JKEpps

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Hello all,

I've been lurking here for quite a while in awe of the wonderful work and knowledge exchanged here. I'm a traditional kit and ARF builder/assembler, but for quite a while, I've wanted to try my hand at composites. I'd like to start trying stuff in the near future, but I do have a few questions.

[ul][*] What would be a good plug candidate to practice creating a mold and doing manual layups with?[*] What role does a oven/heated enclosure play in laying up composites? Does it benefit fiberglass, Kevlar, carbon, etc ... [*] What safety gear should be used when working with composites, e.g. dust masks/respirators, latex/nirtile/poly gloves, blowers/filters etc ...
[/ul]

Thanks in advance,

Jorden

Ed Smith

Start with wheelpants. they are fairly small and the dollar investment is low. After that move on to simple cowlings and then more complex cowlings. If you have success with tose items than you are ready for fuselages. Make a fuselage plug from a popular kit. You might be able to sell some and recupe your loses to date.

I never use heat. All my work is done in my house and is a room temperature cure.

The foregoing is a generalisation and subject to many other suggestions.

The one thing I advocate and will not argue about is always use high quality epoxy resin and never use polyester.

The picture shows the progression, Wheel p[ants, cowlings, fuselage sides.

The other picture shows the finished wheelpants.

Good Luck.

Ed S

JKEpps

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Thanks Ed,

I was puzzling over what to try first, be it a hobby related item or not. I was eyeing my recycling bin in the house for a good candidate. I have a set of wheel pants for my 1/4 scale Skymaster. They are large, but maybe that's what I need to help me get some good practice. I even thought of using a Dubro fuel tank as a victim, errr I mean candidiate.

By the way, here's what I picked up over the weekend from a local West Marine dealer. I couldn't find "Tooling Resin" only their "105, General Purpose Resin". I picked up some gel coat too. If I remember correctly from past posts, the gel coat is for use when doing the layups for a finished product. It is not for use when making the mold, as a type of Tooling Resin. Is that correct?

Thanks in advance,

-Jorden

Dangit! Forgot the PVA! Hopefully the local auto parts store will have some, as the West Marine is a 40 minute round trip. Although, I have read some good things about using hair spray instead of PVA. Any thoughts?

Atlanta 60

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I have never used that West Systems "Gelcoat" you have in your photo but it appears to be a polyester product...I would not use that with Epoxy...

Typically with epoxy you want to use an epoxy "Surface Coat"...

Have Fun...

Chuck

TeamSeacats

You are going to have an easier time finding all the things you need at online suppliers...the drawback being the wait time for shipment...but the prices and availability will be much easier.

The West System Epoxy is what I use for making parts - but the extra strength is not really needed for a mold and is considerably more expensive than a polyester tooling resin. Second the nomination for the gelcoat - it's not recommended to use with epoxy resins.

You can use a standard gelcoat but a "tooling" gel coat is designed for making molds (tools). Then use a laminating polyester resin to build up the structure around the gelcoated plug. Chances are that the gel coat you purchased at West Marine has a wax additive to allow it to cure in open air (the wax floats to the surface and seals the gel coat off). Gel coat will not cure when in contact with air (which is fixed when you are making a mold by constructing the resin and fiberglass around the gel coated plug sealing off the gelcoat and making a great bond). To be sure, check the can of that gel coat to see if it is "air inhibited" - if it is, then it does NOT have the wax. if it has wax, it could affect the result of your mold surface.

http://www.shopmaninc.com/index.html

http://www.fiberglasssupply.com/

http://www.fibreglast.com/

http://www.aircraftspruce.com/

Atlanta 60

My Feedback: (18)

Seacats...What is your experience with heat while using polyester for tooling purposes?? I've always used epoxy...But polyester looks like it's about 1/3 the cost of epoxy which would be nice...I've also worried about stability and shrinkage over time...

"Way back when" I was a toolbuilder for a living...The thought of polyester tooling was laughable...But then again...Companies like Lockheed, Boeing, Sikorsky and McDonnell Douglas were paying for the stuff...A phrase often heard "Polyester is for Pools"...

Now that I'm footing the bill...Using Polyester doesn't seem quite as laughable as it once was...And I like pools...

I've been forking out the cash for Epoxy cause I'm still skerred...But if all you guys are using polyester with success...Maybe I should re-evaluate??

After All...This ain't the Space Shuttle!!

Thanks...

Chuck

P.S. My latest little project...A Classic Pattern Aircraft called the Atlanta...Getting ready to "bondo in" the split line:

Ed Smith

In my early days of glass work I used polyester because of the cost. I am prepared to accept that in those days some/most of what I did was questionable. I was still learning.

Two of my early polyester molds twisted after a few weeks of sitting. I found out that polyester does have a tendency to shrink and in my case twist as it cures. I have never had that problem with epoxy resin molds or parts. I have never used polyester since then.

Ed S

TeamSeacats

I'm probably not the authority on this poly vs. epoxy but I do know of several very large scale poly molds in use for real boats today. I have not had any twisting or shrinking problems with my hull molds - I used a good quality poly tooling resin. I reverted to a box store brand resin when making a rudder mold recently and it twisted badly...so perhaps the resin quality has a lot to do with it.

JKEpps

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Chuck you are dead on. It is polyester resin based. Don't know why I didn't look at that before I bought it. That's a main reason why I post here!

-Jorden

JKEpps

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True, I agree with you. I'm sure I will use an online supplier, but I'm an instant gratification kind of person, so I decided to just jump right in and pick up what I could locally.

That's good to know. I've since seen your other post that say polyester resin based moulds "could" shrink or twist, but probably not if a high quality polyester resin is used. Are Bondo or Evercoat brand resins considered a "High Quality" resin?

Thanks for the links!

-Jorden

JKEpps

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Ed here is the wheel pant I have for my first try. It is kinda large at about 10 1/2 inches long, and 3 inches wide, but I think it'll do. I've seen posts where guys have had success with using Carnauba wax for waxing the plug. I have Meguiar's brand of wax and will probably use that unless someone knows why I shouldn't. Don't be bashful, please let me know if you think it's a mistake.

-Jorden

Oh, forgot to ask, what's the best way to block off the opening for the wheel so that I can begin making the mould?

Thanks again.

TeamSeacats

The resins that you get in a home center or automotive store (Bondo et all) are not high quality laminating resins. They're adequate for some small repair jobs but that's about it. I have used this in a pinch before to try and build some small molds but had very bad results (lots of deformation and twisting). I have had great and very stable results with the "404 tooling resin" found here: http://www.shopmaninc.com/polyesters.html. At $32 a gallon, it's comparable (or even cheaper) than what you can buy locally.

As far as the release wax goes, I am not inclined to think that a liquid wax will do the job adequately. I'm really not affiliated with these guys in any way, just a happy consumer...but here's a great list of release waxes: I use the Partall film and paste wax with great results. The film is an additional time consuming step (and an opportunity for dust to contaminate the part surface) but I have not gained the confidence yet in the release waxes and am nervous about destroying my tooling. http://www.shopmaninc.com/moldrelease.html

As far as filling the opening, several options. Clear packaging tape will work just fine if you are careful in the application, but the edge of the tape will show on the outside or have to be cleaned off. Another option is to fill the wheel pant with plaster or foam, shape the opening and fiberglass or bondo. Personally, I would probably go the plaster route and use bondo and finish off the plug opening with some paint.

Second thought, you could also fill the opening with modeling clay...won't necessarily be a "perfect" surface but should be good enough for sealing it up.

Ed Smith

I would not bother to seal the hole. I would just stick some masking tape inside trhe pant around the edge. When applying the gelcoat go up to the tape. The hole will be cut out anyway.


Do not take chances with mold release wax. I use only wax that is specifically meant for mold releasing. I will not take a chance with any other product.


Ed S

Atlanta 60

My Feedback: (18)

Another little idea you could consider for filling the hole...Scrap balsa sheet to fit the opening...Tack with CA as required...Fill and finish with bondo or whatever material you choose:

TeamSeacats

Ed, what kind of mold release wax do you use?

Ed Smith

Jake,

I use "Formula Five" mold release wax. It is a US product made by Rexco. A 1 pound tub lasts a long time.

www.rexco-usa.com


Ed S

JKEpps

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Ed, I'm having trouble visualizing what you mean. Do you mean that I should run a strip of tape from the inside, but not completely covering the hole? If so, does that mean when I use the parting board, I'll still have an opening in the pant? So I'll apply the gel coat (or tooling resin I assume) up to and incuding the tape. Then when I apply my glass cloth, it will "bridge" the opening? Sorry for the dumbfounded questions.

Ed,
Do you use PVA too, or just the mold release wax?

Also, I see that West Marine carries Evercoat (Polyester) and Shurhold PVA. Are they OK to use, or should I just go with one from an online source?

Thanks again.

-Jorden

Ed Smith

I do not use PVA on the plug I just cannot seem to maintain the high gloss finish for the mold. I use PVA for the first layup in the mold. I can always fix the finish on the first part.

As I said before I never use Polyester. I use only epoxy resin. PVA and quality release waxes are not affected by different resins. So far for me anyway.

The picture shows what I meant for the wheel hole. Just a small part is shown I think you will get the idea. The parting board can bridge the hole. It just saves having to fill the hole. If the hole is filled that surface has to be decent to allow a good release.

Ed S

P.S. Keep asking questions. You will save yourself a lot of heartache.

SCALECRAFT

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Hi All

All good advise and tips here.

THE question of applying heat to the layup. We used this method in the early 90's to speed up or production once the layup was done . We had a hot box, walk in closet type thing, set to around 90F. Also heat can be used to post cure a part. 140F for around 2 hours can yield up to 15% more stiffnes in the part. use caution to avoid deformation of the part, or put it back in the mold. Post curing can be done anytime after part has cured under normal ambient temp.

One thing to note, cooler temps make the excess resin in the weave harder remove due to it being thicker, thereby yielding a heavier part. All our parts and molds are made from West Sys. Some molds are 16 years old and still perfect, even the large composite one piece wing molds.

Steve

JKEpps

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Steve,

Thanks for the info. That was exactly what I was looking for. I think I'll build a hot box in the future to give post post curing a try.

Thanks again,

-Jorden

JKEpps

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Ed,

Thanks for the photo, but sorry I'm having a brain fart and still can't figure out how the parting board goes. Here's what I decided to do. I put clear packing tape over the wheel opening. I then cut out my first ever parting board and added some wood to build a box-like structure. I use some plywood, but realized after I cut it, that using it was a mistake. It would not give me a nice smooth surface without a fair amount of work to close the grain and make it nice and smooth. So I cut out my second one from white laminated shelf board. Melamine I believe it's called. I then epoxied some pink foam to support the pant. My Dremel mighty-mite made short of the foam. As it turns out it workes a little too good. I needed to build up some more supprt, but some tape and thin balsa had me back to where I needed to be. I think I found a local source for Formula Five, and if so, I'll pick up some this weekend. Until then, looks like I'm on hold.

-Jorden

Ed Smith

Jordan,

You are making a career out of it. All the parting board has to be is a flat surface around the centre of the plug. It is used only for the first mold half and then discarded. Support for the plug is not needed. The board must be a tight fit on the plug with no gaps. If there are any unfilled gaps around the seam the gelcoat will leak through and the result will be one miserable joint line.
So fit the parting board to the plug. Then tape the half hole above the board in the manner I show. There will now be an "Edge" all around the plug for the gelcoat to stop at.

The method I advocate takes about fifteen seconds.


Ed S

Atlanta 60

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Fifteen Seconds!! Wow...That is Fast!!

Ed Smith

That is just to stick the tape around the wheel hole. The parting board is extra.

Ed S

JKEpps

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Ed,

I assumed that the parting board also should have a smooth surface suitable for waxing/PVA since it will be removed from the first mold half. Is that not correct? The plywood surface was very course and I didn't think it would wax up too well. I would have to fill in the grain to get it smooth enough to wax well without all of the ridges. Although, the ridges could act as a way to lock in the second half of the mold. Hmmmm.

-Jorden