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Old Jan 11, 2011, 09:34 AM
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Build Log
The Mini Topsky: Compact and beautiful

Look what Ron, our intrepid mailman, brought in from the cold: a box sent USPS all the way from California. I have been following the trials and tribulations of builders on one of the most active threads on RC Groups for quite a while – the thread for the standard size 1.5 meter Topskys – and jumped at the opportunity to purchase the recently released mini Topsky. The interest in smaller dlgs is growing exponentially, for many obvious reasons, so it is understandable that Topsky would want to join the fun with their Mini Topsky. The plane looks gorgeous in the marketing literature and I thought that after their experiences with their full size dlg most of the inevitable kinks would have been ironed out sufficiently for the company to produce a really good junior version of their very successful plane. What Ron delivered is without a doubt a fabulous looking plane.

Let me say a few words about the supplier of my plane. I purchased my mini Topsky from Hobby Club in California. What a deal! They have a special on the plane at the moment that includes two micro servos for a total deal that came out at $135.59, shipping included. At this price one cannot go wrong. I was very pleased to see how they packed the plane – they used three nested stiff cardboard boxes with ample foam to protect the delicate parts. I phoned them on Friday morning and had the plane in perfect shape thanks to the USPS at my door in New Jersey on Monday afternoon. Talk about service.

Building these babies requires a different skill set to those required to complete larger sailplanes. I thought that it would be interesting to start a build thread on the Mini Topsky so that builders and fliers could share their hard earned experiences on their smaller planes with each other. Those of you with invaluable free flight experience are especially welcome to pass on some of your knowledge. I have a number of ideas to share as well, and will post them as I put my plane together.

Alan
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Old Jan 11, 2011, 10:07 AM
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I have had great service also with Alberto at hobbyclub.com. Great people to deal with and always willing to help. kenny
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Old Jan 11, 2011, 11:17 AM
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Already a thread here, not on the first page so easy to miss: http://www.rcgroups.com/forums/showt...ht=mini+topsky

That being said, I nice and detailed build with pictures is always nice!
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Old Jan 11, 2011, 12:59 PM
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New Builds are Welcom

A new fresh build is always welcome in my book. There is a lot of chit chat in the original threads for many planes. Starting fresh is much like an early morning rain shower.
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Old Jan 11, 2011, 01:21 PM
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I just assembled a 'Elf' mini DLG and flew her for the first time yesterday... You should be in for a treat, these little gliders are a lot of fun and in the elf is anything to go by they fly remarkably well.
Like all small models weight control is critical for good duration, the Elf scores in this respect as the complete airframe minus RC gear as only 70g.

Good luck with the build and with flying.

Steve
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Old Jan 11, 2011, 02:31 PM
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Weight, weight and less weight...

Like all small models weight control is critical for good duration, the Elf scores in this respect as the complete airframe minus RC gear as only 70g.

Good luck with the build and with flying.

Steve[/QUOTE]

Steve

You hit it on the head as far as I am concerned. These little gems MUST be built light. This is what I intend to do. That is why I suggested that the smaller dlgs call for a different set of skills to those that are needed for the bigger boys. I am certain that many of you have good ideas on how to shave a gram off here, and another gram off there. So do share your thoughts on building, and especially on building light, as we work along with my build.

Guys, I appreciate the support with this mini build. Yes, fresh ideas are always welcome in our creative hobby. Here I want to get as many good ideas together as possible on building a robust baby that is as near as light as possible, still with the ability to accommodate ballast when called for. And you know what: if we don't build it strong enough we can learn from the 'mistakes' and correct the 'errors' later. Except for some damage to the ego, if any, nothing is really lost in the learning process.

Alan
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Old Jan 11, 2011, 04:13 PM
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Building light is something that flying freeflight models drums home. With a largely pre finished kit there is limited scope for weight saving but the biggest things I watch for are:
  • Keeping the tail super light (one gram on the tail = + 5 grams in the nose!). Use only light wood for the tail feathers, well sanded. Don't add any unnecessary weight by glassing or film covering the balsa, it's not needed for these small models. Just seal the wood according to freeflight glider practice.
  • Use all glue sparingly
  • Lightweight RC gear (obviously!)

I'm not sure what the Topsky uses for rudder and elevator actuation but I like the way it's done on the Elf. It uses tiny 0.8mm dia carbon pushrods. These weigh next to nothing and probably add no more weight to the tail than than a single pull torsion spring system. They are a bit fragile to set up but once installed work great.
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Old Jan 11, 2011, 04:27 PM
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I think you'll find the Elf and Top Sky mini display different flight characteristics reflected by different design principles, my Elf loves to float, I might be wrong but I suspect the topsky launches higher but with faster glide, better in windier conditions, whereas the elf is a dream in flat calm, both nice though.
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Old Jan 11, 2011, 04:41 PM
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Quote:
Originally Posted by mrdoodah View Post
I think you'll find the Elf and Top Sky mini display different flight characteristics reflected by different design principles, my Elf loves to float, I might be wrong but I suspect the topsky launches higher but with faster glide, better in windier conditions, whereas the elf is a dream in flat calm, both nice though.
Both gliders use similar Drela airfoils, have the same span and similar overall proportions and are R/E control, so I see no reason why they should fly much differently other than weight. Yes the Elf is likely always to be a bit lighter due to lighter weight construction, so should float a bit better, but still no reason not to build the Topsky as light as can be. As for launch height, again the extra weight may carry the Topsky a little higher (arguably) but I see no other reason why it should launch higher or cope better in wind. Weight can easily be added to a light model. It's rather harder to take weight away from a heavy one

Certainly in the larger 1.5m DLG class there is always the constant drive for lighter and lighter weight, and I see no reason why smaller DLG should be any different... in fact more so if anything.

Steve
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Old Jan 11, 2011, 07:36 PM
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Here we go...

The time has come to make some big decisions about how to put the plane together. The Mini Topsky does come with a decent set of instructions, and had one to follow them the plane would certainly work out well. There are nine pages of instructions, somewhat faint with all the photocopying, that set out systematically how to put the parts together. But I want to do things my way, of course. If necessary, the plans will assist me, but this is not rocket science, and there is always another way to skin the cat. So here goes.

I don’t know about you, but I sometimes get the feeling that there apparently are some sacred cows in soaring that some pilots or builders think cannot be transgressed. So I am about to bother those who subscribe to the SC syndrome. Tough. Some of my proposals will strike some of you as silly, perhaps even as heretical, but this is bad luck. This creative hobby fortunately has space for mavericks and others.

First, some basic rules. Rule One: The only epoxy I will use is laminating epoxy, sometimes thinned with alcohol; Absolutely no five minute epoxy or thirty minute epoxy: the stuff is far too thick and HEAVY.

Rule Two: Use Kevlar strings and thin music wire for actuating the tails: this method is crisp, easy to do and saves TONS OF WEIGHT over the standard pushrods, horns and sheaths. (And these external pushrods etc. are ugly and generate unwelcome drag when they hang outside the fuselage.)

Rule Three: Use lipos, the smallest servos suitable, and the Berg microstamp receiver with the truncated antennae.

Rule Four: Treat CA with the respect that it deserves. It is lethal and HEAVY.

Let’s get going. To begin with, I will start with the wing. The plan calls for multiple carbon patches, ample glass cloth over the root, nylon screws into steel blind nuts in the fuselage, and globs of epoxy on the hard points where the wing halves meet. I AM DOING AWAY WITH ALL OF THIS STUFF. I want to build a plane with its wing permanently attached to the fuselage. The wing is so small to start with, that storage of a baby dlg with its wing permanently attached will not be a problem. And the car that I use for transporting my planes is large enough for this arrangement. So there is no need to use the other stuff that is usually called for when the wing is removable.

I first need to remove the blind nuts that have been placed in the fuselage. To do this I use my soldering iron, heat the epoxy bonding the nuts to the fuselage and extract them. Weight savings: 1.9 grams.

As the wing will be attached to the fuselage, there is no need for a full strip of cloth joining the bottom surface of the wings. A one inch strip of glass cloth is placed only on the top surface of the wing from leading edge to trailing edge, and a small piece is necessary below the wings where the wing overhangs the fuselage. I am using Alphapoxy, from Aircraft Spruce as the laminating epoxy of choice to wet the glass cloth to join the wing half’s. As we need maximum strength here, I will not use alcohol to thin it. I have cut the glass strip for the top of the wing, and using the laminating epoxy at full strength wetted the cloth out, doing my best to get the wing at the correct dihedral angle.

Let's leave the slow curing epoxy to do its business overnight. Time for a glass of Shiraz and some chili with my wife.

Alan
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Old Jan 11, 2011, 07:48 PM
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Hey guys before you run out and buy more "recently released" Topsky minis - I have been telling everyone NOT to as a new TS Mini SUPER is due out this month and will be on sale. Seems strange that not all vendors would be this open and honest with their customers.....
The Mini is a wonderful little plane! Enjoy it!
-S
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Old Jan 12, 2011, 12:25 AM
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Quote:
Originally Posted by Scott Seidler View Post
I have been telling everyone NOT to as a new TS Mini SUPER is due out this month and will be on sale. -S
Hey Scott, what is the story on the Super? How is it different?

Brian

Alan, you will love the Mini. I hace a TS mini and prob fly it more than any other dlg I have.
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Old Jan 12, 2011, 04:13 AM
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Dear Jet pipe, many thanks for taking time to read and respond to my comment. I thought it pertinent to offer some background to my remarks about the differences between the Elf and Topsky mini.

Design

Elf has undercambered wing section, Top sky to the best of my knowledge is flat
Elf has high aspect highly swept wing planform, Top sky is very low aspect by comparison
Elf therefore has different moment arm resulting in different planform layout
Elf has one piece fuselage with nose cone, Topsky is two piece pod and boom, this results in a completely different design re rc installation, for starters, rx is beneath wing in Elf.

Construction

Elf, one piece wing, no added weight in joining ‘glues’ glass cloth
Elf one piece fuselage, no pod to boom joint
Elf pre-glassed tails, includeing v mount for stab
Elf flying weight, quote from wgeffon ,
I am at a flying weight of 2.97oz / 84.2 g
CG is right at 3" back from the LE of the wing.
Topsky weight from plans 135 gms
That’s a difference of nearly 50 gms ! enough to offer different flight characteristics I would have thought !


To sum up I would suggest that the Elf has been designed from the ground up, its origins in lightweight free flight almost ‘indoor’ designs ( there is one uk free flighter who has plans to fly it ‘free’ without any radio install !)
Whereas the Mini topsky appears to be a scaled down version of the topsky 1.5 metre dlg both in planform and construction technique, no bad thing, both great gliders, but different in my humble opinion. I hope you find my points of use and interest, I try to be polite and offer encouragement whenever I can on the forum and shall hopefully continue to do so, regards mr D
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Old Jan 12, 2011, 05:07 AM
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Originally Posted by buildscapeinc View Post
Hey Scott, what is the story on the Super? How is it different?

Brian

Alan, you will love the Mini. I hace a TS mini and prob fly it more than any other dlg I have.
Hey Brian! Hope your doing well...
THe Super is a 4 servo plane instead of R/E only.
-S
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Old Jan 12, 2011, 06:59 AM
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No argument that the Elf is constructed totally differently and is a lighter glider, and that lighter weight will obviously have a quite significant effect on how it flies.. But aerodynamically there is really not much in it. The span is the same, the wing area near enough the same (11.7dm vs. 12dm).. And so the aspect ratio is also near enough the same (8.5 vs 8.33). Sweepp angles are a little different but not much, about 3 deg vs 5 deg (at 1/4 chord point). Airfoils are a little different but designed for identical purpose and perform almost identically (see graphs attached).

I would suggest that the Topsky was not designed to be 'heavy and fast' but is simply as light as Topsky could make it given their chosen build method and budget.

The key point I was getting at is that saving weight can only be a good thing, (providing adequate strength is retained, obviously)

Steve,

PS.. It was perhaps me you were thinking of regarding the freeflight build. I've come to the conclusion that the basic wing would be great for freeflight but dihedral would have to be increased considerably and the tail would need a lot more area to give adequate stability.
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