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Old Apr 18, 2012, 10:53 AM
The Prez....... again
kenh3497's Avatar
United States, IA, Rockwell
Joined Jul 2011
4,049 Posts
Quote:
Originally Posted by Taurus Flyer View Post
Ken you wrote in your first post in this tread:

"Part of the reason for my question..... "


Because the reason to show your question was the publication ANC18 and you do want to modify the wing structure of your aerobatic plane.


I did answer your your question because this ANC18 cannot be of much difference compared with my book written by people of Fokker.
Second reason for me was, an aerobatic plane of all wood structure can be complicated even it is a model just as the Taurus I did write about
You would be surprised when you know who's plane is was!!


"Beaten to dead", your own words?

Because I see we arrived in your phase of your opinion, thinking and quessing I did copy some parts of ANC18 related to the subject, spars and skin. To be well informed there is more to find in that document of course but you better look for it yourself.

Picture 4 "The modeler and the engineer talking about an aerobatic plane."

Success

Cees

You just went WAY over my head with the technical stuff

You have to live in this area of the USA to fully understand....." I'm just a dumb Iowa farm boy who like to play with toys" The guys here in the states will understand

Seriously, I do understand what you are getting at. I know you are looking out for my best interests and want to save me from trashing what will be a significant investment in time and labor to build this airframe. I do believe this thread will lead to an alternative to finding a suitable spar material other than spruce, which I mentioned is very hard to find these days. Maybe I'll have to get into the business of re-sawing spruce to sizes, we as modelers, can use.

Ken
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Old Apr 18, 2012, 11:03 AM
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Oakland township, Michigan
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Ken,

Good luck with your build. Maybe you can start a build thread once you start working on it.

Teo
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Old Apr 18, 2012, 11:39 AM
I bail out, anywhere, anytime
Taurus Flyer's Avatar
The Netherlands, OV, Almelo
Joined Nov 2010
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Am I lucky I didn;t start writing about ANC18.
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Old Apr 18, 2012, 01:17 PM
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EscapeFlyer's Avatar
United States, MN, Brooklyn Center
Joined May 2009
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Quote:
Originally Posted by kenh3497 View Post
You just went WAY over my head with the technical stuff

You have to live in this area of the USA to fully understand....." I'm just a dumb Iowa farm boy who like to play with toys" The guys here in the states will understand

Seriously, I do understand what you are getting at. I know you are looking out for my best interests and want to save me from trashing what will be a significant investment in time and labor to build this airframe. I do believe this thread will lead to an alternative to finding a suitable spar material other than spruce, which I mentioned is very hard to find these days. Maybe I'll have to get into the business of re-sawing spruce to sizes, we as modelers, can use.

Ken
Have you considered composite alternatives such as carbon fiber laminate, or carbon fiber sq tubes....

Just my thoughts, but I would probably try ripping spruce down to size....

Brian
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Old Apr 18, 2012, 03:43 PM
I bail out, anywhere, anytime
Taurus Flyer's Avatar
The Netherlands, OV, Almelo
Joined Nov 2010
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After the wake up phase there still can be an advice,
No , no idiot diagonal braces, no cutting holes everywhere, just a strategic solution based on ANC18.

After looking at the plans again I would add two spars when switching from spruce to balsa, one on top one on bottom, and add a piece of the main spar in the center section, see the red added parts in the plans.

It looks like the wood of the ribs is there without cutting in lightening holes, the spar cross sectional surface easy can be doubled this way, the skin is better supported in kind of multy cell construction, the stresses of the skin are better devided .

This with single shear webbing (or double as the plans show these!) only for the already existing main spars looks a plausible solution for me.
Why no shear webbing at the added spars, to keep the centre line of flexibility in front of the wing to prevent flutter.


Please comment this solution.

Cees
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Old Apr 18, 2012, 04:54 PM
The Prez....... again
kenh3497's Avatar
United States, IA, Rockwell
Joined Jul 2011
4,049 Posts
Quote:
Originally Posted by Taurus Flyer View Post
After the wake up phase there still can be an advice,
No , no idiot diagonal braces, no cutting holes everywhere, just a strategic solution based on ANC18.

After looking at the plans again I would add two spars when switching from spruce to balsa, one on top one on bottom, and add a piece of the main spar in the center section, see the red added parts in the plans.

It looks like the wood of the ribs is there without cutting in lightening holes, the spar cross sectional surface easy can be doubled this way, the skin is better supported in kind of multy cell construction, the stresses of the skin are better devided .

This with single shear webbing (or double as the plans show these!) only for the already existing main spars looks a plausible solution for me.
Why no shear webbing at the added spars, to keep the centre line of flexibility in front of the wing to prevent flutter.


Please comment this solution.

Cees

That is certainly a viable solution you have there. I don't think it would work for the center of the wing though. Besides, I have that part framed up already (with bass spars) and it would not work on the bottom as the spar in the center section passes directly through the wheel well. I could leave out the retracts I suppose.........

It looks like I'll just buckle and use the bass spars I already have.... I looked at every hobby shop for 150 miles around and nobody has spruce.

I hope somebody has learned a thing or two from this thread. I know I have.

Ken
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Old Apr 18, 2012, 05:15 PM
I bail out, anywhere, anytime
Taurus Flyer's Avatar
The Netherlands, OV, Almelo
Joined Nov 2010
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Ken,

I did ask for comment, so thanks.
First I buy my wood in any wood story I can find, no hobby shop
I saw and use a wood "plane?" and caliper to taper but in a wood store they can saw your wood,and maybe also in flat material of 1/2 inch. after that shape by hand.

Second, the added spar is also to carry the skin see the green ovals there is space between the plate and sheeting.

Near the wheel well there have to be a reinforcement around the well, for example as I show in the sketch.

Just an idea because I cannot read the plans in detail..
Also the location of the added spars, if used!!, is very important to prevent complications of course.

Last picture, I see your problem and maybe the solution is a plywood reinforcement plate as shown in blue color?
I see the main spars are also cut in two pieces for the legs (red oval) so if you want you could use the same methode in the wheel well, that plate, but vertical.

Knowing a little bit more about the construction the end of the story is interesting,
The main spar did have that re´nforcement plate to carry the load on location of the pivot of the main leg but, what load when you change the spar in balsa? Or with better wiords the designer did expect forces in the spar!!
The skin glassed will do the job? No because there is no sheeting on lacation of the mains!!! There is a "big black hole"
in the skin,say sheeting. And that was why the designer did expect forces in the spar!!!!
So while I worried about the top of the wing and promoted the spar mainly for that, the bottom is more complicated when changing material of the spars, what about that!!
.I personally doubt if that wing could have carried the load when balsa spars were used.

Thanks ANC18

Cees


This post was a continuing story of a lot of edits!
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Old Apr 19, 2012, 08:27 AM
The Prez....... again
kenh3497's Avatar
United States, IA, Rockwell
Joined Jul 2011
4,049 Posts
I have the center section framed up and it will be plenty strong. The dihedral braces are full depth 1/8 ply, that extend out into the outer wing panels. You could stand on the center section with no issues. Also the ribs are all lite ply in the center section. If you could see it in real life you would understand. The spars on the outer panels tie into the ply dihedral braces.

Balsa spars are out. I'll use the basswood I have and everything will be just fine I do plan on double shear webbing in any case at least out to mid span and single webbing from there to the wing tip.

Ken
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Old Apr 19, 2012, 08:50 AM
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Oakland township, Michigan
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Sounds like a plan. Good luck.

Teo
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Old Apr 19, 2012, 09:15 AM
I bail out, anywhere, anytime
Taurus Flyer's Avatar
The Netherlands, OV, Almelo
Joined Nov 2010
2,883 Posts
Ken,

Retracts always do make things complicated and that's te challenge
I also considered to use that system of the Zlin in my Orion but later decided to retract sideways, and then there is the D tube.

To make the system even stronger and light I do redesign the legs with 2 pivots, one in the spars and one near the LE,
Then you get this picture, big holes in the D tube.
Now I did need these double shear webs on the spars to get back the torsionlal stiffness.
The bottom is re´nforced so I can make belly landings without any damage (on grass!)

Most important of scratch building is to have your plan because later it is very complicated to change.

BTW can you give an indication of the weight of these brass spars and what would have been the weight when spruce was used or balsa, so the difference! Not in detail, simple estimation.

Good luck with the construction, that result will be fine.

Cees
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