Engine cowlings

[Miguel]

I need for a friend who is also in the process of restoring his Taylorcraft BL12-65, plans for the construction of the engine cowlings.
Someone can help me with it.-
Thank you very much to all.-

[astjp2]

Where are you located? most of that was a compound curve and the drawing suck...but there are a few out there who can help, look for Tom Welsgard or something like that on the forum. Tim

[Miguel]

Thanks, astip2.
I am far of USA, in Uruguay, South America. Yes, I know about Tom Welsgard. Freight from USA to Uruguay are expensives, because this my friend that is an aircraft mechanic want to do the cowlings.
Miguel.-

[Hank Jarrett]

Unfortunately what you really need is a good cowl to copy (by a really good English Wheel man or a set of drawings for al the pieces to make a Buck (the egg crate plywood #D pattern you put the cowl over as you shape it to check the contours. If someone has a buck it would be really nice to get the pieces traced so copies could be made. Of course the BEST way to get a new cowl is to find the factory dies and have one Hydraformed. Wouldn't it be grand to find those old tooling bits?!?!?!

Hank

[Scott]

The top cowlings are flat ie no compound curves.

I get the impression that the BL65 had more compound in the lower cowling than the BC12D, but I think it was mostly created by shrinking the leading edge as opposed to rolling/ stretching. To get a good fitting D model lower cowling, you need to shrink the leading edge where it overlaps the nose bowl. This creates some compounding and improves rigidity, but the rest of the work is trimming and ( non-compound forming). The most difficult part as far as I'm concerned is forming the trailing edge flange and the vents.



There's a blow by blow on fabricating the cowlings, air filter shroud etc. under "Firewall Forward" at c-fclr.blogspot.com (scroll way down)

[Scott]

Oh well, nix all that. BL not BC-65.
Guess I was asleep at the switch

[astjp2]

The top cowlings are flat ie no compound curves.

I get the impression that the BL65 had more compound in the lower cowling than the BC12D, but I think it was mostly created by shrinking the leading edge as opposed to rolling/ stretching. To get a good fitting D model lower cowling, you need to shrink the leading edge where it overlaps the nose bowl. This creates some compounding and improves rigidity, but the rest of the work is trimming and ( non-compound forming). The most difficult part as far as I'm concerned is forming the trailing edge flange and the vents.



There's a blow by blow on fabricating the cowlings, air filter shroud etc. under "Firewall Forward" at c-fclr.blogspot.com (scroll way down)

Scot, FYI my factory 2006 lower cowling was stretched and is a large compound curve in 2 directions. It still took me a day and a half to fit onto the boot cowl and nose bowl. Tim

[Ragwing nut]

bl and bc cowls are the same shape. The factory used a plywood mold to shape the lower cowl too. I saw it when I visited the factory in brownsville many moons ago. the F21 cowl though is flat, no compound curve to it.

[Scott]

Good, thanks for the factory info, good to know.

I guess the point I was trying to make is that you don't nessesarily need to roll/stretch the skin to create the compound. Shrinking along the perifery creates a compound in the body of the skin in perhaps a more even and predictable fashion, with the advantage of not reducing the thickness of the material ( also less skill required!).

I have a bench top Shrinker. Was not expensive but they do make a bit of a mess of the surface finish if your not careful. I use al oxide sandpaper between the jaws and material and end up with the surface marks pictured. Fortunately when you shrink the material it gets thicker, so you can polish out the marks and still end up at the nominal thickness.

any everyone has their own methods, just sayin I achieved a reasonable result without any rolling. Of course it was a little nerve racking after already spending a couple of days on the lower cowling to then start running through the Shrinker, but in the end it was worth it

[Hank Jarrett]

Wish you had done a video of your cowl. I have used an English Wheel and it works great but is a MUCH more dangerous tool than it looks like. It is NOT something you just watch a video of and then go do it. I did make a plywood Buck of the lower closed cowl for a pre war Deluxe but it needs more frame sections to be really usable. I have a ply piece for the nose bowl back plain and firewall as well as pieces for the area in the plain of the latches and a side profile from front to rear on the center line. That isn't enough.

Hank

[3Dreaming]

bl and bc cowls are the same shape. The factory used a plywood mold to shape the lower cowl too. I saw it when I visited the factory in brownsville many moons ago. the F21 cowl though is flat, no compound curve to it.

The prop flange for the Lycoming on the mount is about 2" shorter than the continental. So the cowlings can be similar, but not the same. I modified a BL open cowl to fit a Continental conversion. I used the same nose bowl, but made new rear sections.

[Scott]

By they way, I used a similar edge shrinking technique to create compound curves on the nose bowl doubler I made. You can see where I shrunk along the inside radii and lower flange. This is 2024 T3 material and so takes a lot more convincing to change shape!

[Ragwing nut]

The prop flange for the Lycoming on the mount is about 2" shorter than the continental. So the cowlings can be similar, but not the same. I modified a BL open cowl to fit a Continental conversion. I used the same nose bowl, but made new rear sections.

you talking open or closed?

[3Dreaming]

I am talking open. It doesn't really make any difference, because the distance from the firewall to the prop flange doesn't change between open and closed cowls.

[CaptainJon]

How difficult would it be to get a fiberglass/carbon cowling accepted as an alternative materials "owner produced" part? Maybe Terry has an opinion on this? Or is this Taylorcraft heresy? Carbon nose bowl and top cowlings too....... ooooooh! wouldn't that be nice!?

Sorry, I don't think I got enough sleep..........I must still be dreaming............