IO390 + Showplanes/James cowl + Hartzell composite prop

Hello,

I tried searching to see if anyone has done the above combo, but I wasn't able to find a thread ( sorry if it does exist).

My husband and I working on an RV-8, and we really like the look of the James or showplane cowl, but I do know it is difficult to fit the angle valve engine in it, and the prop likely not clear the inlets ( at least on the James cowl). Haven't seen anything yet about the showplanes cowl. I've read that DanH made his factory cowl look like a James cowl.
If anyone else has experience with this combo, I would appreciate any inputs. We are also trying to avoid the use of the prop extension.

L

Hartzel

Hartzel has a hub for the composite prop that works with the James Cowling.

Bob Martin said:

Hartzel has a hub for the composite prop that works with the James Cowling.

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Yes, the hub extends the pivot axis of the blades, but the hartzell spinner is what makes it clear the cowl while not having to modify the nose of the cowl. Plan for it.

There is a reduced G limit on the extended hub.

What is the g limit of the extended hub?

The James RV8 cowls will fit around a 390 but it is tight around cyl 1 & 2. They will require either an extended hub prop or prop extension. The only blade issues will be with the Hartzel composite prop because the blades are very wide. If Hartzel has a fix for this I would like to learn more about it. There are no G restrictions I know of with the Hartzel extended hub prop. Order early, we currently have about an 8 month lead time.

Hwood said:

What is the g limit of the extended hub?

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I asked about this a few years ago before this hub was the standard recommendation. I was told 4G, sitting right there in the Hartzell factory office, but it did not sound like an engineering recommendation at the time. Hopefully, some analysis has been done and that has improved.

I stuck with the Sabre extension and standard hub. This choice was made before Vans connected with the fact that the blades could hit the cowls, and their spinner would not work.

Keep in mind the extended hub or extension moves the mass significantly forward relative to the crank flange, so it may be a limit presented by Lycoming. The overhung moment with the composite blades is less than the aluminum blades, but more than the aluminum with standard hub. You should check the flange thickness of your engine. The standard production is nearly the same as the aerobatic flange now. It was on my M1B.

Planning Planning planning

Capflyer said:

The James RV8 cowls will fit around a 390 but it is tight around cyl 1 & 2. They will require either an extended hub prop or prop extension. The only blade issues will be with the Hartzel composite prop because the blades are very wide. If Hartzel has a fix for this I would like to learn more about it. There are no G restrictions I know of with the Hartzel extended hub prop. Order early, we currently have about an 8 month lead time.

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Mike, I have the James long cowl and used the extension on my 7. The cowl had to set 5/8" farther back than the standard method of aligning with the Vans spinner to allow enough clearance to the prop at full (coarse) pitch. Again, this decision was made because there was no definitive information on the Hartzell spinner at the time. Anyway, that setback resulted in having to extend the nose of the cowl. It can be avoided by using the Hartzell spinner - and some more $$$. Be sure to verify this in writing with Vans, or get dimensions from Hartzell, not just part numbers.

Your James cowl has the spinner face and inlets in the same plane, unlike the Vans cowls where they are set back. Removal of the prop governor an adapted plate and 30 psi of air will advance the pitch for fitting.

One thing. For 8 owners, since they are faster than a 7 and using the 390 even more so, the lowest governable rpm may be less than 2400. Well - it will be reduced relative to the aluminum blades. Why? because the Vans version of that prop limits the pitch change of the composite blades. And, since the RV is so fast, it will hit the pitch stop. Don't waste time and $$ I already spent to find this out.

Maybe nobody cares about causing at 1900 rpm and 20" MAP to get extended range, but if you do, be dang sure to investigate this for your plane in advance.

BillL said:

The overhung moment with the composite blades is less than the aluminum blades, but more than the aluminum with standard hub.

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In which case I would recommend against a prop extension or extended hub with a 390. An -8 is already heavy in pitch (stick force vs G) and runs out of elevator trim on approach when solo, with a 390 and metal BA, no extension.

I've read that DanH made his factory cowl look like a James cowl.

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The only thing they share is a round inlet shape. The velocity ratio is lower, the inlet duct shape is less critical, the inlets are above the centerline, and the external profile of the inlet lips is larger in radius. There are no wetsuit sleeves or potential misalignments in the intake stream. There is a reason for each difference, but relevant to this discussion, the reason underlying most of it was to avoid a prop extension.