Cowl Fabrication

[Daddy O]

I have searched our posts here and have not seen any reference to making a cowl, using a plug. I have formed my plug and need advice on Vacuum forming or any other proven suggestions. I need to make at least 4 of these cowls.

I have made my plug from blue foam board. I would be willing to destroy it to create a cavity for a fiberglass mold. At present vacuum formed ones will do. I was told the might be a means of doing some sheet forming without a vacuum frame.

Well there you have it. Your help and suggestions will be appreciated.

I'll checking with some of those guys in RC using other than surface radios, also.

[AndyKunz]

You would do well to use your plug to make a glass mold. Once you have that, you can do whatever pleases you.

If you are only looking for a few of them, you could try somebody like Electric Thunder's Tracy Osterhout. He will do short runs like that for guys for a fair price.

I would probably just make 4 glass ones off the mold, though.

Andy

[FrankW]

I would suggest to not vacuum form anything... It's a big pain in the ass. I know... I vacuum form, LOL. Plus, a good vacuum former is very expensive. For a good one that will fit most cowls, you're looking at atleast a $400 investment, and you need an oven on top of that.

-Frank

[Daddy O]

Thanks for the pointer.

I'm sure here in Dallas there is a shop that can help me.

With your experience, is my blus foam plug adequate for a pull? Might need to seal it? Coat it? what?

You also seam to give the impression that the formed part would not be useful.

Thnx Frank
_____________________________________________

So Andy

You said not more than 4 pops off a mold. If I take my initial plug and slick it up with primer to seal and wax it up. Do my fiberglass mold.. you think I'd only get 4 copies???? no savy.

[AndyKunz]

Originally posted by Daddy O
So Andy

You said not more than 4 pops off a mold. If I take my initial plug and slick it up with primer to seal and wax it up. Do my fiberglass mold.. you think I'd only get 4 copies???? no savy.

No, what I said was that if I were only making 4 (like you said at the top) then I would make them all from glass. For 4 pieces it isn't worth the extra hassle of making the vacuum mold. If you were making 100 of them, yes, go for plastic.

Use the piece you made (sealed, waxed, and PVA'd) to make a glass mold. Make as many in the glass mold as you want.

There are threads in the Builders section which describe the technique if you need to look that up.

BTW, you may use Elmers white glue as PVA. Thin it with water first.

Andy

[FrankW]

Vacuum formed cowls would be great.

The foam will likely melt due to the tempurature the plastic has to be at (300 - 350 for ABS). It's best to use at least balsa, or a nice hard wood.

Never, ever "finish" a mold when trying to vacuum form. The paint, wood sealer, etc., will stick to the plastic and you will probebly have destroyed the plastic part and mold.

I usually make a wood mold, then form some thick ABS (0.040 - 0.060) over that, then use the "part" to make a mold out of Durhams Water Putty... which I can smooth out, sand, etc.

-Frank

[Ryan_from_OHio]

From my understanding, in the production runs (like at Parma etc.) The make the original part and put it into plaster to make a mold, then in turn the use aluminum epoxy for the master plug, which is used to vaccum form the stuff.

Its been quite some time since I was toying with the vaccum forming ideas, so I may be slightly off.

Take it for what its worth.

*just had to fix some type O's, I really should get to bed :)

[FrankW]

If I plan to have a mold to last for a hundred or more formings, I make it out of 2-part tooling resin. But usually I don't go that far, since most of my projects don't need many formings.

-Frank

[ztarum]

I'm just curious, but has anyone tried forming a cowl out of aluminum sheet? I'm starting a scale project, and the real boat had an aluminum cowl. I was thinking it would be nice to do the model cowl in aluminum too, but I kind of gave up on the idea before even trying. It seems like it would be hard, but I though I would throw it out there and see if anyone had heard of that being done.

Zach

[Daddy O]

I just wanted a simple means of creating a cover for my motor. Now it seams that I need to look more like, I must develop new skills and patience.

The blue foam plug I made was enlightining, not to mention the studying of the shape and how to obtain my desired item. Even techniques to obtian it with such a delicate media.

Now to consider recreating this in a more resilient material. One that will surely take more than the 1 1/2 hours to have in it's desired surfaces and shape.

An alternate might be to seal my delicate treasure with this water based glue and start making that mold of fiberglass. Holy cow I read an artical on making a mold using my Plug. I'm not sure these folks ever do anything on a small scale. They were refering to use of LUMBER to keep the mold stable. Oh and not to mention all the supplies, from waxes, tool makers this and that. It was a 15 section report that boiled down to needing build that extension to the shop. I'm not too sure the War Department will pass that Bill.

I'm having fun with this and hope to hear other suggestion from those of like interests.

Wax? Now there is a thought, "lost wax". I think there is a lightly scented red and white chunk favoring "Ole St. Nic" in the hall closet. Might I dare try that. I'm sure it has been forgotten, if not I could always say "Didn't you wrap it in a hat box for the "Family Chinese Christmas gathering?" Just kidding all.

[T.S.Davis]

Daddy O,

I'm having exactly the same problem. Just wait until you try to wittle that balsa down to the shape you want. Now that's a pain. Especially if it takes multiple chuncks glued together. APPARENTLY, I NEED MORE TOOLS. AGAIN.

Couldn't we seal the blue foam with something(I'd like to know what too) and then use plaster to make a mold? Then fill the mold to make the plug?

Try this http://www.castcraft.com/prod12.htm for vacuum forming. It can be done cheap at home on a small scale. There's also a book available from the same site for hobbiests. It's written in laymans terms.

Terry

[Daddy O]

Hello T.S.

Friday I went out and bought a Balsa Plank, 2.5" x 3.5" x 30".

Sunday morning out in the back yard a new plug emerged after 1 1/2 hours of carving, sawing and delicate sanding. Band saw and my cordless drill w/ the 1 ¼ “ sanding drum were the main time savers. I’ll start sealing the balsa tonight with two part automotive primer. My final plug will be 4 ½” x 11” flat with the cowl plug mounted on it. My scratch built Hydromite Plus is the intended use. Using the Hughey gear reduction will require this taller cowl. The look it has is that of the new Alcohol drag boat canopy.

I know I’ll make 2 covers for my boat, static and a sport one. The static will have a blown Hemi motor from the 1932 Ford roadster, Muscle Cars, of Funline. These cars are sold at most hobby stores. The scale of this motor looks perfect on the hull, just cut off the block below the heads and whalaa.

(T.S.) I’ll try to email you a .bmp of my plans, I’ve tried several time to post my drawing here, without luck yet. I have no idea how to convert a Acad 2002 drawing into a gif or jpg. Anyone got a suggestion?

[T.S.Davis]

Don't ya love it? To save an object/drawing from Acad to bitmap you just type "bmpout" at the command prompt. It will ask you for a file name and then you can select objects to save. You can also save to a tiff format by typing saveimg but it comes out kind of sketchy. Not sure on gif or jpg. I'm sure it can be done.

I'm still curious about the sealed foam idea. I may experiment with that one.

Terry

[RCBoatingNewbie]

For anyone wanting to convert a .dxf to some image file (who might not have access to a CAD program, say, if you download some .dxf's and need to see what's in 'em), you might try a product called "Able DXF Manager" (search the web, can't remember where I got it at the moment). The trial version is free, but you get a blurb in the middle of the image ("demo" or something). I think the app's like $19.95 if you want to have the "UnDemo'd" version.

The Following isn't my work, it's from the readme.txt for this program.... A bit about the features...

** Begin File **

Able DXF manager is a program that enables you to easily view, print and convert graphic files in normal (file by file) and batch (many files at a time) modes.

Input formats:
- Drawing Interchange Format (DXF) generated by most CAD programs,
- TIFF Bitmap (TIF;TIFF)
- JPEG Bitmap (JPG;JPEG;JPE)
- PaintBrush (PCX)
- Windows Bitmap (BMP;DIB;RLE)
- Portable Network Graphics (PNG)
- Windows Metafile (WMF)
- Enhanced Windows Metafile (EMF)
- Targa Bitmap (TGA;TARGA;VDA;ICB;VST;PIX)
- Portable Pixmap, GreyMap, BitMap (PXM;PPM;PGM;PBM)
- Windows Icon (ICO)
- Windows Cursor (CUR)

Output formats:
JPG,TIF,PCX,PNG,BMP,TGA,PXM,PPM,PGM,PBM.

Features:

Drag and Drop supported
Batch Process
Displayed entities (DXF-files)
- Line
- Circle
- Arc
- Polyline
- LwPolyline
- Text
- Hatch
- 3DFace
- Blocks (including multiple inserted, scaled and mirrored)

Displayed properties of entities (DXF-files)
- Color (including Bylayer and Byblock)
- Linetype (Solid, Dashed, Dot, Dashdot, Divide,Bylayer,Byblock)
- Width (for polyline and lwpolyline)
- Text rotation (any angle)
- Text justification (left, right, center, middle, top, bottom)

Viewing
- Two color mode (color and monochrome)
- Any size (5 modes of a sizes setting)
- Extents selection (4 items)
- Any aspect ratio
- Any image resolution at saving to file
- Zoom (in, out, fit, window)
- Zoom filter (7 items)
- Scroll

Converting (saving) to
- JPEG Bitmap (JPG)
- TIFF Bitmap (TIF)
- PaintBrush (PCX)
- Portable Network Graphics (PNG)
- Windows Bitmap (BMP)
- OS/2 Bitmap (BMP)
- Targa Bitmap (TGA)
- Portable PixMap (PXM)
- Portable PixMap (PPM)
- Portable GreyMap (PGM)
- Portable Bitmap (PBM)

Status information (size, zoom, position, progress bar of file opening)
Printing
- Any system printer (from dialog window)
- Color or monochrome printing.
- Print fit to paper.

All program settings are kept.

** End File **

[AndyKunz]

With your balsa plug you can use a 2L soda bottle (aka pop bottle or coke bottle), a heat gun, and about 30 seconds to make your vacuum-formed cowl. Quality of finish is directly related to quality of plug finish.

Andy

[FrankW]

Acually, that wouldn't be vacuum-formed Andy. That would be Thermo-formed. Yes, it's just semantics... but please try to use the correct terms.

LOL, just buggin' ya Andy.

EDIT: BTW, if you want something vacuum-formed and it's not much longer than 15 inches... send the mold my way and I can do a few for you. But, if you want a lot done... I'll have to charge you. LOL.

-Frank

[Daddy O]

The thermo forming over my plug may not work. I have use 5/8" concave radii on the lower edges of the canopy. I know I used an improper term calling it a cowl.

I'm not sure the material would pull in on my radius, but tend to average the highpoints. I have seen the artical on forming a cowl from a round plug inside a soda bottle. I believe I should try the thermo forming prior to adding and sealers or paint to the plug, to eliminate bonding. I'll give it a shot, just to satisfy my curiousity. Once I get my prototype complete, I just may contact you FrankW. My canopy and cover combination will be near 12" x 5" x 1 5/8"deep. Thanks for the offer Frank.

The balsa plug is now at 2 hours, to create. This symetry issue added the additional 30 minutes.

[T.S.Davis]

Thought you guys might find this interesting.

Carved a hatch for a Force 21 out of foam. Sealed the foam with finishing epoxy (the kind with the wax in it). Thin coat of vasiline. Splashed it with plaster and berlap. Pulled the foam out of the form after an hour. Let the form dry overnight. Vasilined the form and filled it with plaster. After an hour I was able to crack the form off of the plug. Now I have a perfect plaster form that I can vacuuform. Seems like a lot of work but the foam is so much easier to carve into shape. Plus, I just had to know if I could do it. I'm working on something a bit larger. I'll keep you posted.

Terry

[Daddy O]

Gosh, I wish I had some time to finish my projectt. You see the ball and chain bought some interior latex. I should have broke and ran off, but I'm through, except replacing the door knobs. I sprayed the doors.

Back to my stuff. Aaaaaaahhh

[T.S.Davis]

Daddy O,

You've heard the saying "burning the candle from both ends". You just need one of those big 3 wick candles and your all set. I am one those people that gets antsy if I don't have every second of my time taken up by one project or another. If I don't have a project I'll invent one. I painted my kids room over the last week too. AAARRGGGHHH. Made my hatch plug between coats and after kids went to bed.

I'm going to need a nap now.

Terry