RC Gliders, Sailplanes and Slope Soaring Discuss rc gliders,rc sailplanes and slope soaring in this forum. Thermaling techniques, airfoils, tips, etc

ratio question

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Old 06-15-2017, 07:35 PM
  #1  
blvdbuzzard
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Default ratio question

I have an idea in my head, I know I should never let my mind wander, it always gets into trouble.

Any way, I an designing a thermal plane. I want to have a V tail. Is there a set ratio for the V tail to wing span or wing area?

While I am here, is there one for span to length?

So far, I have been working with the ratios of a Wanderer 72.


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Old 06-16-2017, 06:11 AM
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Antares100
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There are some guidelines if you search in this group, I don't remember any keywords to search with but I have read the area of the "V" tail should be the sum of the areas of the stab/elevator and rudder of a conventional tail setup for the sailplane you are building. Let us know how you make out.
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Old 06-16-2017, 10:32 AM
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I have search but have not found the answers I need. I think I will follow the TLAR guide lines of engineering. That has worked well for me in the past. So it should work here.

T hat
L ooks
A bout.
R ight.



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Old 06-16-2017, 05:35 PM
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Take the area of the flat stabs and add 20%. A couple things you didn't ask but are worth mentioning. Angle should be close to 110 degrees and for best performance you should have ruddevator differential. With rudder application the downward ruddevator should have more travel then the upward one. This will require some trial and error as to the amount but when correct will eliminate the tendency to pitch up with rudder input.
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Old 06-16-2017, 08:07 PM
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Nothing wrong with working with a proven tail area sizing as found on the Wanderer. But it's not as simple as looking at the top and side views of the tail areas. You may want to look at this

Charles River Radio Controllers - Quick V-Tail Sizing
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Old 06-17-2017, 06:42 AM
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Originally Posted by speedracerntrixie View Post
...Angle should be close to 110 degrees...
110* might be a good place to start but it's a littly flat for a glider that needs proper vertical stabilization to handle the aspect ratio at slow flight, perhaps especially for a thermal glider I would think.

Thermal pilots seem to prefer a conventional X-tail on their planes and it's probably not without reason, that said if you want to make it a V-tail consider that the actual angle on it significantly alters the behavior of the glider. As an example perhaps the most successful F3B glider in the last decade the Freestyler-3 have an angle at 101,5*, my Fosa F3B gliders with a staggering aspect ratio of 18:1 had a much steeper angle to cope with the extreme plan form at about 95*.
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Old 06-17-2017, 08:22 AM
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Thanks for the help. I am just kicking this around in my head and a few pencil sketches. Nothing formal. I was actually thinking of making a enlarged Wanderer. I would like to have something built for this years desert season. We have a tow plane we use to launch gliders. I was thinking of making one of those "AHH DAMN" type of planes. Easy to build, cheap, but flies like a dream or at least flies .

I have a pretty full shop, foam, balsa, foam cutter, feather cut, vacuum pump, bags, tables and all of the fun stuff.

How does a 2x Wanderer sound?

Would love to have one of the Art Hobbies Orion's. I just need to build it on a budget. Have all the servos, batteries, Rx. Just need a sleek plane to go with it.

ART HOBBY - Designer and Producer of Gliders and Electro Gliders RC


Thanks.

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Old 06-17-2017, 09:37 AM
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The art hobby gliders are really nice and from my point of view very affordable indeed, about scratch building your own glider my advice is; don't get too ambitious about the size, keep it manageable and reasonably simple. It's a world better with a 1,5m glider that you actually accomplish and get to see soar - rather than a 2,5m glider that never gets to the finish line.
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Old 06-17-2017, 06:30 PM
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ibuild. I will design, think about, draw, test, think about, think about, forget, try to forget, think about, then say what the heck. I am lucky in that I grew up BUILDING planes. It was way before ARF's. To me, once I put knife to balsa, it is GAME ON!!!. I really hate wasting balsa, so if I cut it, I will build it.

I have a 50% wanderer, couple stick and tissue style planes, a 50" rubber powered Taylor craft I used a 10 gram electric motor, 2s lipo. Weights in at 5 1/2 ounces ready to fly. I have been building smaller planes as I have not been able to get into the garage. Back problems have kept me away from my bench. I had to build something small enough to fit on my desk in the back room. Built a bunch of foamies, simple easy planes. Just to keep my mind going. I have hated not creating anything in way to many years. This started as an idea for building a straight winged wanderer. Well if I do that, I may as well make it different in some way. I have a 1/2 sized one, why not make a 2 times one?

I have been kicking this idea around for a couple years. Just a thought here and there. I may clean the bench next weekend or I may never build it. If nothing else I have learned the V tail should be around 110 degrees, the Orion has a tail 106 degrees. I am not looking for a contest plane, rather just something to lean back in the chair, fly by trims. Just a floater. I have the fast planes and helicopters if I want to raise my blood pressure.

I figure this would give me a little practice back into molding with carbon and glass. I have not molded anything in 5 or 6 years. So I could use a simple project to get back into it.

I have the vacuum setup and never got a chance to use it. Plus I have all the stuff on hand to build a vacuum molder. Was thinking of using ABS plastic for the pod, fishing rod blank for the fuse, foam core balsa sheet-ed wings.

I just have to throw a lot of junk away and get into the garage and start making some balsa dust.

If or when I start, I will have a build thread.

Thanks.

Buzz.
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Old 06-18-2017, 06:51 AM
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Alright mr.Buzz, but think of what you are saying; " I have hated not creating anything in way to many years..." then I really think you should start out in the right end to make sure that happens.

How about building an original Wanderer?
The truth is if you get to a RC gathering with your own scratch build plane no one is going to look at it a second time and no one will bother to take a picture out of interest, thats just how ignorant people are. However if you have a scratch built original classic - someone is likely to pay some serious attention to that. Think about it... if you go to a car gathering and you see a classic car that have been rebuilt and styled to the unrecognizable thats a great achievement but so what, but if you see a classic car that have been rebuild to its absolutely original condition like new - that's really something anyone would admire.

I believe that the beneficial thing about finding an existing and proved plan that you like and sticking too it is that it is more likely to finish the project within a reasonable time window, it takes away all the thinkering and the second thoughts and the regrets that might slow you down until you eventually get tired of it and wants to do something completely different. But if you really need to make it your own then using an existing and proven plan as your basis and slightly modify it in to your own design would be the best thing to do - just like you are suggesting.
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Old 06-18-2017, 07:07 AM
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I am not really worried about pictures as I do not fly with a club or group of people. Not an issue for me. Closest place is about 75 miles one way, plus the cost is way to much to bother with fly there.

But yes I hear you. That is why I have been building the little planes or scaling them down to 50%. Keep the skills alive. I just need to think about building something different. I have a couple scale gliders, they fly but they do not fly "well" They do look very good in the air, that is where the performance ends. They look like a million bucks, fly like a fifty cent piece.

Plus building is a large part of my enjoyment. It is a form of meditation for me. Think about the plane, forget about the troubles of the day. There is a kind of peaceful bless at the bench.

Again, this is all about the thinking part. I have yet to set anything in wood, so I am just on the hunt for information at this point. I may give up and go on to a power plane in a week, may break out and start building. I am at the very beginning, so easy enough to change directions.


Thanks.

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Old 06-18-2017, 01:13 PM
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Perhaps look around the web at different drawings and plans, and then get back to your own plan and see if that is still what you really want to do.

I had an Arthobby Colibri 1m V-tail glider once, I was just amazed of how well it soared in both calm conditions and in more windy conditions as well. I used a bungee catapult to launch it to get some starting altitude, it could stay up on the lift from a treeline facing the wind even at a flat field.
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Old 06-21-2017, 09:22 AM
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You asked about a double size Wanderer. Something to ponder over a 12 foot span wing is that the loads on it are going to scale up a lot. And the rib spacing and open style construction that relies on the covering for torsional stiffness will need some help since the covering does not scale up the same and would leave the wing fairly flexible in torsion at a 12 ft span. And it would require additional ribs just to aid in supporting the covering in a good way.

This stuff and other factors is always something that crops up when we want to scale an existing design either down or up to a large degree such as half or double size. In the end you end up with a new model inside that happens to sort of look like the original on the outside.
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Old 06-21-2017, 11:21 AM
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When I built my 1/2 sized Wanderer, I thought about using 1/32 balsa for the ribs, after breaking 3 out of the first 5 with my 10 pound sledge hammer hands, I used 1/16 and left out 4 ribs in the inner panels. Used all of them in the otter panel, even though I could have taken out 2 and never noticed.

In some of the other up scaling plans I have done before. After you get a rough drawing, you can see if the spacing is off. I scaled up an old timer. When I saw I had about an 8 inch wing rib spacing, I knew I had to shift things over. I ended up adding a bunch of ribs. I think I like the little bits of change you have to add. it makes it a unique build. It will be something no one else has.

I have a few sketches now. I may mold the boom out of glass, it is going to be big enough. Still might go the easy way and see if I can find a fishing pole blank. Some times finding one that is stiff enough yet lite enough is the hard part.

As I am in the wondering, thinking, what if, figuring mode. I found I would need to get 4 bundles of 1/16"x36" balsa to make up the 4 wing skins. So that works out to be about $50.00 for the wing skins. I am looking into if I could lay up some glass skins for less. In place of balsa I have taken so 1-2 ounce glass cloth, wet it out, set it on a polished flat surface to cure. in other words, I just made a single layer glass sheet. Took a few tries to get just enough resin to leave a smooth surface without adding to much weight. I used different weaves, thickness's of glass, epoxy, marine resin. They turned out pretty good. I then used then to sheet a foam core. I compared them to a balsa sheeted one trying to get the same weight. I have been thinking of vacuuming the wings with glass skins.

I see this as a way to enjoy building, experimenting, learning new techniques. If all I did was to assemble ARF's, I think I would be bored pretty quick.

I would have to call this a feasibility study. Just to see if it can be done, how easy or hard it will be.

Thanks.

Buzz.
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Old 06-23-2017, 12:44 PM
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Making prefabricated fiberglass skins is an interesting way to go, but I would absolutely make a smaller model first to get it dialed in. In my experience I need to do anything at least 3 times before I really know it, the first time it might be usable but I will not be entirely happy with it, the second time it will likely be usable but there will still be some things that I know I want to do differently the next time. You don't want to do all these experiences with an 8 foot plane, try to find the interesting part of making a smaller model first or make the stabilizers first at least with the same method so you don't put a lot of work and time in to a still born project - it will drain you doing that.
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Old 06-26-2017, 11:42 AM
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ibuild, sounds like me. Even with kits, I was never really happy with them when they were done. I always tried to make the changes on the next kit and the next.

Before I put the effort into the big boy, I would make a few samples. Even when cutting the foam cores. I usually cut spares as I may or may not like the first set.

I think this will be an interesting build. As it will be more of a try this and see what happens, then make the big part.


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