Dorsal Fin Replacement - Revision history

Bob Steward: Changed "under construction" header and annotated Gil Alexander's comment with user name and quotes

2009-05-23T15:15:17Z

Changed "under construction" header and annotated Gil Alexander's comment with user name and quotes

← Older revision		Revision as of 15:15, 23 May 2009
Line 1:		Line 1:
	This is ~~a placeholder for~~ the ~~Dorsal Fin Replacement page, which needs to be written.~~		This page is still under construction, the installation of the dorsal fin on the channel has not been documented completely.

	~~Submissions of photos, descriptions~~ of the ~~work, etc. are welcome~~.

	----		----
Line 35:		Line 33:
	It is a little more difficult to remove the flush rivets than the domed head ones, if only because they tend to have the center hole plugged with the steel mandrel, right to the surface, making the pre-drilled centering hole on the domed rivets not so easy to use on the flush ones. Using the automatic center punch mentioned before, drive the mandrel back into the rivet, and then drill through the head with a 1/8" bit, and snap the head off with a 1/8" pin punch. This prevents drilling into the aluminum channel and damaging the hole(s). Once the plastic has been freed from the aluminum channel, the remainder of the rivet bodies can be pulled from the back side with a pair of diagonal cutters. Correctly used, the cutters will squeeze the rivet right at the joint of the body and the mandrel's bulb, pulling the mandrel back further, and allowing the body of the rivet to collapse and easily come out of the channel.		It is a little more difficult to remove the flush rivets than the domed head ones, if only because they tend to have the center hole plugged with the steel mandrel, right to the surface, making the pre-drilled centering hole on the domed rivets not so easy to use on the flush ones. Using the automatic center punch mentioned before, drive the mandrel back into the rivet, and then drill through the head with a 1/8" bit, and snap the head off with a 1/8" pin punch. This prevents drilling into the aluminum channel and damaging the hole(s). Once the plastic has been freed from the aluminum channel, the remainder of the rivet bodies can be pulled from the back side with a pair of diagonal cutters. Correctly used, the cutters will squeeze the rivet right at the joint of the body and the mandrel's bulb, pulling the mandrel back further, and allowing the body of the rivet to collapse and easily come out of the channel.

	''[Gil Alexander]'' ~~Another~~ alternative - if you have an original plastic part that is already junk - is to just sand off the rivet heads (and the surrounding plastic) with a 2 inch disk grinder.		''[[User:Az_gila\|Gil Alexander]]'' suggests an alternative method to remove the rivet heads - "if you have an original plastic part that is already junk - is to just sand off the rivet heads (and the surrounding plastic) with a 2 inch disk grinder."

Bob Steward: Added text and picture "Fitting the New Dorsal Fin"

2009-01-13T02:27:26Z

Added text and picture "Fitting the New Dorsal Fin"

← Older revision		Revision as of 02:27, 13 January 2009
Line 41:		Line 41:

	[[Image:Channel_holes1.jpg\|right\|thumbnail\|With the dorsal fin removed, you can see holes from previous installations or factory pilot holes that went unused.]] Surprise! There may be extra holes in the aluminum mounting flange. In this case, there were 3/32" pilot holes that the factory made, but that were missed during manufacture. Note that you may have additional holes from previous replacements, or the holes may be over-sized or not round. Standard sheet metal methods for repair are applicable. It may be necessary to respace your rivet holes, or flush doublers can be installed on the inside of the flange, such that the rivet holes can be re-drilled. By dimpling the channel flange and using 3/32" flush rivets, it is possible to make an invisible repair, allowing for new rivet holes. Hopefully you are doing the first repair, and won't have to deal with "swiss cheese" from many extraneous holes. The rivet bodies can be removed from inside the channel by gripping them with a pair of diagonal cutters. Placing the cutters just below the bulb at the end of the mandrel, one can squeeze the rivet and pull the mandrel out. This leaves a nice pilot hole for a 1/8" drill bit to remove the rest of the rivet without oversizing the hole or distorting the channel from twisting or pulling on the rivet.		[[Image:Channel_holes1.jpg\|right\|thumbnail\|With the dorsal fin removed, you can see holes from previous installations or factory pilot holes that went unused.]] Surprise! There may be extra holes in the aluminum mounting flange. In this case, there were 3/32" pilot holes that the factory made, but that were missed during manufacture. Note that you may have additional holes from previous replacements, or the holes may be over-sized or not round. Standard sheet metal methods for repair are applicable. It may be necessary to respace your rivet holes, or flush doublers can be installed on the inside of the flange, such that the rivet holes can be re-drilled. By dimpling the channel flange and using 3/32" flush rivets, it is possible to make an invisible repair, allowing for new rivet holes. Hopefully you are doing the first repair, and won't have to deal with "swiss cheese" from many extraneous holes. The rivet bodies can be removed from inside the channel by gripping them with a pair of diagonal cutters. Placing the cutters just below the bulb at the end of the mandrel, one can squeeze the rivet and pull the mandrel out. This leaves a nice pilot hole for a 1/8" drill bit to remove the rest of the rivet without oversizing the hole or distorting the channel from twisting or pulling on the rivet.

			----

			'''Fitting the New Dorsal Fin'''

			[[Image:Dorsal-testfit2.jpg\|left\|thumbnail\|The new dorsal is probably only rough trimmed from the mold, and will require trimming to match your airframe.]] The new part, regardless of source, will require some trimming to match your airframe. The part is probably too long, too tall, and very likely not straight on the bottom edge. Each of these must be dealt with to achieve a smooth fit without gaps.

Bob Steward: Added text to removing rivets from mounting channel

2009-01-13T02:19:46Z

Added text to removing rivets from mounting channel

← Older revision		Revision as of 02:19, 13 January 2009
Line 40:		Line 40:
	'''Removing the Rivets from the Mounting Channel'''		'''Removing the Rivets from the Mounting Channel'''

	[[Image:Channel_holes1.jpg\|right\|thumbnail\|With the dorsal fin removed, you can see holes from previous installations or factory pilot holes that went unused.]] Surprise! There may be extra holes in the aluminum mounting flange. In this case, there were 3/32" pilot holes that the factory made, but that were missed during manufacture. Note that you may have additional holes from previous replacements, or the holes may be over-sized or not round. Standard sheet metal methods for repair are applicable. It may be necessary to respace your rivet holes, or flush doublers can be installed on the inside of the flange, such that the rivet holes can be re-drilled. By dimpling the channel flange and using 3/32" flush rivets, it is possible to make an invisible repair, allowing for new rivet holes. Hopefully you are doing the first repair, and won't have to deal with "swiss cheese" from many extraneous holes.		[[Image:Channel_holes1.jpg\|right\|thumbnail\|With the dorsal fin removed, you can see holes from previous installations or factory pilot holes that went unused.]] Surprise! There may be extra holes in the aluminum mounting flange. In this case, there were 3/32" pilot holes that the factory made, but that were missed during manufacture. Note that you may have additional holes from previous replacements, or the holes may be over-sized or not round. Standard sheet metal methods for repair are applicable. It may be necessary to respace your rivet holes, or flush doublers can be installed on the inside of the flange, such that the rivet holes can be re-drilled. By dimpling the channel flange and using 3/32" flush rivets, it is possible to make an invisible repair, allowing for new rivet holes. Hopefully you are doing the first repair, and won't have to deal with "swiss cheese" from many extraneous holes. The rivet bodies can be removed from inside the channel by gripping them with a pair of diagonal cutters. Placing the cutters just below the bulb at the end of the mandrel, one can squeeze the rivet and pull the mandrel out. This leaves a nice pilot hole for a 1/8" drill bit to remove the rest of the rivet without oversizing the hole or distorting the channel from twisting or pulling on the rivet.

Bob Steward: Changed page break lines

2009-01-13T02:07:09Z

Changed page break lines

← Older revision		Revision as of 02:07, 13 January 2009
Line 20:		Line 20:
	At the aft edge of the dorsal there are a series of #6 flush sheet metal screws and dimpled washers that attach the dorsal to the vertical stabilizer. Remove all 12 screws and washers. The fin is now held by friction and 3 clips on the turtledeck that the aluminum mounting channel slides aft into. To release the dorsal, the fin must slide forward about 1.5". Due to the tight fit of the clips, age related distortion of the plastic fin causing the aluminum channel to bind, and in some cases, non-standard sealant or filler that owners or paint shops have applied to the edges where the fin and the turtledeck meet, the fin may not move easily. If there is any sort of sealant around the base, slide a thin putty knife under the fin to break the sealant loose, and work around the entire periphery to free the fin. Slide the fin forward, using caution to not SLAM it into the ELT antenna base on those equipped with Narco ELT 10 and similar antennas that protrude up out of the dorsal. The fin will become very loose as it begins to slide, and using excess force to begin its movement can cause it to damage the aluminum mounting channel when the fin suddenly frees up and slides forward, impacting the ELT antenna base. After moving the fin assembly forward to free it from the clips, carefully extract the ELT antenna from the hole in the top of the dorsal.		At the aft edge of the dorsal there are a series of #6 flush sheet metal screws and dimpled washers that attach the dorsal to the vertical stabilizer. Remove all 12 screws and washers. The fin is now held by friction and 3 clips on the turtledeck that the aluminum mounting channel slides aft into. To release the dorsal, the fin must slide forward about 1.5". Due to the tight fit of the clips, age related distortion of the plastic fin causing the aluminum channel to bind, and in some cases, non-standard sealant or filler that owners or paint shops have applied to the edges where the fin and the turtledeck meet, the fin may not move easily. If there is any sort of sealant around the base, slide a thin putty knife under the fin to break the sealant loose, and work around the entire periphery to free the fin. Slide the fin forward, using caution to not SLAM it into the ELT antenna base on those equipped with Narco ELT 10 and similar antennas that protrude up out of the dorsal. The fin will become very loose as it begins to slide, and using excess force to begin its movement can cause it to damage the aluminum mounting channel when the fin suddenly frees up and slides forward, impacting the ELT antenna base. After moving the fin assembly forward to free it from the clips, carefully extract the ELT antenna from the hole in the top of the dorsal.

	~~----~~
	'''Inspection'''		'''Inspection'''

Line 29:		Line 28:
	With the hardware inspected and replaced as needed, the aluminum channel should be similarly inspected for condition. The 70's production planes had little if any corrosion protection on the channel. Also it could have had previous repair attempts made, and the holes in the mounting flanges might be over-sized or new holes may have been drilled, leaving the flange with the appearance of swiss cheese, due to all the extra holes.		With the hardware inspected and replaced as needed, the aluminum channel should be similarly inspected for condition. The 70's production planes had little if any corrosion protection on the channel. Also it could have had previous repair attempts made, and the holes in the mounting flanges might be over-sized or new holes may have been drilled, leaving the flange with the appearance of swiss cheese, due to all the extra holes.

	~~---~~

	'''Removing the Plastic Fin'''		'''Removing the Plastic Fin'''
Line 39:		Line 37:
	''[Gil Alexander]'' Another alternative - if you have an original plastic part that is already junk - is to just sand off the rivet heads (and the surrounding plastic) with a 2 inch disk grinder.		''[Gil Alexander]'' Another alternative - if you have an original plastic part that is already junk - is to just sand off the rivet heads (and the surrounding plastic) with a 2 inch disk grinder.

	~~---~~

	'''Removing the Rivets from the Mounting Channel'''		'''Removing the Rivets from the Mounting Channel'''

	[[Image:Channel_holes1.jpg\|right\|thumbnail\|With the dorsal fin removed, you can see holes from previous installations or factory pilot holes that went unused.]]		[[Image:Channel_holes1.jpg\|right\|thumbnail\|With the dorsal fin removed, you can see holes from previous installations or factory pilot holes that went unused.]] Surprise! There may be extra holes in the aluminum mounting flange. In this case, there were 3/32" pilot holes that the factory made, but that were missed during manufacture. Note that you may have additional holes from previous replacements, or the holes may be over-sized or not round. Standard sheet metal methods for repair are applicable. It may be necessary to respace your rivet holes, or flush doublers can be installed on the inside of the flange, such that the rivet holes can be re-drilled. By dimpling the channel flange and using 3/32" flush rivets, it is possible to make an invisible repair, allowing for new rivet holes. Hopefully you are doing the first repair, and won't have to deal with "swiss cheese" from many extraneous holes.
	Surprise! There may be extra holes in the aluminum mounting flange. In this case, there were 3/32" pilot holes that the factory made, but that were missed during manufacture. Note that you may have additional holes from previous replacements, or the holes may be over-sized or not round. Standard sheet metal methods for repair are applicable. It may be necessary to respace your rivet holes, or flush doublers can be installed on the inside of the flange, such that the rivet holes can be re-drilled. By dimpling the channel flange and using 3/32" flush rivets, it is possible to make an invisible repair, allowing for new rivet holes. Hopefully you are doing the first repair, and won't have to deal with "swiss cheese" from many extraneous holes.

Bob Steward: Adding Text and Pictures

2009-01-13T02:05:06Z

Adding Text and Pictures

← Older revision		Revision as of 02:05, 13 January 2009
Line 38:		Line 38:

	''[Gil Alexander]'' Another alternative - if you have an original plastic part that is already junk - is to just sand off the rivet heads (and the surrounding plastic) with a 2 inch disk grinder.		''[Gil Alexander]'' Another alternative - if you have an original plastic part that is already junk - is to just sand off the rivet heads (and the surrounding plastic) with a 2 inch disk grinder.

			---

			'''Removing the Rivets from the Mounting Channel'''

			[[Image:Channel_holes1.jpg\|right\|thumbnail\|With the dorsal fin removed, you can see holes from previous installations or factory pilot holes that went unused.]]
			Surprise! There may be extra holes in the aluminum mounting flange. In this case, there were 3/32" pilot holes that the factory made, but that were missed during manufacture. Note that you may have additional holes from previous replacements, or the holes may be over-sized or not round. Standard sheet metal methods for repair are applicable. It may be necessary to respace your rivet holes, or flush doublers can be installed on the inside of the flange, such that the rivet holes can be re-drilled. By dimpling the channel flange and using 3/32" flush rivets, it is possible to make an invisible repair, allowing for new rivet holes. Hopefully you are doing the first repair, and won't have to deal with "swiss cheese" from many extraneous holes.

Bob Steward: Adding pictures and text

2009-01-13T01:53:51Z

Adding pictures and text

← Older revision		Revision as of 01:53, 13 January 2009
Line 28:		Line 28:

	With the hardware inspected and replaced as needed, the aluminum channel should be similarly inspected for condition. The 70's production planes had little if any corrosion protection on the channel. Also it could have had previous repair attempts made, and the holes in the mounting flanges might be over-sized or new holes may have been drilled, leaving the flange with the appearance of swiss cheese, due to all the extra holes.		With the hardware inspected and replaced as needed, the aluminum channel should be similarly inspected for condition. The 70's production planes had little if any corrosion protection on the channel. Also it could have had previous repair attempts made, and the holes in the mounting flanges might be over-sized or new holes may have been drilled, leaving the flange with the appearance of swiss cheese, due to all the extra holes.

			---

	'''Removing the Plastic Fin'''		'''Removing the Plastic Fin'''

	Removing the plastic dorsal without distorting the aluminum channel or doing damage to the mounting holes is the next challenge. As with the clips on the turtledeck, the plastic fin is held to the aluminum channel with Avex rivets. The difference is that they are flush rivets instead of domed head. (Avex 1604-0412 rivets, which are 1/8" nominal diameter with a 120 degree flush head are the correct call-out. Some parts manuals refer to the older "Chobert" rivets, but the Avex is the current replacement.)		[[Image:Rivet-drill2.jpg\|right\|thumbnail\|After centerpunching the mandrel down into the rivet body, drill with a 1/8" bit]]Removing the plastic dorsal without distorting the aluminum channel or doing damage to the mounting holes is the next challenge. As with the clips on the turtledeck, the plastic fin is held to the aluminum channel with Avex rivets. The difference is that they are flush rivets instead of domed head. (Avex 1604-0412 rivets, which are 1/8" nominal diameter with a 120 degree flush head are the correct call-out. Some parts manuals refer to the older "Chobert" rivets, but the Avex is the current replacement.)

	It is a little more difficult to remove the flush rivets than the domed head ones, if only because they tend to have the center hole plugged with the steel mandrel, right to the surface, making the pre-drilled centering hole on the domed rivets not so easy to use on the flush ones. Using the automatic center punch mentioned before, drive the mandrel back into the rivet, and then drill through the head with a 1/8" bit, and snap the head off with a 1/8" pin punch. This prevents drilling into the aluminum channel and damaging the hole(s). Once the plastic has been freed from the aluminum channel, the remainder of the rivet bodies can be pulled from the back side with a pair of diagonal cutters. Correctly used, the cutters will squeeze the rivet right at the joint of the body and the mandrel's bulb, pulling the mandrel back further, and allowing the body of the rivet to collapse and easily come out of the channel.		It is a little more difficult to remove the flush rivets than the domed head ones, if only because they tend to have the center hole plugged with the steel mandrel, right to the surface, making the pre-drilled centering hole on the domed rivets not so easy to use on the flush ones. Using the automatic center punch mentioned before, drive the mandrel back into the rivet, and then drill through the head with a 1/8" bit, and snap the head off with a 1/8" pin punch. This prevents drilling into the aluminum channel and damaging the hole(s). Once the plastic has been freed from the aluminum channel, the remainder of the rivet bodies can be pulled from the back side with a pair of diagonal cutters. Correctly used, the cutters will squeeze the rivet right at the joint of the body and the mandrel's bulb, pulling the mandrel back further, and allowing the body of the rivet to collapse and easily come out of the channel.

	''[Gil Alexander]'' Another alternative - if you have an original plastic part that is already junk - is to just sand off the rivet heads (and the surrounding plastic) with a 2 inch disk grinder.		''[Gil Alexander]'' Another alternative - if you have an original plastic part that is already junk - is to just sand off the rivet heads (and the surrounding plastic) with a 2 inch disk grinder.

Bob Steward: Adding pictures and text

2009-01-13T01:49:08Z

Adding pictures and text

← Older revision		Revision as of 01:49, 13 January 2009
Line 17:		Line 17:
	'''Taking the Fin Assembly Off'''		'''Taking the Fin Assembly Off'''

			[[Image:Dorsal1.jpg\|right\|thumbnail\|Here are 6 of the 12 screws that hold the Dorsal fin to the vertical stabilizer.]]
	At the aft edge of the dorsal there are a series of #6 flush sheet metal screws and dimpled washers that attach the dorsal to the vertical stabilizer. Remove all 12 screws and washers. The fin is now held by friction and 3 clips on the turtledeck that the aluminum mounting channel slides aft into. To release the dorsal, the fin must slide forward about 1.5". Due to the tight fit of the clips, age related distortion of the plastic fin causing the aluminum channel to bind, and in some cases, non-standard sealant or filler that owners or paint shops have applied to the edges where the fin and the turtledeck meet, the fin may not move easily. If there is any sort of sealant around the base, slide a thin putty knife under the fin to break the sealant loose, and work around the entire periphery to free the fin. Slide the fin forward, using caution to not SLAM it into the ELT antenna base on those equipped with Narco ELT 10 and similar antennas that protrude up out of the dorsal. The fin will become very loose as it begins to slide, and using excess force to begin its movement can cause it to damage the aluminum mounting channel when the fin suddenly frees up and slides forward, impacting the ELT antenna base. After moving the fin assembly forward to free it from the clips, carefully extract the ELT antenna from the hole in the top of the dorsal.		At the aft edge of the dorsal there are a series of #6 flush sheet metal screws and dimpled washers that attach the dorsal to the vertical stabilizer. Remove all 12 screws and washers. The fin is now held by friction and 3 clips on the turtledeck that the aluminum mounting channel slides aft into. To release the dorsal, the fin must slide forward about 1.5". Due to the tight fit of the clips, age related distortion of the plastic fin causing the aluminum channel to bind, and in some cases, non-standard sealant or filler that owners or paint shops have applied to the edges where the fin and the turtledeck meet, the fin may not move easily. If there is any sort of sealant around the base, slide a thin putty knife under the fin to break the sealant loose, and work around the entire periphery to free the fin. Slide the fin forward, using caution to not SLAM it into the ELT antenna base on those equipped with Narco ELT 10 and similar antennas that protrude up out of the dorsal. The fin will become very loose as it begins to slide, and using excess force to begin its movement can cause it to damage the aluminum mounting channel when the fin suddenly frees up and slides forward, impacting the ELT antenna base. After moving the fin assembly forward to free it from the clips, carefully extract the ELT antenna from the hole in the top of the dorsal.

Az gila at 20:19, 28 December 2008

2008-12-28T20:19:19Z

← Older revision		Revision as of 20:19, 28 December 2008
Line 34:		Line 34:
	It is a little more difficult to remove the flush rivets than the domed head ones, if only because they tend to have the center hole plugged with the steel mandrel, right to the surface, making the pre-drilled centering hole on the domed rivets not so easy to use on the flush ones. Using the automatic center punch mentioned before, drive the mandrel back into the rivet, and then drill through the head with a 1/8" bit, and snap the head off with a 1/8" pin punch. This prevents drilling into the aluminum channel and damaging the hole(s). Once the plastic has been freed from the aluminum channel, the remainder of the rivet bodies can be pulled from the back side with a pair of diagonal cutters. Correctly used, the cutters will squeeze the rivet right at the joint of the body and the mandrel's bulb, pulling the mandrel back further, and allowing the body of the rivet to collapse and easily come out of the channel.		It is a little more difficult to remove the flush rivets than the domed head ones, if only because they tend to have the center hole plugged with the steel mandrel, right to the surface, making the pre-drilled centering hole on the domed rivets not so easy to use on the flush ones. Using the automatic center punch mentioned before, drive the mandrel back into the rivet, and then drill through the head with a 1/8" bit, and snap the head off with a 1/8" pin punch. This prevents drilling into the aluminum channel and damaging the hole(s). Once the plastic has been freed from the aluminum channel, the remainder of the rivet bodies can be pulled from the back side with a pair of diagonal cutters. Correctly used, the cutters will squeeze the rivet right at the joint of the body and the mandrel's bulb, pulling the mandrel back further, and allowing the body of the rivet to collapse and easily come out of the channel.

	Another alternative - if you have an original plastic part that is already junk - is to just sand off the rivet heads (and the surrounding plastic) with a 2 inch disk grinder.		''[Gil Alexander]'' Another alternative - if you have an original plastic part that is already junk - is to just sand off the rivet heads (and the surrounding plastic) with a 2 inch disk grinder.

Az gila at 20:08, 28 December 2008

2008-12-28T20:08:22Z

← Older revision		Revision as of 20:08, 28 December 2008
Line 33:		Line 33:

	It is a little more difficult to remove the flush rivets than the domed head ones, if only because they tend to have the center hole plugged with the steel mandrel, right to the surface, making the pre-drilled centering hole on the domed rivets not so easy to use on the flush ones. Using the automatic center punch mentioned before, drive the mandrel back into the rivet, and then drill through the head with a 1/8" bit, and snap the head off with a 1/8" pin punch. This prevents drilling into the aluminum channel and damaging the hole(s). Once the plastic has been freed from the aluminum channel, the remainder of the rivet bodies can be pulled from the back side with a pair of diagonal cutters. Correctly used, the cutters will squeeze the rivet right at the joint of the body and the mandrel's bulb, pulling the mandrel back further, and allowing the body of the rivet to collapse and easily come out of the channel.		It is a little more difficult to remove the flush rivets than the domed head ones, if only because they tend to have the center hole plugged with the steel mandrel, right to the surface, making the pre-drilled centering hole on the domed rivets not so easy to use on the flush ones. Using the automatic center punch mentioned before, drive the mandrel back into the rivet, and then drill through the head with a 1/8" bit, and snap the head off with a 1/8" pin punch. This prevents drilling into the aluminum channel and damaging the hole(s). Once the plastic has been freed from the aluminum channel, the remainder of the rivet bodies can be pulled from the back side with a pair of diagonal cutters. Correctly used, the cutters will squeeze the rivet right at the joint of the body and the mandrel's bulb, pulling the mandrel back further, and allowing the body of the rivet to collapse and easily come out of the channel.

			Another alternative - if you have an original plastic part that is already junk - is to just sand off the rivet heads (and the surrounding plastic) with a 2 inch disk grinder.

Bob Steward: small grammer edit

2008-12-28T19:18:23Z

small grammer edit

← Older revision		Revision as of 19:18, 28 December 2008
Line 12:		Line 12:
	The Travelers from 72-73 had a smaller aluminum dorsal fin that was riveted to the turtledeck. The 74 up models and all the Cheetahs and Tigers, including the AG series planes have a removable dorsal fin assembly, with the visible fin pull riveted to a stamped aluminum channel. The AG series had fiberglass fins from the factory. The 70's production planes had fins made from ABS plastic, like the elevator tips, HS inboard fillets, tail cone, sump fairings, main wheel pants, etc. As with all the other plastic parts, the 70's plastic dorsal fin ages, and then it cracks and warps. The repair for this is to replace the plastic with a fiberglass replica. There have been many sources for them over the years. Some PMA approved, some commercially produced but not approved, and more than a few have been made as "owner produced parts", using the OEM plastic as a form to build a replacement on.		The Travelers from 72-73 had a smaller aluminum dorsal fin that was riveted to the turtledeck. The 74 up models and all the Cheetahs and Tigers, including the AG series planes have a removable dorsal fin assembly, with the visible fin pull riveted to a stamped aluminum channel. The AG series had fiberglass fins from the factory. The 70's production planes had fins made from ABS plastic, like the elevator tips, HS inboard fillets, tail cone, sump fairings, main wheel pants, etc. As with all the other plastic parts, the 70's plastic dorsal fin ages, and then it cracks and warps. The repair for this is to replace the plastic with a fiberglass replica. There have been many sources for them over the years. Some PMA approved, some commercially produced but not approved, and more than a few have been made as "owner produced parts", using the OEM plastic as a form to build a replacement on.

	This article covers the work required to remove the existing dorsal from the plane, disassemble the aerodynamic fin from the mounting channel, ~~and~~ the fitting and attachment of the fin to the mounting channel.		This article covers the work required to remove the existing dorsal from the plane, disassemble the aerodynamic fin from the mounting channel, the fitting and attachment of the replacement fin to the mounting channel.

	----		----