Getting scale details into fiberglass parts (lost foam method)  
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All Forums >> RC Airplanes >> Composites Fabrication And Repair >> Getting scale details into fiberglass parts (lost foam method)
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Getting scale details into fiberglass parts (lost foam ... - 8/26/2008 6:30:53 PM   
Bigshark


 

Posts: 136
Joined: 12/1/2004
From: St. Louis, MO, USA
Status: offline 		I am going to be making a cowl for a fourstar 120, using zpoxy and laying fiberglass on a foam mold. The idea is to try to mimic the cowl from the radial engined ki-100. The ki-100 had cowl vents that flaired open at the back. I had two thoughts on this. First I though to put the detail directly into the foam block and working the expoxy and glass into the grooves. I had also thought about begining the cowl with a few layers, cutting out the vents completely and setting them back in place with the next few layers of glass.

Any thoughts?

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RE: Getting scale details into fiberglass parts (lost f... - 10/22/2008 4:30:54 AM   
Avaiojet


 

Posts: 413
Joined: 9/25/2002
From: East Greenwich, RI, RI, USA
Status: offline 		Big,

IMO, I would use polyester laminating resin. Make the cowling first then detail it.

That's what I would do.

I've always done lost foam. I need to learn how to lay up a fuselage from a plug.

This cowling was made by lost foam



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< Message edited by Avaiojet -- 10/22/2008 4:31:41 AM >

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RE: Getting scale details into fiberglass parts (lost f... - 10/22/2008 6:04:22 PM   
FLYBABY6


 

Posts: 97
Joined: 7/8/2008
From: TULSA, OK, USA
Status: offline 		another option would be to make the cowling seperate from the vents, then make the vents mold and set aside until the cowling mold is complete and then resin and glass the vents into place. Just remember the molds have to come off of the plug and not get stuck because of curves or sharp angles that dont alow it to come right off of the plug, thats why I would make them seperate and add to each other in a later step.

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RE: Getting scale details into fiberglass parts (lost f... - 10/24/2008 3:33:18 PM   
Bigshark


 

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From: St. Louis, MO, USA
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To Avaiojet: Other than the smell (horrific from what I've heard) what's the difference between working with polyester and epoxy?

To Flybaby6: No worries about gettin the cowl off the mold. I'll be using a foam mold the will be dissolved the get the part out. As a matter of fact, a truely scale KI-100 cowl would be very difficult to mold over a traditional plug since it bells out a bit at the front and gets smaller toward the body. The original had the cover a radial engine mated to a KI-61 body designed for an inline engine.

I didnt think of making the vents completely separately and then gluing them on later. I can see the merits of that though.

Thanks,
Rich

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All attempts at artificial aviation are doomed to failure from an engineering standpoint.
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RE: Getting scale details into fiberglass parts (lost f... - 11/28/2008 6:02:28 AM   
Avaiojet


 

Posts: 413
Joined: 9/25/2002
From: East Greenwich, RI, RI, USA
Status: offline 		I've never used Epoxy. I always thought it was les flexable compaired to Polyester laminating resins.

I can remember a time when a Vendor, for model cowlings and wheelpants, advertised that they now had an Epoxy that was "New Flexable Epoxy."

This was 10 years ago.

Charles

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RE: Getting scale details into fiberglass parts (lost f... - 11/28/2008 8:34:49 AM   
Ed Smith


 

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Joined: 12/29/2001
From: Brantford, ON, CANADA
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quote:

To Avaiojet: Other than the smell (horrific from what I've heard) what's the difference between working with polyester and epoxy? [/quote

Avaiojet will probably not agree even though he claims he never uses epoxy, but whatever properties, ease of use you are looking for with polyester resin, epoxy resin will outperform them all in every respect. Epoxy resin does not smell and is nowhere near as hazardous as polyester. I will not allow polyester resin in my house.

Ed S







< Message edited by Ed Smith -- 11/28/2008 8:35:30 AM >

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RE: Getting scale details into fiberglass parts (lost f... - 11/28/2008 10:37:57 PM   
Avaiojet


 

Posts: 413
Joined: 9/25/2002
From: East Greenwich, RI, RI, USA
Status: offline 		Ed,

It's more complicated than just the smell.

Interesting thing is, if you read again and take a look at my other Epoxy vs. Polyester Thread, it's quite obvious my original questions were never answered.

Charles

(in reply to Ed Smith)
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RE: Getting scale details into fiberglass parts (lost ... - 11/28/2008 11:43:26 PM   
Ed Smith


 

Posts: 2875
Joined: 12/29/2001
From: Brantford, ON, CANADA
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quote:

Interesting thing is, if you read again and take a look at my other Epoxy vs. Polyester Thread, it's quite obvious my original questions were never answered
.

Avaiojet,

Did not the following quote from the other thread answer your questions all in one sentence? You should try using the material then you can speak from experience like everybody that answered your questions.

quote:

Polyester resins are more brittle, weaker materials and shrink more than epoxies.


Ed S

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RE: Getting scale details into fiberglass parts (lost ... - 11/29/2008 1:46:16 AM   
Avaiojet


 

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From: East Greenwich, RI, RI, USA
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Sorry Ed, I honestly don't know how to respond to that?

Charles

< Message edited by Avaiojet -- 11/29/2008 2:02:21 AM >

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RE: Getting scale details into fiberglass parts (lost ... - 11/29/2008 2:10:43 AM   
Mike Emilio


 

Posts: 568
Joined: 3/17/2003
From: TorontoOntario, CANADA
Status: online 		Charles, , ,

I believe your questions were answered.

The one that stands out was which one was better, polyester or epoxy.

Simply put, it depends mostly on the job your doing.

Both are ok for small stuff, if you can accept one being a bit more harder than the other.

But if your doing big stuff, then epoxy gives a longer working time.

If your vacuum bagging small stuff, they both work quite well, but if your bagging bigger stuff then the working time is very important so epoxy would be highly recommended. Some epoxies can tolerate a 40 minute working time.

To vacuum bag bigger stuff using polyester, it would be recommended to have a polyester spray system. Spraying allows for a quicker lay of resin, thus giving the added working time needed to get the job bagged.

So , , , you can see how both work quite well, but it really depends on the type of job and how much working time you need to get it done.

Like yourself, I like polyester. Mostly because it's far cheaper than epoxy.
I use it quite extensively for small parts, for big stuff, even though I have a spray system, it's about a 50/50 deal when it gets to the 10 foot size of parts.

Sorry bigshark, , , it's all a bit of a carry over from another thread.

< Message edited by Mike Emilio -- 11/29/2008 2:29:20 AM >

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RE: Getting scale details into fiberglass parts (lost ... - 11/29/2008 6:20:42 AM   
Props4ever


 

Posts: 1743
Joined: 8/3/2005
From: Canada, ON, CANADA
Status: online 		Hey Mike,

Thanks for explaining these elements in such a nice and easy way to understand, i wanted to know answers to these questions too so this thread is great for it.

I always thought that epoxy is the way for making big parts as they would come out stronger but when i got my big Arrow and asked Brad what resin he used, he said poly well it changed my opinion on poly now. The only draw back i knew about poly is that it stinks when mixed and cures after application so i don't like using it as most of the stuff i do is inside. Yet again i see both have advantages and disadvantages also.

I guess it really boils down to what you are working at/with.

Once again Thanks Sir...



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