Winter Radiator/Cooler Mods

[HighWing]

On my first Model IV, I put radiator shutters on it. They worked pretty well. There was an interesting result when closing the shutters, though. On the IV with the belly mounted radiator when the shutters were closed, there was a minor, but difinite nose down pitching moment. I could control pitch by a degree or so by opening and closing the shutters.

Something that might also be of interest to some, I used NACA vents on the side of the cowl for ventalation and made what I called doors that were controllable to close them off in cool weather - I also have them on my current IV. The reason I mention it is that when helping a friend finish his V with 7 FWF, we pretty much did the same with the NACA vent on the bottom of the cowl that feeds air to the radiator and oil cooler. It is cable controlled with a mechanism we designed. Unfortunately the owner has had work challenges that have precluded him from flying so can't report on the function, but it is soon, I understand. When we cut the cowl to the NACA shape, we left the forward edge uncut to act as a fiberglass hinge and added joggles on the sides and aft edge of the door to snug against the cowl when the door is closed. We also put springs on the mechanism so open would be the natural position in the case of a cable failure. I should mention that the mechanism reversed the cable motion so that when the knob is pulled to close the door, it pushed the mechanism that closed the cowl. The push allowed for a ball and socket joint so no tools would be needed when removing the bottom cowl.

This shows the door with joggles and the foam stiffeners on the aft edge.
Cowl Flap Glass.jpg
This shows the arms that run through the duct housing.
Cowl Flap 1.jpg
This shows the control rod and the adjustable housing through arms for the door control.
Cowl Flap 2.jpg
This shows the mechanism that reversed the cable pull and the socket for the control rod.
Cowl Flap 3.jpg

[Dorsal]

Regarding the flow to the cabin heater...
Don Hudgeon

I wonder if a good solution is to set it up so the "by-pass" line is through the cabin heater core. When it is hot the thermostat is open and most coolant goes to the radiator, when cold more would be forced through the heater.

HighWing, Thoughts on putting your thermostat after the T for the heater?

[kmach]

Curioius about the bypass line. Why do you feel it is necessary.

I like the bypass line for redundancy , if the thermostat fails closed.

I also think the bypass line helps keep the circulation going to supply the cockpit heater when the thermostat closes.

I have tried the llc thermostat , it worked well last winter ,it has a hole in the thermostat for the bypass , the bypassed fluid still runs thru the radiator, which cools it. I feel at -15 C that this is not helpful for keeping the temps up. It may be just in my mind!

When I did the 5 year hose change this year I decided to try the thermobob, I have run it at -5 C in the spring and this fall.

[HighWing]

HighWing, Thoughts on putting your thermostat after the T for the heater?

I have mine before the T. I find that in my climate - Sierra Nevada Foothills - the most significant benefit is the quick warm ups to minimum oil temps before flying. I suspect after the T, warm up would be a bit slower, as it would divert almost all pre warm up fluid through the heater core, but it might be worth trying. You would be essentially substituting a smaller radiator for the larger one. Until I put this one on my current Model IV, I had the radiator shutters which closed off the air flow through the core. My low temps here are typically well above freezing in winter. I also use the oil cooler shutters.

[Dorsal]

Thanks Lowell, I think I will give that a try, will contact with an order

[jrevens]

Curioius about the bypass line. Why do you feel it is necessary.

If I am analyzing it correctly, I believe that the small "bypass" hole in the thermostat of Lowell"s unit, which is slightly enlarged from it's original size, serves the same purpose basically, in that it allows a small amount of flow through the system when the t-stat is fully closed (not as much as a full bypass). His (Highwing's) unit may also actually have a couple of desired advantages over the Thermobob ... first, it allows the thermostatic element portion of the t-stat to be bathed in moving fluid, and this should allow the t-stat to react sooner when the temperature of the fluid warms up (although the fluid may warm up slightly slower), as opposed to the element being behind the "wall" of the closed t-stat in a stagnant area with no flow over it. The other thing is that with the Thermobob, bypass of the radiator would seem to possibly be occurring still, even with the fully open t-stat, as the pressure drop through the thermostat & radiator is probably greater than the drop through the bypass line. In other words, there may be some loss of flow through the radiator during hot weather, even when the t-stat is fully open. If the bypass mechanically closed off when the t-stat was open that wouldn't be the case, but I don't believe it does that looking at the pictures. I could be wrong... just my 2 cents worth.

[kitfox2009]

Hi Guys
With an in cabin controllable valve "auto heater style" on the heater circuit I just leave the heater closed off until operating temps are reached. Until then there will be no heat anyway.
I notice in the summer at plus 30C on a long climb to altitude the coolant temps will rise to around 200F. I cannot remember if this was the case before installing the thermostat. I suppose there may be some loss of rad efficiency due to the bypass line but in my mind not very critical.
I hope to fly more this winter so may have better info by March
Cheers
Don
Vixen FOXK 912UL IVO IFA

[Dorsal]

Don,
Are you measuring coolant temp directly or CHT? ( I am assuming by the temps listed it is coolant) and if so where in the circuit do you measure?

[kitfox2009]

Hi Dorsel
The sensor is in the standard Rotax pocket in the cylinder head. I suppose it really is CHT but at this point I would think they would be the same.
Cheers
Don

[Dorsal]

So based on this thread I am going to install a coolant thermostat after my heater "T". To do this efficiently I need to shorten the 90 degree elbow pipe that was supplied with my kit that attaches to the far end of the radiator. This means cutting the pipe and re-beading (suggestions on how to do that?) or purchasing a new beaded elbow if I could find one.
Thoughts or suggestions on beading or buying appreciated.