EZFlap wrote:Wow! Somebody was really trying hard to solve a cooling problem !

CamTom you're correct... I meant to write that it would take LESS energy to exit the air on the top of the cowl than the bottom. But, I think it would be good enough for most airplanes that exiting the air on the sides probably gives you 3/4 of the benefit you would have gotten from a top exit, with a lot less effort and re-design of the cowling. For a top exit, you're really looking at a total re-design to an updraft system, where with the side exit you can still leave the existing downdraft system mostly alone.

The overall point is that exiting the air on the bottom is the worst way to do it, and almost anything is better.

That's not to minimize the fact that a poorly designed air intake at the front of the cowl can cause its own set of problems, such as contributing to a complete reversal of intended cooling flow at high AoA on some airplanes.

Back to this point. I've been thinking about it a lot and I think if I end up having to add something to aid cooling, it'll be to the sides of the cowl so I don't have to redesign/rebuild the baffling.

I was thinking a set of moveable ramps. Almost like cessna cowl flaps, only inverted. Closed the sides of the cowl would be flush and in the same shape as the current cowl, but they would open inward at the front and hinge at the rear. This would make a ramp to the back and should minimize turbulence as the air speeds up to meet the boundary layer. A standard cessna-type cowl flap would create a larger vacuum and move more air, but would add considerable drag when open. My thoughts are that I shouldn't have to move that much more air than I'm currently exiting, since even with terrible baffle rubber it's only a couple of inches of pressure difference from where it should be. It'd be nice to not add a ton of drag on hot summer days when they might be partially open even at cruise. What are your thoughts? I got the idea from the NACA reports.

But like I said before, I really think just sealing the existing baffles better will fix the cooling issues. We'll see though!

100% agreed on the movable ramps. Make sure there is a generous radius inside the cowl around the opening for the ramp, and it would not hurt to radius the leading edge of the ramp if it is going to be inside the cowling. These radii make a very significant difference in the effectiveness of the exit, allowing the air to smoothly accelerate towards the opening without flow separations, whistling, and "stalling". Well worth the extra bit of effort.

First attempt at the battery box wouldn't fit right. It left almost no room for toes above the brakes in the right seat. Oh well, I was going to have to make new cables for it to work and I didn't feel like doing that, anyway.

Here's version 2. It fits in there nicely with the added benefit of the original battery cables still reaching the terminals with the adapters installed.

Now to bend some metal. Well, maybe tomorrow or so.

Cam,

Any progress? Thanks for sharing your work. Interesting stuff and its generated some good discussion.

Brett

No real progress. I couldn't find a metal brake to use so I hired a custom auto body shop to build a battery box for me. I need to make some time to go out and finish the install and put the interior back together. Next project is baffles, but I need to line my schedule up with Gilbert's for that one.

well, good news and bad news...

I spent a LOOOONG (and still unsuccessful) time trying to mount the new battery box. the holes line up, its just nearly impossible to hold the box in place, hold the nut behind the tab that's fractions of an inch from the firewall, and thread the bolt through. I got two in loosely and dropped two nuts trying to get the third (of four!) in. I was pretty ticked. I still only have 2 of 4 bolts in. Tomorrow's going to be fun.

BUT,

Dropping those two nuts caused me to pull the passenger seat (easier than I thought it would be) and pull up the rest of the sheet metal floor (harder than I thought it would be) to try and find them. I ended up finding them, and also a lot of carpet fuzz, dirt, etc. Plus a small fuel leak from my fuselage sump drain. Its been seeping for a minute, based on the staining down there. So I took it all apart, cleaned, fuel-lubed, and reassembled. I took the opportunity to replace that quick drain assembly as well. The o-ring looked ok, but I've already had one from the originals on the plane munch its o-ring so I bought replacements for all of them and figured I might as well swap it out while I was in there. Seemed to be dry when I got done, but the floor's still up (and will be until I get the battery box on, just in case I drop another nut) so I'll make sure it's dry before I put the interior back together. I'm glad there was a silver lining to my clumsiness.

I'm going to bring the shop-vac out tomorrow and suck up all the random detritus that's accumulated in the last 150-ish hours, too.


Really looking forward to getting this project done. My back's getting pretty sore from cockpit contorting.

Sounds like your (2) arms are too short. You need a third arm (w/fingers)

Hard to give advise (but maybe you're not looking for any!) without seeing the situation. This is for an under-seat battery box location?

Maybe you can position a wrench holding the nut, and tape it in place? (PS be sure to use an open end wrench!!) I've done this when having to install a nut on a bolt through the windshield strap or firewall.

I agree, I need at least 2 more arms to get this done.

Hotrod180, I appreciate the help! It's a firewall mount (cabin side). Even using the old tape and box wrench trick it wasn't doing. I even taped the bolt into a socket on an extension to reduce chances of dropping it and to try and get better angles.

Today when I re-attack, I'll try just taping the nuts on the back of all the tabs with the box down. they'll be covered, so who cares if the tape stays. Maybe I'll just call it "chafe tape" to keep the metal battery box from scratching my beautifully painted mounting tabs? If that doesn't work, I'm toying with the idea of building longer cables and just strapping the battery into the passenger seat.

I'll post pictures when I get back out there later this afternoon. It's a really awkward angle to get at, otherwise I'd have been done last night!

If you can get the nuts onto the bolt threads from the cabin side, then just put Vise-Grips onto the head of the bolts, and zip-tie or clamp the vise-grips to something in the engine compartment. Then you can go around and tighten the nuts carefully.

One important thing that many people forget: A drilled bolt and castellated nut are good for more than just "rotating" joints. They are very good when you have just this type of situation where it's a pain in the ass to tighten a self-lock nut five full turns with little or no access to the bolt head. If you use a castle nut, you can spin the nut with your fingers 90% of the way without causing the bolt to spin. You only have this tightening problem for the last turn of the nut.

In an extreme situation, just make four custom bolts (the Poor Man's Hi-Lok... or My-Lok ):

Put a plain nut onto the bolt threads. File or grind two flats on the threads so you can get a small open end wrench on it. Then run the nut back and forth a few times over the filed threads to clean the edges of the threads. Now you can tighten a self-lock nut and hold the bolt from the same side of the firewall.

Using magnets to help install washer and nut on a hard to reach bolt. Short video https://www.youtube.com/watch?v=18GSHK8ViN4

Thanks guys! Tabs and all are on the cockpit side of the firewall. It's the fractions of an inch behind the tab to work the wrench plus awkward quarters that made it tough. 3 of 4 in and tight right now. Ran outside for a test fire to see if I let any smoke out.



Interior's still pretty bare.



Idling right now to recharge the battery. Somehow I picked up some alternator noise in the left side ics and disconnected the right, so I'll get to fixing that before I button up the interior.

Oh....

Well for goodness sakes... just put a Tinnerman Clip Nut on the steel tabs first, then the battery box, then just screw in the bolts with a socket wrench. Safety wire the bolt heads if you want to be a Boy Scout, or use lockwashers and/or Loctite.

No need to put a wrench between the firewall and those steel tabs. This is a poster-child example of why clip nuts were invented way back when.

And that's a mighty fine lookin' Pacer, BTW.

Lol, that's the best idea yet! Need to get some tinnermans.

I'm slowly building my "shop stock." I'm going to put those on the list.

Done. And fixed the ics issue. It was a loose nut in between the ear cups.

EZFlap wrote:And that's a mighty fine lookin' Pacer, BTW.

And thanks!

Interior buttoned back up and one more test fire for the heck of it. Mostly I just wanted to hear my airplane run .



There's still a little alternator noise in the ICS, but my ANR seems to diminish it quite a bit. I think I'm going to re-route all of the the alternator-related grounds to see if that will get rid of it, but I'm not going to worry about it until after Christmas.

Glad to have one of the projects I've been carrying around on the to-do list complete!