Sabremech Cowling Mod Testing (Ongoing)

[Bob_Belville]

18 minutes ago, Marauder said:

Bob -- everything I do is at full throttle  I will take whatever MP I can get and adjust RPM to get to the percent power setting I want. We may be seeing a difference due to the efficiency of the Van's intake. One way to know for sure is to open my ram air at 7500' and see what I get. I went through my old photos and found another 7500' flight. I always run 80 degree ROP. 

The difference however could be due to different pressure. What was your barometric pressure on today's flight? The flight below was at 29.92", the one above was at 30.07". Could account for some of the difference?

30.01. (OAT @ 7500 was -6C. GPS altitude was ~300' lower than baro altitude.)

[Marauder]

3 minutes ago, Bob_Belville said:

30.01. (OAT @ 7500 was -6C. GPS altitude was ~300' lower than baro altitude.)

I'm sure one of our esteemed colleagues can do the math for us. I do know that I consistently get 1.2" of MP with the ram door open. That would translate into 23.3' if I opened the ram door on the flight above. Matches your number sans any temp and barometric differences. So maybe the Van's inlet gets us what we had with the ram door...

[Bob_Belville]

Just now, Marauder said:

I'm sure one of our esteemed colleagues can do the math for us. I do know that I consistently get 1.2" of MP with the ram door open. That would translate into 23.3' if I opened the ram door on the flight above. Matches your number sans any temp and barometric differences. So maybe the Van's inlet gets us what we had with the ram door...

I hope so... my RAM is no more!. I think David and Matt said RAM meant only 0.4 on his F after doing the SabreCowl. 

I always saw 1.0-1.1 difference on my E which is quite a lot.

[Bob_Belville]

@Sabremech David, fyi, I've now had the top cowl on and off a half dozen times and after trimming the baffles to match my plane the fit is great. Baffles seals are getting memory and need very little tucking in. 

Bob

[Sabremech]

12 minutes ago, Bob_Belville said:

@Sabremech David, fyi, I've now had the top cowl on and off a half dozen times and after trimming the baffles to match my plane the fit is great. Baffles seals are getting memory and need very little tucking in. 

Bob

Hope you’re still liking it? Still trying to figure out what was different from Matt’s to cause a fit issue on the baffling. I expected a little, but sounds like you had more. 

David

[Bob_Belville]

5 minutes ago, Sabremech said:

Hope you’re still liking it? Still trying to figure out what was different from Matt’s to cause a fit issue on the baffling. I expected a little, but sounds like you had more. 

David

Yes I like it. I suppose the difference that caused us to cut down the baffles would be the interior dimensions of my much modified and repaired top cowl. All good though I think Lynn would prefer to get the baffles sans the seals. He could trim the baffles before mounting the seals.

Tomorrow we're installing the second landing light and replacing some of the aluminum tape with Van like dams.

Does anyone here have any informed opinions on what the effect of the tightness of the lower baffles might be? I'm talking about the sheet metal under the cylinders than are tightened via 2 1/8" or 3/16" rods running front to back. I'm thinking they make quite a lot of difference re CHT.

[Guitarmaster]

An interesting side note to this whole conversation. Today we started the annual on the airplane and borescope the cylinders. I found lots of lead deposits on the top of the Pistons and around the intake valve. I remember some time ago a discussion about the cylinders need to be a little bit higher temperature in order to activate the lead in the fuel.
If my memory serves, I think the discussion centered around about 360 degrees was the ideal temperature.
I don't know what is causing all the lead deposits, but my cylinders would run very very cool pretty much all year round and during the summer I was lucky to see 340. In the winter it was difficult to get the cylinders over 300.
I am now wondering if the Uber cool cylinder temperature is actually causing the lead deposits. If it is, then the Sabrecowl, yes that's what I'm going to call it now, will be perfect!

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[Marauder]

An interesting side note to this whole conversation. Today we started the annual on the airplane and borescope the cylinders. I found lots of lead deposits on the top of the Pistons and around the intake valve. I remember some time ago a discussion about the cylinders need to be a little bit higher temperature in order to activate the lead in the fuel.
If my memory serves, I think the discussion centered around about 360 degrees was the ideal temperature.
I don't know what is causing all the lead deposits, but my cylinders would run very very cool pretty much all year round and during the summer I was lucky to see 340. In the winter it was difficult to get the cylinders over 300.
I am now wondering if the Uber cool cylinder temperature is actually causing the lead deposits. If it is, then the Sabrecowl, yes that's what I'm going to call it now, will be perfect!

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I doubt it. I never had a lead problem in the 27 years of owning my IO-360 and I run just a cool as you did. If lead deposits were due to that, wouldn’t all your recent hours at the higher temps resolved it? I lean aggressively on the ground and always when below 75% power in flight.


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[mike_elliott]

12 hours ago, Bob_Belville said:

Does anyone here have any informed opinions on what the effect of the tightness of the lower baffles might be? I'm talking about the sheet metal under the cylinders than are tightened via 2 1/8" or 3/16" rods running front to back. I'm thinking they make quite a lot of difference re CHT.

They absolutely do, and at least on stock E's and F's are critical.

[jetdriven]

Whats optimal. I set mine where the baffle is 1/8-1/4” off the barrel fins. 

[Sabremech]

13 hours ago, Bob_Belville said:

Yes I like it. I suppose the difference that caused us to cut down the baffles would be the interior dimensions of my much modified and repaired top cowl. All good though I think Lynn would prefer to get the baffles sans the seals. He could trim the baffles before mounting the seals.

Tomorrow we're installing the second landing light and replacing some of the aluminum tape with Van like dams.

Does anyone here have any informed opinions on what the effect of the tightness of the lower baffles might be? I'm talking about the sheet metal under the cylinders than are tightened via 2 1/8" or 3/16" rods running front to back. I'm thinking they make quite a lot of difference re CHT.

Good morning Bob,

What I found from an article by Kent Paser is a little more than an inch gap at the barrel portion of the cylinder and 2.25 inches of gap at the cylinder head fins. This is the gap between the wrapped baffling around the bottom of the cylinders and the inter cylinder baffle. Will be checking Matt’s airplane today.

David

[Bob_Belville]

22 minutes ago, Sabremech said:

Good morning Bob,

What I found from an article by Kent Paser is a little more than an inch gap at the barrel portion of the cylinder and 2.25 inches of gap at the cylinder head fins. This is the gap between the wrapped baffling around the bottom of the cylinders and the inter cylinder baffle. Will be checking Matt’s airplane today.

David

That's helpful, I'll measure mine. (Lynn did the tightening on mine this time and I noticed that he left the baffle looser than I have in the past. But I am bad to over tighten stuff if I don't get out a torque wrench. 

[Browncbr1]

I’ll try to measure mine too.  Flew to Kissimmee today with nice tail winds. I added a little more tape to #1 more like the photos of the angled aluminum pieces.  My 1,2, and 3  are now within 1 degree of each other and 4 is now my coolest by 15 degrees.  Thanks bob!  

[Bob_Belville]

We cut a big hole in our SabreCowl @Sabremech this afternoon to add the 2nd landing light. Lynn @AGL Aviation is right in his wheelhouse doing fabrications. 

This one is going to look much nicer than it did in the old cowl covering up the oil cooler hole.

[Mcstealth]

On 3/8/2018 at 5:59 PM, Bob_Belville said:

Quick update for @Sabremech and interested kibitzers. The plane has been ready for test flights for a couple of days after trimming on some baffling for a better fit but the weather has not cooperated. I hope to fly tomorrow and if possible for several hours to get some speed and CHTs data as well as shoot 6 approaches. We still have to install the second landing light for symmetry which should be one more day's work before taking it to Hawk Painting.   

The cowl looks as good in person as the pictures above! I continue to be a very happy camper. May have to include some cheese head nose art. 

Kibitzers????

Is this a Northern thing again?

[Guitarmaster]

Taking Riley to Florida tomorrow. This will be a good long flight test of the Sabrecowl and all the work that has been put into it.

David has been working hard to get the temperatures under control. After a test flight yesterday, it looks like we're getting very close to being where I want to be. We are seeing 390 in The Vy Climb and about 350 in cruise at 100 ROP and 70%. Of course, it's about 20 degrees Celsius hotter in Florida so we shall see. There's going to be a lot of heavy, long climbs on this trip.

It is my understanding that this is running cooler than the LoPresti cowl now.

We have not stopped the modifying process. David has some other ideas that he wants to investigate to try to get the temperature lower. I feel very positive we're going to be able to get rid of another 10 degrees at least.

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