Frank, A good way of doing that would be to cut the horizontal baffle and the box so you have abbout a 1" gap between them and the firewall. Then just rivet some 2" wide silicone baffle seal to the baffles so it closes the gap. You can see how it looks on the baffle of the C-140 I just finished.
Frank, here is a video that illustrates vibration being transmitted via the baffles:
<a href="https://www.youtube.com/watch?v=Pla43oLRZoo" data-cke-saved-href="https://www.youtube.com/watch?v=Pla43oLRZoo">
This video is selling a particular brand of baffle seal but it does show the reason why the engine and airframe must be isolated from each other. Baffle seal material is the standard method for isolating the baffles while retaining the very important air seal. Be sure you orient the seals so the high pressure on the upper half of the baffles forces the material to seal against the cowl rather than opening up a route for air to escape.
Take a close look at a certificated or well-designed experimental engine installation to see how the seals are designed. Pittsdriver3's photo is an excellent example.
Last edited by Sam Buchanan; 11-10-2015 at 10:26 AM.
Pretty impressive video.
Dale
Dale Cavin
Florida Panhandle
Current Project: Airdrome Aeroplanes Full Size Nieuport 17
Did some adjusting on the baffling, cutting it back from the firewall and trimming a bit back from the cowl, as well as putting in a reinforcing strip on the horizontal pieces.
I'll put some flexible baffle sealing between it and the cowl, and then just use some aluminum tape on the back to the firewall.
I noticed that there's some sunshine where the cowl meets the fuselage, particularly around the ends of the engine mount. I think I'll just put some felt there.
The opinions and statements of this poster are largely based on facts and portray a possible version of the actual events.
A couple pics of my, um, baffling solution.
As Sam pointed out to me, it can either be attached to the engine or to the airframe, but not both (unless I want to replace it due to cracking), so I opted to stick with keeping it attached to the engine.
A fin underneath gives it some stiffness, and it now floats free of the firewall.
The hole with the oil lines was enclosed with aluminum tape.*
Here's the other side with tape along the end where it meets the firewall to seal it off, along with tape along the seams of the box around the Diehl case.
The white stripe is some stickum tape for the gap seal where it meets the cowl. That'll get a strip of aluminum over it and some rivets - I just wanted to see if it would fit and work.
* Yes, it's ugly. Yes, it's lazy to cover up my lack of metal working ability with tape. And yes, it should work, as it's industrial ducting tape rated for high temps.
I ran the engine to see how much it moves, and it moves quite a bit (well, it looked that way to me, but it's probably an eighth an inch at low idle) with the engine, but it moves with the engine, and the tape along the firewall and the gap seal when the cowl let it move a bit as well.
From the cockpit it doesn't feel any more vibration-y than before it was on.
The opinions and statements of this poster are largely based on facts and portray a possible version of the actual events.
Frank, That aluminum tape won't last long at all and you need to seal all the way around the sides and front where it contacts the cowl. Do yourself a favor and get some baffle seal material and do the job once. I also see that cable going to the carb. If that is the throttle cable or even the choke it needs more support. It should have a bracket a couple of inches from the arm with the outer cable clamped to the bracket. As it is now when the engine moves around the arm will move also, not good. Not picking on you, just want you to be safe. Don
Thanks for your comments! That's why I post here - to get opinions, and I really appreciate them.
On the cowl - it actually does seal along the sides and the bit in the front steers it to the top. Remember I have an open cowl!
The cowling actually hits the baffling forward of the first plug.
Where the cowl goes around the firewall, I'm going to put in some baffling material to ensure there's a seal there.
On tape - I did some idle tests to look at flex, and some slow taxi to see how it held up to being under the cowl and at higher revs. I think it'll be okay; time will tell and I may revisit it. This is an aircraft that will fly for about two hours at a time under gentle conditions (think ultralight - early mornings, late afternoons) under gentle flight profiles.
On the throttle cable - I've also had concerns, but the photos don't show a lot of scale. It's only four inches of cable out when at idle. The cable sheathing is held to the firewall with a mount - it just doesn't show in the picture.
Looking out for my safety isn't picking on me - it's something I hope everyone does.
The opinions and statements of this poster are largely based on facts and portray a possible version of the actual events.
I did a test of the baffling using some slow taxi work.
As always, there were a few little things I noticed that were fixed afterwards.
The baffling, however, stayed in place and didn't rub in a bad way against the cowl or anything.
The opinions and statements of this poster are largely based on facts and portray a possible version of the actual events.
Simply awesome! As a long time follower of this thread, I find myself getting excited for you. The airplane is just beautiful. Congrats!
Rick
THE big day is coming ....
are you sure that there was no high speed "taxi" allong the runway with the camera OFF ?
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