[Vlad]

After searching for a while for the source of ready-made fiberglass plenum I quit.

Spent couple weeks reading how other guys did that I took a plunge. Using three types of foam I could find in the shop and throughout the house, bent aluminum trim and cardboard, I shaped something.




Then I covered everything and plastered it. Tomorrow will lay one more coat of plaster, let it dry and sand. Will do fiberglass this weekends





Do you guys have any remarks/suggestions/corrections? What kind of mold release should I use over the plaster?

 

[N941WR]

Vlad,

My suggestion is to make two. One for you and one for me!

For mold release you can:
1. Use automotive wax. I use Meguiar's® Gold because that’s what I have in the garage.
2. Cover everything with clear packing tape
3. Stretch Saran wrap over it

BTW, to sand down the plaster, dip a sponge in water, wring it out good and rub it on the plaster. You will go back and forth between the plaster and the bucket a number of times but you don't have to deal with the dust.

When working in the house, I will staple bath towls to sections of 2x4's and use that so I get a smooth joint w/o making a lot of dust.

 

[jasperlv]

Mold Release

i suggest covering your plaster with 2" packing tape. should the packing tape may not adhere as well to the plaster as you like, lay down a layer of duct tape and apply the packing tape over the duct tape.

will take 15 min to lay out the tape versus hours of applying, reapplying and 'waxing' the mold release. my experience with mold release doesn't always 'release' even in very smooth surfaces.

i've heard some plenums suffer from flexing as the pressure builds up at speed. adding a 'bump' might increase the strength. recall the 'X bump' or groove in the side of old jerry cans? those were in there for strength in a flat piece of sheet metal. i imagine the same effect could be achieved by laying out 2-3 sheets of glass then lay out an X with 1/4" plastic tubing (a couple straws from mcdonalds would work also) and put a couple more layups over the top of that. this suggestion may be overkill. just an idea.

your plenum is going to look very nice.

 

[miyu1975]

I am new to this layup glassing stuff, but someone mentioned earlier to me that you could layup the glass on top of the foam and then use acetone which will eat away the foam leaving just the glass...not sure if that would work or be the best option for you....but I will be standing by waiting for results..looks great so far.

 

[N941WR]

...i've heard some plenums suffer from flexing as the pressure builds up at speed. adding a 'bump' might increase the strength. recall the 'X bump' or groove in the side of old jerry cans? ...

Good idea. You can make the bump by rolling up some FG cloth and then laying your sheet of cloth over it or by simply taping crossing pieces of wood dowl rods on top of the plaster and covering them with packing tape and then fiber glassing the entire thing.

 

[Bob Martin]

plenum

I would love to make one for my -6.....so I'm watching your progress.

I have actually purchased one from a builder on this site, I think he used the inside of the top cowling for a mold, not sure, but it is a raw untrimmed piece of fiberglass.

The real issue for me......and it will be for you too and hopefully now is the time to address it is, the connection to the cowl inlets.
The James guys use a round ring and rubber connector.
Seems like we could use some inlet shaped ring that fit around the outside of the inside of the inlet.....similar to the way the carb air intake in the cowling fits into the FAB snout.
I know for me, I have the factory "ramps" in place that would have to be removed so the top cowling could slide into the ring as it is installed.
Remember, the engine will shake....and vibrate while running, but the cowl inlets don't......hopefully.
Just my thoughts......it is experimenting for sure!

 

[scsmith]

plenum connection to standard inlets

Kevin Horton did this on his RV-8. There are some good pictures on his website showing some of the details.

I would mold some fiberglass retainer rings that fit into grooves molded onto the cowl inlets, and then make rubber boots that fit those rings. Remember that with a plenum, the standard intakes are bigger than needed, so don't feel too bad if you use up 3/16" or so around the perimeter building up the shoulders of the groove for the ring to set into. (Hope that makes some sense).

I opted for baffle seals for now, but I thought about this a lot, and I may make a plenum in the future.

 

[petehowell]

One example.......

Hi Vlad,

Here is how I did mine:

http://www.vansairforce.com/community/showthread.php?t=35428&highlight=plenum

I have about 100 hours on it now and still very happy with it. I used packing tape for the release - no issues.

Make sure you use high temp epoxy like EZ-Poxy, then paint it black to make it sexy.

 

[Kenny Gene]

CHT's

Are any of you with plenums having high CHT's with #3??

Kenny Gene

 

[Vlad]

Vlad,

My suggestion is to make two. One for you and one for me! :.

Bill it seems I will be short of cloth a bit but I have enough resin. If your engine is the same size and baffles are the same (on my O-320 I trimmed them 1" from top cowl) get me some cloth and I'll do my best make one for you. Remember I am not a composite pro.

i've heard some plenums suffer from flexing as the pressure builds up at speed. adding a 'bump' might increase the strength. recall the 'X bump' or groove in the side of old jerry cans? those were in there for strength in a flat piece of sheet metal. i imagine the same effect could be achieved by laying out 2-3 sheets of glass then lay out an X with 1/4" plastic tubing (a couple straws from mcdonalds would work also) and put a couple more layups over the top of that. this suggestion may be overkill. just an idea.
.

Thanks for good suggestion Louis about reinforcement

you could layup the glass on top of the foam and then use acetone which will eat away the foam leaving just the glass...not sure if that would work or be the best option for you....

Ryan, I tried that method on other thing and it didn't work as I would like, it requires a lot of liquid to dissolve the foam and clean up is totally different story...

it will be for you too and hopefully now is the time to address it is, the connection to the cowl inlets.
The James guys use a round ring and rubber connector.
Seems like we could use some inlet shaped ring that fit around the outside of the inside of the inlet.....similar to the way the carb air intake in the cowling fits into the FAB snout.
I know for me, I have the factory "ramps" in place that would have to be removed so the top cowling could slide into the ring as it is installed.
Remember, the engine will shake....and vibrate while running, but the cowl inlets don't......hopefully.
Just my thoughts......it is experimenting for sure!

Bob experimenting with rings for stock cowling is honestly beyond my abilities

Kevin Horton did this on his RV-8. There are some good pictures on his website showing some of the details.

I would mold some fiberglass retainer rings that fit into grooves molded onto the cowl inlets, and then make rubber boots that fit those rings. Remember that with a plenum, the standard intakes are bigger than needed, so don't feel too bad if you use up 3/16" or so around the perimeter building up the shoulders of the groove for the ring to set into. (Hope that makes some sense).

Steve the rings are just too much for me now but it makes good sense to fabricate them. May be in my next aircraft...
Thanks for reference to Kevin's site.

Hi Vlad,

Here is how I did mine:

http://www.vansairforce.com/community/showthread.php?t=35428&highlight=plenum

I have about 100 hours on it now and still very happy with it. I used packing tape for the release - no issues.

Make sure you use high temp epoxy like EZ-Poxy, then paint it black to make it sexy.

Pete honestly I stole your idea about foam Thanks for step by step explanation.

 

[petehowell]

Kenny - Temps

Hi Kenny,

No temp issues, 3 runs cool. 4 runs a bit rich.

 

[petehowell]

Stealing Ideas......

Pete honestly I stole your idea about foam Thanks for step by step explanation.

Giddy Up! - We'll swap some stories at Oshkosh..... Hope the plenum turns out great!

 

[fl-mike]

Hi Kenny,

No temp issues, 3 runs cool. 4 runs a bit rich.

Hey Pete,
What's that "-" in front of the OAT reading mean? I've never seen that on mine.

 

[petehowell]

Hey Pete,
What's that "-" in front of the OAT reading mean? I've never seen that on mine.

It means it is not mosquito season in God's country, YET!

 

[whiskeypapa]

Wow, Vlad. Very impressive! You around this weekend? I'm working in JC all weekend and I'd love to have a look.
Billy Prouty

 

[Vlad]

still at work

Bill I do not know yet if I am able to get home this morning. Looks like my relief guy is not coming (not called yet) . I will PM you tomorrow morning. My weekend to work.

Wow, Vlad. Very impressive! You around this weekend? I'm working in JC all weekend and I'd love to have a look.
Billy Prouty

 

[Vlad]

Progress report on plenum

So far so good. Looks like a cooling plenum. Layed couple three coats considering all suggestions as for reinforcements and mold release. It's flexible but I think 50+ platenuts will hold it tight. Lesson learned - all little wrinkles from packing tape were exactly imprinted on the inside of the plenum. Pay better attention to your mold smoothness guys. Will do some finishing touch ups tomorrow and painting.