Electric Orange - Gee Bee D " Park Racer" - Page 3 - RC Groups
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Oct 25, 2004, 11:20 PM
On patrol.
Cary Reeves's Avatar
Photo 6: Fuse outside
Photo 7: Fuse inside
Photo 8: Close up of forward section from underneath
Photo 9: Fire wall closeup
Photo 10: Battery hatch/cockpit floor with formers attached

Scott:

1) I wasn't exactly sure how the hatch/cockpit assembly went together. Did I get it right? Do you hold it on with tape?

2)The hole for the control rods is below the RC shelf so I assume you mount your servos upside down and access is by taking the wing off?
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Oct 25, 2004, 11:23 PM
On patrol.
Cary Reeves's Avatar
Photo 11: Battery hatch/cockpit complete
Photo 12: Battery hatch/cockpit bottom view
Photo 13: PU glue reinforcement bottom of fuse. Note servo cutouts (big) and battery strap slots (small).
Photo 14: " " top of fuse


I decided to give PU glue a try since Vyceroy and others seem to use it alot. I'm using the technique I picked up from other build threads.
Oct 25, 2004, 11:28 PM
On patrol.
Cary Reeves's Avatar
BTW, as most of you already know, Scott's designs are very clever. They go together like a 3D puzzle and are almost as much fun to build as they are to fly.
Oct 25, 2004, 11:35 PM
On patrol.
Cary Reeves's Avatar
Scott:

I didn't find the triangular deck piece for the bottom rear of the fuse in my plans. It is easy enough to cut one, but, unless I'm mistaken, you need to add one to the plan.

How much dihedral in the wing?

What are the aileron dimensions?

Did you use torque rods or just a control wire straight to a horn on each aileron?

One wing servo or two?

CG location?

You mentioned that for speed you recommend more downthrust and less incidence. I'll build it to plan first, but I assume that decreasing incidence is merely a matter of shimming the front of the wing down by putting a spacer at the front of the wing saddle between the wing and fuse? How much of a change in the angle would you think necessary to give a noticeable difference?

A picture of your wing assembly would be helpful. If all this is coming with the UC detail, I'll wait patiently .
Last edited by Cary Reeves; Oct 25, 2004 at 11:40 PM.
Oct 25, 2004, 11:36 PM
On patrol.
Cary Reeves's Avatar
Good night.
Oct 25, 2004, 11:39 PM
Registered User
WDuck's Avatar
Cary, Are you using a Carbon Fiber rod for a motor stick? If it is, what size?

*Edit*

Saw it was an Arrow shaft on Page two...
Last edited by WDuck; Oct 25, 2004 at 11:41 PM.
Oct 25, 2004, 11:45 PM
On patrol.
Cary Reeves's Avatar
WDuck: I would normally use a std 10mm motor stick. I am trying a .280 arrow shaft in this build and I will drill out and hot glue a ~1" piece of motor stick over the arrow shaft so that I can make several motor sticks to try different angles.
Oct 26, 2004, 12:30 AM
I crash, therefore I FLY!
mad mike's Avatar
I see you have discovered just how much the PU glues expand!

I think the key to Vyceroy's method of using it is that he first "spot welds" the joints with just a little foam-safe CA. Once the structure has been established that way, he goes back in with the Probond.

I've tried mixing a little water with the PU glue (Elmer's Probond,) and then paiting it on with a cheap brush. I've never been happy with that method as it is messy and I've never been quite conviced the joint was as strong as it could be.

Now, I'm careful when I puncture the tip of the applicator so that I get the smallest hole in it that will allow the glue to pass thru. I apply the glue in as *thin* a layer as possible, sometimes going back over the bead of glue with the edge of a stick of plastic or wood, to remove any excess.

Then I use a small brush to wet the other side of the joint with some water and press the parts together. Usually, I use tape to hold the parts in place. It doesn't hurt to run that brush with water over the joint again, just to make sure it gets wet.

Any glue that expands out of the joint on to a surface that will be seen should be wiped clean with a damp cloth. Once this stuff dries, it is sandable, but it doesn't sand as easily as the foam, so it is all too easy to remove foam when trying to remove the excess glue.

I really wish JK Aerotech hadn't discontinued selling their Jungle Milk glue. Its a rather thin contact cement, probably a caisen (sp?) based glue. I painted the edges of the internal structure of the Cub with it, then painted all the parts of the fuse sides and bottom where it contacted the frame.

As soon as I completed that, I simply pressed the fuse bottom in place, then the sides, stoping at the rear of the internal frame work. Then I was careful to bring the two fuse sides in together, to attach them to the fuse bottom, working my way from front, back to the tail. I did that to avoid having the last half of the fuse to bend to one side, as it did when I built the Frog.

But that was all it took! with a completed internal structure, it only took about 5 minutes to complete the fuse, with the exception of the turtle deck. I left that off to make it easy to install the control rods.

The Jungle Milk gives a very strong bond that doesn't dry brittle. And it is very light-weight. You just paint both surfaces with it and let it sit for about 5 minutes. You can wait longer, maybe 15 minutes or more, but bonding after 5 minutes gives you plenty of holding power so you don't have to clamp or tape the parts together, but you can still make some adjustments if it isn't quite right. Waiting 15 minutes and it bonds instantly, with little change of making any corrections.

Ever have a tape hinge pull free in flight? I found that painting the area that the tape sticks to with the Jungle Milk and letting it completely dry before laying the tape down prevents that from happening.

For me, the Jungle Milk was the perfect glue for foam. It's the only glue I used on the Frog, including those wing section joints. I did some dreadful th ings to that poor Frog, but none of the glue joints have failed.

I've done some looking around and think I've found something just as good. I'm waiting for email to let me know if it is available in pint bottles or just in gallon jugs. A pint would do at least 5 or 6 models. That goes for under $8 US. The gallon is about $36 and that's just a bit more than I'd want to spend to find out if it is as good as its supposed to be.

The web site I found it on, an art supply shop in California, says it's only available in gallon jugs in the product description. But then they give two item numbers and prices, one for a gallon, one for a pint.

If it is available by the pint, I'll get some and try it out. If it is as good as I hope, I'll post a link to the web site along with the item number.

Mike S.
Oct 26, 2004, 06:01 AM
Electric Orange
scotta's Avatar
Cary,

Dam your fast. Yep, now that I remember I even had to cut a fuse bottom on the run as I did not do a template. As you said it's a simple triangle but I will do a drawing, will have to be tomorrow though.

Have you checked the battery hatch onto the fuse? If it sits Ok it is probably correct. From memory I had the formers on top of the Hatch floor but I did stuff around a bit to get it to site properly. Sanding the mating surface a bit.

You can read me to well. The battery is again secured by velcro straps - thanks PaulC I will use that one forever.

Now, the wing. I do not have the remains of the Racer (RIP after mid air with Cub) here with me (still at my workshop at the farm) but I think the ailerons were 30mm deep. Torque rods and a single servo. The wing is still intact so I will take some pics of the wing an UC so that you can see how I built the prototype and also show the weakness in the UC.

When you go to put the tail surfaces in you will need to trim the inner sides of the fuse where the vertical stab goes in. That way it will all sit together nicely.

Thanks Cary, I think you are doing the construction pics for this build ;-).

Scott
Oct 26, 2004, 06:08 AM
Electric Orange
scotta's Avatar
Cary,

Sorry there were to many questions in your posts - CoG is again 25 - 30% of the cord. The further aft the more lively whe will handle.

On the Park Ugly Stick I have tried the combination of down thrust and wing incidence that I want to use on the Racer. Down Thrust of 3 degrees and incidence of 1 degree. The Racer currently has down thust of 2 degrees and incidence of 2 degrees. The Ugly Stick does not have the nose up tendency and just gets faster with throttle - the way I wanted the Racer. So if you would like, especially with your carbon tube you could add a little more down thrust and shim the LE of the wing down a small amount.

This will all depend on your preference or whether you feel the need for speed - well park speed anyway..

Scott
Last edited by scotta; Oct 26, 2004 at 06:11 AM.
Oct 26, 2004, 07:59 AM
Opus
mhmitchell's Avatar
On joints that would be seen on the model I aply a thin layer of probond then use plastic mailing tape to seel the joint so it doesnt expand much in that direction. I use a spray bottle to mist all joints from the inside.
I use a sure form tool (Stanley) to remove expanded glue on the outside. I have never had a problem with tearing the foam. After the surefoam I sand untill the glue appears as a thin line in the joint.
Oct 26, 2004, 10:09 AM
Registered User
Peteohms's Avatar
Quote:
Originally Posted by Cary Reeves
.....Take the pizza cutter to the fuse inside to soften it up. Roll it w/o cutting it. Mash and roll it with your fingers to get the fuse bent to shape.....
I use a screen installation tool which won't cut the foam. It's like a pizza cutter but has a round edge instead of a sharp edge.
Oct 26, 2004, 10:17 AM
Opus
mhmitchell's Avatar
Bic pen work well too for scoring foam.
Oct 26, 2004, 10:29 AM
On patrol.
Cary Reeves's Avatar
Scott: Thanks for the info. How much dihedral on the racer?
The battery cover seems to fit fine the way I built it. This is probably a good application for small magnets to hold it on. I didn't notice the seam in your pictures so I thought you might have taped it.

Mike/mhmitchell: I used the "mix with a little water and brush it on the joints" technique. I believe all the foaming will be out of sight. I've not heard of the Jungle Milk glue. For tape hinges, I have sprayed glue on before putting down the tape. I have used actual pinned hinges, tape hinges, hinges cut from a tyvek envelope, and hinges cut from floppy disc media and none have ever failed in any way. My favorite is tape.

Pete: The screen tool is good. Mine has two ends, one is round and one is sharp, make sure you use the right end; don't ask . I was working in the house last night so I just grabbed the pizza cutter.

I am also planning to paint this one and not use any tape on the fuse to save weight.
Last edited by Cary Reeves; Oct 26, 2004 at 10:57 AM.
Oct 26, 2004, 11:30 AM
I crash, therefore I FLY!
mad mike's Avatar
When using tape hinges, do you have any problem getting water based acrylic paints to stick to it?

Mike S.


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