by **cessna170bdriver** » Wed Jun 21, 2006 5:57 am

Now ya tell me, after I spent most of the evening with a shot bag and dolly making ONE of those silly patches!

Miles

sea1dww · Post by **sea1dww** » Wed Jun 21, 2006 2:26 pm

Miles

Since you're already making them, how about making a set for me. I expect that you probably have an assembly line going. You could go into the cowl plug STC business and provide hole plugs to everyone who does an exhaust swap. Just think of all the money you can rake in. Yea, Thats the ticket ...

Dave

Metal Master · Post by **Metal Master** » Wed Jun 21, 2006 4:15 pm

Dave,

You got that done in a hurrry. Just saw you Saturday with the pipes in your hand. Was that you I just saw land at BFI Wed 6/21/06. @ 9:00.

Jim

cessna170bdriver · Post by **cessna170bdriver** » Wed Jun 21, 2006 6:06 pm

sea1dww wrote:Miles

Since you're already making them, how about making a set for me. I expect that you probably have an assembly line going. You could go into the cowl plug STC business and provide hole plugs to everyone who does an exhaust swap. Just think of all the money you can rake in. Yea, Thats the ticket ...

Dave

I'm not thrilled about how they're coming out, and I doubt you would either. I'm fairly certain that I'll come up with something that will block the air without ruining the cowl, but to get the aesthetics, I think this is going to ultimately end up being a job for the Bondo-Man.

One of the things that makes it a bit difficult is that because of the wear of the old pipes in the holes, the holes aren't round anymore. Each of mine are different from each other, and I suspect, different from each of everyone else's. I think jwild had the best idea which was to find a good english wheeler and hire him to make whole new lower cowl panels.

Miles

N170CT · Post by **N170CT** » Wed Jun 21, 2006 8:45 pm

Miles is, as usual, so right. I did mine and they were certainly different. Luckily, one was almost perfectly round and the other was round except for a small area that looked almost like a blister. For hours, it was file and fit check, file and fit check. Actually the most difficult part was getting the compound curve in the patch without a shot bag. But as noted by others, "There is no mechanical problem that brute force and ignorance cannot overcome."
chuck

sea1dww · Post by **sea1dww** » Thu Jun 22, 2006 3:14 pm

Jim

It was just coincidence that led to the quick install. I found those inspection covers and Rollie had some free time.

I've flown it twice since the weekend. I think the pipes really change the cabin environment. I found myself chatting with my passenger during taxi and suddenly realized we didn't have our headphones on. During cruise the sound is a rumble coming from the floor instead of surrounding the cabin as it did before. I was able to reduce the squelch on the intercom so that it required much less voice volume to activate the intercom. Much more comfortable.

Dave

PS I havn't been to BFI with this airplane yet, must have been some other lucky 170 owner.

sea1dww · Post by **sea1dww** » Thu Jun 22, 2006 7:01 pm

Miles

Mine has some worn areas as well. The trimming and fitting to create that perfect patch, will be left to the guy who builds the new cowling doors, repairs the nose bowl, and mends the crack by the air dam in the lower cowl. Of course, at the same time I will have my rudder and elevator reskinned and the flaps and ailerons checked for correctness. Hmmmm ... sounds like the perfect time for a paint job as well .... let me see $0.89 in my piggy bank ... that leaves ..... well maybe next spring.

Dave

cessna170bdriver · Post by **cessna170bdriver** » Wed Jun 28, 2006 5:58 am

jlwild sent me some pictures to post of his attempt at cowling patches, and of his final solution of having new panels fabricated. I've also sent some before and after pictures of my "lazy (poor?) man's solution". My AI, Ken runs http://www.recover-your-cub.com and sold me the covers cheap. He's impressed at how well they conform to the compound curves.

Enjoy, Miles

Post by **Bruce Fenstermacher** » Wed Jun 28, 2006 1:35 pm

You know Miles a couple rivets around the outside of those inspection covers to make them permanent and a little paint and your flying.

Of course you could just install the cowl as is and just go flying.

Just my thoughts.

Post by **GAHorn** » Wed Jun 28, 2006 3:32 pm

Some leather boots riveted to the lower cowl, allowing a couple of machine-gun barrels to protrude, a-la a P-40 ....

cessna170bdriver · Post by **cessna170bdriver** » Wed Jun 28, 2006 3:43 pm

gahorn wrote:Some leather boots riveted to the lower cowl, allowing a couple of machine-gun barrels to protrude, a-la a P-40 ....

I like it!

170C · Post by **170C** » Thu Jun 29, 2006 2:17 am

Miles, have Jim send you some photos to post of his new paint job. We can see it in Kelowna, but I'd like to see it sooner and I bet a bunch of folks that may not get to Kelowna would like to see it too. I saw Jim's scheme, etc. at Petit Jean, but nothing like a fresh new photo.

I also kinda like the gun port/ala P-40 idea, but wonder if you could put a couple of scoops there and make some sort of ram air to boost the HP on these ole birds? Guess the drag from the scoops would offset the ram air effort

jlwild · Post by **jlwild** » Thu Jun 29, 2006 3:42 am

OLE POKEY,

Plane is still in paint shop. Hopefully will pick it up this weekend. Time is getting short before lift off to Kelowna.

Jim

PS: Will send before and after pictures as soon as possible

The International Cessna^® 170 Association

Exhaust reroute tip

Exhaust reroute tip

JWild Photos