MTK

Randy,

Nice work. Your weights are in line with what the experienced guys build. Unless your finishing goes haywire, you will make weight easily. A rule of thumb on weight loading is about 16 ozs per 100 sq inches....1000 sq inches should be around 10 lbs for better flying

MattK

ROOKIE PILOT

Ryan
I think you need to start building a plane, You never know how a plan is going to turn out unless you try. Patience goes a long way in building a plane if you don't have any it won't be easy. I have been into R/C about four years total. I have built four sport planes, two from kits and two from plans. This is my first build from scratch. This is also my first time making molds and composite parts. I've done a little fiberglass work on race cars in the past but nothing like this.

ROOKIE PILOT

Thanks Matt
I was hoping someone would tell me how my weights were doing. I thought I was doing ok but on your first build it's kind of hard to tell. I own a paint & body shop so I'll use every trick that I know to make it look good and stay light.

MTK

Bryan is about the best around on finishing planes. I am sure you are talking with him. It isn't difficult to keep them light...just a lot of elbow grease and good eyesight

mattK

kochj

When you make the pieces out of fiberglass, you are using the Inside of the mold and not the out side right??

Or are you just draping the fiberglass pieces over the Green/cleared plugs and having the outside of the plug not have the
Weave filled by the plug, so you have to do that yourself.

If you use the inside of a mold the outside is nice, shiny, precious.... LOL...

Could you just fill me in....
Thanks
..

ROOKIE PILOT

Kochj
I'm using the green plugs to make a female mold. it is this mold that I use to make the final part. I'll try to get some photos of the molds posted today. Randy

MTK

Kochj,

You will find a nice tutorial on CST The Composite store web site on producing female molds (clam shell molds too). There are many other sources for sure but I found this one especially helpful at least 15 years ago when I started playing with molds. Their technique of laying up the first layer of the mold with carbon black has been particularly helpful...it becomes the mold surface agianst which the glass part is laid down. With a clear glass part it's easy to see unwetted areas in the glass. It doesn't help for carbon cloth lay ups but for glass lay ups it's very helpful.

BTW the better wax I've used and highly recommend is Partz All. There are several others but this one works easily and with fewer coats and is high temp rated

MattK

dreadnaut

My Feedback: (5)

The tutorial from CST was also my starting point. One of the things that I have been told about the carbon additive, and my experience backs it up, is that it helps lower the friction coefficient of the surface. This helps a little in pulling the parts from the mold. I was also told that Turtle Wax and Kit Wax are adequate mold release waxes. One ruined mold later, it was back to Partall. I used the Kit Wax on my car.

Jetdesign

My Feedback: (8)

Rookie, what is the time frame you've been working on this project?

ROOKIE PILOT

Joe
I started construction right after the first of the year. The wings are ready to sheet so I should be able to do that in the next few nights. I'm still working on the chin cowl mold, when that's done I'm ready to start a lot of sanding and glassing.

ROOKIE PILOT

A few photos of the chin cowl plug and the nose and canopy molds.

cdodom

I'm digging that green on the plug.

pitstop000

My Feedback: (26)

Very nice work Randy, What are you using for the finish on the plug?

ROOKIE PILOT

Paul, It's just Dupont single stage urethane.

kochj

Could you point me twards that website please??...

I had saw others using that carbon stuff, I couldnt' understand why, now I know!!

I saw one guy use expanding foam laid on top of the fiberglass.....

How do you apply gelcoat??
ever used that ?
Is it applied "in the mold"?
or is it done after it is finished?

ROOKIE PILOT

kochj
The tutorial is on the cstsales.com website. I think their site has a problem because I have trouble getting to it also. I didn't use gelcoat on my mold or the final parts. Actually I have never used gelcoat at all.

doxilia

My Feedback: (3)

Randy,

As a learning experience, I'd like to make a small glass cowl starting from a plastic one. The plastic one comes in two halves. Would it be preferable to join the plastic cowl halves, fill it (with expanding foam?), finish it as needed (plaster and then paint?), wax it and then produce the female mold or is it better to make a mold from a single half, produce two glass halves and then glue them together?

Also, in post 20 you show the first step in producing the female mold by pouring what I imagine is an epoxy based liquid over the male plug. What is in that black mix? Milled CF and West Systems? How should this compound be made? Much like epoxy and glass fibers?

Finally, is the same wax used on the female mold as on the male plug? Does the glass layup require a vacuum or do you just lay down the glass cloth and wet it out in each half?

I hope you don't mind the 20 questions but since you're in the midst of it, I thought you might be able to help a fellow modeler.

Many thanks in advance, David.

ROOKIE PILOT

David
This is my first atempt at making composite parts and they seemed to come out great, but I may not have the experience to answer your question correctly. Maybe someone with more experience will join in. In my opinion you need to support the plastic in a way to keep the heat of the resin from altering its shape. I also think I would attach the two halves to make the complete cowl then make a two piece mold.
The black mix that you are referring to in post 20 is West Systems resin and graphite powder mixed to a thick creamy consistency. It is spread over the plug about an eighth of an inch thick or so. It dries to a hard very slick surface which makes it easier for the mold to release. And yes I use the same wax on the plug and the mold. I also sprayed a coat of PVA release agent on both the plug and mold. I didn't have any problem at all with the parts releasing. I also didn't use any type of vacuum device. I hope I have helped you a little at least and good luck with your project.

Randy

doxilia

My Feedback: (3)

Randy,

they sure did - they look beautiful! Your reply has been most helpful.

I think it's a matter of gathering all the necessary products and giving it a shot. Since you didn't use a vacuum on the glass layup, I assume you're building them up with rather thin glass - maybe 2 oz cloth or thinner? Did you use a uniform 3-4 layers or more glass in key areas? Also, did you consider using CF in the actual layup or is this just expensive and unnecessary?

I hope you won't mind me posting a couple of photos of the cowl in question (I can always remove them). I'll join the two halves, fill the seam smooth and then fill the cowl with expanding foam so it becomes a solid non flexible piece. I'll have to figure out a way to deal with the heat issue so it doesn't melt. Maybe I need to make a foam plug like you did and use plaster.

If anyone else has any suggestions, they'd be most appreciated.

Thanks again, David.

ROOKIE PILOT

David
the cloth that I used was 3.1 oz. and I used 3 layers. Your cowl is smaller so you would probably be fine with two layers. I thought about using CF but I think it's a little more difficult to work with but I will give it a try soon. Randy

dreadnaut

My Feedback: (5)

My first mold was pulled from an ABS cowl from a Goldberg Ultimate. I made a couple of plywood formers to hold the shape, filled the seam, scuffed and painted it. It came out fine. Lay up a couple layers of 3 oz cloth, then let it set until dry to the touch. Repeat until you have the thickness you need. This should eliminate the overheating problem. You just need to make sure that you do not let it fully cure between layups. I have found that I can layup West System 1/16" thick without it getting too hot. 1/8" seems to be the "Critical mass".

doxilia

My Feedback: (3)

Gents,

thanks for the replies.

I don't have 3 oz cloth but have 2 oz. Any reason I couldn't use 3 layers of that for a "6 oz" cowl laminate?

Dave,

that's the approach I initially thought of but I don't follow how it can produce a mold. It strikes me as though it results in the actual cowl if I layup the glass atop the painted ABS part. Am I missing something?

If I opt out of the mold and just make the glass part per above, is there any reason not to use Z-poxy finishing/laminating resin rather than West Systems? I have the former, but would have to buy the WS.

Lastly, this is a cowl for a 30 size plane (50" span). If I layup 2 layers of 2 oz cloth, let it set overnight, can I come back and add a third the following day if necessary? Will it bond?

David.

dreadnaut

My Feedback: (5)

I left out some steps, like the parting board. I used the ABS cowl to make a plug as described, then layed up the mold over it. I did it a little at a time. If you lay up too thick with West System, it gets hot. The first layer to go against the plug (will become surface of female mold) should be the lightest you can find, like 1/2 oz. This prevents getting a weave pattern in the mold. then lay it up with 3 oz until tou get to about 1/32-1/16" thick. Let this set until it is just dry to the touch, but not fully cured, then lay up another layer, using heavier cloth to build up faster. I use lighter cloth on the inner layups because it conforms to corners, like the parting board, better.

I like Z-Poxy, but is is not good for mold making. It is not as stiff after it cures as WS. I use it to glass my plugs because it is pretty sand able.

dreadnaut

My Feedback: (5)

Rookie,

What kind of painting set up do you use? I have ordered some Nelson Hobby Paint because I need to keep the wife happy, and spraying Urethane Auto Paint in the garage I share with the washer/drier is not an option. I would hate to have to take it to an Auto Body shop to have them do it for me ($$$). Do you know if the Nelson stuff is good for painting plugs? (I will use their clear coat, but have heard something that makes me think it may be stinky.)

ROOKIE PILOT

Dave
I guess I have an unfair advantage in the paint department because I own a auto body shop. So I know nothing about any of the hobby paints. If you used automotive paint it can be sprayed outdoors on a nice day. I sanded my plugs with fine sand paper and polished them to a very smooth finish, so if you got a little dust in the paint it would be removed in this step. I wouldn't attempt to paint an entire plane outdoors but just a plug should be fine.
Randy