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Old Oct 08, 2014, 07:55 AM
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United States, FL, West Palm Beach
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How much does precision matter?

I'm pretty handy and will be able to get things pretty close but I want to set my expectations realistically. I've never actually built something like this before, all of my craftiness is in working with wood (building workbench, chair railing, trim accents, etc). I am confident I can get things within a few mm's. Will that be close enough. As in other hobbies, failure can be a difficult pill to swallow. But I have had good luck so far with my Blade 350 and UMX Radian.

Unfortunately as a noob I ordered a FlySky T6 with a receiver but it's not compatible with my current flyers. Now I have three options: Return is and suck up the restocking fee, sell it here, or build a plane big enough to carry FPV equipment. I always like a challenge and have been watching the videos from Experimental Airlines on YouTube. I feel confident and I have a Dollar Tree 3 minutes from my house for an endless supply of foam.

I guess we all have to start somewhere. I like the Axon from another thread in the scratchbuild section. Opinions?
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Old Oct 08, 2014, 08:04 AM
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United States, NY, Albany
Joined Sep 2011
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Hack out a couple Flite Test planes and see how you like it. FPV gear will work well on their Versa wing and it's not a hard build. Plus it's good practice for how to deal with foam. Or just follow EA's videos and cut away, but the Flite Test stuff has plans you can follow to make it easier your first time.

Using the plans and build videos with a sharp xacto knife, a long ruler and I think you'll be surprised how accurate you can be. If you just get things close all will be fine, especially with foam. However the closer you get it the nicer it turns out and the better things fit using less glue and saving weight. I worked up this one in a couple days using just the tools I listed above...

http://www.rcgroups.com/forums/showp...&postcount=675
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Old Oct 08, 2014, 08:13 AM
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Nothing beats the simplicity (both construction and flying characteristics) of a simple delta (more-or-less equilateral triangle planform). The layout is also "naturally" extremely strong. And it will typically have low wing loading because of all that area.
There are dozens of examples of "simple delta" on this site alone (some with plans - many of foam board) - do a search for "simple delta".
Put on small angled winglets for roll stability (and maybe even drooping leading edge cuffs for the outboard third of each wing to prevent tip stall) - you'll have a well behaved, docile, stall resistant plane and any crashes will be fairly easy to repair.
You can make it between 45 and 60 inches span and certainly be capable of FPV.
So what's the catch? - A delta does not have great glide ratio and will drain your battery quicker than a high aspect ratio design with the same weight and wing area. But for your very first scratch build it is an excellent choice.

It will also tolerate quite a lot of imprecision.

Badly asymmetrical delta, but flies decently with trim adjusted appropriately:

Flight of Vectored Thrust Delta with takeoff landing (1 min 40 sec)
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Old Oct 08, 2014, 08:21 AM
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I think a Delta is a bit more intimidating because of the angles. That one looks pretty unstable at the start but maybe flies better than the initial takeoff.

But if the general consensus is that it's more forgiving to imperfections then maybe it's a good place to start. Realistically, it wouldn't cost too much for a few extra components. If I don't like how it flies I can strip them out and use them in another design. If it does then I would have two new planes to fly!
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Old Oct 08, 2014, 08:22 AM
An itch?. Scratch build.
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Joined Mar 2003
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Often it's not the accuracy of the bits you cut and glue together, it's amazing just what will fly.

The more important areas are the linkages between servos and control surfaces, the lack of twists and warps, and that the finished model balances roughly where the designer indicates. Roughly, as even that does not have to be that accurate, (+- 2mm) to start with, and you may want to move it after some test flights.

Can't quite understand why you would need to do options 1, 2 or , ".. build a plane big enough to carry FPV" equipment.", unless you actually want to fly FPV.

The main limit of model size lends to be the weight of the gear you need it to carry. With just the RC gear you would only need to build big if you were stuck with enormous very heavy servos that had to be used.
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Old Oct 08, 2014, 08:28 AM
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eflightray: I WANT to do FPV. I am kind of just using this as an excuse. I think it would be awesome to see it from the bird's eye view. I couldn't believe how light a plane could be with just the bare essentials. When I hold my UMX Radian it's almost like it's not there. But that thing flies great and even handles some decent wind without becoming uncontrollable, even for this rookie.

NewtoPro: You are right about what will fly, I have seen some crazy things with a motor strapped on and they stayed airborne. That being said, I would like a quality flyer, not a handful to keep off of the ground. I imagine that good balance and lack of flexing/bending/twisting/etc go a long way. You can adjust to flaws as long as they are consistent. Flying something that flops around inconsistently seems like it would be nearly impossible.
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Old Oct 08, 2014, 08:43 AM
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Quote:
Originally Posted by lucky53s View Post
That one looks pretty unstable at the start but maybe flies better than the initial takeoff.
That's exactly my point. That plane has very warped foam and is very asymmetrical in every way - the left wing has way more lift than the right. And despite that it can take-off and land on a hard surface beautifully. No need for a field full of tall grass to cushion the landing. Also, did you notice how slow I landed that thing? That's not so easily done with a high aspect ratio plane.
And yes, a delta may wobble around at slow take-off speed, and despite that will only stall at very high angle of attack - they are very stall resistant compared to higher aspect ratio airplanes.
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Old Oct 08, 2014, 08:48 AM
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I see two questions, one on plane construction and a second on radio selection. On plane construction, foam builds more like cabinetry and other woodworking (moldings, etc as you mentioned) than does conventional balsa stick. Accurate, square lines and edges go together better infoam, just like larger projects. However, foam is way more forgiving than plywood! If you cut your slots a bit big, you can fixture the pieces with masking tape and fill gaps with Gorilla glue foam. (Use the white fast cure type). As ntp said, a sharp knife and good straight edge are important. A good technique with DTF is to make cuts in 3 strokes: first with just the sharp tip to slice the surface, second about half way through, third all way through. Lots more tips in threads in this forum. As for planes, build a few practice ones to get the weight and balance and build techniques down before your magnum opus! Browse the 600 planes sticky thread at top pf first page. And humor me by clicking on my username and looking in my blog for the list of "onesheeters", all but a couple designed for dtf building.

On the radio, the protocol that your flysky T6 uses is the same as the Turnigy 9x which is also made by flysky. I and several fb's have them, and they are rock solid performers. You can get 3 ch rx's for around $6 and the 6ch like you got for $9 from HobbyKing and other places. Your umx's are Spektrum protocol, and it is hard to criticise the largest selling brand in the world, but nearly all my friends who fly Spektrum have had crashes where right before we hear the 'smack' we hear "I lost it!" So far i know of only one incident with the flysky radios where a guy was out a couple hundred feet and plane went down. When we checked it over, we discovered he had inadvertently pulled the antenna wire clean off the rx at some point! Said all that to say you have a good radio, don't bother to return it. Rx's are cheap, and the system works well.
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Old Oct 08, 2014, 09:16 AM
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Springer: I read good things about the FS-T6 also. At the time I didn't know there were different systems. As you state, receivers are cheap. I think it's worth trying and the more I read, the more I'm convinced. For $55 vs $200 and receivers at a fraction of the cost, I'm think I'll put something together soon and see if it flies.

Lots of awesome designs in your blog. Some more advanced but I live on a lake and would love to work up to a float plane after a few attempts at something on dry land.

Nute: I can see how one big flying wing will land much easier than a smaller wing with basically dead weight dragging it down. My UMX Radian doesn't have landing gear so I have no landing experience. I guess this would be a good time and a cheap way to learn.
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Old Oct 08, 2014, 09:32 AM
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If you live on a lake, ya gotta do some seaplanes! It is like having an infinitely large runway! Just make sure you use corrosionX on all the electronics! Check out the polaris and slowboat threads! And don't be intimidated by apparent complexity, it is only foam, and at a buck a sheet, you can afford to throw away one you don't think is "good enough". But also, foam is incredibly repairable, so you can cut and fiddle to get it right. Lots of opportunities!
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Old Oct 08, 2014, 10:20 AM
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I have to drive all of 1/2 mile to an open field to fly. If I had a seaplane I could step out of my back gate and drop it in the water. So convenient!

This is off topic but I think I'm allowed to derail my own thread: What happens if you submarine a plane in fresh water? Replace all electronics? Or can you dry some things out? Not an issue of losing it if it's made of foam. I think my quad would sink so I don't fly over the lake too much.
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Old Oct 08, 2014, 10:34 AM
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Generally most foamie sea planes are designed to protect the electronics, but water finds a way in no matter how you try to keep it out in my experience. That's why you use CorrosionX or something like it. you apply it to the electronic gear and it waterproofs it, so it will take a dunking without shorting out and letting the "magic smoke" out!

I got the 16 oz bottle (squirt, not aerosol) and I put some in a medicine bottle with dropper. When I need to waterproof an ESC (the most important item) I drip the CX into one end of the heat shrink, til it comes out the other, then drip in the other til it comes out. So far that has worked. I also take the case off my rx's and soak the pc board in it. Motors are pretty much impervious to fresh water, although I have a couple where the stator rusted and dragged on the magnets because I didn't blow all water out. Eventually the water will get into bearings as well, but failure isn't catastrophic like a toasted ESC. Batteries aren't bothered as far as I have seen. Servos can get weird, and rust up, but their electrics are pretty well protected inside the cases so dunking in CX is mostly optional. On the other hand if you dunk an unprotected plane, you can get smoke and stink, and sometimes flame as the esc toasts itself and sometimes takes other stuff with it. i had one plane almost start on fire when I missed the landing and plopped it into my pond about a foot from the shore!

If you do dunk one and things quit working or work odd, but don't smoke, First, don't run the motor up! Remove battery, set it aside, and at your leisure, take everything out and dry off, with towel, hot gun, etc.
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Old Oct 08, 2014, 11:43 AM
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Back to the original question

Precision is not critical as long as you take reasonable care in construction. Experimental Airlines as well as the Flite Test airplanes are great ways to get started. The cost of the electronics is reasonable and the cost of the airframe is extremely low. Give it a try and if you have problems just build another. You will quickly gain experience.
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Old Oct 08, 2014, 11:56 AM
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Springer: Great info. I really appreciate it. I'll add CX to the list when I venture into aquatic airplanes.

JB: You are right on about airframes being inexpensive as far as foam goes. Even electronics aren't bad unless you start buying Spektrum. With so many other brands out there I see no reason when many others are very good as well.
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Old Oct 08, 2014, 12:16 PM
Hot glue held together by foam
United States, WA, Vancouver
Joined Aug 2010
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A very good plane for first time scratch building is the EzFly R3 . It is a SUPER stable flyer , and it's a pusher prop so the motor/prop are not the first thing to hit the ground in a nose first crash . And being a pusher prop makes it nice for FPV , you can mount the camera on the front without having the spinning prop in the way . For FPV you can scale it up to 150% or 200% . I have made dozens of EzFlys out of Dollar Tree foam .

http://www.rcgroups.com/forums/showthread.php?t=1174874

Here is the thread of a 14 year old who had never built or flown an RC plane before , who built an EzFly R3 . There's a video of his first successful flight on page 11 .

http://www.rcgroups.com/forums/showthread.php?t=2118564

Here's a video of a Dollar Tree foam EzFly I made , lightweight for slow flight ( light wing loading ) .

Al
Copy of EzFly with under-cambered wing (1 min 57 sec)
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