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Old Jun 15, 2011, 10:24 AM
Slopeaholic
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Roseville, California, United States
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What a neat idea! I didn't really notice this thread when you first started it, but I have to say I have been hooked for a while now. Amazing work!

Are you going to set the straw up on some sort of standoff so that it is not right up against the finished mold face? I imagine with a little material around the straw leakage isn't really a concern. The straw is pretty much the non removable mold for the heating water tube if I am guessing your thinking correctly.

-hutch
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Old Jun 15, 2011, 11:32 AM
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Yes, Hutch, you're following....I will put down two layers of surface coat, two layers of very light weave, and also a layer of continuous strand veil cloth before I place the straw conduit into the sandwich....

One of the first places to wear on a multi-piece mould like this, is the edge along which you trim semi-green parts just prior to joining. As a result, it's a very slow and tedious process to try and freehand.

This aluminum insert in the mould face will help to provide a nice durable trimming edge face. Notice the external grooving to aid in bonding with the tool surface coat.

It will also form an overflow channel to give excess resin during joining a place to go.

It might also provide a calibrated groove in which a custom trimming blade jig might ride...

Here's a source link (for future reference, 36" weighed in at 205 g)

http://store.workshopsupply.com/cata...ck-p-2954.html

...and here's the idea...



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Old Jun 15, 2011, 11:39 AM
Just fly it!
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Cody, WY
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Are you concerned about the significant higher coefficient of thermal expansion of the aluminum over the GFRP....especially in mold that will undergo a heat treatment? Steel has a much closer CTE to the GFRP.
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Old Jun 15, 2011, 11:46 AM
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Quote:
Originally Posted by wyowindworks View Post
Are you concerned about the significant higher coefficient of thermal expansion of the aluminum over the GFRP....especially in mold that will undergo a heat treatment? Steel has a much closer CTE to the GFRP.
If it were solid, or an enclosed cross-section, I would not do this, but the nature of the open groove, should handle the situation over the 18" length. (there be only one way to know for sure matey, and fortune favours the brave....)
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Old Jun 15, 2011, 11:55 AM
Just fly it!
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Cody, WY
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Quote:
Originally Posted by Slow & Low View Post
If it were solid, or an enclosed cross-section, I would not do this, but the nature of the open groove, should handle the situation over the 18" length. (there be only one way to know for sure matey, and fortune favours the brave....)
Ahhhh....18" is a pretty short span. You should be good to go.
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Old Jun 18, 2011, 04:39 PM
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OK, first of all - thank you for your patience - I know that this takes forever, and now I've gone and switched things all around on you....

We still have the semi-spherical registration keys - but there are fewer of them. Fewer means less effort in keeping them clean and free from build-up. In an effort to maximize their effect however, they are placed at the extremes of the mould sections.

We still have the 1/4"-20 thread inserts for joining. There are a couple new ones. You can also see that I've countersunk the two on the end faces so that they will not interfere with removing the leading edge section.

The new bits are the extruded aluminum T-slot ways. I've filled them with clay, and then screwed them down to the parting board.

They will provide a nice flat, and wear-resistant face to trim against.

They will also act as an overflow channel during assembly.

But mostly, they give me the option of speeding things up considerably if needed at some time down the road. By vacuum sealing across the flange face and controlling resin flow into each of the nine overflow channels, while drawing vaccum from the underside through the gear bays it will be possible to infuse parts rather quickly.

I left the conduit for the heating circuit on top just for the sake of the picture: of course it will be embedded in the layup.












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Old Jun 21, 2011, 03:56 PM
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These bright white LED's will provide some light in the cavities where the control rods will extend past the trailing edge during final assembly.

(...because I'll be sure to be an old grey man with bad eyes by the time this thing's done!!)


How do you like my scale bullet holes in the wing skins in this first close up shot!?



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Old Jun 21, 2011, 05:22 PM
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Hemet California
Joined Jul 2009
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Hello,

Why not just a simple two piece mold like has been done on wings for years? You could be flying one by now.

Your mold heater idea works well. I saw a guy do one and hooked it to his water heater which recirculated hot water through it. He used plastic hose from the hardware store though.

Looks cool, have fun!

D.E.
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Old Jun 22, 2011, 08:11 PM
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Alright, it's been 8 weeks setting up the first section of the wing mould. But it's good news / good news: I'll be starting the layup this evening / the next sections will be much quicker.

I've added some artwork that will be cast into the end faces of the mould (just for a little fun) and I've also updated the tool ID tag.

Stay tuned, there'll be ongoing pics, and so without further adieu...




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Old Jun 24, 2011, 05:56 AM
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Old Jun 24, 2011, 07:03 AM
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That's the first coat of tool coat applied, with particular attention to over hangs. Generally I mix up about 100 grams and put it into tight corners like where the part meets the parting board first while it still flows like no tomorrow. Once it starts to get a little thicker I move onto vertical walls, overhangs and the like.

I'll let this set up for an hour or two, and then I'll give it a second coat of tooling epoxy. I'm shooting for about 1/16" thick and complete coverage.

Haha - my tool ID tag fell off, but both bulldog tags stayed put - can't win for losing. I'll stick the tool ID tag on later I guess.

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Old Jun 24, 2011, 07:46 AM
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Maybe this will be of use to someone else too.
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Old Jun 24, 2011, 10:03 AM
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2 of 2 coats applied tooling epoxy

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Old Jun 24, 2011, 11:32 AM
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This is very light cloth. Mostly it's scraps of 1/2 and 3/4 oz/^yd
that I've set aside when covering other models in the past. I haven't laid any epoxy on it yet, just put it down on the tacky surface coat.

This is what you won't see a lot of others doing: they should.
I've placed it into all of the tight corners. What you do not want are air bubbles and voids. A heavier cloth will show through the tool coat over time and the surface veil will not stay in the tight corners.

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Old Jun 24, 2011, 12:21 PM
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I've wet out the light cloth ensuring that it's into all the tight spots.

OK - I've now been working for 8hrs straight (can you say morphine) and I'm just about to start putting down surface veil. I hope you can see that this is something for which you need to set aside a couple of very long days and nights. Once you start, you don't want to stop or you'll need to sand the entire thing before continuing. (it never works out...)

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