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Modified RV-10 cowl??

Carl Froehlich

Well Known Member
I keep looking at the much improved RV-14 lower cowl with envy. The significant drag reduction from this design should be a good model to replicate on the RV-10.

I’m curious if anyone has gone down this road. My thinking:
- A horizontal injected Cold Air Sump IO-540 can be ordered from Van’s. This would support a flatter bottom (like was done on the new RV-14 cowl). Talking with Lycoming they report the standard compression Cold Air Sump engine cranks 275hp as compared with 260hp on the standard vertical induction engine. I suspect the standard compression will support burning 93 ethanol free mogas.
- Cutting off the bottom exit area of the cowl and making the exhaust tunnels would be a pain, but clearly doable. The lingering question would be if the existing exhaust will still fit. If not perhaps Vetterman can come up with a new crossover design that does.
- I’m thinking that a movable cowl flap can be installed between the aft edge of the nose gear and the firewall. If not there than two smaller ones on each side of the bottom cowl. This would be a nice feature to keep climbs cool but closed for drag reduction during cross country.

For those who missed it, here is the very well done video on how Van’s came up with the new RV-14 cowl: https://www.eaa.org/Videos/Webinars/Aircraft-Building/6207071245001

Carl
 
The lingering question would be if the existing exhaust will still fit.

It is rather likely that it would not.

The redesign of the RV-14 cowl and exhaust was done in parallel and it took a number of iterations to get the cowl where we wanted it and still have an exhaust system that had sufficient clearances to the cowl and items on the engine.
 
It has been done very recently. The purpose was to take hot exhaust gases away from the air conditioning condenser intake. This achieved a considerable improvement in core temp and A/C performance.

Downside is you cannot use the standard exhaust.

The exit air had to be played with to solve cooling issues. The SDS was retuned with a more reasonable timing map. Then the typical CHT numbers were regained.

The exit tunnels were enlarged to get the oil temp sorted which was solved. Cooling flow is still not as good as before but the owner can live with it given the A/C improvements.

Zero speed gains.

This plane is still running the standard sump and FCU, so no HP gains were included.
 
I believe the Showplanes RV-10 cowling may be what you are looking for: snorkle intake, horizontal induction, cold air sump, airflow plenum, attractive.
Pretty well thought out.
 
You can also check out the "aerodynamic kit" from Jazz Aero which includes an improved cowling, intake, exhaust, etc.

Good example of a cooling intake set up for internal diffusion, although the left inlet appears to be greatly compromised to clear something like a governor or AC compressor. He only shows the right intake in the relevant video. Note the prop extension to get the necessary diffuser length.

The large filter media air box is a step in the right direction, but the little flat box section immediately under the carb doesn't promise clean flow into the throat. I'd want to see more of the alternate air door hinge too. Broken hardware there can be a real problem.

I don't know what he is trying to do with the cowl exit. He seems to be talking about drag, but if it really needs that much area, the internal diffusers can't be doing a very good job.
 
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