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Cowl mold

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Old 07-04-2013, 05:59 AM
  #1
rt3232
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Default Cowl mold



Hi Guys

About 20 or so years ago I made a female mold for a cowl, to fit a dragon lady and every time I changed the engine type I would pull a new cowl, well on this last engine I said fuee just run it un cowled and have for 5 years well I dum thumbed it on final so it is in the repair stage,So I figured as long as it is in repair why not fab a new cowl, Now the problem dug out the old mold but I am finding it is about 1/2 to short, So is there a expandable foam I could use for a new plug ,over fill the mold, pull it and cut and sand to shape to get the extra length and then take acowl from that ? this would be a one time thing so I need to limit the $$$$

Got my training in pattern and mold making in the early 50's and have not followed the technolagy, so any help would be great


Cheers Bob T
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Old 07-04-2013, 06:27 AM
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Default RE: Cowl mold

You want fast, cheap, and dirty. Pull a cowling from your original mold, abrade the inside around the mating area that fits the fuselage, now carefully take 1.5" wide masking and wrap several times around the outside allowing the tape to extend beyond the edge of your cowling about .75". Now just layup a couple of plies on the inside extending from about .500" from the inside of the cowling to the edge of the tape outside the cowling, allow to cure, peel tape, clean up and...

Bob
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Old 07-04-2013, 06:34 AM
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Default RE: Cowl mold

Sensei. Good solution.

Although I would use aluminum duct tape if not a compound curve type situation.


Steve
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Old 07-04-2013, 07:48 AM
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Default RE: Cowl mold

Many good ways to skin a cat. I did the same thing by taking a peice of blue foam and shaping it to just fit in the back of the cowl. I then put a layer of packing tape on the " form ", inserted it into the cowl an inch and layed new glass on top of it and 2" onto the exterior of the original cowl. Feather sand and paint.
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Old 07-04-2013, 08:11 AM
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Default RE: Cowl mold

You could lay up a new cowl, then pull it out and lay up just the back 1" to make a ring and then use seam tape to glue this new 'ring' to the cowl you just made to extend it.
Make the 1" ring thicker and you could use it to screw to and keep the rest of the cowl thinner to reduce weight.

Tim
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Old 07-04-2013, 02:19 PM
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Default RE: Cowl mold

Ok Guys

Great suggestions, and I just did not think this thru,
Another Question when I pulled the last cowl I ended up with a chip in the old gell coat , so what would be an easy fix ?, in the old days I used PVA as th parting layer after I had put a few coats of wax on the surface, but it would fisheye as we used to call it. so what would be a better parting agent? or just go with what I know.

Cheers and thanks for your help

Bob T
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Old 07-04-2013, 03:09 PM
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Default RE: Cowl mold

GellCoat would make me assume you were using polyester resin in your layup. Epoxies are much better to use. You could spray a coat of 2 part epoxy primer before the layup. Part comes out pre primed. Your PVA fish eyed because of the wax that was used. Part all # 2 wax is what I use
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Old 07-04-2013, 04:36 PM
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Default RE: Cowl mold


Well like I said I learned what little I know about pattern and mold making back in the early 50 at Gen/dyn Convair in San Diego so I used what they used the fish eye only happaned if the PVA was applied to heavy it was allways a bugger, and you are absolutely right.

So Partall #2 will be what I will try to find. Any suggestions on who might handle it ?

Cheers Thamks for your help

Bob T
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Old 07-04-2013, 04:59 PM
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Default RE: Cowl mold

Bob, the part all #2 is readily available, just type it into your browser. I even found it at Amazon.com. There are a great many new mold releases available today and some in an aerosol form. Some of the other guys are more experienced at what is readily available then I am. Myself I have never been let down with the Partall PVA system but it is a slow process to some.
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Old 07-04-2013, 05:39 PM
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Default RE: Cowl mold


I went to google and I did find it but was looking for it hear in Saint Paul MN but I will look farther and thanks for your help.

I will keep posting as things come along, but for now it looks like I will have to do my on looking and that is fine


cheers Bob T
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Old 07-23-2013, 03:56 AM
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Default RE: Cowl mold



new sowl is done and ready for some tuch up and paint


Thanks for the help

Cheers Bob T
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Old 09-02-2013, 03:19 PM
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Bob Sensei if you catch up to this, help me out please, I'm going to do this one right.

I want to make a fiberglass cowl using the kit PVC one to make the mold for a fiberglass one. It's a 1/4 scale Sig Spacewalker 11 and it's available from the Specialties guys but I want to make my own. Zpoxy ? cloth weight, release agent and step by step. This would be no problem for you and I want to save the mold on this one. Be great having your help. Remember the Tiger bash cowl I did,?. Well I don't want a repeat of that, ha ha.

Regards, Leroy
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