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#1 Knoll53 Oct 09, 2012 04:23 PM

Samurdactyl
 
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If the Plank 101 works out good, I might have another plank up my sleeve. Inspired by winggerd's contribution and the swallows in Big Sur. Same construction technique as the Plank 101, but with a box spar and 1/8" fiberglass rod LE.

Kent

Edit: I have renamed this project. Samurai sword meets Pterodactyl

#2 Jon Snow Oct 09, 2012 05:42 PM

Sweet!:popcorn::popcorn:

#3 Knoll53 Oct 09, 2012 05:47 PM

Maybe it should be a "swing wing" for that Peregrine falcon dive. ..:D

Kent

#4 Quick61 Oct 09, 2012 07:01 PM

I really like the box spar design. I was scratching about just last night on the CAD exploring the concept. I would be very interested in hearing more about material type / thickness, design parameters, etc., that you are thinking about. Are there any more examples of the box spar out there to be reviewed?

Mark

#5 foamdave Oct 09, 2012 09:53 PM

Lurking...

Dave-

#6 Jon Snow Oct 09, 2012 11:51 PM

Quote:

Originally Posted by Knoll53 (Post 22957169)
Maybe it should be a "swing wing" for that Peregrine falcon dive. ..:D

Kent

Double jointed variable sweep........:censored: stop putting ideas in my head:mad:.....inner half span moves forward,outer moves backward,cog should move forward......central pivot,pull/pull out to half span pivot......:censored::confused:................:p
:D Stuart

#7 Crozzie Oct 10, 2012 03:36 AM

@Stuart#6
Not too difficult to arrange Stuart, many projects ago in response to the Eddie Eagle article in RCME , I drew up a linkage to do just this working off one centrally placed homebrewed servo much like your screwjack. Why didn't I pursue it? well I couldn't get a good working solution to the glove arrangements at the joints. I'll have to look for my old doodle pads now!
How's the swing wing coming on?

Trev

#8 Jon Snow Oct 10, 2012 04:41 AM

Morning Trev-the glove thing is on my mind as a possible problem area.I think I have an idea for the l/e-sort of a U shape segment.Still in head cad stage:p.
T/e more difficult I think.
As to the here and now,I've just cut a nice square piece of foam,new templates in the works,some pics later if I make enough progress before duty calls.
Regards Stuart

#9 Knoll53 Oct 10, 2012 09:30 AM

1 Attachment(s)
Quote:

Originally Posted by Quick61 (Post 22957768)
I really like the box spar design. I was scratching about just last night on the CAD exploring the concept. I would be very interested in hearing more about material type / thickness, design parameters, etc., that you are thinking about. Are there any more examples of the box spar out there to be reviewed?
Mark

Box Beams are used in construction, often with a 2x4 top and bottom and plywood sides. Very stiff.

The value here is that by making the spar wider, you get torsional strength too, so no D tube sheeting is needed. Just a spar and ribs, like the Plank 101. It's a quick way to build.

I'm thinking 100" wing span. Lots and lots of CAD work to create the files for laser cutting. wing gerd did a beautiful job.

Kent

#10 Jon Snow Oct 10, 2012 11:07 AM

Just had a look at Gerds build log again,to see what he did where the angle changed.With those internal diagonals it's a really strong structure.Be interesting to see your take on this.
Regards Stuart

#11 Crozzie Oct 10, 2012 11:28 AM

Quote:

Originally Posted by Knoll53 (Post 22962261)
Box Beams are used in construction, often with a 2x4 top and bottom and plywood sides. Very stiff.

Kent

My experience of inspecting aircraft designed with box spars in the Jodel range of homebuilt aircraft and their series cousins Robin DR300/400 etc shows how quite large wooden wings can be built very strong whilst still light and stiff. CAD definitely useful in our model sizes to build a ply spar with tongues and notches as in Gerd's build to avoid the need for glueing battens.
Must get a CAD/CAM program somewhen, now that my fretsawing arm is not what it once was the fun seems to fade after cutting the first couple of feet, and certainly cannot match the consistent accuracy of a machine:o

Trev

#12 Knoll53 Oct 10, 2012 11:37 AM

Quote:

tongues and notches as in Gerd's build to avoid the need for glueing battens.
I would think that they are still glued.

Creating tabs in CAD is quite a tedious process. When you discover how to model tabs in CAD "easily" please let me know how it's done. I use Rhino 3D. It has a boolean tool that is some help in accomplishing this, but it fails to work in many instances. I'm looking for an automatic, guaranteed fit up method. Have not found it yet.

At this point, I don't use tabs. Certainly not for lite ply. The material is so weak any way, that I just use a butt joint. Wood glue is normally adequate, but using epoxy would probably develop the full strength of the wood.

At least that is my approach for prototype models.

Kent

#13 Knoll53 Oct 10, 2012 11:49 AM

Quote:

Originally Posted by Stupot46 (Post 22963013)
Just had a look at Gerds build log again,to see what he did where the angle changed.With those internal diagonals it's a really strong structure.Be interesting to see your take on this.
Regards Stuart

wing gerd uses a wide lite ply box beam, with sticks added next to the vertical shear webs. The diagonals prevent the wide lite ply from buckling but do not add to bending strength. I would think that the beam strength would be limited by those wide lite ply top and bottom plates. They are taking the majority of the bending loads. Such a spar will be quite rigid until it fails, unlike a simple stick, that will flex a lot before it fails.

For any new spar design, testing of a mock up is a very good idea. Until you prove your design with a mock up, it's all just theory.

Kent

#14 Crozzie Oct 10, 2012 12:05 PM

I didn't mean not glued, just meant no battens or quadrants in the corners and hence more work and weight, instead having tabs/notches increases the glueing surface over a straight butt joint. Personally I prefer to use the more expensive aviation grade ply though group buying full sheets comes out about the same as liteply from the hobby store, and it's nicer to work.

I'm afraid that I am utterly clueless about CAD and niavely assumed that designing in tabs might be "easy". With your more considerable experience in this field, you've just given me a reality check!

Trev.

#15 Knoll53 Oct 10, 2012 12:37 PM

Even with it's limitations, I still recommend Rhino 3D for modeling work. Plenty powerful NURBS modeling features and a free full working demo version available. If you can make the demo version sing, then the student version is only $200. Still a lot of cash just for modeling. There are certainly easier/cheaper programs available, I'm just not familiar with them.

Kent


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