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Jul 27, 2008, 06:08 PM
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Mr._Mulligan

Keep up the pics, they are appreciated.

Richard
Last edited by The Tellurian; Jul 27, 2008 at 06:17 PM.
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Jul 28, 2008, 01:17 AM
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Okay, the wing panels are ready for shaping. Probably will start with a razor plane to get close, then switch to 80 grit, then to 200.
Jul 28, 2008, 10:08 AM
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Frans Bal's Avatar
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Just came back for the DM in Salmdorf, so i didn't follow the thread for a few days.
Great to see the progression you are all are making, keep it up.
I am very interested in you findings.

Frans
Last edited by Frans Bal; Jul 28, 2008 at 12:51 PM.
Jul 28, 2008, 01:40 PM
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Frans Bal's Avatar
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Quote:
and the boom length on mine came out at exactly 20 inches
Hi Nightowl,

I measured the length of the boom on the DWG (autocad) plan and it's 510 mm long.
20 inches (508 mm) will do nicely.
The Skyshark boom has imperial measurements. Diameter will be 1/4" (6.35 mm) i think.


Mr._Mulligan,

Quote:
Cutting these thick chunks of balsa got me thinking. If I can't get really light balsa, perhaps I can glue up some heavier balsa sheet, and leave a couple channels down the middle. With a single spar in the middle, I should be able to have two trapezoidal channels to the fore and aft of the spar, and get significant weight savings. I see two main benefits:

1. I can use thinner sheets, which are cheaper.
2. I can use heavier sheets, which are not only cheaper, but they are more readily available.

I need to try this out with the next project.
Sounds interesting. Strong but light balsa is indeed hard to find.
Once a friend searched through a shipment that just had come in at a hobbystore and out of 250 sheets of 12 mm balsa he found 10 that where lighter than 110 gram (10 x 100 x 1000 mm).

I don't think you will get a big weight saving. You have to glue the sheets and glue has weight.
My wing was to heavy to my liking so i made those blind holes. It saved 10 grams. Great you will think, but no, i was all used up by covering the wing with oracover light.

Made some sketches.
Is the first sketch what you have in mind?







Frans
Jul 28, 2008, 01:53 PM
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Mike Payne's Avatar
Hello Frans
Thanks for sending me your plans, how have you finished the wings and tail surfaces? Are they just plain balsa, I saw that you mentioned that you used Oracover for at least one of them.

Mike
Jul 28, 2008, 02:06 PM
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Frans Bal's Avatar
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Hi Mike,

Yes on the wing i used transparant oracover light.
Any other good covering material will do, but it has to be light.
It's also possible to use a thin layer of filler dope.

On the tale surfaces i used a thin layer of filler dope.
Just apply it with a rag and rub it in. Two of those thin layers will do the job.

A disadvantage of a thin layer of filler dope is that it will protect against picking up durt but it won't make it 100% water proof. Water (rain) will warp your tail surfaces.

Frans
Jul 28, 2008, 03:05 PM
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Quote:
Originally Posted by Frans Bal
Yes, this is pretty close to what I was thinking of. You are right that glue has weight as well. I've found that acetone glues like Ambroid or Duco can be very light, due to their high volatile content. However, to your point, there is a lot of surface area being covered by glue.

Here is a crude sketch of my idea.

Jul 28, 2008, 03:17 PM
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Quote:
Originally Posted by Frans Bal
I think this is the construction shown on Dr. Drela's wood Apogee:

http://www.charlesriverrc.org/articl...gee40_wood.pdf
Jul 28, 2008, 03:24 PM
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Frans Bal's Avatar
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Quote:
've found that acetone glues like Ambroid or Duco can be very light,
Never heard of those brands, but you probebly never heard of Bison Tix or pattex contact.

Are those glues appied on both sides, left to dry for a bit and then firmly pressed together? Contact cement?
If that's the case they are a pain to sand.

But than again if you don't try, you will never know!!!

Frans
Jul 28, 2008, 03:52 PM
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Quote:
Originally Posted by Frans Bal
Never heard of those brands, but you probebly never heard of Bison Tix or pattex contact.

Are those glues appied on both sides, left to dry for a bit and then firmly pressed together? Contact cement?
If that's the case they are a pain to sand.

But than again if you don't try, you will never know!!!

Frans
What you mention are contact cements, and yes they are a pain to sand. Ambroid is a "classic" model airplane cement. It has the stigma of being associated with "glue sniffing" for a high, but it is a very light glue, because it has very little solids. It also sands well. Joints are weak, unless you double glue. You apply a coat to the both sides, and allow to dry. Then, you apply a small amount and assemble the parts. The glue grabs very quickly, but you can still make adjustments.

Duco is a another brand sold as a craft glue. It dries clear, rather than amber color of Ambroid. It is used the same way as Ambroid.

I just started shaping the wing panels this morning. I am using this Stanley plane: http://www.stanleytools.com/xhtml/literature/T5344.pdf

It is such a pleasant experience to generate long curly shavings. It combines two of my hobbies. Woodworking and model airplanes.
Jul 28, 2008, 04:01 PM
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Frans Bal's Avatar
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Quote:
It is such a pleasant experience to generate long curly shavings. It combines two of my hobbies. Woodworking and model airplanes.
Yep, i really love the smell of fresh balsa shavings in the morning too.

I know now what type of glue you want to use. It's Known here as UHU Hart.

That's a fancy plane, i am using this.


Frans
Jul 30, 2008, 01:30 AM
Registered User
Hi Frans, I think you're right about the UHU Hart.

Okay, here are some more progress photos. The sanding templates worked very well. The sound of the sanding changes once the plywood is hit. Unfortunately, due to the glue joint on the LE, the sound was more difficult to detect there. So, I used the old FF method of marking up the area to sand away with a marker, then sanding until the marks disappeared.
Jul 30, 2008, 09:35 AM
Registered User
Hmmm...I just weighed my wing, and it is about 90 grams. I guess 5.5 lbs balsa was not really the ideal weight. Unfortunately, real 4 lbs balsa is really hard to come by. After sealing the wood, I'll probably have 100 gram wings.

I suppose I could cut sections out, and retroactively add ribs, but I have to worry about how much the covering will add. I'll probably just move forward with a solid wing. I could always cut out sections later, if so inclined.
Jul 30, 2008, 10:47 AM
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Frans Bal's Avatar
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Quote:
I suppose I could cut sections out, and retroactively add ribs, but I have to worry about how much the covering will add. I'll probably just move forward with a solid wing. I could always cut out sections later, if so inclined.
Covering the entire wing with a light iron on material will ad some 10-12 gram.
A good alternative is to make circular holes and afterwards only cover the holes with a circular patch covering material.
I guess you will lose some 15-18 gram.

Frans
Jul 30, 2008, 11:22 AM
Registered User
My glassed wing came out at 71 grams complete with throwing peg. I weighed all the components for the DLG and my AUW should be in the region of 145 - 150 grams. It is a little heavy but should be ok? What are your typical weights Frans?


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