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Old Jun 22, 2013, 02:48 AM
Hallo von Dresden
Joined Sep 2012
55 Posts
Hello Gents,

Bare, after several attempts also known as destruction testing ... a well made glue joint is typically stronger than the surrounding material (when using wood). So although a spar with slots is in its unassembled form is logically weakened ... after proper assembly is as strong as though the thing had no slots.

A long time ago I was a member of the EAA and I spoke to one of the experts there who told me that upon inspection a sample glue joint must be provided ... the assembled parts are then torn apart .... the rule is: the glue must hold! the wood can break. Seemed reasonable then as today. I tried this on several test spars .... the result was always the same, the spar broke but never at the glue joint. ofcourse this neat little trick only works if you have a good fitting glue joint. Slop will not work.

Taurus flyer, very nice work

Jens
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Old Jun 27, 2013, 04:34 AM
Designing something...
United States, CA, Cameron Park
Joined Jan 2004
1,680 Posts
Jens,

Hallo from the Darmstadt area.

Just to avoid confusion...I designed the Horten III that previously built here on RCG. Uwe (TailSaw) helped by reviewing and providing feedback on the aerodynamics. The CAD files are available to anyone as they have been posed to the scalesoaring.co.uk site. I'm also very willing to share the aerodynamic files (.flg) if anyone is interested.

As far as helping you out on the design/CAD work for your design(s)... sure but probably but not for the next few weeks.

Gruß,
Brian
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Old Jun 27, 2013, 08:12 PM
Registered User
Canada
Joined Nov 2000
6,885 Posts
Erm OK But So what?
The glue won't break first.. No news there.
But certainly the Material that it's glued to, at 90 degrees to the material's inherent strength directions.. Will.. break first.
Result is the same Is it not?

A typical single 2x4 piece of construction lumber will support an automoblie in Tension And Compression.
IF one can hold the thing vertical /and steady :-).
I find it Elegant to fully exploit the inherent strengths advantages of the materials used.. Bit more labor involved to do so though.
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Old Jun 28, 2013, 06:38 AM
Hallo von Dresden
Joined Sep 2012
55 Posts
Hello Gents,

Brian, technically speaking all i would really need is as previously suggest a set of drawings with the ribs shown perpendicular to the main spar ... the rest is not too bad to do by hand. If you can do this that would be fantastic but likely it is a bit of work even with a PC to assist. Time wise I am nowhere near a build right now as the garage needs to partially converted to a shop to actually build models. So of later in the year .... ??

Bare, yup the result is the same, I was replying to another comment that I understood to mean that a slotted main spar would be weaker because of the slots ... that is to me however not really true. A well made glue joint was the point I was going after and a simpler less involving way to build a wing and get good results. A spar cap would still be there (top and bottom of-course). Since I tend to hand cut-build early everything with wings I am looking for a simpler way to get to the end result. Straight as opposed angled cuts are one way to do that.

I am a traditional builder (old fashioned in other words) and stuff like cabon fiber or fiber-glass (or similar high tech stuff) is something I a not a big freind of. Not that there is anything wrong with those materials but my models are so light that as rule they do not need this type of material. Simple plywood and balsa is all that is needed and as result the models are simple and affordable to build.

I greatly admire the high tech stuff and am amazed at what builders accomplish with it ... but I like wood, it smells good does not cause rashes or requires the use of safety gear (cutting carbon comes to mind here). Simplicity is my thing.

Jens
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Old Jun 28, 2013, 08:54 AM
Designing something...
United States, CA, Cameron Park
Joined Jan 2004
1,680 Posts
@Jens - Sounds like fun. I won't be able to work on anything for a couple more weeks. If you can just shoot me an email with the details. e.g. span, sheeting thickness...etc.

Gruß,
Brian
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Old Jul 30, 2013, 03:37 PM
Registered User
North London ENGLAND
Joined Dec 2006
1,644 Posts
Ribs aligned with airflow, nerdy comment.

If you want to get really nit-picky about rib angles, first fly a wing with ribs where convenient, but with wool tufts or threads where ribs wanted, fit a camera in a short mast to observe the wool tufts etc at best angle, probably vertical. and then you know the TRUE alignment of ribs for local airflow, (which aint fore and aft of course) as those angles vary root to tip. Repeat over a range of speeds, angles of attacks for better accuracy. This procedure needs to be done both over and under the airfoil, since the angles will differ,(if they didnt there would be no induced tip vortex). You might find therefore that half ribs would be needed, half for top side and half for bottom, although a strangely twisted rib might be able to do both. If the foregoing procedure seems unduly complicated, just stick the ribs where convenient, probably little measureable difference, or cut a foam wing and skin with something smooth and pretty.
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