walter

walter

Well Known Member
I'm at the point where I should take care of any needless air gaps in the lower inter-cylinder baffles. There are a few gaps that I think should be sealed with silicone or other because the gap doesn't seem like it's doing anything more than letting too much cooling air pass by the cylinder fins. I've marked the areas with arrows that I think should be sealed in the images below. Any comments would be helpful.

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Yep. I did the same thing on the Rocket. Dont be afraid to bend the tabs near the cylinder base nuts toward the barrel to tighten the gap a bit too. Speed tape and rtv go a long way toward sealing all these gaps.
 
Walter,

Turn the lights out until it's pitch black and shine a flashlight in between the cylinders and look underneath. Light will shine through the gaps. YOu'll be amazed at all the gaps that are there, and you want to seal them all.

All told, I seem to recall it made 10 or 12 degrees difference in CHT on my 7A.

Scott
 
I am blown away that such small gaps make any difference at all. I have started my baffles and I will have a plenum and seeing threads like this make me wonder how I will ever get my plane finished. I had the fuselage and wings done before I knew there even were baffles!

Is it poor cooling that is the result of the leaks? Speed? Maybe a bit of both?

Thanks for the pictures. I can see these baffles are going to take more time than I guessed.
 
alpinelakespilot2000 said:
What's speed tape, Mike? Is it something that holds up to heat pretty well?
Click to expand...

Also known as "300 MPH tape" or "mach tape", it is an aluminum foil with an adhesive that comes on a roll (like duct tape). It makes good temporary (and in some cases permanent) repairs to small holes in aircraft skin. I've seen some C-130's that seemed to be held together with the stuff. Quality varies, but the aircraft stuff is a fairly heavy guage and has great adhesive.
 
rockwoodrv9 said:
I am blown away that such small gaps make any difference at all. I have started my baffles and I will have a plenum and seeing threads like this make me wonder how I will ever get my plane finished. I had the fuselage and wings done before I knew there even were baffles!

Is it poor cooling that is the result of the leaks? Speed? Maybe a bit of both?

Thanks for the pictures. I can see these baffles are going to take more time than I guessed.
Click to expand...

If the air is going anywhere but through the fins or the oil cooler, it is costing you cooling and adding drag. It does not take much time to do the inner baffles - especially if the engine is still on the stand. The more "stuff" you add to the engine, the harder it gets.
 
A piece of flexible plastic tubing taped to the end of your caulking gun will help to get the RTV where it belongs.
 
Aluminum-colored silicone caulk from the home stores will fill gaps very well and blends with the engine color. It can also be used to make cylinder wraps by squeegeeing it into fiberglass cloth and cutting to size. Holds up well.
 
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Heat the 1/4" od tubing and press it over a center punch to create the conical end. Then put a little chapstick around the end and push it into the standard nozzle, this way it won't get pushed out with pressure.

Note the staged extension to reduce the hand force needed for dispensing product.
 
I would think twice about sealing the gap on the bottom of the cylinder head, that is a cooling fin too. For that fin to cool properly air needs to flow on both sides of it...maybe consider reducing the gap some, but I wouldn't seal it completely.
 
sstocker31 said:
I would think twice about sealing the gap on the bottom of the cylinder head, that is a cooling fin too. For that fin to cool properly air needs to flow on both sides of it...maybe consider reducing the gap some, but I wouldn't seal it completely.
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Nahhh. The gap is only going to cool 1/2" along that fin on the outside. I sealed it. Insignificant.


If you are worried about this, are you getting air to the rear of #3 and the front of #2 where there is insufficient fin height for air passage to the dozen fins on the bottom of the head? THAT IS significant, and many don't bother, or seemingly suffer any adverse affects to the engine (except some CHT offsets)
 
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