The Tool Shed (s/n 1013 rebuild)

[WesRagle]

Hi Brock,

Yes, I'm happy to report that adding the wraps as well as blocking a few spots did take care of my cooling issues ...

BTW - in the end the wraps were easy to make. Just took a bit of effort to fit them the way I liked.

That's great news! If you get a chance I would really like to see any details you can offer. VW fliers can always use CHT cooling tips :-)

Thanks,

Wes

[BRS]

... If you get a chance I would really like to see any details you can offer. VW fliers can always use CHT cooling tips :-)...

Here is more information. Start with the drawings from RevMaster, below. Cut them out and drape them over the cylinders. Mark them up for changes, cut new ones. Once you are happy then paste the final versions on some sheet metal (I used 6061 .032" since I had it on hand).

On the heads I found it was not necessary to fasten the bottom except for in one place. You can see my solution for that one cylinder was to drill a fin for safety wire. I happened to have some fire-resistant foam on hand. This I used in several places to make sure air was not leaking out where it was of no use. Seal ALL the leaks. Now some pics...

Note: pics look really large on the forum. You might need to save them in order to view the entire image.

More pics on next post.......

[BRS]

More pics...

[GraemeSmith]

Note: pics look really large on the forum. You might need to save them in order to view the entire image..

Just click on each image - most browsers will then enlarge the box it appears in or display it in a pop up hover over the page.

[WesRagle]

Thanks Brock,

I'll stash the pics and give it a try next time the Onex is down for mods.

Wes

[karmarepair]

... If you get a chance I would really like to see any details you can offer. VW fliers can always use CHT cooling tips :-)...

Here is more information.

Great stuff. Lighter than the "Super Cool Tins", and perhaps a little better at keeping the cooling air flow attached to the heads and barrels for as long as possible, to pick up as much heat as possible before dumping into the lower cowl.

[BRS]

The Cowl is out at the painter's so I've been working on misc stuff. Today I decided to pull out the sonex and taxi a bit sans cowl. After pulling it back in the hangar I took the following picture....

Condensation.

ColdIntake.jpg (154.04 KiB) Viewed 2485 times

I thought it interesting that you could see just where the intake gets cold by the condensation. This is just where Joe at RevMaster said he would expect any ice if it were to ever happen. Fascinating. I would hope that with the cowl on that this would be plenty warm and not in danger of icing up. What do you think?

Oh, I don't yet have carb heat of any sort. Still trying to decide if it is needed. The air temp was around 40 with 90% humidity.

[WesRagle]

HI Brock,

I doubt anyone wants to tell you carb heat isn't needed. I don't want to take that responsibility :-) So, just for discussions sake, and to add a little context, I'll start.



If it's going to happen, you performed a pretty good test today.

This post sticks in my mind.

https://sonexbuilders.net/viewtopic.php?f=7&t=4114&hilit=carb+ice&start=10#p31305

I can say that I flew my AeroCarb equipped Sonex, with no carb heat, and cold air induction, in the heart of the icing curve with no indication of icing.

There used to be a good video put out by Ellison that showed the type of icing possible on their slide carb but the Ellison site is all jacked up right now and I can't find it :-(

Anyway, of all the slide carb vendors, Ellison says you must have carb heat. Rotec says it's up to you.

AeroConversons says:
10. Impervious to Carb Ice:

Due to its design with no venturi and no butterfly, no factory AeroCarb/AeroInjector installations have ever used carb heat. There has also never been a documented case of carb ice in any AeroCarb/AeroInjector installation or any of the injectors in the same family including the Lake Injector and POSA carbs which are well into the tens of thousands of flight hours.

That still leaves the question of induction ice down stream of the carb.

As for me, I intend to switch to a slide carb in the future and I will not have carb heat.

BTW, what does RevMaster say about it?

Edit: Never mind, I found it.

RevFlow Says:
Since the RevFlow injector carburetor does not contain a venturi, nor a butterfly valve, the fuel and air is mixed further downstream, beyond the float type venturi refrigeration chamber. The absence of these parts accounts for the decreased likelihood for ice in this type of system.

If ice were to form, it would most likely collect in the intake manifold T area, however, tightly cowled engines with internal exhaust systems would retard or preent this from happening. The alternate air source/ram air cut off valve also assists in this matter. When the ram air is cut off, the engine will digest warm air through the alternate air filter. The exhaust system we usually have in the KR air frame is a four into one, whereas the #4 exhaust pipe runs parallel to the intake manifold. This exhaust heat keeps the intake system above freezing.

The higher the pressure drop in the intake tract, the more likely the system could ice. At higher power settings the pressure drop is lower and less prone to icing. At lower power settings, the pressure drop is much higher and more prone to icing. Auto fuel vaporizes more completely in the same time as 100LL. Thus, a lower air temp will result. This will create a lower threshold for icing. This should be considered when switching over to auto fuel.

Wes

[GraemeSmith]

The bigger risk - in my mind - is the air filter icing over if you have blast air from outside directed at it and you are in very humid or near freezing air.

Injected certificated aircraft that don't have carb heat but that duct air from outside in a closed duct - with a filter on the cowl are prone to this risk - though generally in IFR when it IS 100% humidity. They have a bypass inside the cowl. A sprung flap. If the filter blocks with ice - the negative induction pressure overcomes the sprung flap and draws air from inside the cowl.

[GordonTurner]

The spring loaded automatic bypass is a great idea, just be careful with the implementation. Vans offered this and had numerous problems, some years ago, with ingestion of various bits of hardware. I guess that advice actually goes for any hardware located in the induction path…