Engine Baffles - Revision history

Markm at 21:23, 29 October 2013

2013-10-29T21:23:27Z

@@ Line 4: / Line 4: @@
 The rubber baffle seal needs to be thin and flexible, and it should have some fiber reinforcement to prevent tearing.  The orange silicone rubber is too thick (1/8"), has no reinforcement, and tears easily.
 When installing a lightweight starter such as the Sky-Tec, the front metal baffles on the 75 Traveler and all Cheetahs and Tigers must be trimmed to clear the different contour of the starter motor and solenoid.
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 [[Image:Sky-tec-gaps.jpg]]
 Also check all of the baffle attach points.  This AA5B broken bracket was hard to see, but was obviously not doing it's job.  It is attached to the baffles by the oil cooler and held by the upper left engine mount bolt. A previous repair was less than effective. New brackets are available at Fletchair.

Bob Steward: Added photo and description of pilot side baffle mod for Sky-Tec starter

2009-09-21T03:30:45Z

Added photo and description of pilot side baffle mod for Sky-Tec starter

← Older revision		Revision as of 03:30, 21 September 2009
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	[[Image:Skytec-seal.jpg]]		[[Image:Skytec-seal.jpg]]

			This is seal for the pilot's side of the starter, that allows one to clear out the baffle to a larger rectangle, and then rivet on a cover plate that can be trimmed to match the starter contour without multiple removals of the baffling. This is very similar to the design used by later American General and the Tiger LLC plane's baffles. It is also workable to install the add-on plate with sheet metal screws, rather than permanently attach it with rivets.

			[[Image:Skytec-seal_pilot-side.jpg]]

WikiSysop at 12:34, 12 April 2009

2009-04-12T12:34:00Z

← Older revision		Revision as of 12:34, 12 April 2009
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	==Cooling Outlet Ducts in Lower Cowl==		==Cooling Outlet Ducts in Lower Cowl==
	[Gil Alexander] After the air has passed over the cylinders, it still needs to leave the cowl area. The pre-78 fibreglas ducts are somewhat heat sensitive, and will deform over time, reducing the area of the air outlet. An example is shown here -
	[[Image:Tiger-sagging-outlet-duct.jpg\|thumb\|200px\|left]]		[[Image:Tiger-sagging-outlet-duct.jpg\|thumb\|200px\|left]]
			After the air has passed over the cylinders, it still needs to leave the cowl area. The pre-78 fibreglas ducts are somewhat heat sensitive, and will deform over time, reducing the area of the air outlet, as seen in this photo from Gil Alexander.

Az gila: /* Cooling Outlet Ducts in Lower Cowl */

2009-04-12T02:13:33Z

Cooling Outlet Ducts in Lower Cowl

← Older revision		Revision as of 02:13, 12 April 2009
Line 62:		Line 62:

	==Cooling Outlet Ducts in Lower Cowl==		==Cooling Outlet Ducts in Lower Cowl==
	After the air has passed over the cylinders, it still needs to leave the cowl area. The pre-78 fibreglas ducts are somewhat heat sensitive, and will deform over time, reducing the area of the air outlet. An example is shown here -		[Gil Alexander] After the air has passed over the cylinders, it still needs to leave the cowl area. The pre-78 fibreglas ducts are somewhat heat sensitive, and will deform over time, reducing the area of the air outlet. An example is shown here -
	[[Image:Tiger-sagging-outlet-duct.jpg\|thumb\|200px\|left]]		[[Image:Tiger-sagging-outlet-duct.jpg\|thumb\|200px\|left]]

Az gila: /* Cooling Outlet Ducts in Lower Cowl */

2009-04-12T02:12:08Z

Cooling Outlet Ducts in Lower Cowl

← Older revision		Revision as of 02:12, 12 April 2009
Line 63:		Line 63:
	==Cooling Outlet Ducts in Lower Cowl==		==Cooling Outlet Ducts in Lower Cowl==
	After the air has passed over the cylinders, it still needs to leave the cowl area. The pre-78 fibreglas ducts are somewhat heat sensitive, and will deform over time, reducing the area of the air outlet. An example is shown here -		After the air has passed over the cylinders, it still needs to leave the cowl area. The pre-78 fibreglas ducts are somewhat heat sensitive, and will deform over time, reducing the area of the air outlet. An example is shown here -
	[[Image:Tiger-sagging-outlet-duct.jpg\|thumb\|200px]]		[[Image:Tiger-sagging-outlet-duct.jpg\|thumb\|200px\|left]]

Az gila at 02:11, 12 April 2009

2009-04-12T02:11:36Z

← Older revision		Revision as of 02:11, 12 April 2009
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	One last note. I was supplied the silicone type baffle seal material by the shop where the seals were initially replaced. I've found that this material isn't necessarily the best for seals as it is rather thick and does not "set" (retain a curved form) so you have to wrestle with it and be careful of the fit anytime you need to close the cowl or install the nose bowl.		One last note. I was supplied the silicone type baffle seal material by the shop where the seals were initially replaced. I've found that this material isn't necessarily the best for seals as it is rather thick and does not "set" (retain a curved form) so you have to wrestle with it and be careful of the fit anytime you need to close the cowl or install the nose bowl.

			==Cooling Outlet Ducts in Lower Cowl==
			After the air has passed over the cylinders, it still needs to leave the cowl area. The pre-78 fibreglas ducts are somewhat heat sensitive, and will deform over time, reducing the area of the air outlet. An example is shown here -
			[[Image:Tiger-sagging-outlet-duct.jpg\|thumb\|200px]]

Az gila at 07:20, 6 May 2008

2008-05-06T07:20:58Z

← Older revision		Revision as of 07:20, 6 May 2008
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	[[Image:Skytec-seal.jpg]]		[[Image:Skytec-seal.jpg]]


			[Gil Alexander] The seal is a little harder to form on the outboard side of the starter due to the starter leads. One example of sealing is here. The baffle material is extended as much as possible over the top of the starter to get into the gaps created above the starter.

			[[Image:Sky-tec-gaps.jpg]]

	Also check all of the baffle attach points. This AA5B broken bracket was hard to see, but was obviously not doing it's job. It is attached to the baffles by the oil cooler and held by the upper left engine mount bolt. A previous repair was less than effective. New brackets are available at Fletchair.		Also check all of the baffle attach points. This AA5B broken bracket was hard to see, but was obviously not doing it's job. It is attached to the baffles by the oil cooler and held by the upper left engine mount bolt. A previous repair was less than effective. New brackets are available at Fletchair.

Mboyd: /* Finding Problems */

2008-03-21T14:26:49Z

Finding Problems

← Older revision		Revision as of 14:26, 21 March 2008
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	I started by simply taking a flashlight and looking into the cooling air intakes in the nose bowl. I found several places where the seals did not sit flush against the cowl. In one location the seal bowed enough to create a quarter sized hole. This occurred because in the replacement of the seals, the multiple separate pieces of seal material were replaced with a few single longer strips of seal material that would buckle when pressed against the cowl where they were supposed to seal. Where the seals along the back and sides overlapped, they were attached together in such a way as to pull them away from the cowl. So, I removed these attachments and determined where to cut slits in the seal material so it would sit flush.		I started by simply taking a flashlight and looking into the cooling air intakes in the nose bowl. I found several places where the seals did not sit flush against the cowl. In one location the seal bowed enough to create a quarter sized hole. This occurred because in the replacement of the seals, the multiple separate pieces of seal material were replaced with a few single longer strips of seal material that would buckle when pressed against the cowl where they were supposed to seal. Where the seals along the back and sides overlapped, they were attached together in such a way as to pull them away from the cowl. So, I removed these attachments and determined where to cut slits in the seal material so it would sit flush.

	I then started looking around the nose bowl seals and found a number of locations where the seal fit was as poor as the seals against the cowl doors. I had to pull the cowl and hold the nose bowl in position as best I could (by holding it relative to the spinner/prop just as it looked when the cowl was attached) and inspect the seal fit. I used a marker to mark the locations where the seal did not fit well and made a number of additional slits in the ribbons of seal material. Often these slits were made where the contours of the cowl or nose bowl change. There was also a location near the alternator where a longer strip of seal material was needed to close a hole caused by the additional distance between the baffle and the nose bowl in that area.		I then started looking around the nose bowl seals and found a number of locations where the seal fit was as poor as the seals against the cowl doors. I had to pull the cowl and hold the nose bowl in position as best I could (by holding it relative to the spinner/prop just as it looked when the cowl was attached) and inspect the seal fit. I used a marker to mark the locations where the seal did not fit well and made a number of additional slits in the ribbons of seal material. Often these slits were made where the contours of the cowl or nose bowl change. The seal near the landing light needed to be trimmed to fit the contour of the landing light recess in the nose bowl. There was also a location near the alternator where a longer strip of seal material was needed to close a hole caused by the additional distance between the baffle and the nose bowl in that area.

	After 20 or more new slits in the baffle seal material and a new piece near the alternator, I put things back together and used a combination of drop lights and flashlights to check how well the seals were seating. Everything looked good, so I reassembled the cowl, checked the baffles one more time, and waited for the warm summer days to return for the tests.		After 20 or more new slits in the baffle seal material and a new piece near the alternator, I put things back together and used a combination of drop lights and flashlights to check how well the seals were seating. Everything looked good, so I reassembled the cowl, checked the baffles one more time, and waited for the warm summer days to return for the tests.

Mboyd: /* Gathering Data */

2008-03-21T14:20:21Z

Gathering Data

← Older revision		Revision as of 14:20, 21 March 2008
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	===Gathering Data===		===Gathering Data===
	Stumped, I decided to try collecting some figures on the cooling. I constructed a simple water manometer to determine the pressure differential between the high pressure and low pressure side of the baffles. After some searching around the internet, I found that for effective cooling you need a pressure difference of at least 6" of water. We ran the tubing ends of the manometer from the cockpit out the canopy and in thru the oil door with one tube on each side of the baffle in the cowl. In flight we were able to determine that in cruise around 120 mph IAS the pressure difference was right around 6" of water. In a 100 mph IAS climb, the pressure dropped to around 5". So, the numbers indicated that I still had some issues as I was just barely coming into an acceptable cooling pressure range in cruise.		[[Image:Manometer.JPG\|thumb\|100px\|right\|Manometer]]Stumped, I decided to try collecting some figures on the cooling. I constructed a simple water manometer to determine the pressure differential between the high pressure and low pressure side of the baffles. After some searching around the internet, I found that for effective cooling you need a pressure difference of at least 6" of water. We ran the tubing ends of the manometer from the cockpit out the canopy and in thru the oil door with one tube on each side of the baffle in the cowl. In flight we were able to determine that in cruise around 120 mph IAS the pressure difference was right around 6" of water. In a 100 mph IAS climb, the pressure dropped to around 5". So, the numbers indicated that I still had some issues as I was just barely coming into an acceptable cooling pressure range in cruise.

	===The latest (and hopefully last) find===		===The latest (and hopefully last) find===

Mboyd: /* Conclusion (sort of) */

2008-03-21T14:16:39Z

Conclusion (sort of)

← Older revision		Revision as of 14:16, 21 March 2008
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	===Conclusion (sort of)===		===Conclusion (sort of)===
	Of course, by the time we found and fixed this issue, the hot summer temperatures had given way to cooler ones of fall. The oil temperatures have looked good since the last fix, but I guess I won't know for sure if the problem is resolved until summer returns again. I'll probably try the manometer again to see what it says...when my mechanic and I get a chance. I'll keep you posted. In the meantime, I hope this information helps if you have a Cheetah experiencing similar issues.		Of course, by the time we found and fixed this last issue, the hot summer temperatures had given way to cooler ones of fall. The oil temperatures have looked good since the last fix, but I guess I won't know for sure if the problem is resolved until summer returns again. I'll probably try the manometer again to see what it says...when my mechanic and I get a chance. I'll keep you posted. In the meantime, I hope this information helps if you have a Cheetah experiencing similar issues.

	One last note. I was supplied the silicone type baffle seal material by the shop where the seals were initially replaced. I've found that this material isn't necessarily the best for seals as it is rather thick and does not "set" (retain a curved form) so you have to wrestle with it and be careful of the fit anytime you need to close the cowl or install the nose bowl.		One last note. I was supplied the silicone type baffle seal material by the shop where the seals were initially replaced. I've found that this material isn't necessarily the best for seals as it is rather thick and does not "set" (retain a curved form) so you have to wrestle with it and be careful of the fit anytime you need to close the cowl or install the nose bowl.