[Ettore]

Hi guys, can anyone tell me if the circular vents for the engine cowling (watch the pic) are an optional that should be selected when you purchase the kit, or is it a change that can be done after?

Thanks, regards.
Ettore

 

[N941WR]

Brian has a Sam James cowl and cooling plenum. Search the forum for "james cowl" then Google it.

When you order your FwF kit delete the Van's cowl. There is very little cost difference between the two cowls.

One word of caution, they are a good bit more work than the stock setup.

 

[Ettore]

Brian has a Sam James cowl and cooling plenum. Search the forum for "james cowl" then Google it.

When you order your FwF kit delete the Van's cowl. There is very little cost difference between the two cowls.

One word of caution, they are a good bit more work than the stock setup.

Thanks Bill!

 

[DanH]

Hi guys, can anyone tell me if the circular vents for the engine cowling (watch the pic) are an optional that should be selected when you purchase the kit, or is it a change that can be done after?

You can buy a cowl or modify the stock cowl. It's just fiberglass.

 

[flion]

Dan is not wrong but he's making light of what is actually a big task. The SJ inlets are aluminum; you would have to fabricate your own. Also, Sam has spent a lot of time developing his design and the associated plenum; it was not without difficulties to get to the current end result. Obviously it can be done or we wouldn't have the innovations we see in the third-party market. But it's not 'just fiberglass'; done wrong, you can cook an engine or worse.

 

[N8RV]

... It's just fiberglass.

Good one, Dan! You know, we are not all Composite Wunderkinds like you. You might as well have said, "It's just quantum physics."

 

[Terry Lutz]

Round Engine Inlets

Kelly Johnson once said: "Round engines like round air."

 

[scsmith]

round inlets and plenums

Bear in mind that the primary reason for the round inlets is to make a simple interface for the plenum to connect to. The rings nest into groves in the mating cowl rings. It is easiest to do this with round holes, so you can turn the rings on a lathe.

But, many have used plenums and adapted to the more stock inlet shape.

There is no intrinsic aerodynamic advantage to the round cooling inlets, and if not done right (size, lip radius) it is possible for them to be a disadvantage. The stock inlet shape spills flow very gracefully and does not cause much spillage drag. At high speed, there is sometimes flow coming out near the spinner, and going in over the outboard portion of the opening.

For some, it is probably an aesthetic thing.

 

[DanH]

Bear in mind that the primary reason for the round inlets is to make a simple interface for the plenum to connect to.

Fair to note a ducted plenum connection isn't really required with a low velocity (large diameter) inlet. An example might be the Mooney Acclaim, or the 0.3F inlet in CR3405.

 

[cnpeters]

Buon giorno - benvenuti al mondo di Van's Aircraft.
To add to the above comments, the Sam James cowl needs little exterior finishing from the example I saw today - very smooth. But, in looking at speed and temperature data, with and without the Sam James plenum (sold by a different location in Florida), I have truly seen negligible differences. For me, it is a matter of aesthetics, with the SJ cowl much sexier looking, albeit at the price of more work (though I'm not at this stage yet, a builder today told me that the Van's baffle kit is wonderful and fits well with their cowl. With the SJ cowl, there will be many hours more work).
As an aside, there are a dozen or so RV builders in Italy. There is a Luca P not far from you, but don't know him and if he still has his flying RV. Not too far from Verona south of Milano near Lodi is Lucio Castrogiovanni, building an RV-7. I visit him every year - a great guy. Message me if you want his contact information.
Arrivaderci,
Carl

 

[Ettore]

Buon giorno - benvenuti al mondo di Van's Aircraft.
To add to the above comments, the Sam James cowl needs little exterior finishing from the example I saw today - very smooth. But, in looking at speed and temperature data, with and without the Sam James plenum (sold by a different location in Florida), I have truly seen negligible differences. For me, it is a matter of aesthetics, with the SJ cowl much sexier looking, albeit at the price of more work (though I'm not at this stage yet, a builder today told me that the Van's baffle kit is wonderful and fits well with their cowl. With the SJ cowl, there will be many hours more work).
As an aside, there are a dozen or so RV builders in Italy. There is a Luca P not far from you, but don't know him and if he still has his flying RV. Not too far from Verona south of Milano near Lodi is Lucio Castrogiovanni, building an RV-7. I visit him every year - a great guy. Message me if you want his contact information.
Arrivaderci,
Carl

Hi Carl, thank you so much for your kindness.
I know some RV owners here in northern Italy and UK, three of them have the -7 and the fourth has a -9A. They all have standard cowls.
But don't worry, I have plenty of time to think about it, I've just ordered the preview plans.
However, I definitely think I will mount SJ cowl. I love it!

Thanks a lot for your help, ciao!

 

[hydroguy2]

....the Sam James cowl needs little exterior finishing from the example I saw today - very smooth. But, in looking at speed and temperature data, with and without the Sam James plenum (sold by a different location in Florida), I have truly seen negligible differences. For me, it is a matter of aesthetics, with the SJ cowl much sexier looking, albeit at the price of more work....

The James cowl still requires a lot of pin hole filling. I would guess the actual work to fit and prep is equal with the Vans cowl. The Plenum is tougher than straight baffles.

As far as cooling and performance, I will say, cooling can be an issue. But careful sealing and tuning I run as cool as most. Performance I think I am a touch faster than other RV-7's w/parallel valve 360's.
Hard to snap a good pic when doing a full power speed run. I have a 2kt error at this speed so call it 188kts

At cruise speed yesterday I was showing 179KTAS at 8.1gph. (~177actual)

I chose the James Cowl based on looks also. The extended Long Cowl with prop extension is a way to stretch the lines of the sometimes stubby looking side by side RV's. Also chose my paint for the same reason...Longer just looks faster.