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Old Sep 18, 2011, 06:39 AM
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tele1974's Avatar
USA, OH, Olmsted Falls
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Question

When the vapor came out it was the same construction that I thought when make a great indoor ultra micro 3d plane. And here it is. I was very happy to find this thread.

Question: Could the frames that you are building be molded some how. Maybe someone with some plastic pour molding experience could comment.
Just curious.
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Old Sep 18, 2011, 08:36 AM
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USA, MA, Swansea
Joined Mar 2003
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Rocky,
What are the thoughts in using Cabon Fiber arrow shafts for a fuselage center longeron instead of the balsa center? I have some that are thin walled about 5/16th inch and some thicker walled around 1/4 inch. They are around 32 inches long also and the thin walled shaft is fairly light and very strong. I have used these plastic motor mounts also in a few of my planes. They can be cut shorter in length. The arrow shafts can fit the mounts tightly also with little work.

The arrow shafts can be drilled for the small 1mm CF rods to pass through it also which will make a pretty rigid fuselage. Where did you find the kevlar thread? What are the thoughts of using hair thin copper magnet wire to make the terminal end bindings? To or three wraps would do the job. After the drop of CA glue is applied it can't be to much difference in weight. Of course my build would not end up as light as yours but in general it would still be light enough to be a good flyer as a sport flier.

Do you think there is any merit to this?
**Neons** Bob
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Old Sep 23, 2011, 06:32 AM
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United States, TX, Lubbock
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Quote:
Originally Posted by **neons** View Post
Rocky,

What are the thoughts in using Cabon Fiber arrow shafts for a fuselage center longeron instead of the balsa center?

Where did you find the kevlar thread?

What are the thoughts of using hair thin copper magnet wire to make the terminal end bindings?

Do you think there is any merit to this?
**Neons** Bob
Dear Bob

You flatter me with your questions. Iím just returning back into the hobby after a 15 year hiatus, am struggling through each challenge that I encounter as I build the RELAX, and, on most days, feel very humbled by problems I cannot solve quickly. For the sake of conversation, I can give you my opinion but by no means should it be interpreted as authoritative or necessarily credible.

Carbon fiber shafts for the fuselage longeron:
The ideal fuselage longeron for an aircraft like the ďRelaxĒ should be stiff as well as light. But the question can be raised as to how stiff should it be without becoming too heavy? In my opinion, the longeron only needs to be stiff enough to prevent the long fuselage from warping. The weight of the tube should be given at least equal consideration. The RELAX was designed for flying indoor precision aerobatics at a slow speed. Such performance characteristic was achieved by minimizing the flying weight. The Relaxís wing loading is unbelievably low. I estimate that my badly overweight model will have a wing loading less than 1.5 oz/sq ft. (This is in stark contrast to the pattern airplanes that I flew in the West Texas winds, circa early 1990ís, which had wing loadings about 12 to 15 oz/sq ft). To acquire lower weight requires discipline, careful planning of the material/equipment as well as the building methods used. Having grown up with larger balsa models, I am having difficulty transitioning to ultra-light indoor planes. The selection of the longeron is a good place to start and I appreciate the reason why you ask this question.

I donít have any experience with carbon fiber arrow shafts and thus cannot offer any specific comment as to their merit. I have, however, searched for lightweight round carbon tubes and my initial find was discouraging. For example, a 8 mm (OD) Ė 6 mm (ID) carbon tube weighed 34 grams when I was hoping for tubes closer to 2 grams. The balsa stick was the best I could find when I began construction. Later, however, I read that there are two kinds of carbon tubes, extrusion and wound types (http://www.radicalrc.com/category/Carbon-Rod-Hollow-410). The latter is cheaper and lighter. But, at this time, I have not purchased a wound-type tube.

Where to purchase Kevlar thread:
Kevlar thread is commonly sold in stores specialized for fly fishing. You can order the thread over the internet from stores like http://www.edgeangling.com/Fishing-T...=kevlar+thread. There might be different types of Kevlar threads. The ones that I like are those that remain wound as you handle them. I can tie the joints more neatly with this type of thread (purchase from the store in the above hyperlink). The other type unwinds into a bundle of very fine fibers and is more difficult to handle. However, I donít know which type of thread is stronger and I donít know whether they are identifiable by different names.

What are the thoughts of using hair thin copper magnet wire to make the terminal end bindings?
The need for tying the carbon rods arises because the minimal surface that each tip of the rod makes contact at the glued joint. So when considering an aircraft constructed with extensive truss elements, you might appreciate that the greatest structural stress occurs at the glue joints, not in the carbon rods themselves. Lantsov Alexey apparently understood this and incorporated the method of tying each rod using the Kevlar thread. Kevlar thread accomplished two things. First, winding each joint with thread Ė in effect -- increased the glued surface. Second, because of its high tensile strength, the thread itself contributed to the strength of the joint. Kevlar thread has a tensile strength equal to that for the equivalent weight of steel. I suppose that the copper wire can be used in place of the Kevlar because the wire would increase the glued surface. But copper wire does not have as good strength and weight characteristics.

Do your proposed methods have any merit. The answer is of course they do. The merit, however, depends upon the desired cruising speed and aerobatic performance. I just doubt that anyone would wish to invest the amount of time, effort, and money that this aircraft requires just to build a good sport flyer. May be I'm wrong.

Sincerely,
Rocky

PS Ė I have finally got the servos and receiver satisfactorily installed. Iíve been trying for about 1 Ĺ months Ė which is far more time than I anticipated. That includes working through 7 failed attempts plus the ancillary work of their removal. The latter is time consuming as it is not easy to remove joints and material that were tied with Kevlar and glued with CA. Additionally, the removal of the failed attempts incurred unintentional slips of hand that often resulted in damage to nearby support braces. The 0.6 and 0.7 mm diameter rods fractured easily but the 1 mm rods survived the abuse quite well.



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Old Sep 23, 2011, 07:15 AM
Old age is not for sissies
Azarr's Avatar
Dayton Intl, Ohio, United States
Joined Jan 2000
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Goodwinds.com the kite store has 48" .5mm rods for $2.39 and the price decreases with quantity, $1.99 for 24+.

The also have wrapped 32.5" tubes weighing 9g.

I've bought a lot from them over the years and the have good customer service.

Azarr
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Old Sep 23, 2011, 07:52 AM
leliommarino
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United States, MA
Joined Nov 2007
656 Posts
how do you covey one of these? i know they are covered with mylar but i looks like they are all built in one piece/ also are these painted if so what kind of paint
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Old Sep 23, 2011, 09:43 AM
slow but inefficient
Ron Williams's Avatar
Riverhead NY USA
Joined Dec 2000
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Quote:
Originally Posted by leliommarino View Post
how do you covey one of these? i know they are covered with mylar but i looks like they are all built in one piece/ also are these painted if so what kind of paint
There's a video earlier in the thread that show's Alexey covering the elevator on one of his planes. The technique should be adaptable to the whole plane.
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Old Sep 23, 2011, 09:54 AM
slow but inefficient
Ron Williams's Avatar
Riverhead NY USA
Joined Dec 2000
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Rocky -

A much lighter connection between the control horn on the flying surfaces and the pushrods is to use heat shrink tubing CA'd to the rods. it doesn't seem like it would hold up but it does. The tubing is flexible and long lasting.
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Old Sep 23, 2011, 02:33 PM
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**neons**'s Avatar
USA, MA, Swansea
Joined Mar 2003
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Rocky
Thank you for your very good explanation on the use of carbon fiber rods and kevlar threads. It is well covered here. Very helpful to me and I am sure others here. One problem I found when I split a rod or shaft is it can leave very sharp splinters. I have split CF many times and very carefully block sand them before I use them. I do not want to run my fingers along a split rod or shaft. I do not think getting a splinter is the best thing to do with carbon. Your work is very nice and I enjoy following what you are doing.
**Neons** Bob
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Old Sep 25, 2011, 01:29 PM
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Sweden
Joined Oct 2002
815 Posts
Hey Alexie! This is Mike The American you use to fly with in St. Petersburg! Nice plane you have posted here! I have a question. Did I see one of your planes for sale in the hobby shop down near Gorkovskaya metro? It was a carbon mylar plane and I said that has to be lantzovs work! I see lots of people are asking about the "metalized mylar covered carbon rods" I still fly one of my planes with a couple of those rods installed. Even years later I can find NOTHING like them. It would be good to see you and the guys again! Tell Sasha I said hello! And thanks for posting your work. & I miss the plane you sold me! It was surley one of the best planes I owned!
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Old Oct 22, 2011, 03:35 AM
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Michigan
Joined Aug 2002
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Rocky,

Hats off to you on your build. I know exactly how difficult and time consuming this type of construction can be. Beautiful job! Looking forward to seeing it completed.

Let me share a couple of different ways to connect the CF rods. Not the lightest but different and possiblt these wil get thought processes going for others.

About this time last year I built my first CF framed plane but did not like the idea of tying all the joints so I laid up some 2 oz CF cloth on a glass plate and punched out 1/4 inch circles with a paper punch. After taping all the rods in place I went around and placed a dab of epoxy and a CF circle at each joint. This is not the lightest way to do it but I just could not see myself tying all the joints. The plane was then covered with baloon mylar- again not the lightest way to go but the baloon mylar was easily found at the party store.

Here are some pictures of that method.

George
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Old Oct 22, 2011, 03:46 AM
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Here is the second method I used on my second CF framed build.

I cut different size circles from CF veil and after taping down all the rods I went around at each joint and placed a piece of plastic under the joint followed by a CF circle. A drop of thin CA was then placed on the CF circle, the plastic was quickly folded over and pressure was applied with a piece of foam to mash the CF circle down around the CF rod joint. This method is lighter than the first but also more time consuming. The plane was covered with 5 micron mylar.

Here are some pictures.

I hope these methods spark some thought as to diferent ways to go about connecting the rods other than tying.

George
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Old Oct 22, 2011, 11:05 PM
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USA, OH, Olmsted Falls
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Lantsov since the fuse is a bilayer and probably air tight it would be interesting to see if blowing some helium in their reduce its weight. Crazy, I know.

Nope I found an equation for it and it would only be about 10 grams...hydrogen would be better.
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Old Oct 23, 2011, 02:08 AM
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Andycap's Avatar
Leeds
Joined Mar 2003
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Helium only lifts 1g per litre so that theory doesn't stand up.

You would be lucky to have a volume of 1 litre in the fuselage and you would add more than a gram making it helium proof!

I'm sure Martin Muller tried something like this years ago
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Old Oct 23, 2011, 05:03 AM
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K thanks Andy.
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Old Oct 26, 2011, 02:35 PM
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United States, TX, Lubbock
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Quote:
Originally Posted by Ampbomber View Post
Rocky,
Hats off to you on your build. I know exactly how difficult and time consuming this type of construction can be. Beautiful job! Looking forward to seeing it completed.
George
George
I enjoy your description/photos of alternative approaches. Please continue. I'll be trying the carbon-tissue joint reinforcement on my second aircraft.
With regard to my first attempt, I completed construction and have briefly test flown it. Here are a couple of photos. At home, I really thought the transparency scheme looked cool. But after I took off on my first flight, my opinion quickly changed. In the indoor facilities where I fly, the upper half of the walls and the ceiling are poorly illuminated and my plane almost disappears from view. In fact, within seconds of my first take off, I collided with a ceiling beam. Miraculously, the plane fell to the floor without a scratch. My next aircraft will have a similar color scheme but with an opaque white background -- to improve visibility.

Rocky


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