Riff Raff carb induction changes?

[wingman]

Light on her feet...

[TWD]

Can someone help me understand why the upper cylinders would run hotter with a scoop on top?

[wingman]

Can someone help me understand why the upper cylinders would run hotter with a scoop on top?

I have been wondering the same thing....

[AE88]

Yes, it would have looked better being a little wider but Stew's hood scoop was a compromise to still allow some accessibility to the engine through the side cowlings.

I monitored his telemetry and we never had a problem with CHT on the course. The airframe CHT was on the # 1 cyl (top aft) and I put the telemetry reading on # 3 right next to it. They were always very close with each other. It would have been nice to install CHT's on each cyl but since it was never an issue we decided not to.

The big spinner closes the cooling inlet to 1 3/8" and was worth 10-15 mph speed increase depending on the day and the pilot. We did find that we had to reinforce the baffling on the engine- the big spinner would beat it up. It's amazing that it ran as cool as it did. I remember flying with Dad in Howard's Fury to an airshow in Roswell back in the 90's. I could see the CHT gauge around him and noticed it was sitting just below 100 deg C at cruise power which was usually around 27" and 1700 rpm. I mentioned it to him and he said "yep, that's where it runs..."

Reason for engine failure + hood scoops may be the simple addition of manifold pressure. The stock induction from the wing inlets only gives 57-58 inches at Reno. On Stew's I have seen 63" coming down the chute and a steady 60" to 61" on the course. Temp and weather and speed affects those numbers. Regarding Stewart's last engine that failed at Reno- you have to consider that it was on there for 13 years! As Stew said when it failed "It doesn't owe me anything..."

It was always a fun rivalry with the Riff Raff guys! Hi Ray!
AE

[MRE]

I was always interested in those spinners. Were they made with pre preg and auto claved or were they just hand layed without an oven. I never got a chance to look at the back side of one. Would of liked to see how they were reinforced.

[AE88]

MRE

Larry Burton initially had all the tooling built for standard size and the big spinner. Dad ended up with the tooling after a botched deal with Larry for some Alameda 3350’s that never materialized. I don’t remember all the details but I believe someone hosed Larry on the engines and Dad was caught up in it having sent money.

The first generation were all wet layups and built by Texas Composites in Boerne, TX. Sometime in the late 90’s or early 2000’s they started using a prepreg system and autoclaving. Those units were amazingly light- I think around 18-20 lbs for the assembly. They would ring like a bell when you bumped them.

Sometime in the mid 2000’s, TX Composites got too big for us and we had to pick up all the tooling. The few that were made after that were all back to wet layups in a job shop. Quite a disappointment after the prepreg units.

The only internal structure was a bulkhead ring that was bonded to the interior surface. It interfaced with a machined hub that was bolted to face of the aeroproducts propeller.

AE

[cragdweller]

Yes, it would have looked better being a little wider but Stew's hood scoop was a compromise to still allow some accessibility to the engine through the side cowlings.

I monitored his telemetry and we never had a problem with CHT on the course. The airframe CHT was on the # 1 cyl (top aft) and I put the telemetry reading on # 3 right next to it. They were always very close with each other. It would have been nice to install CHT's on each cyl but since it was never an issue we decided not to.

The big spinner closes the cooling inlet to 1 3/8" and was worth 10-15 mph speed increase depending on the day and the pilot. We did find that we had to reinforce the baffling on the engine- the big spinner would beat it up. It's amazing that it ran as cool as it did. I remember flying with Dad in Howard's Fury to an airshow in Roswell back in the 90's. I could see the CHT gauge around him and noticed it was sitting just below 100 deg C at cruise power which was usually around 27" and 1700 rpm. I mentioned it to him and he said "yep, that's where it runs..."

Reason for engine failure + hood scoops may be the simple addition of manifold pressure. The stock induction from the wing inlets only gives 57-58 inches at Reno. On Stew's I have seen 63" coming down the chute and a steady 60" to 61" on the course. Temp and weather and speed affects those numbers. Regarding Stewart's last engine that failed at Reno- you have to consider that it was on there for 13 years! As Stew said when it failed "It doesn't owe me anything..."

It was always a fun rivalry with the Riff Raff guys! Hi Ray!
AE

Are you talking about the baffling between the heads and the cowling? That's interesting. Because the larger spinner forced the air to flow closer to the cowling?

[AE88]

Are you talking about the baffling between the heads and the cowling? That's interesting. Because the larger spinner forced the air to flow closer to the cowling?

No, the baffles around the cylinders on the engine. The were only .040" formed aluminum and attached to the cylinders with a couple of bolts, some dzus fasteners at the power case and snaps to the upper baffle around the valve covers. Usually they cracked out around the leading edges that were edgewise into the slip stream. They were formed to wrap around the forward cylinder and keep the air tight around the cylinder as it made its way around it. The opposite side of the cylinder directed cooling air to the rear cylinders. We always had to fix baffling on Stew and Howard's airplanes when we go home until we reinforced them. Guess they were intended for Skyraider speeds...

Now that I think about it, the inner lip of the leading edge nose bowls and spinner afterbodies cracked until we reinforced those too. I always wanted to put a pitot gauge up there to see what the speed of the air coming through there was. Judging by how well it cooled it must have been impressive.

We did have a strip of foam rubber that sealed between the outer cowling and the centerline of the engine baffles to force all the air through the engine.

Sorry I don't have pictures- maybe Neal or Will has some good closeups of the engines uncowled for those that are curious.
AE

[RiffRaffRay]

Ashley! Your finally out of school! The last few years your dad used to tell me you were off to school. Yes we had a fun rivalry. Very close on speed and just a matter of who qualified faster most of the time. Picture is of a certain astronaut placing an "aerodynamic" Riff Raff sticker on Stu's plane. If I remember correctly the Reno police conveniently showed up the next day and hand cuffed Mike. Charges were dropped?Also one of your dad, the Marlboro man as we called him.
Ray

[AE88]

[QUOTE=RiffRaffRay;n266129]Ashley! Your finally out of school! The last few years your dad used to tell me you were off to school. Yes we had a fun rivalry. Very close on speed and just a matter of who qualified faster most of the time. Picture is of a certain astronaut placing an "aerodynamic" Riff Raff sticker on Stu's plane. If I remember correctly the Reno police conveniently showed up the next day and hand cuffed Mike. Charges were dropped?Also one of your dad, the Marlboro man as we called him.
Ray

Well, like most plans they got changed after I got here! Good shot of dad and Mike there-

Yep, Stew and Hoot were always within a few mph of each other. Definitely not enough for any passing advantage. Made for some good shots for the pylon photographers though!

I think the arrest must have happened after 2008, I'm not remembering that one. There were always jokes being played back and forth with you guys and the Furias crew since we were always on the same row. Was it you guys that did this one on Stewart's Fury during the week? I think the statute of limitations is up but if secrets need to be kept, then so be it!

[wingman]

[/URL]

We were grateful...

[RiffRaffRay]

We can't take credit for that one but I do like the idea. Here's a couple pictures from 2009 with the nose bowl and cowl off. Not sure if that's what your looking for.
Ray
Ray