[miyu1975]

Thought I would share the beginning of my plenum building..Last night I cleaned and waxed the mold (made from upper interior cowl) and layed 4 layers of S glass. I just got finished pulled the dried epoxy/glass and I am pretty happy with the initial results. It will need a little modifying, but all in all, very good so far....more to come...

the Mold.

While pulling out of the mold...it released very easily and I only cut myself a few times on the edges

 

[N941WR]

Looks great!

 

[miyu1975]

thanks Bill..

I little more progress here. Cleaned up the edges and fitted it to the baffle...mostly.. Still some work to do on the left side rear, there is a gap and I have not decided how I am going to handle this yet. Also, I need to rework the inlets and widen them about an inch.. Haven't decided the best plan of action there either yet.

Left side rear gap.

I am thinking possibly to cut on the line here and move the outer piece where I need it and then lay glass over the gap.. ??

 

[BSwayze]

Ryan,
I'm very interested in following your methods and progress on this project. Please keep the details coming! Do you have a website or more pics somewhere online?

 

[scsmith]

just scarf the edges and lay on more glass

Your idea for the inlet widening is fine. Just grind the edges down to a thin edge, creating a tapered lap joint with the new glass.

Same thing for the gap in the back. You can tape a piece of cereal-box cardboard inside to form the shape a little bit, cover it with packing tape, and build up glass over it to extend the edge of the plenum out to where you need it. Again, just grind a scarf angle on the original glass to bond to.

The tricky part is going to be making the rubber boots to seal the plenum to the cowl intakes. Dan Horton has made some interesting reinforced rubber parts, you might check out his postings

 

[Pilottonny]

Benefit??

Hello,

Can anybody explain to me what the benefit of this is?? To me it looks a lot more work, more weight and less access to the top of the engine than the standard setup with rubber baffle seals against the inside of the cowling.

Regards, Tonny.

 

[DanH]

Can anybody explain to me what the benefit of this is??

The elimination of leakage, which has a host of benefits.

To me it looks a lot more work, more weight and less access to the top of the engine than the standard setup with rubber baffle seals against the inside of the cowling.

All true......there's no free lunch.

 

[jdeas]

Very cool

Love using the top as the mold! I am one step behind and now rethinking the project to mold my top the same way.

Great work!

 

[hevansrv7a]

A further question

I think I understand the purpose. I have a SJ plenum under my SJ cowl. However, if I understand both the principles and the design of the SJ version, there is more to it than just reducing leakage.

As I understand it, as the air enters the volume above the cylinders, it is expanded because of the difference in intake area versus volume, taking into account speed. The speed is thus reduced. As I understand that, reducing the speed increases the pressure. The increased pressure is supposed to aid in the transfer of heat from the aluminum to the air. And so on.

In addition, the SJ version is gradually greater in volume toward the rear, an apparent technique for managing cooling rates of the individual cylinders. On mine, it seems to work quite well.

So my question is whether or to what degree that whole subject was applied to this design. To my unpracticed eye and taking the description of the use of the cowl and the mold, it was not. Lost opportunity?

 

[Vlad]

Can anybody explain to me what the benefit of this is??

... also locks all baffles preventing cracks in oil cooler corner by stiffening it


Looking good Ryan just watch that gap between the cowling and plenum by the prop.

 

[miyu1975]

Thanks all for the replies...I have a few ideas for the inlets, until then....

Part III.. Tonight I used stock alum to make the edges that the plenum will sit on, soon to be held down by nutplates and screws. I will add some of the black baffle material between the alum and plenum edge to make a tight seal..

although I like the cereal box idea to make a fiberglass edge...I had already began on this fix...this was the rear left piece with the large gap.

here is the pic with the stock angle on the top edges of the baffles...this was a lot of work to make the curves right...

and here the plenum sitting on top nice and tight..

that's all for now...Next I'll finish drilling the rear holes for the screws..and then begin to work on widening the inlets. thanks again, and suggestions are welcomed.

 

[miyu1975]

Part IV....
I have spent that last few days working on the inlet widen part. After coming up with a plan and building up lots of courage I sliced the 2 inlets in half.

here's the right side...

stole the cereal box idea too, in order to add some backing so I could someone clamp the two pieces together. This worked well.

glassing over the gap..

with a few lessons learned the other side was a little easier, except for the giant hole I had to cut out and reshape later.. the original was way to high with the new position.

once the top dried I flipped it over and glass the inside and again used the cereal box to fix that hole I cut out..

A little bit of filler and some more glass on top...all done......well almost

the inlets are now the right size..

 

[miyu1975]

Almost to the final the stages of my plenum fab...today I painted it with engine paint from the local auto store. Next is to paint the remain green aluminum piece in the front...but first I need to lay up some glass and use the engine as a mold, to prevent air from leaking there. And then onto the inlet fitting, which is going to require a little modification on the cowl.