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Cabin ventilation question

amerkarim

Active Member
Hi All,

I just started the SB fuselage last night, was been going through the plans, just have a question about the ventilation system please:

I plan to install the aero sport vents for the front panel and the rear seating. Where I am flying it is very hot all year round so I doubt I will ever need the cabin heat. Do I then need to install the scat tubes and vent system? Or can I leave it all out and save some weight? Does the ventilation and ducting system serve any other purpose apart from passenger cabin heat?

Thanks in advance and happy landings :)

Amer


Kitfox 7 SS Turbo/Intercooler - Built and Flying (Since Aug 2017)

RV-10 SB (Since June 2018)
EMP Done
Wings Done
 
Just heat...

The firewall heatvalves and scat tube are there to provide heat. I have read where some folks do not use the front heat...don?t see any reason you couldn?t eliminate both, except for resale price on the airplane.
 
If you plan to use the airplane for travel, eventually you're likely to go somewhere (or travel at a time of year) where cabin heat will come in handy.
 
If you plan to use the airplane for travel, eventually you're likely to go somewhere (or travel at a time of year) where cabin heat will come in handy.

I agree with Kyle. It will impact resale value and doesn't add any significant weight. It also gets cold at 15k' regardless of where you live.
 
That said,

you could consider doing what I'm doing. Install only one (stainless steel) heat selector box, with one heat muff, feeding a Y-connector in the tunnel for front and rear heat, probably with a 3/4" air restrictor on the rear baffle feed to the muff.

None of the above ideas are original with me. Collective wisdom from the VAF.
 
you could consider doing what I'm doing. Install only one (stainless steel) heat selector box, with one heat muff, feeding a Y-connector in the tunnel for front and rear heat, probably with a 3/4" air restrictor on the rear baffle feed to the muff.

None of the above ideas are original with me. Collective wisdom from the VAF.

My experience of flying in the Midwest requires that I have independent control of both the front and rear heaters. In the winter, when its below freezing on the ground, I typically fly with the front heater pulled out about 1/4" and the rear one wide open. It doesn't take much out of the front to start cooking you and the avionics. :eek:
 
My experience of flying in the Midwest requires that I have independent control of both the front and rear heaters. In the winter, when its below freezing on the ground, I typically fly with the front heater pulled out about 1/4" and the rear one wide open. It doesn't take much out of the front to start cooking you and the avionics. :eek:

Bob - appreciate your input! I'm at work right now, but believe independent control (which I hadn't considered beforehand) would be easy to implement with sliding shutters (or similar) over the heater outlets. Is that misguided?
 
Bob - appreciate your input! I'm at work right now, but believe independent control (which I hadn't considered beforehand) would be easy to implement with sliding shutters (or similar) over the heater outlets. Is that misguided?

Possible, but in my opinion not probable.

1. It?s awkward place to reach the front vents. How are you going to control the louvres.

2. You be exposing the tunnel to heat if you block the output ports, whereas the plans doesn?t let heat into the tunnel when closed. This is huge, since that heat is sitting right next to you fuel lines which increase the potential for vapor lock.

I personally think it?s going to be difficult to come up with a solution that beats the plans without a whole lot of engineering and work.
 
I have no horse in this race, but will provide this little bit of insight. A few weeks ago enroute to Oshkosh we were at only 4500' but the large weather system around Michigan and Wisconsin produced some sudden changes in air temperature. Yup, even in July I found myself reaching for the cabin heat control.

There's no way I'd build an airplane without an effective cabin heat system - being cold is no fun when you're flying, and even less fun when your windows are icing up on the inside!
 
I live in Florida but I think my RV-10 has enough cabin heat to melt the windows. I have flown it several times at 17,500? with OAT in single digits and just a crack of forward heat is more than enough. I have the aft heat scat re-routed to supply carb heat to my 0-540. Just opening the firewall valve on the aft heater and letting in the warm air from the cowling is enough heat in the back for me. I could split the single (forward heat scat in the tunnel) to feed both front and rear vents but don?t feel the need yet. I will not make any permanent changes to the design (removing one heat damper from the firewall) to retain resale value.
 
Possible, but in my opinion not probable.

1. It?s awkward place to reach the front vents. How are you going to control the louvres.

2. You be exposing the tunnel to heat if you block the output ports, whereas the plans doesn?t let heat into the tunnel when closed. This is huge, since that heat is sitting right next to you fuel lines which increase the potential for vapor lock.

I personally think it?s going to be difficult to come up with a solution that beats the plans without a whole lot of engineering and work.

Sincere question, Bob... I don't understand how partially restricting the output vents for the front would expose the tunnel to more heat. Seems like less flow would decrease the heat that could be shed through the walls of the SCAT inside the tunnel. Heated air stagnated inside the tubing could only shed its BTU's once, rather than perpetually if continually replenished by more hot air coming through the tubing.

I agree my plan is not a perfect solution, and I have NO IDEA how well it will work in practice, but I went for it because it offered weight and tunnel heat reduction (one less valve on the FW heating the front of the tunnel). My research in the old "tunnel heat" threads pointed to the heat selector boxes as the likely source of high tunnel temps. I have taken the steps of reducing the heater boxes from two to one, and interposing a layer of Fibrefrax and stainless foil between the selector box and the firewall. If there is too much heat in front or back with this single-control system, I anticipate having PLENTY of cold outside air available to cool off anyone who gets disproportionately hot. May not be perfect, but hopefully workable. I imagine a sliding plate(s) over the front heat vent opening(s), operated by a Bowden cable(s), might be easy to rig up.

I'll be sure to let y'all know in a few years how it's working out.
 
Bill,

Here is a post I did on RV-10 cabin heat. I offer it does what you want, but is much easier and avoids potentially problems.

One other suggestion, replace the 2” SCAT hose in the tunnel with 1.5” hose. Still plenty big enough for rear heat flow but is easier to route in the tunnel. A 2” to 1.5” reducer at both ends makes it work.

Carl

I used some of this between the cabin heat boxes and the firewall, then had it extend over the top of the boxes, then down the front of the boxes: http://www.aircraftspruce.com/catalo...clickkey=31128

The result is the hot cabin heat air, when the heat boxes are shut, bounces off the Koolmat then down toward the cowl exit, not right at the engine mounted fuel pump.

I also put a 3/4” restrictor on the back of the baffle 2” cabin heat SCAT hose flanges (a piece of aluminum with a 3/4” hole with some aluminum tape to hold it on the edge of the flange, the SCAT hose slides over it). This does two things:
- Less air to be heated so less hot air dumped into the bottom of the cowl. The RV-10 heat is way more than I’ll ever need. Even with these restrictors I have just the rear heat on part way on the coldest days.
- Less engine cooling air bypassing the engine, but still enough to keep the SCAT hose from getting too hot.

This setup has worked well - and I recommend it.
 
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