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Help with cowl mold (pics)

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Old 12-19-2012, 07:17 AM
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a70eliminator
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Default Help with cowl mold (pics)

My cowling bit the dirt and would like to fab a new one, I have plenty fiberglass experience boat building ect. I'm looking for some advise on where to start. I already know to fill the chipped gelcoat and smooth the entire surface. The inside surface is unfinished fiberglass so making a male plug is not likely so i'll have to somehow make an imprint of the outside with clay, palser paris, paper mechet, or something, also it looks like the wedge shape will require it be cut in half for a two piece mold, I 've seen you guys make some really intense molds and this would probably be a breeze to you, so what would be your plan of action? thanks.
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Old 12-19-2012, 07:38 AM
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Default RE: Help with cowl mold (pics)

You will need to patch, shape, sand and prime the existing cowl to make a plug.  Then make a mold from your plug.  Here is a link to a set of videos that gives you excellent step by step instructions on how to make your new cowl. http://www.fibreglast.com/fibreglast...old_fibreglass
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Old 12-19-2012, 07:59 AM
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Default RE: Help with cowl mold (pics)

Yep that is a easy mold... One thing you will have to fill all the cut out area's also.. the other thing that will help alot is after you fill those cracks etc. on the outside and sand, prime is shoot a base coat of color and let cure really well... you will have to mount it to a board and then make the seam joint. maybe the video will show you this.. then when we have a virgin plug it gets 10 coats of wax with each one being buffed off by hand. after that we use PVA several coats sprayed on and let dry. then to glass work. we make our molds out of 6 oz and 8 oz cloth usually about 6 layers,it depends on the product and how many we are making. Once the glass is done, the mold now gets 10 coats of wax and then PVA prior to the lay up of final product... this is a real short version of the steps and maybe the video shows this...

We use for the general layup the West System epoxy... easy to work with.

What plane is this for ?

Also if you don't want to monkey with it we do glass work.

S.
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Old 12-19-2012, 08:22 AM
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Default RE: Help with cowl mold (pics)

Hi and thanks for the replies so quickly, the cowl is for an Ace kit Weeks Special by Miles Reed. I built one of his first basement built kit's back in the 70's and the cowl was built up from balsa, the ace kit plans do not depict the balsa build up cowl.
I'm doing another scratch build of the biplane with a friend so we need to make two of everything, may just opt to build cowl from balsa.
I do not have the equipment for spraying gelcoat is it possible to brush on? Sounds like for me the balsa build may be a better option.

Daytonarc what a great video tutorial, I'll book mark that one for sure. I guess you can brush on the surface coat lol, sure looks like alot of time goes into making a mold, not hardly worth it unless i plan on mass production lol. but I still want to do it, I have more time than money.

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Old 12-19-2012, 08:57 AM
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Quote:
ORIGINAL: a70eliminator

Hi and thanks for the replies so quickly, the cowl is for an Ace kit Weeks Special by Miles Reed. I built one of his first basement built kit's back in the 70's and the cowl was built up from balsa, the ace kit plans do not depict the balsa build up cowl.
I'm doing another scratch build of the biplane with a friend so we need to make two of everything, may just opt to build cowl from balsa.
I do not have the equipment for spraying gelcoat is it possible to brush on? Sounds like for me the balsa build may be a better option.

Daytonarc what a great video tutorial, I'll book mark that one for sure. I guess you can brush on the surface coat lol, sure looks like alot of time goes into making a mold, not hardly worth it unless i plan on mass production lol.

Watch the videos. If youneed2then making a mold is the way to go. Also you will have the mold for future use if needed (in case of radio failure). No spray equipment needed. The videos will show you exactly how to make a perfect 2 piece mold using epoxy and brush method. The videos are a very user friendly explanation of the method described by PatternPilot
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Old 12-19-2012, 09:40 AM
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Default RE: Help with cowl mold (pics)

10 coats of wax is absolutely absurdly more work than is necessary. After 4 coats the build up is negligible between each additional coat afterwards.

I have been using 3 coats of partall's paste wax on all of my plugs and molds, all of which are entirely more complex than anything i have seen posted on any of these web groups. 3 coats of wax with buffing in between, then a coat of pva sprayed no greater than 12 hours before you begin your layup (pva absorbs moisture which can reduce its effectiveness), is all that is needed.

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Old 12-19-2012, 10:12 AM
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Default RE: Help with cowl mold (pics)

well we have not ever had a bad release in either a plug or mold and we have 100's of pulls from molds. we have even had a pva failure and still got a clean release. Maybe be over kill but it works and no problems.. I do agree on the PVA do not spray and let sit around for days.

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Old 12-19-2012, 06:45 PM
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Default RE: Help with cowl mold (pics)


Quote:
ORIGINAL: PatternPilot

well we have not ever had a bad release in either a plug or mold and we have 100's of pulls from molds. we have even had a pva failure and still got a clean release. Maybe be over kill but it works and no problems.. I do agree on the PVA do not spray and let sit around for days.

A70 - sent you a PM


scott
Instead of spraying the PVA have you ever tried a foam brush? I tried spraying years ago and never liked the results. I get a nice even flow when brushed and no orange peel.

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Old 12-20-2012, 12:03 PM
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Default RE: Help with cowl mold (pics)

I have brushed pva on with an epox brush. It worked fine as the stuff kind of self levels as it dries.
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Old 12-20-2012, 12:07 PM
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Default RE: Help with cowl mold (pics)


Quote:
ORIGINAL: PatternPilot

well we have not ever had a bad release in either a plug or mold and we have 100's of pulls from molds. we have even had a pva failure and still got a clean release. Maybe be over kill but it works and no problems.. I do agree on the PVA do not spray and let sit around for days.

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scott

To each there own! Personally, other than making molds, i no longer use wax and pva on large molded parts. I have switched to a semi-permanent mold release system called frekot. Each application of mold release is supposedly good for multiple parts, but since it is a simple, "wipe on", "wipe off" (yes, no pause in between) for each 2'sq. section and the. Let sit for 15-20 minutes before starting a layup, i have saved myself allot of time and effort in eliminating all of the waxing and pva drying time. Its release properties are better so far as well, even on a very "green" mold with only one pull from it.
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Old 12-24-2012, 05:15 PM
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Default RE: Help with cowl mold (pics)

I have a good badger dual action airbrush to spray the pva.. I spray at 35 psi.

s.
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Old 12-26-2012, 11:19 AM
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Default RE: Help with cowl mold (pics)

I have done molds using polyester products. I even made my own gel coat from a mix of resin and body filler. If you use polyester resin for the mold, you need to wait a bit for the mold to completely cure. I heard anywhere from 3 days to a week. I've not done a lot of mold building and they were all pretty simple and all were polyester based. I did have one stick on me and it was a "adventure" to say the least.

Ken
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Old 12-29-2012, 03:02 PM
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Default RE: Help with cowl mold (pics)

simple,,,,foam......cover with a large balloon, and glass....pulls out when done
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