R

RV8R999

Well Known Member
My very last task for the F/W forward is deciding whether to blank off the open side of the cabin heat box kit from Vans. As per its design, whenever the heat valve is closed (no cabin heat) the air from above the cyl is venting continuously into the lower cowl section. I see two issues with this:

1. This is wasted cooling air that could be normally used for cyl cooling whenever cabin heat isn't used. When cabin heat is used it must be colder outside so the loss in cooling should be marginal and made up for by colder cooling air (in theory).

2. The venting to the lower cowl may equalized the differential pressure between the cooling plenum and the lower cowl further reducing cooling effectiveness.

So...I don't see why fabricating a cover plate for the open side would be a bad idea but for the life of me cannot see what VANs had in mind leaving it open? Any thoughts?

Ken
 
1" Hole maybe?

The section of the exhaust pipe covered by the heat muff would overheat if there were no airflow is the reasoning behind leaving it open. I blanked it off then drilled a 1" hope to dump some air. I think it was on a Beachcraft where I saw a 1" hope that gave me the idea.
Best of luck
 
Ken,
I tried to comment on your post and must have hit the wrong button. I'm sorry. Please repost.
Danny
 
Last edited by a moderator:
Ken,
I first flew with a two inch hole in the baffle feeding into two inch scat tube, into the heat muff, then into the heater control box. Everything was two inch. At cruise speed there was way too much airflow into the heater. I made a cover plate for the opening in the baffle and drilled a one inch hole in it, then riveted it over the original hole. That cut the airflow into the heat muff by more than half, and there is still plenty of airflow into the heater. That's the way to save cooling air. Like already stated, you cannot cutoff the airflow into the muff, or it will meltdown.

I don't like the location of the heater control box as per plans. The pilot will have hot feet and the passenger will be cold with that set up. I located the heater control box so it would enter the lower forward cargo compartment near the vertical wall. From there I ran two inch scat tube to an outlet mounted in the upper aft corner of the forward cargo compartment just inside the right gear tower. From there the hot air can hit the pilot and pass between the right side of the pilot seat and cockpit wall, directly to the rear passenger. It works! I use the heater year round! Builder Doll is warm on those long nostop flights from Texas to Oshkosh and back at 8500' curising levels.
 
heater box and cooling air

Thanks Dan!

The manufacturer of my exhaust agrees some cooling air is smart and from what I've read 1" is plenty so I'll do what you've done at the baffle position to reduce the flow.

As far as heat to the cabin is concerned I connected 2" tube from the F/W to a Y-tube and fab'd a butterfly valve to control the mix of cold and hot air. The single control cable is connected in series with the mix valve and the heater box valve so as I want more heat I pull the cable which closes the butterfly to the cold air and opens the heater box door allowing only hot air to the panel mounted ball valve. Here is a pic..
k1c8z9.jpg
 
Air mix valve

Wow! That's great work. When you fly, please give us a review. You might get offers to build and sell a system or two!
 
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