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Big Cowling

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Old 03-22-2013, 03:29 AM
  #1
sensei
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Default Big Cowling

They say a picture is worth a thousand words, so for those interested; here is a short pictorial of building a simple engine cowling plug, lay up block, and cowling from beginning to end.

Bob
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Old 03-22-2013, 03:32 AM
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Continued.
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Old 03-22-2013, 03:34 AM
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Default RE: Big Cowling

Continued.
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Old 03-22-2013, 03:40 AM
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Default RE: Big Cowling

End.

Bob
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Old 03-22-2013, 06:45 AM
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Default RE: Big Cowling

Nice story in pictures. What kind of foam block did you use and where purchased? What glue did you use to adhere the blocks together? I've got a future project in mind that will use foam for body shaping, hence the questions. Thankx
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Old 03-22-2013, 09:49 AM
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Quote:
ORIGINAL: GarySS

Nice story in pictures. What kind of foam block did you use and where purchased? What glue did you use to adhere the blocks together? I've got a future project in mind that will use foam for body shaping, hence the questions. Thankx
That is just your run of the mill 1-1.5 lb. density styrofoam, I get mine from a place here in San Antonio, but I am sure if you google you can get it someplace near you. I glue everything together with either Gorilla glue and/or hot glue sticks from Lowe's or Home Depot then I start shaping with my wire brush and sand paper.

Bob
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Old 03-24-2013, 04:54 PM
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Nice post! You used epoxy resins. If you wanted to use polyester then the foam would need to be sealed.
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Old 03-24-2013, 05:16 PM
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Your right, I always use epoxy resin, it is just easier to glass directly to styrofoam.

Bob
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Old 03-26-2013, 06:52 PM
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Default RE: Big Cowling

Nice work Bob but you leave much out when you do a illustration like that. I suppose others can figure out the left out details like the desolved foam method or the hack and whack or maybe it just slid off. Nice job just the same. Looks like you could use some cup gaskets, you wouldn't have to tie a rag around your gun.

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Old 03-27-2013, 02:38 AM
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Quote:
ORIGINAL: Leroy Gardner

Nice work Bob but you leave much out when you do a illustration like that. I suppose others can figure out the left out details like the desolved foam method or the hack and whack or maybe it just slid off. Nice job just the same. Looks like you could use some cup gaskets, you wouldn't have to tie a rag around your gun.

Leroy
Thanks Leroy,

I figure if someone wants to know more, all they need to do is ask and I will be happy to explain.

Bob
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Old 03-28-2013, 04:41 PM
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Default RE: Big Cowling

I have some questions Bob, if you don't mind.

In pictures 9 & 10 in post 3, it looks like you are using some fan fold foam as a filler when you are laying up the cowl. Can you explain what that is all about?

And also, what the heck is picture 11 in post 3 supposed to be showing? Is that some lost foam there? It looks like a suction hose there. What's going on?

Regards,

Dennis
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Old 03-28-2013, 05:56 PM
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Picture 9 is me laying up 4 oz. cloth, .125" thick PVC core and the use of E-Z Poxy 10 laminating resin. Picture 10 is me laying up the solid ply areas with 6 oz. cloth doublers. Picture 11 is the consolidation of the layup using a perforated release media, a 4.5 oz. breather, and the use of a vacuum bag, the hose you see is the vacuum source to the bag. The reason I used the PVC core is simple, it allowed me to produce a cowling this large with a finished weight of under 2 lbs. by using less glass and resin. Now in comparison to a 50% Bill Hemple Extra 260 cowl I personally weighed of a stocky 5+ lbs. this 55% Extra 260 cowling is very light for it's size.

Bob
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Old 04-03-2013, 10:28 AM
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Wow great work! What light brown body filler is that you are using?
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Old 04-13-2013, 06:11 PM
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Quote:
ORIGINAL: dbsonic

Wow great work! What light brown body filler is that you are using?
Thanks for the kid words, the filler is just some run of the mill bondo from the local automotive store.

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Old 09-23-2013, 09:08 AM
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Hello. I have decided to try my hand at making a glass cowl. Your pics are excellent, but I do have a question. How do you remove the foam core?
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Old 09-23-2013, 10:40 AM
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It comes out as part of the master model, or you can poor a little acetone on it and within minutes it melts to a very sticky liquid that you poor out.

Bob
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Old 09-23-2013, 11:23 AM
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I really love threads like this, there is nothing in the hobby more satisfying than the craftsmanship of modelers...
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Old 09-23-2013, 12:20 PM
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Thanks foodstick.

Bob
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Old 09-23-2013, 08:30 PM
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If you coat the foam with packing tape, then glass it the foam comes out much more cleanly.
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Old 09-24-2013, 03:19 AM
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Quote:
Originally Posted by soarrich View Post
If you coat the foam with packing tape, then glass it the foam comes out much more cleanly.
If you did not notice, the foam was shaped and glassed with epoxy resin on purpose, this gave me a stable master model that I tooled from. The master model was then demolded clean, and in one piece. The use of packing tape on shaped foam is fine for those that wish to skip the tooling process and fly the molded splash off the foam but those are usually heavier due too the comedic aspect prior to paint and not something I would personally consider on any one of my airplanes but that is just me. Now I have used mylar tape on foam and cardboard plugs in the construction of things like fuel tanks, but then again I am not trying to create a smooth paintable surface. The picture below illustrates the packing tape process I used on this tank some 14 years ago.

Bob

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