Cabin heat with an Aerovee - another approach

[Bryan Cotton]

I've made some more progress on my heat installation. A big problem was where to mount the heater control knob. I had very little panel real estate. It looked like I could mount it to the left of the trim wheel, so I 3D printed a mockup and taped it in place. One attempt to use the trim and that was shown to be unworkable. I have a real vernier type mixture control, which uses a huge nut to fasten it to the panel. The body of the mixture is an approximately 1/2" OD steel housing. So I thought I would try to use an adel clamp and mount it to the mixture under the panel. Here is the bracket:

means for holding heater cable.png (494.33 KiB) Viewed 3030 times

Before I made it all nice, I tried it in place. Seemed pretty good.

Heater knob mounted temporarily.png (643.33 KiB) Viewed 3030 times

The black heater knob was actually a choke cable from Amazon: https://www.amazon.com/dp/B07NQ6RNPJ
It was hard to see under the panel, so I painted it white and turned the choke icon into an 'H' for heat.

Painted heater knob.png (452.32 KiB) Viewed 3030 times

Here is a closeup of my flapper, clevis and swivel. The flapper and clevis are stainless. I bought some titanium off of ebay for the flapper, but it snapped when I tried to bend it in my sheetmetal brake. Back to stainless! Also the hinge is a stainless hinge I bought off of ebay. I took it apart and got two sections with no screw holes, so I could put in my own rivet holes.

flapper with stainless clevis.png (504.33 KiB) Viewed 3030 times

Here are both ends of my cable mount cleaned up. They are 7075-T6 angles that I had in the junk box. The cable sheath grabber is stainless. First I made the rounded hat section around a drill bit,using the vise. Then I cut off a little piece of an AN3 bolt that was a little shorter than the hat section so I could form the ends around it. It seems to hold the spiral sheath really well when socked down.

Heater parts.png (615.88 KiB) Viewed 3030 times

I can't remember how many pictures per post is allowed so I'm going to do another post for part 2.

[Bryan Cotton]

So the big dilemma is locating the parts before drilling holes in the firewall. I had these things to consider:
1) Clearance for my feet
2) Clearance for the control cable with respect to the rudder pedals
3) Clearance on the engine side of the firewall

I took my drill template, temporarily riveted the cable end bracket to it, and taped it in place. Seemed ok from the inside, so I used a center punch to mark where I would be holesawing the 1.75" hole. Then I marked the firewall on the engine side with a sharpie on the center punch dent. I taped my simulated firewall that was in my videos to the real firewall. I taped a piece of paper to the 1.75" hole with a hole in the center, and centered that on my mark. Immediately I had clearance issues. The valve body hit the engine mount. Also my mixture cable was going right through the air inlet tube. So I figured I could move it up about 5/8", and inboard about 1/4". I tried that out and it seems good.

prototype cable routing.png (483.66 KiB) Viewed 3027 times

For attaching the valve body, I put nutplates on it. Would be a major pain to put nutplates in the firewall with the floor installed. So I'll have to screw it on from the inside. I'm using #8 screws.

valve body with nutplates.png (505.29 KiB) Viewed 3027 times

Two of the mounting screws pick up this deflector I made. Idea is to send the hot air largely downwards, rather than shooting directly out.

deflector.png (508.89 KiB) Viewed 3027 times

So I am about to pull the trigger on this and install it. So far my parts weigh 0.256 lbs, minus the control cable, 6 screws, 4 rivets, and a short piece of scat tubing. So probably about 1/2 lb. If I can save that in clothing I have to wear then I have definitely won!

[BobDz]

Looking forward to a success story.

[Bryan Cotton]

Looking forward to a success story.

Thanks Bob!

My deep holesaw was too big to get on either side of the firewall with my drill. So I bought a low profile holesaw. I took my drilling template to a piece of plywood, and made some pilot holes for woodscrews, Plus I also piloted the 1/4" hole for the holesaw, and for the top mounting hole I brought it up to #18. This let me hold the plywood in place with an AN4 and a #8 screw while I installed the lath screws from the other side.

plywood backup from outside.png (678.67 KiB) Viewed 2802 times

I replaced the drill bit with an AN4 bolt, since I already had the guide hole in the firewall and plywood. Success!

hole sawed.png (276.2 KiB) Viewed 2802 times

Took off the plywood, and deburred the hole. Now I need another set of hands to dimple a couple of rivet holes.

plywood removed.png (266.07 KiB) Viewed 2802 times

In case anybody was wondering, drilling stainless still sucks. This is especially true when you have no room. The first #40 pilot holes were the worst. I had to drill 11 of them.

[Bryan Cotton]

In theory, I've almost got heat.

flapper closed.png (598.38 KiB) Viewed 2758 times

flapper open.png (640.66 KiB) Viewed 2758 times

valve body mounted.png (704.38 KiB) Viewed 2758 times

valve body mounted underneath.png (691.25 KiB) Viewed 2758 times

hose routing to valve body.png (640.44 KiB) Viewed 2758 times

deflector installed.png (618.21 KiB) Viewed 2758 times

Total weight added is 0.5 lbs. A half pound.

[BRS]

Question: So during the winter when you most need the cabin heat, yet need less oil cooling (don't some folks block off the oil cooler in winter) is there still enough reserve oil heat to warm the cabin without cooling the oil too much?

[Bryan Cotton]

Question: So during the winter when you most need the cabin heat, yet need less oil cooling (don't some folks block off the oil cooler in winter) is there still enough reserve oil heat to warm the cabin without cooling the oil too much?

Same cooling. The air after the cooler is divided between the cabin and the reverse scoop. I am probably going to block off half of the oil cooler exit. That would be the left side oil cooler exit.

[Bryan Cotton]

Question: So during the winter when you most need the cabin heat, yet need less oil cooling (don't some folks block off the oil cooler in winter) is there still enough reserve oil heat to warm the cabin without cooling the oil too much?

Same cooling. The air after the cooler is divided between the cabin and the reverse scoop. I am probably going to block off half of the oil cooler exit. That would be the left side oil cooler exit.

I think the real answer is - we will see! I'll report back if the weather is ever flyable again. Thinking of starting the annual.

[Bryan Cotton]

If you remember, I have two reverse scoops to pull air out of the oil cooler exit plenum. For the Arctic temperatures we are experiencing, I made this easily removable block off plate for the left side. The cabin heat exit is plumbed to the right side.

Screenshot_20240113-182234-033.png (497.3 KiB) Viewed 2634 times

Edit: this is intended to reduce oil cooling and keep the temperatures up.

[Bryan Cotton]

Adam was off today for MLK day and was the first to fly with the heat. Ambient temperature was only -3F. In Celsius (for the Canadians, Europeans and Australians), that is frigging cold. Oil temps maxed at 145F during a climb to 2500' MSL, or 1700' AGL. Otherwise oil temps were 130-140. But he did report he could feel heat during full power climbs. Not as much in cruise. Oil temp is too cold, despite my inlet blockoff plates.

I am going to add some blockoffs on the exits, and try to get temps up. Considering he felt anything at -3F, it seems promising to me.

And, Adam has discovered the ultimate Aerovee performance enhancement. At a density altitude approaching -4000', he said it climbs better than a 180HP Skyhawk, solo, in the summer.