Monocote over a Plug
11-27-2002, 11:41 PM
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Monocote over a Plug
Hello All
I was wondering if anyone has used Monocote to cover a plug before making a mold. This would be a lot quicker then glassing the plug.
Thanks
Scott Yeo
I was wondering if anyone has used Monocote to cover a plug before making a mold. This would be a lot quicker then glassing the plug.
Thanks
Scott Yeo
11-28-2002, 04:11 AM
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Seams
Dave Platt is the first that I heard of to use the technique of temporarily applying Monokote over certain parts of a plug, in order to make a separate part. I believe (but am not sure) that he also gave the Monokote a coat of PVA.
The example I first saw was with a wing that had gear door outlines in it. He temporarily covered them with Monokote, then did a glass layup over that area, then cut out parts that would become gear doors. Simple, but unless your plug is intended to be almost perfectly smooth, there are certain "issues"...
If there are any seams or other irregularities in your Monokote, they'll show in the molded parts. Monokote will not allow small details, such as panel lines and rivets to show through, if they exist. In fact, it will form a small "tent" over such 3D details. Even if you could get it to cling 100%, you're still adding (in the case of rivet detail) or subtracting (in the case of etched panel lines) the thickness of the Monokote to those details.
Advantages of normally-glassed plugs: (fuselage example)
You can use the details molded into them to produce other "sub molds". First, I make the primary fuselage mold, and thoroughly clean the plugs. Let's say I need a nose gear door, and the outlines are already imprinted in the fuselage plug. I just put a coat of PVA on the area around the door outline, and then do a glass layup right on that area, which then produces a shallow female mold, with the gear door outlines imprinted in it. (I make these molds just as thick and stiff as any other mold.) You can use the same method to reproduce any other detail on your original plug.
That eases tension on the builder later, because they don't have to try and cut a door out of a fuselage (losing some material in the process) and then make it fit again. They just cut out the opening, discarding the pieces, and use the separately-molded door. And, if you think about a typical nose gear door being on the fuselage centerline, then you'd appreciate the fact that the separately-molded door doesn't have a seam and a piece of glass tape running down the center. (from joining the fuselage halves)
Everybody has their own way of doing these things. I'd like to hear more "tips" from those of you with plug and mold making experience. We all benefit.
The example I first saw was with a wing that had gear door outlines in it. He temporarily covered them with Monokote, then did a glass layup over that area, then cut out parts that would become gear doors. Simple, but unless your plug is intended to be almost perfectly smooth, there are certain "issues"...
If there are any seams or other irregularities in your Monokote, they'll show in the molded parts. Monokote will not allow small details, such as panel lines and rivets to show through, if they exist. In fact, it will form a small "tent" over such 3D details. Even if you could get it to cling 100%, you're still adding (in the case of rivet detail) or subtracting (in the case of etched panel lines) the thickness of the Monokote to those details.
Advantages of normally-glassed plugs: (fuselage example)
You can use the details molded into them to produce other "sub molds". First, I make the primary fuselage mold, and thoroughly clean the plugs. Let's say I need a nose gear door, and the outlines are already imprinted in the fuselage plug. I just put a coat of PVA on the area around the door outline, and then do a glass layup right on that area, which then produces a shallow female mold, with the gear door outlines imprinted in it. (I make these molds just as thick and stiff as any other mold.) You can use the same method to reproduce any other detail on your original plug.
That eases tension on the builder later, because they don't have to try and cut a door out of a fuselage (losing some material in the process) and then make it fit again. They just cut out the opening, discarding the pieces, and use the separately-molded door. And, if you think about a typical nose gear door being on the fuselage centerline, then you'd appreciate the fact that the separately-molded door doesn't have a seam and a piece of glass tape running down the center. (from joining the fuselage halves)
Everybody has their own way of doing these things. I'd like to hear more "tips" from those of you with plug and mold making experience. We all benefit.
