DIY Plenum

[petehowell]

I really like the sticker on the back of the baggage compartment that says EXPERIMENTAL - it (ok, the certificate) gives us the ability to try new things (within reason) and see how they pan out. I have already done this to varying degrees with things like headsets, nav lights, landing lights, interior lights, canopies, O2 systems and trackers. For the most part, they have worked out well and saved me a few bux in the process.

My latest musings were around a plenum for engine cooling. My cooling has always been OK, but I have always thought it could be better. So I set out to copy some plenum designs I have seen here and on the web. My only criteria were to make it reversible in case I liked the baffle seals better, and it had to be pretty cheap to make. I only have about $60 into the design, so I think I have that one covered. The reversible design worked out OK, too, but I think it led to a less than optimal inlet design.

Here is the finished product:



I started with a sheet of 2" stryo from Aviation Depot and started shaping with a surform and 40grit paper. The goal was to have the plenum fit inside the standard baffles and use the same holes for mounting.



Progress



Shape, fit, repeat. When I got close, I started fitting the upper cowl for clearance. Once it was shaped and I got a good fit, I blew off the dust and covered it in packing tape, and paste waxed it for good release.



I mixed up the EZ Poxy (good thermal properties) and applied 5 layers of 9 oz cheapo Fg cloth I found on sale at Av Depot.



I popped it off the mold, and trimmed the edges. Then, I fit it to the baffle sides and molded the ramps in place on the plane.



More to come in Part II.....................

[petehowell]

Here is the plenum trimmed, fitted with nutplates and installed. It is sealed with speed tape for initial evaluation.



Another View



And a final view after painting - the Sky Pig 2 enhances the background view.



I sealed the edges with black silicone and it looks pretty nice. How does it work? Well, it does seem to cool a bit better. On hot days, I can climb longer before I hit 400 CHT and back off. The cylinder temps are nicely evened out with the exception of #1 that needs a blocker(this is in work). Speed has increased 10 kts. Alex P and I have decided that you always claim 10kts on a drag reduction project. In reality I don't think it made a difference b/c the inlets were not resized. That may be the next project, so no real speed increase at this time.

Inlet as of now



Temps balanced nicely



Was it worth it? Qualified yes- no great transformation occured, but it does run cooler and the there is room for inlet optimization and area reduction that should lead to better cooling and less drag. 10kts - Always claim 10 kts........ I did have fun and learned a few things, too. And for an aviation project, it was cheap.......

Watch for Part 3 when I rework the inlets

[scard]

Alright! I'm watching. Looks just like where I left mine, for now. Very interested in your exploration . Great work, keep going.

[pierre smith]

....Pete. Do a search on Alan Judy. He has really small inlets....removable ones for hotter days....and a pretty fast airplane too. There is an optimal inlet ramp and sides angle that I've read about somewhere. Someone on here should know and chime in.

Regards,

[AlexPeterson]

I noticed almost 10 knots speed increase just by being in the same hangar...

[petehowell]

I have seen Alan Judy's amazing work and will use it as a reference.

[FredMagare]

(these "how to" posts are always the best!)

BTW, Pete - I'm seriously considering stealing your paint scheme!

[Ironflight]

I love it Pete! I keep thinking I need a "do-able" project now and again....that looks pretty simple - and simple is elegant design.

Paul

[petehowell]

Here are all the photos in case anyone is interested:

http://picasaweb.google.com/fly.rv9A/Plenum#

http://picasaweb.google.com/fly.rv9A/Plenum2#

Set 2 has some captions.

Here are the materials I used:

EZ-Poxy http://www.aircraftspruce.com/catalo...ges/ezpoxy.php 1.5 qt is plenty = $35

FG Cloth http://www.3m.com/us/auto_marine_aer...ml?itemNbr=576 5 packs on clearance = $15

Damaged Foam Sheet from HD = $5

Shop hardware and leftover paint = $5

[gasman]

Pete....... Dave Anders got his plenum chamber right after much research. It is not just a motor cover. Yes, and done right, you will see 10 mph increase.

Dave has made a number of modifications to his RV-4 resulting in a substantial improvement in performance. He is able to achieve a top speed of 260+ MPH. Here is a link to his notes.

http://sacrvators.com/Aircraft%20Efficiency%20N230A.pdf

Please be sure to read page 3 and page 8 .......good luck....have fun....