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Drywall compound for cowl mold? - Or maybe 3D print the cowl?


Bill Allen
 

Yes, making cowlings is a lot of work, and can be satisfying to your inner sculptor. But if you haven’t got much of an inner sculptor, it can be frustrating.

I got sick of all that, particularly if you’re making a cowl with ducts and intakes in it - it becomes a multistage, split-mould marathon. I got to thinking, “Couldn’t we just scan the engine bay and create a virtual cowl from which a 3D print could be done....”
It so happens that one of my sons is into 3D printing, but all the printers are so small.
I said “could we make a big 3D printer?”
He said “all it would take is time and money”

So this is where we’re at a year later. Much has been learned. Much has been spent. I’ll soon be able to make cowls, wheelpants and much more.

It’s all about education and recreation. And money. Did I mention that?

Best 

Bill Allen

On Mon, 11 Jan 2021 at 19:19, Ryszard Zadow <ryszardzadow@...> wrote:
I use pour foam without reservation, but not quite like your attempting too. It's great to fill areas and build up a big spot, but little or thin stuff isnt really a good application for it. If I get messed up and find I oversanded or didn't' contour correctly I just cut out the section and plug urethane foam back in. 

Another good technique is use templates and grid lines as much as possible. You have to have a way to keep things symmetrical. 

The "rough out" is the most important part. Then it's details. The horizontal groove is routed out and is the overlap of the two cowlings. Laid up the nottom, then covered the plies in the groove with duct tape, then laid up the top cowl. The part line was the groove and made a perfect overlap. 

Used the same technique on the IO-240 for the Varieze, but I pulled a mold off it and vac bagged the cowling halves. Lots of work for a one of a kind.. 
On Monday, January 11, 2021, 12:01:59 PM CST, Steve Stearns <steve@...> wrote:


Ryszard, you said, "The key to using drywall mud is to make sure your foam plug is as close to the shape you want before applying it." and I think this hits the key to the problem that I'm trying to solve.  Maybe you have some more guidance for me.  My key issue is that I suck at getting the foam plug "close to the shape".  I invariably, when cutting, sanding, shaping the pour-foam (X-30) end up over-shooting or gouging etc. and need to add "just a bit"  (possibly over a wide area) and, with pour-form adding "just a bit" ends up with a big blob and I'm back where I started.  I was hoping having an additive material that both sands better and is easier to control would help.

Sounds like I'll still need a combo of the two approaches (and that I just need to keep upping my skills but I'm impatient...)

Steve Stearns
O235 Longeze
Boulder / Longmont CO

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Doug Kan
 

They have large 3D printers now, large enough to build a boat or house. Next maybe an airplane? But they are expensive. Lets face it though, most of us building planes try to watch our costs. I am struggling with baffles right now, the other side to the cowl.

 

Doug

 

Sent from Mail for Windows 10

 


aviationeyes
 


I've seen big items made from little printers. You just have to use segmenting/slicing software and smartly cut up the part in the software into chunks the printer can handle. Then spend a few weeks printing out the segments to glue together. 
--Jose

On Mon, Jan 11, 2021, at 2:13 PM, Bill Allen wrote:

Yes, making cowlings is a lot of work, and can be satisfying to your inner sculptor. But if you haven’t got much of an inner sculptor, it can be frustrating.

I got sick of all that, particularly if you’re making a cowl with ducts and intakes in it - it becomes a multistage, split-mould marathon. I got to thinking, “Couldn’t we just scan the engine bay and create a virtual cowl from which a 3D print could be done....”
It so happens that one of my sons is into 3D printing, but all the printers are so small.
I said “could we make a big 3D printer?”
He said “all it would take is time and money”

So this is where we’re at a year later. Much has been learned. Much has been spent. I’ll soon be able to make cowls, wheelpants and much more.

It’s all about education and recreation. And money. Did I mention that?

Best 

Bill Allen


On Mon, 11 Jan 2021 at 19:19, Ryszard Zadow <ryszardzadow@...> wrote:

I use pour foam without reservation, but not quite like your attempting too. It's great to fill areas and build up a big spot, but little or thin stuff isnt really a good application for it. If I get messed up and find I oversanded or didn't' contour correctly I just cut out the section and plug urethane foam back in. 

Another good technique is use templates and grid lines as much as possible. You have to have a way to keep things symmetrical. 

The "rough out" is the most important part. Then it's details. The horizontal groove is routed out and is the overlap of the two cowlings. Laid up the nottom, then covered the plies in the groove with duct tape, then laid up the top cowl. The part line was the groove and made a perfect overlap. 

Used the same technique on the IO-240 for the Varieze, but I pulled a mold off it and vac bagged the cowling halves. Lots of work for a one of a kind.. 
On Monday, January 11, 2021, 12:01:59 PM CST, Steve Stearns <steve@...> wrote:


Ryszard, you said, "The key to using drywall mud is to make sure your foam plug is as close to the shape you want before applying it." and I think this hits the key to the problem that I'm trying to solve.  Maybe you have some more guidance for me.  My key issue is that I suck at getting the foam plug "close to the shape".  I invariably, when cutting, sanding, shaping the pour-foam (X-30) end up over-shooting or gouging etc. and need to add "just a bit"  (possibly over a wide area) and, with pour-form adding "just a bit" ends up with a big blob and I'm back where I started.  I was hoping having an additive material that both sands better and is easier to control would help.

Sounds like I'll still need a combo of the two approaches (and that I just need to keep upping my skills but I'm impatient...)

Steve Stearns
O235 Longeze
Boulder / Longmont CO



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