12.3.6 Nose Mounted Oil Cooler

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The first step is to cut out the hole for the NACA scoop that supplies cooling air to the oil cooler assembly. The scoop is pre-marked on the fuselage.

Fuselage - Oil Cooler NACA Scoop Hole

Here's the initial fuselage cut for the NACA scoop used to supply air to the forward oil cooler.

The factory also pre-molds the actual scoop. It’s made oversize so trimming is required to get it to fit in the hole. Here’s a photo of the scoop after I’ve trimmed it.

Fuselage - Oil Cooler NACA Scoop

And here's the actual factory made scoop that gets installed in the hole.

After a bunch of sanding and grinding to get it to fit, it’s time to epoxy the scoop into the hole. I’m using the popsicle sticks to help hold the scoop tight against the fuselage opening while the epoxy cures.

Fuselage - Oil Cooler NACA Scoop Installed

The popsicle sticks are used to force the edges of the scoop against the hold while the epoxy cures.

And here’s the inside view of the scoop.

Fuselage - Oil Cooler NACA Scoop Inside View

Here's a view of the scoop from the inside showing the BID layups used to lock the scoop in place.

Once the strengthening lay-ups are cured I drilled some holes in the flange and did a test fitting of the cooler. It fits perfectly. The manual suggests digging out some of the fuselage wall to make more room for the cooler. I didn’t need to do that.

Although I did this much later in the process, here’s a photo of me doing some finish work on the scoop. For some reason the photo came out a bit blurry but you get the idea. As with all finishes, I used Velocipoxy with Microballoons and then sanded and sanded and sanded until I got it smooth!

Fuselage - Air Scoop Finishing

Sorry about the focus. I'm working on finishing the NACA air scoop inlet for the oil cooler.

I had to remove the oil cooler temporarily to do that finish work.

Fuselage - Oil Cooler Temporarily Installed

This photo shows the position of the oil cooler attached to the NACA scoop.

The air exit duct for the oil cooler includes the cabin heat flapper valve. The kit includes an aluminum metal plate that needs to be cut according to the supplied template. The photo below shows the finished cut plate. (I rubber glued the template to the metal plate making it real easy to do the cut.) With all of that said, this initial cut is just that. I ended up doing a lot of trimming in order to get the valve plate to fit properly into the duct.

Fuselage - Oil Cooler Heater Flapper Valve

Template attached to the metal plate to be used for the heater flapper valve. This is just for the initial cut.

The exhaust duct comes as one piece. However, that piece needs to be cut in half. The factory does pre-mark the cut point. Once it’s cut in half, a flange is added so that the two pieces can be reattached later. In the photo below, I’ve already done the cut and added BID for the flange. You can see the gray duct tape on the one piece used for separating everything once the epoxy cures.

Fuselage - Oil Cooler Exhaust Duct

The outside air flows into the NACA scoop, through the oil cooler, then through this exhaust duct which flows the air back outside again.

Here’s a closeup of the data plate for the oil cooler for future reference - just in case of a recall!

Fuselage - Oil Cooler

A closeup shot of the data plate for the oil cooler - for future reference should there be a recall on the part.

In this photo you can see that the flange that I added is now trimmed. The two pieces fit together perfectly once again! And here I’m also working on test fitting the heater flapper valve to make sure that it works properly. Like I said earlier, it took a lot of grinding and filing to get it to fit perfectly.

Fuselage - Heater Flapper Valve Test Fit

I'm test fitting the flapper valve to make sure it operates smoothly inside the duct.

The exhaust duct does not come with a pre-made flange. The can’t really do that in the factory because every oil cooler and every installation is a bit different. So, I’ve got to make my own. I took the oil cooler out of the fuselage, taped it up good with duct tape, then did the BID lay-ups per the manual to create the flange. I’m using the boards and clamps to make a nice tight fit where the oil cooler flange mates with these flanges.

Fuselage - Oil Cooler Exhaust Duct Flange

The exhaust duct comes without a flange because every installation fits a bit differently.

While the lay-ups were curing on the exhaust duct flange, I decide to mount some nut plates in the NACA scoop flange. The manual says to attached the oil cooler to the flange with sheet metal screws! I didn’t particularly like that idea, so I decided to install nut plates on the flange. I can easily bolt the oil cooler to that flange. In the end, I’m happy I did that. It’s easy to get the oil cooler in and out, if needed, and makes for a sturdier installation, in my opinion.

Fuselage - Oil Cooler NACA Scoop - Nut Plates Installed

Six nut plates are now installed in the scoop's flange for bolting the oil cooler tightly to the scoop.

Now that the epoxy is cured, here’s the finished, trimmed up version of the flange I made for the exhaust duct. I think it came out nice! It also fits tightly.

Fuselage - Oil Cooler Exhaust Duct Flange (1)

And here's the finished flange after being trimmed.

I also continued to work on the rest of the exhaust duct. Here’s the completed lower assembly. The two tubes are used to supply heat, via scat tubing, into the cockpit. Eventually I’ll attach the heater control cable to this assembly. I’m still trying to figure out the best location for that control.

Fuselage - Oil Cooler Exhaust Duct - Heater Flapper Valve Completed Assembly

Getting all of this to work correctly took longer than I thought it would!

And here’s the completed assembly. What I didn’t show is another fuselage cut I made in the bottom for the exhaust duct. The factory pre-marks that, and I did use that mark, but I must say it was a bit of a scary cut since the factory says it’s only approximate. Still, I really had no choice. In the end, the marking was just about perfect. The duct fit (after a bit of grinding and trimming) and is now permanently epoxied into place. There is still a bunch of work that needs to be done to finish the output side of the duct on the bottom of the fuselage, but that’s going to wait until the whole fuselage gets flipped upside down later for other finishing work.

You’ll notice that the exhaust duct is not screwed down to the oil cooler. The manual recommends just silicon sealing the duct to the cooler. Even if I were to add nut plates to the duct flange and screw it down, once the top is on there’s no way to get those screws out, so silicon it will be!

Fuselage - Oil Cooler - Completed Assembly

And here's the final assembly!

The next step is to run the control cable from the cockpit to the heater control flapper valve. The factory supplies the control cable but it’s too long (better than too short!) so once I determined the run for the cable, I had to trim it down. A good metal hacksaw took care of that, but I had to remove the actual internal cable first since that needs to be longer than the sheath.

And here's the other end of the cable - it opens and closes this flapper.

And here’s the other end of the control cable. I had to make a bracket to hold it in place. I decided to place it about as low as I could on the keel so that it doesn’t get in the way. I figured that a good place to put it was right below the parking brake control. The weird thing about this control is that, when it’s closed, as shown here, we get heat in the cabin. It needs to be pulled out to turn off the heat. That’s somewhat backwards in my book. Some people have designed a mechanism to reverse how that works. I may do the same thing eventually, but for now I just wanted to get it finished.

Fuselage - Cabin Heat Control

The factory supplies the control cable but I had to make the bracket to hold it in place.

Finally, after installing some tubing through the canard bulkhead, I attached scat tubing from the heater valve into the cockpit.

Fuselage - Cabin Heat Plumbing

Scat tubing is installed to feed air into the cabin through the small openings.

The manual actually recommends that the oil lines be installed before any of the above work is done. Well, that’s nearly impossible and even if I did do that, there’s a good chance I could acidentally damage the lines while doing the other work here. The lines are now installed and you can see that process in section 12.2.1.


ui© John Trautschold 2018