I am in the process of building new cowl doors for my project, PA-18-150. I have the new nose bowl installed, I have clecoed the hinge and the rear bow to form the curve. My question is what is the next logical step to 1. fit the latches 2. trim the forward and rear sides. I had to build new ones as they did not aline with the nose bowl to my satisfaction, the latches on the old ones fit ok but the line on the nose bowl was bad. I still have the old ones for a pattern. would it be best to go with the pattern for the latch position and then trim to the nose bowl or trim first? any help please.
Cowl doors
- Thread starter Glidertow
- Start date
mike mcs repair
Registered User
chugiak AK
did you roll shape into it yet?
absolute last step is trim front edge.... leave that till you must.. it will be changed each other thing you mess with...
off top of my head steps... and order of operations...
absolute last step is trim front edge.... leave that till you must.. it will be changed each other thing you mess with...
off top of my head steps... and order of operations...
- start with oversize piece of aluminum at least 3" big each way
roll shape top to bottom
roll some front bottom corner twords top rear corner just at front
now find out where it lays best & cut for top hinge
cleco hinge
add rear stiffener
trim bottom edge just enough so latches will go in sockets
mark latch positions using latches themselves installed and cut holes
cleco latch mount angle(i always put this upside down so as to not cut a chunk out of it...) on door and latches to mount, add washers as needed to latch door, make sure you do NOT have anti chafe on nose bowl for now...
trim back edge (it may not be a strait line, bows backwards for big openings like 180 horse)
now mark and trim front edge using a 1" masking tape stuck in front of where you want to have edge on nose bowl and place a piece on door directly over that one.
trim bottom edge
install chafe and try... should be tight now...
Scooter7779h
PATRON
Anchorage, Alaska
@Mike mcs Repair: The master reveals his secrets!
11 years later and my cowl you build still fits like a glove.
11 years later and my cowl you build still fits like a glove.
mike mcs repair
Registered User
chugiak AK
Scooter7779h said:
1996 i think... 14 years
cubdriver2
FRIEND
upstate NY
My friend Mark used Tar paper for the layout, stiff yet flexable and cheap for the layout, then transfered it to Al for a final cut.
Glenn
Glenn
mike mcs repair
Registered User
chugiak AK
qsmx440 said:What a great idea. Will buy some today.
cubdriver2 said:
white poster board too... (colored ones will run if you use them for like window patterns and then leave them in when you spray dope...
)Cowl door
Well Mike I have not roll it. I have a small combo brake/roller but frankly i have never gained enough experience to use it. The doors i took off had the steel bend piece in the back edge and were not rolled, must have been replaced before. If I try to do it now I may not have cut the piece large enough to allow for the initial insert into the roller, but I may have. although I have already drilled the hinge line and the rear curved brace. Is there an alternative?
Well Mike I have not roll it. I have a small combo brake/roller but frankly i have never gained enough experience to use it. The doors i took off had the steel bend piece in the back edge and were not rolled, must have been replaced before. If I try to do it now I may not have cut the piece large enough to allow for the initial insert into the roller, but I may have. although I have already drilled the hinge line and the rear curved brace. Is there an alternative?
mike mcs repair
Registered User
chugiak AK
Re: Cowl door
no idea, have always rolled them, seen them rolled...
you will likely have more cracking at top and bottom of that steel former.. i always add rivets at ends of those anyway....
Glidertow said:
no idea, have always rolled them, seen them rolled...
you will likely have more cracking at top and bottom of that steel former.. i always add rivets at ends of those anyway....
mike mcs repair
Registered User
chugiak AK
just a side thing I meant to show, hope I didn't already post this....
I never trim door front edges till cowl goes on for last time just before painting...
to simply mark for trimming the cowl doors....
I didn't take a good picture of the first step, but you can see that tape I put down in step 1 in picture on step #8 after done.. sorry.. confusing...
click pictures for the bigger versions...
I never trim door front edges till cowl goes on for last time just before painting...
to simply mark for trimming the cowl doors....
I didn't take a good picture of the first step, but you can see that tape I put down in step 1 in picture on step #8 after done.. sorry.. confusing...
click pictures for the bigger versions...
- with cowl door open out of way, you place a piece of tape on nose bowl with back edge exactly where you want the finished edge of cowl door to end up, usually 3/32 or 1/8" behind joggle in nose bowl, if its too close the door will cut into nose bowl and make those ugly black streaks down doors...(no picture, sorry)
- close and latch door, no anti chafe in gap yet
- place a piece of tape directly over the first one, following front edge... the back edge now shows where you want to cut...
this is just an example picture.. the next picture is how you put the tape over
after its cut, now you can put anti chafe in and check for final trimming if needed at all.
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Gordon Misch
MEMBER
Toledo, Wa (KTDO)
Mike, you are brilliant - such a simple thing as to double the tape over the top - - But takes a really smart guy to think of the simple things - - - Probably never woulda thought of it here, and gonna need it. Thank you!!!
mike mcs repair
Registered User
chugiak AK
Somewhere in one of my old post here I do a step by step for that, you will have to search, unless someone remembers which thread it's in.... Also there is a couple videos about cowl at my YouTube , not sure if that part made it yet....
Binty
Registered User
South Island, New Zealand
To continue with this thread (im just starting the cowl fabrication for my super cub) Id like to hear those tips for rolling but I cant find them in the archives Mike...
Im fabricating new side doors, top and bottom cowls but hoping to utilise the old beat-up nose bowl.
As my machine is a rather well worn example, Im unsure of what is orig or repair in many cases... and if my cowl doors are surviving original parts or not? My doors have a 90deg folded alloy reinforcing strip running fore/aft along the latch line which was spot welded on and has riveted patches around the latch holes at each bottom corner.
1. I presume the strip is stock but the corner patches/doublers are not?
2. How do you attach that lengthwise reinforcing strip? Rivets or spot weld? If spot welds, how exactly?? (my fuel tank covers have spot welded reinforcing strips also which have to be rebuilt so I need to know what you guys do)
The thread above will be very helpful. Any more tips much appreciated!
MainlandCub
Registered User
New Zealand
The spot welds were done by Piper at the factory and the riveted patches around the latches etc. were done in the back of a hangar at Palmerston North or Canterbury or somewhere.
You're best to rivet the angle on. I recommend soft rivets ("A" rivets) as the material you will use for the cowls is soft. If you want a period look you could use AN455 rivets, which are available from Univair. I did a set of cowls with countersunk rivets - partly to replicate that smooth surface where the angle is from the spot welds, but I don't recommend using countersunks because they began to work after a couple of hundred hours.
You need to salvage the steel stiffening strip running vertically near the back of the cowl and use it on the new one. I double up on the rivet spacing to help prevent working rivets. Those rivets are best driven with a punch as the groove in the back of the strip is quite narrow.
With respect to rolling, you put the ali in the roller and turn the handle. You can wind the adjustment at one end to get more of a curve in it at the front. If you haven't got a set of rollers you can probably pull it around a fence post or something, I know at least one set of cowls that were done like that. There is a flat spot on the nose cowl just down from the hinge where it is quite difficult to get the side cowl to sit down on snuggly, but this is exasperated if you use heavier material than the originals. It was the norm in the Ag days to make the cowls out of .050 to stop them falling apart. I am not sure I would do that for our low utilisation aeroplanes as the lighter material will probably sit more neatly around the nose cowl.
Andrew.
