When a DLG pilot takes up S400 racing...

[SoarNeck]

Hi all,

Just thought I'd share a couple of spy-shots of my newest Calgary 400 racer (min 150sq"). You can see the plug for my pod mold in the background as well, since this racer will be a pod/boom style model.

I incorporated a bunch of changes from the V3 model, and am rather happy with things so far (V3 -> http://www.rcgroups.com/forums/showt...hlight=Calgary)

For those interested in these types of building techniques, I'd advise you to pick up a copy of Phil Barnes' DVD, which was my inspiration to try a carbon/kelvar version:

http://www.paonline.com/hayman/video.htm

[SoarNeck]

The wing is 1.8 oz right now before trimming the flashing, which is a little heavier than an all-glass version (1.6 oz for V3 I think), but much stronger and more durable.

Biggest changes:

-larger carbon LE to reduce aeroelasticity. 2.9 oz uniweb material. Basically, the last wing was a little bendy!
-1.7 oz kevlar skin for durability and live hinges.
-integral vertical grain 1/32" balsa aileron shearwebs, which you can see as a line in front of the carbon aileron reiforcements. Both intended to eliminate flutter issues from previous models.

I've stuck with the transitional 5.9%-5.5% series airfoils that have been so successful in past versions, but have reduced the area from 165sq" to 153sq". For those that are interested, the planform is 5"->3.75" over 17.5" halfspan.

The small carbon rods are a local reiforcement for the aileron servos, which I've moved out into the wing itself. Not as clean as the previous versions with the servos in the fuse, but much more positive since it elimates the nasty torque rods. It also means that my pod can get much slimmer.

[SoarNeck]

It's amazing what lighting can do to these photos...kind of cool.

More updates to follow as I make progress.

[bidule]

Great job and is true is a super Video . I receive my copy and I'm bagging a GLG wing !

[SoarNeck]

Thanks, I'm having fun here! I may not win many races yet, but I enjoy the building process.

Here's the latest shot of my molds. The top one is the racer pod, and the bottom is an enlarged SuperGee DLG pod. The parting board frames are 1/4" balsa with a layer of 14mil mylar c/a'ed to them, with the final gap filling done with clay. Very quick and easy.

I waxed them with a couple of layers of Dolphin Wax (or whatever it's actual name is), and finish with a paranoia-inspired layer of PVA (hence the greenish hue).

I also finished off trimming the wing, and I'm very happy with how the ailerons turned out. By scoring the hinge line like Phil mentioned, the aileron action is freer than with tape hinges...but the hinge is indestructable. The shear web helped immensely as well with torsional stiffness.

[SoarNeck]

Mold making supplies are pretty simple with the CST method. I use West System 105/206 resin/hardener, and use a healthy amount of graphite powder and thixotropic (sp?) agent (cotton fibre, milled glass etc). Mix until the tooling layer is the consistancy of peanut butter, and won't run on a vertical surface.

Tip: if you add all the powder on top of the unmixed resin and hardener before stirring, you will not get any bubbles. Doing so raises the viscosity of the fluid, and the bubbles that are normally produced by the stir stick cavitating ("stalling") in the resin don't actually form. Just make sure to stir the mix well to get an even distribution.

[SoarNeck]

Add a layer of the mix to a depth of about 1mm or so, and make sure to get into all the corners.

[SoarNeck]

After the gelcoat dries to the point where it's sticky but not wet (~1.5 hours at 24C), add strips of cheap fibreglass cloth (4->6 oz) on top of the plug. The strips will tack down to the gelcoat happily, and will conform to the strange corners better than one big piece of cloth.

[SoarNeck]

Overlap the strips by about 1/4" or so, then wet out with resin. You can do 2 or 3 layers at once with epoxy without worry that the heat buildup will warp things.

Make sure to use a popsicle stick or the like to push the cloth into the corners of the plug, but don't be too aggresive...you can thin out the gelcoat with too much pressure.

[SoarNeck]

Next add another layer of cloth, then one of chopped fibreglass matt. This is a loosely bonded collection of fibreglass strands, and is only used to build up thickness in the mold. Cover it with another layer of glass. Let dry to a tacky state.

Add another layer of matt, and a final layer of glass strips.

[SoarNeck]

...and finish with a single full layer of 2 oz glass. This last layer is just to prevent you from getting any slivers of glass in your fingers after the mold is cured. Trust me, the last layer is worth adding!

[SoarNeck]

When that side is fully cured, take it out to the bandsaw and trim off the flashing. You can do it by hand if you want, but we're talking about 1/4" of solid fibreglass!

Add some balsa supports underneath the part so you can work on the other side.

[SoarNeck]

Next, scrape off the plastacine that was used to fill in gaps between the plug and the parting plate. Drill a series of light divots into the mold surface, which will fill with epoxy and form keys to guide the mold halves into alignment.

Wax and PVA the mold, and repeat the above process.

[SoarNeck]

And wa-la..instant mold. Drill some holes to allow the mold halves to be screwed together, and you're done.

Hope this has helped someone.

[SoarNeck]

Hi all,

Just thought I'd finish off this thread. I finished my model tonight after much delay...which is good because I'm looking at having to pack up and move in the next short while.

The finished model came in at 14.1 oz w/8 500AR cells, and I think I can get sub-14 if I shorten some wiring. Conforms to the Calgary 400 rules, and I think this represents the lightest yet strongest model that I've made so far.

Motor is the std 6V Speed 400, controller is a Jeti 14, the wing servos are MX-30's, the elevator servo is a 50HP, and the signal processing duties are handled by a 555.

Not the prettiest model I've ever made, but effective nonethless. The pod is 2 layers of 1.4 oz kevlar with reinforcement, and the boom is from a Photon DLG.