Piper J3

Piper J3

Well Known Member
I flew to Father’s Day breakfast fly-in last Sunday and another fly-in today. Both days had Heat Dome temps near 90F in the Ohio Valley… I used cooling fan to suck heat out of cowling when parked. Engine is nicely cooled for return flight…
 

Attachments

  • IMG_9120.jpeg
    IMG_9120.jpeg
    1.5 MB · Views: 217
I can attest to the effectiveness of the concept. I had troubles restarting after short turn-arounds (re-fueling, Young Eagles, picking up or dropping off passengers etc). This exhaust fan cost about $20 to make and solved the problem. It's on a timer so that it will only run for 1 hour, then shut off. It only draws a small amount of current but I didn't want it to run the battery down if I couldn't get back to it.


IMG_0646.JPGIMG_0617.JPG
 
My "Huffer" ...

I live in the Central San Joaquin Valley of California and the summertime temps in my corrugated sheet tin hanger can easily top 120*F on a mid summer day. I also have a very efficient plenum on my Rocket (lots of heat generated ), and worry about "stagnated" heat above the cylinders after shut down. Opening the oil access door does nothing in the way of heat rejection, because it's above the sealed plenum. So what I do, when I come back to the "roost" - no matter winter, summer, spring or fall, is to plug in my "Huffer" and let it run for an hour and a half to sweep all the super heated, stagnated air trapped there at shutdown. Before I started doing this, the sides of the cowling would hover around 200* for a while before any level of cooling was realized. With this system, in just a few minutes, most of the trapped air is evacuated and now the incoming air cools the engine/accessories as they radiate heat.

HFS
 

Attachments

  • Rocket - “Huffer”.JPG
    Rocket - “Huffer”.JPG
    1.4 MB · Views: 187
Piper J3 said:
I flew to Father’s Day breakfast fly-in last Sunday and another fly-in today. Both days had Heat Dome temps near 90F in the Ohio Valley… I used cooling fan to suck heat out of cowling when parked. Engine is nicely cooled for return flight…
Click to expand...
Do you by chance have the part number for the fan, or have an Amazon link that you can share? Sounds like a great idea!
 
homeap said:
Do you by chance have the part number for the fan, or have an Amazon link that you can share? Sounds like a great idea!
Click to expand...
12VDC Standard Brushless Cooling Fan 120mm x 25mm Dual Ball Bearing 3.0 Watt 45 CFM (Amazon - $10). Fan draws 0.25A so it can run for long time with minimal battery drain. Fan plugs into battery charging pigtail, so no installation to speak of.
 
homeap said:
Do you by chance have the part number for the fan, or have an Amazon link that you can share? Sounds like a great idea!
Click to expand...
If you’re looking for the rechargeable one I use, search Amazon for “Aluan desk fan”.
 
Last edited:
Piper J3 said:
12VDC Standard Brushless Cooling Fan 120mm x 25mm Dual Ball Bearing 3.0 Watt 45 CFM (Amazon - $10). Fan draws 0.25A so it can run for long time with minimal battery drain. Fan plugs into battery charging pigtail, so no installation to speak of.
Click to expand...
On the premise that more is better, I opted for this 80 CFM 12v fan. the fan is smaller (80 cm) as I wanted it to mount in a frame so it wouldnt fall in through the oil door opening. It is louder, and does tend to draw onlookers when the plane is parked at a fly-in or something.


IMG_1870.jpeg
 
I should preface the reason for using a cooling fan when aircraft is parked is to midigate the possibilty of Vapor Lock. Perhaps pilots new to the RV-12 are unaware of this…

Having experienced Vapor Lock first-hand using winter blend fuel in warm early-spring temps… I strongly suggest that RV-12 pilots become familiar and have a complete understanding of conditions that can lead to Vapor Lock.

I have included links to Service Letter SL-00078 dealing w/ Vapor Lock specific to RV-12 / 12iS and YouTube presentation dealing with seasonal blends of auto fuel (Mogas) used in aircraft and the risks assciated with using a winter blend in warm temperatures.

​

https://www.vansaircraft.com/wp-content/uploads/2022/10/SL-00078-RV-12-12iS-Vapor-Lock-Rev-1.pdf

 
My battery is in the back so I just use a 9v for the fan, lasts for a couple of hours.
It's a bit weak but better than nothing. I used to occasionally get vapor lock this time of year when stopping for fuel.
 

Attachments

  • RV Fan.JPG
    RV Fan.JPG
    1.1 MB · Views: 73
I have a tight plenum and the heating above the cylinders (fuel injected engine) is a big issue - causing vapor lock issues. Is there any benefit to trying one of these "fan in the oil door" options? Seems it wouldn't really help move the heat build up due to the plenum keeping the hot air confined.
Any other solutions that are practical for fuel stops or short stops during a trip? (ie. easily portable and not hangar based).
Would putting a fan in the main air inlets behind the prop be helpful? Anyone done this with a lightweight small portable system??
The only other place I can think of is to try to put an extraction fan where the exhaust pipe exits the lower cowl (4 to 1 Exhaust).
Thanks
 
One technique I’ve read is to park your plane with tail into the wind. The wind will go up the cowl exhaust and exit out the cowl inlets, taking advantage of hot air rising.

Carl
 
What’s the temp delta between passive cooling with the door open and fan cooling? Somebody please take an IR thermometer shot in one hour and let us know the difference.

It sounds like a good idea but without the data to back up the theory………..
 
I am going to make one these. I have had trouble with hot starts with 100LL on days over 100 degrees. We have posts about this calling it carb pressure lock
 
Webb said:
What’s the temp delta between passive cooling with the door open and fan cooling? Somebody please take an IR thermometer shot in one hour and let us know the difference.

It sounds like a good idea but without the data to back up the theory………..
Click to expand...
For $20, an hour of my time, and no other downside, I didn't see it as worth the data acquisition effort. I will say that my empiric observation over last summer and so far this summer, including nine 20-minute Young Eagles flights a couple of weeks ago, is that the device accomplishes what I expected from it.
 
Webb said:
What’s the temp delta between passive cooling with the door open and fan cooling? Somebody please take an IR thermometer shot in one hour and let us know the difference.

It sounds like a good idea but without the data to back up the theory………..
Click to expand...
If you put a 70 cfm fan on your oil door after landing and put your hand 6” in front of the fan you won’t be able to keep it there. Compared to an open door the heat escaping with the fan is significantly higher.
 
Last edited:
seagull said:
If you put a 70 cfm fan on your oil door after landing and put your hand 6” in front of the fan you won’t be able to keep it there. Compared to an open door the heat escaping with the fan is significantly higher.
Click to expand...
Exactly my experience. Plenum aside, evacuating heat from the engine compartment can't be a bad thing, I'm thinking.
 
MacCool said:
Exactly my experience. Plenum aside, evacuating heat from the engine compartment can't be a bad thing, I'm thinking.
Click to expand...

For those of you who do this (and it sounds like a good idea or at least one where there's no downside), do you block the air inlets so you're drawing air up through the cylinder fins? Otherwise, you may be pulling air in through the inlets and (mostly) above the cylinders, as opposed to through them.
 
Kyle Boatright said:
For those of you who do this (and it sounds like a good idea or at least one where there's no downside), do you block the air inlets so you're drawing air up through the cylinder fins? Otherwise, you may be pulling air in through the inlets and (mostly) above the cylinders, as opposed to through them.
Click to expand...
I don't. When I park, I just open the oil door, plug the thing into the battery charging connector, turn it on and walk away.
 
Kyle Boatright said:
For those of you who do this (and it sounds like a good idea or at least one where there's no downside), do you block the air inlets so you're drawing air up through the cylinder fins? Otherwise, you may be pulling air in through the inlets and (mostly) above the cylinders, as opposed to through them.
Click to expand...
For the 360 engines the oil door is behind the baffle seal area. I guess it's the same on the Rotax.

I just open my oil door and also remove the dipstick just enough to let it vent the engine moisture. Heat rises, so by the time I've fueled, or had a coffee, or lunch, the back of the engine has usually cooled quite a bit. Air also flows out the cowl inlets. Using a temperature gun I was surprised by how low the temperature is behind the engine right after shutdown. I did this to try to see how hot the ignition cases were.

Certainly a fan will accelerate the cooling!
 
As long as we are sharing, here is my version of the muffin fan cooler. I 3D printed the sides to fit my RV-12 cowl opening. The fan makes a big difference. I like the @pauldan181 design better but my cowl door is smaller.

Also, part of my SOP on a hot day is to run the electric fuel pump for a few minutes before cranking up for a second time to get some cooler fuel in the lines.
 

Attachments

  • IMG_3236.jpg
    IMG_3236.jpg
    2.4 MB · Views: 63
dpansier said:
Solar powered vent fans are widely used on sailboats and the like, designed to fit into a 3 - 4" dia hole



View attachment 65417.
Click to expand...
Great idea, but for my part I'm just trying to mitigate high temps under the cowl that might affect fuel vaporization in the lines, which in turn might lead to hard short-turn-around restarts. I've found no value in active venting for more than an hour even on hot days. A MOLEX connector on the batteries is pretty simple, so....plug and play for me.
 
You must log in or register to reply here.