Dusts high altitude heating system

[dust]

OK, so today we started the real tinkering with the heating system, fortunatly i had the advice of a non builder to help me through the process.

 

We started off with the assumption of just adding a duct to the top of the exhisting duct, simple enough.

 

We then went forward to plan the use of this extra duct and promptly ran into the wheel well on the other side of the instrument panel, where the original duct ends and gets directed to each side.

 

after consulting each other, and letting Dave, Thane and largeprim's wife continue to do "real work" on plane parts in the basement, we concluded to build a high narrow duct from the current location to just in front or better said before the rudder pedals. This should deliver all airflow from that duct to your toes.

 

We then decided to take the additional duct, which will be located on top of the original duct and end it at the instrument panel and vent it to the pilot and front passenger's area, with vents for the rear passengers.

 

So, we have doubled the size of the available airflow to the passenger compartment.

 

we then went to the firewall and started hacking and whacking, largeprime was quite excited to be allowed to use a dremel and sander to remove the plans tube to feed the main duct.

 

After that was removed we looked at the finely made piece that dave had hand crafted and we had just destroyed and realized that it was too small for the main heat duct that it was feeding. It was about 1 1/2 inches in diameter and the duct it was supplying was about 3 x 1.75. We will now fab ducts from the heat muff, to be build as part of the engine installation, that will supply the entire volume of the original duct.

 

It appears that we may have a 100% airflow increase from the original duct and a 200% increase from adding the new duct, giving us quite a bit of additional flow with which to heat our tootsies at 25000 feet.

 

The only thing in our way for the new duct is the botton of the map pocket, which now has a bolt through it for the elec air brake actuator and the manual pivot point for the airbrake which we have already replaced with the electric one, so both can be removed to no harm.

[John Slade]

If I remember my thermodynamics, doubling the flow area will MUCH more than double the flow capacity.

 

Keep in mind that there are normally quite a few cables and wires along the top of the heat duct. You might end up with a pretty big arm rest.

 

Also, if you're bringing a lot of air in, you'll need somewhere for it to get out.

 

Interesting experiment. I hope it works out.

I hope mine works out too.

[dust]

Question for those that can get into the plane and work the rudder pedals, is there room next to the wheel well for a 3/4" x 6 " duct, I'm worried about the 3/4 inch or could it be 1"?.

 

Could someonecheck this out for me, we are still on rickety saw horses.

[John Slade]

No, Mike.

My calf muscle rests against the wheel cover about 2.5 inches above the floor. The main point of contact is right at the base of the window in the wheel cover. Anything that forced my right leg to the left at all would be forcing my legs close together and would get uncomfortable quite quickly. You have, at most, about 2 inchs wide by 2.5 inches high (maybe a 2 inch OD pipe) along the join between the floor and the wheel cover which wouldn't get in the way. There's more room on the fuselage wall, but you probably dont want to route the air that way. Why not let it out under the front of the seat and let it track along you're legs to you're tosies.

[Aaron]

Originally posted by John Slade

If I remember my thermodynamics, doubling the flow area will MUCH more than double the flow capacity.

John that was a fluid mechanics course you're trying to remember.

 

The theromodynamics course was where you learned that air/air heat exchangers are big, inefficient and heavy, compared to water/air systems

[John Slade]

I think they rolled fluid dynamics and thermodynamics into one course. There wasn't as much data on the subjects back then

 

Back to the heating issue. Why not bite the bullet and use you're hot fluid - oil. How many velocities are there flying out there? Ever hear of one having oil in the cabin problems? I didn't. If you want redundancy, use two oil coolers - one in back and one in front. Connect them (via pipes in the sealed heat duct) using solenoid valves to shut of flow to the cabin. Use spring loaded solenoid valves that fail closed.

 

I think you have more chance of staying warm at high altitudes if you use a liquid for heating. Another plus - if you have marginal engine cooling problms, run both coolers during taxi & climb.

[LargePrime]

John;

Are you saying dust would be better to not go out the 3/4" and up the full 6 inches he suggested? He would be better to build a squater box about 2 inches high and 2 inches wide?

 

Or perhaps this is a better question. dust wants to extend the current heat duct exit point to somewhere near the end of the wheel well. What shape would you recomend? Is should have about 2.5 square inches of cross section area.

 

And thanks.

[dust]

ok so a 1.5x1.5 duct wrapped around the bottom of the wheel well should work, sold.

 

I also have a great heat source right near the firewall that i am going to shroud, the turbo, just have to make sure the temp of the air isn't too hot.

 

And for air flow I have a naca scoop right above it for supply, but I

'm getting ahead of myself, those items come later.

 

as of right now i have one duct to the tosies at the rudder pedals

 

a seperate duct to the front cabin/rear passenger cabin.

 

Both ducts are better than twice the size of the original.

 

A naca scoop above to supply air

 

A turbo in the middle to supply unlimited heat, which needs cooling.

[John Slade]

Are you saying dust would be better to not go out the 3/4" and up the full 6 inches he suggested? He would be better to build a squater box about 2 inches high and 2 inches wide?

 

Yes. I think Mike's got it. Anything higher than 2 inches off the floor will get in the way of you're leg.

[dust]

The current plans system seems to give you 40 or 50 degrees over ambient temperature.

 

So, I want 100 over ambient.

 

I think I can get it, with this configuration and I think, won't know for a long time yet, that this relatively modest tweek of the current system should give it to me with a small weight and complexity penalty.

 

If i didn't have a 1000+ degree heat source at my fingertips, I would seriously consider the oil cooler solution.

 

It's not the possibility of leakage that disuades me, it's that "MY"(he he he) solution "APPEARS" to be simpler and lighter.

 

We have also viewed the back seat armrest situation from the larger duct work.

 

I view this plane as a 2+2 It will normally carry 2 + a dog. or in Thanes case, two.

 

When more than two are in the plane, the smallest passenger or passengers will be in the back, hopefully that won't be me!

 

Speed or Space, like leer, I choose SPEED

[codensr]

Back to the heating issue. Why not bite the bullet and use you're hot fluid - oil. How many velocities are there flying out there?

Talked to one of our EAA members about his heating system (Velocity XL) Said the nose mounted oil rad was not adequite. The radiator gets hot enough but the high speed airflow over the radiator cool to much for good cabin heat.

[chuckthedog]

Do you guys always strain knats and swallow camels?

Weight,complexity,safety,weight!

Every pound saved is one more pound of the wife's stuff you can haul.

[mplafleur]

If air flow is too high, then restrict the air flow.

[LargePrime]

codensr;

 

I was very worried about just this thing. I have suggested to dust a cabin air recycle system. By reheating the cabin air i belive he will be able to get LOTS of heat. It will require a blower tho.

 

The cold incoming air will require a tremendous high tempature heat source or a very long dwell time to get warm enough. High temps are a concern with Glass. A cabin recycle system acts as a long dwell system.

 

Funny how it's just like a car?

[LargePrime]

chuckthedog;

 

And I can't make the 12V pants any better.

 

Your suggestion is by far the best I have heard. But dust's wife won't where electric clothes I understand. And there is a dog too!

 

And I can't make the 12V pants any better. I might be able to help dust make the stock heat system better.

 

Anyone reading this should know that plug in pants/socks/jacket should kick dust's system's, and everyone else's, butt!

 

EDIT

I should have said jacket and socks, not pants. The socks get heat right next to the skin ( in the cold part of the aricraft, the nose) and wrap that heat in insulation. And they do it for a few amps and a few ounces. Very hard to beat.

The above goes for the jacket too!

[chuckthedog]

My dog(Chuck) won't wear nothing. Not even a leash. I only wear the pants when plowing the taxie way on my tractor. The socks and coat are plenty in the plane. Have you gone to the gerbings web site and looked at the jacket liner? www.gerbing.com It looks just like a wind breaker.

[dust]

OK, the match is on, my butt isn't going to be kicked, i have a slave, I mean helper, whos butt will be kicked if the system ain't great. You hear that largeprime.

 

Am very excited to start on the engine/heating/turbo, but won't for 6 or so months, all in it's time.

[LargePrime]

DOH!

[dust]

Thinking, thinking, just can't get what people say out of my head. It just might be imposible or imposible enough to get hot air up to my toes, i might have to rely on fluid and fan, the book is open, it will be interesting to see the end. if i were to make a fluid system, what would be the best fluid?? it could be a very light weight afair and seperate from the engine or not.

 

I like to gather info on problems over time, without being stuck in a rut, then when the one i counted on doesn't work, i already have a backup plan.

 

enjoy the build

 

mike

[Joe Patterson]

Dust,

 

I've been reading over this thread as I also want to fly high (however, here in the Rockies temperature for the tootsies is always an issue)and I am interested in all solutions you deem worthy of "Plan A/Plan B/etc.etc.etc."

 

Is electrical heating pad out of the question?

[Jim Sower]

<... Is electrical heating pad out of the question? ...>

Pretty much. Someone on another thread did the math a while back and it was a huge drain. Now, they do make electric drawers that don't use a lot of power, but they cost a king's ransom, and I don't know what to expect if there's a short or something.

 

<... i might have to rely on fluid and fan, the book is open ...>

What if you were to weld/braize a couple of nipples to the oil pan (at the level of maybe 3-4 qt above the bottom, find an electric motor that will pump hot oil and plumb it to a little heat exchanger in the cockpit (those little 2-tube highly finned hydraulic coolers that used to be fastened to power steering systems years ago come to mind). You could install it for chump change. It's low pressure (like 3 psi) so it won't leak, enters/leaves the pan above the 4-qt level in case it does leak, totally idle when not in use.

 

If simplicity is a consideration ....

[Joe Patterson]

Now, they do make electric drawers that don't use a lot of power,

 

A-hem....are we speaking of Undershorts?........ cause I ain't stickin my toes in no underwear.

 

One of my biggest concerns when looking to build the Cozy or for that matter any "pusher", Was.......How to get warm air in front of the engine???????.......I assume when I get the plans the designers thought of this, and i just can't picture it yet.

[dust]

I just don't like breaking into the engine for the oil. I'm more apt to put a coil at the exhaust and have a seperate system. Could probebly rig it up with less than 8 pounds, wonder how much fluid and how large a pipe, like if i send 3/8 od worth of 600 degree fluid to a small radiator in the cabin, will that give me enough? just don't know enough yet but appeciate the thoughts

 

enjoy the build

 

Mike

[No4]

Adopting a very British Household Cavalry accent, twiddling my handlebar moustache in a heavy leather armchair with a large malt whiskey....

I remember, when I was in Africa, back in the last century, I actualy had a shower attached to my truck.

About 45 minutes before arival I would switch on a small electric pump, which would pass water through a 1/4 inch copper pipe that was tightly wound around the exhaust pipe. Hey presto! 50 litres of hot water, and lots of happy campers.

You don't want it to overpressurize though, I don't imagine hot steam all over the cockpit would be too pleasant.

 

[John Slade]

The plans Cozy method is a hot air muff around the exhaust ducted to the front. It's apparantly tolerable at best. The Velocity (and Jack Wilhelmson's Cozy for one) has an oil cooler up front which works pretty well if you don't mind piping you're life blood that far.

 

I have an automotive heater core. It has a valve in front of the pilot seat which controls the feed (requires liquid cooling, of course).

 

I like the sound of a separate liquid system for heating. A small pump and a closed system makes a lot of sense.

 

And to answer someone's private email - yes I've been busy on the plane. Today I spend about 4 hours performing "arthoscopic (sp?)surgery" on the throttle quadrant with a set of long needle nose pliers and a couple of screwdrivers. I have three Vans push/pull cables in there now. Throttle, cowl flap & waste gate. Plus 2 landing light actuators. Getting all the cotter pins in, the microswitches for the voice warnings lined up right, and the wiring all tied down properly was an exercise in pure frustration. Phew. Whoever said "simplicity is a good thing" was probably right.