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Old Aug 17, 2006, 09:58 PM
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Spinner Plug

With just a few more coats of wax and some PVA I should be ready glass my spinner plug. The basic plan is to give it a coat of polyester resin, let it tack up a bit and then go with the glass layer(s).

My question is, should I use a single piece of light glass for the initial layer, or will it bunch up? And what about the subsequent layers?

Thanks, Pete
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Old Aug 17, 2006, 10:40 PM
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I'm not the most experienced guy but I would go for a coat of gel coat tooling first, avoiding any bubbles then gel coat tooling+ cabosil (or something to make it thicker) and be able to form a thick coat of it and trying to soften the hard angle at the bottom of the plug after that several coats of FG mat (I might even consider to chop it to conform to the angle at the bottom again).
I'm not sure what kind of paint you used on your plug, but just to let you know polyester resin is quite strong, on my first try it went through my PVA and wax and chew on my plug paint and it was all a mess.
Just my $ 0.02
Fernando
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Old Aug 18, 2006, 10:18 AM
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Quote:
Originally Posted by SchiessCo
With just a few more coats of wax and some PVA I should be ready glass my spinner plug. The basic plan is to give it a coat of polyester resin, let it tack up a bit and then go with the glass layer(s).

My question is, should I use a single piece of light glass for the initial layer, or will it bunch up? And what about the subsequent layers?

Thanks, Pete
Pete,

A couple thoughts for you, including some you might want to consider for future projects:

1) For small projects like yours, you might want to consider mass casting techniques. I've been using a filled urethane casting resin with good success -- it is cheap and fast.

2) Surface coat will give the best surface finish. However, there are several homebrew surface coats that work pretty well, e.g., resin mixed with fumed silica and/or powered carbon. I've also tried the method when you intentionally entrain air into the mixture by mixing it with small brush by drill to make the mixture like mayonnaise.

3) You might need/want to use filler around the intersection of the spinner and the base. FG does not like tight radiuses. Whether you need to use filler at the intersection will depend upon the weight, weave, and finish of the FG use.

4) After you have your surface coat on and it has gelled, apply an adhesion coat of resin, and start the lamination with light weight FG (2 oz or less) strips cut on bias. Move to heavier cloth strips cut on bias after everything is covered with light FG. If you are using polyester resin, you have to be careful of heat generation and adhesion between layers. It has been a while since I've worked with polyester, but I would never apply more than about 1/8" of thickness at a time and sprinkled milled FG or cotton flox over the surface for the next layer to attach to...
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Old Aug 18, 2006, 12:56 PM
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One other thing you may (should? MUST?) consider is how are you going to take the part out of the mold!!

I made a spinner mold a few yrs ago and had to hammer the parts out of the mold at the tip and ended up damaging the mold. The spinner that came out was great...

I thought of putting a screw flush to the surface at the tip but never took it further.

P
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Old Aug 18, 2006, 01:16 PM
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Personally I would cut glass strips about 3/4" wide a little longer than the plug and overlap them bit by bit about 3 times.

If it were mine my layup schedule would look something like this.

-brush a batch of straight epoxy resin onto the mold. and let get tacky
-mix a batch of epoxy, graphite powder (not necessary but nice to have) and cabosil. Get that thick enough to not run off the vertical sides and make sure to get a nice fillet at the bottom edges.
-lmmediately lay a layer of .75oz glass over the whole thing cutting in strips again and wet it out.
-lay 3 or 4 layers of 6oz glass over the whole thing.
-Kazaammm!!! you now have a beautiful black mold with a spinner stuck in it!! Be gentle and get that plug out. Wax about 5 times more than you think you need to, use PVA. I would also make sure the mold extends well into the base so you can get something under the lip to get it off. Use compressed air and warm water to help remove it. You should be OK without marring the mold.

Good luck, RJ
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Old Aug 18, 2006, 02:47 PM
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Thanks for all the input guys. There were a number of good ideas that I hadn't thought about (but seem so obvious now).

I was originally going with polyester since I was going to lay it up on a weeknight, and after years of dinging and repairing surfboards, I'm pretty good at getting the resin to kick off fast. But it looks like I'm going to hold off 'til Saturday, so I'll go with epoxy instead. The plug currently sits with about 10 coats of carnuba wax and Part-All, and will definitely get a coat of PVA.

I'll post the results for all to enjoy.

Pete
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Old Aug 18, 2006, 05:02 PM
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PLEASE DO post the results!! With pix if y can!!
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Old Aug 21, 2006, 12:04 AM
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Success! (sorta)

I ended up going with epoxy not polyester, and RJ's basic layup schedule using a graphite/cabosil/epoxy slurry followed by light glass on the bias followed by a number of 6oz. layers. Then left it in in the sun for about 36 hours.

Popped it out tonight with mixed results. The base was pretty easy to loosen and after a few minutes of gently prying and twisting, the bottom quarter of the plug came out . I had laminated pieces of ultralight MDF together to make the plug and when it got wet it started to come apart. So I soaked it for about 20 minutes, popped it against the garage floor and it came right out. There were a couple small areas were the paint from the plug was stuck to the mold, but with a little soaking they came right off. So I definitely learned a couple things about materials selection and plug prep. Most importanly, don't rush these things - take your time and give everything time to dry!

Next up, lay up the spinner - which is not going to be as exciting as it may seem. The spinner is going to be grafted on to the front end of a PSS ship, so lay-up and balance aren't that critical. If this was going to be a real spinner I'd probably trash it and start over, but this is a great lesson. Man there's a lot to learn!!!
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Old Aug 23, 2006, 07:38 PM
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I'll suggest something here.

Take that male spinner plug and put 1-layer of Blue masking tape over it. This will take some time because you'll end up using small strips near the top. Wax this up REAL good. Then build a dam around your flashing area taller then the spinner and cast onto the spinner/tape assembly and fill it to the top. You'll need to use a urethane here. Anyway, open the mold assembly, and remove the blue masking tape. Now you have a male mold to act as a press into your newly cast female mold. The gap between the two has been established by the application of the masking tape.

Do your layup in the female side by applying mold release and let it dry. Brush epoxy into the female mold and start laying your cloth. When satisfied with the layup, pour a little more epoxy in and then insert the male press. Use C-clamps to really crank it down. Excess epoxy will ooze out. Let cure, open the mold by driving wood wedges between the flashing.

That's a free one, the next will cost you

Sean
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Old Aug 23, 2006, 08:41 PM
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Perhaps it's just me, but why would he want a flexible urethane mold for his outer surface when he already has a nice rigid (and smooth) composite one?

The more conventional technique (IMHO) would be to make a silicone (or urethane) rubber male plug to mate with his composite female mold. This is how I've made many similar parts, including motor case parts and spinners.

The trick is still getting the cured part out of the one-piece female mold, but there are tricks that work well. The flexible female tool would be helpful here, but you sacrifice surface finish and tolerance.

-David
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Old Aug 23, 2006, 08:50 PM
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He does not have a female mold yet though. I guess, really, what he needs to do is cast a rigid female mold from the male plug. Then, like you say, make a slicon male mold press.

I don't like flexible male presses though. I prefer the rigid ones that set the part thickness reguardless of the fabric used. Plus, silicon presses leave the cloth pattern raised on the inside of the part.

I guess it's really personal preference and the desired finish results that dictate material usage for cold-press molding.

Sean
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Old Aug 23, 2006, 09:28 PM
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See the picture of the nice, shiny mold he posted in post 8.

Sure, if you have two rigid tools then you can have control over both faces of the part. So long as the two tools are accurately keyed to one another, you can also make the argument that laminate thickness should be a touch more consistent... but thickness control is not exactly bad with a silicone plug.

Since this is a spinner, I don't think a little weave texture on the inner surface would be a problem. It has never seemed to hurt any of the F5B spinners I've made this way.
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Old Aug 23, 2006, 10:36 PM
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Rigid and flexible both have their uses. As dave said, depends on the layup and how much pressure the layers need to form them properly into the mold.

Sporters tip with the masking tape works well, have made one off keels from deep nosecones using this method. Takes time & patience though!

For quick squish mold pluggings, car body filler (aka bondo) works a treat!
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Old Aug 23, 2006, 11:21 PM
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Sorry Dave,

I missed the description of the picture in Post #8.

Anyway...

Sean
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