Thread Tools
Apr 25, 2018, 09:34 AM
What could possibly go wrong?
Thread OP
Build Log

Das Ugly Stik Modified, scratch build


Hi, obviously what the world really needs is another variation on the Das Ugly Stik, right? This will be a scaled up scratch built version specially built to let me use my Satio 130TD, a flat twin 4-stroke with dual glow plugs in each cylinder. This came from a very kind man who has always been very supportive of me ever since I got into RC about 2.5 years ago (you know who you are ), not counting when I was in school in the 80's and built a Goldberg Gentle Lady which never flew. I consider I've really been in RC since late 2015, a while after that I built an RCM Trainer 60 from plans, then a BTE Venture 60 which are only available as REAL kits you build yourself. I can't say enough good things about the Venture 60 or BTE in general, the quality of the design, kit and support was all first rate. The trainer has been a big success too. All three of these models are/will be powered by Saito 4-strokes which I think are just great.

This older-style 130TD is quite different from the later 130T, other than dual plugs it is ABC not AAC is much heavier at 1.3kg / 46 oz. including two exhaust pipes and wiring for two cylinders. I chose the Das Ugly Stik and a scaling factor to suit this engine, I want enough wing area to give me a wing loading around 15 or 16 oz/ft^2 and as I plan to get into pattern a basic Stik will be a reasonable choice. I'm just keeping the shape and the basic ratios of the Stik design and otherwise throwing away the plans, the structures will all be my own selection - almost everything will be different to the original plans. There's a later CAD version of these, and a later update of that, too.I scaled that version up by 1/6, for a wingspan of 70" / 1.78m. That version of the plan uses a fully symmetric Selig 8035 aerofoil, kind of an improved NACA 0014 for aerobatic RC use. I think I got it from Outerzone but I forget under what title, it didn't turn up with a quick search, so I'll attach the plans to this post.

I'm using various ideas I've been wanting to try. The fuselage will be based around a core "strong box" concept, with a Warren truss rear fuselage from about the wing TE back. Rudder and elevator servos will be on a sub-frame towards the rear of this frame to help balance the engine. The core box will be made of 1/8" aircraft plywood with 1/8" balsa skin. It will have lightening holes cut in such a way as to mimic the Warren truss of the rear fuselage. The other major feature of this build is to use moulded sheet LE construction. I would have used a D-tube or torsion tube anyway, but I'd seen this idea and wanted to try it, where the D-tube sheeting wraps right around from the top spar over the nose of the ribs and back to the bottom spar - there is no solid LE piece, just the ribs with sheeting. So it has to be moulded over a former first and soaked for flexibility to bend that far. I've tried a test piece and it basically works but needs refinement. Other mod's and features will make it more like an Ultra Stik than a Das Ugly Stik as I've never really been keen on that rounded Eindecker-style fin, and I want to use it to improve my aerobatic flying and get into pattern. I also plan to use flaps, probably a 3-servo wing (rather than 4, I'll get to that) like an Ultra Stik. So it will be a hybrid both in design and construction.

I've already had some excellent help and guidance planning for this build and deciding on the overall design. Many thanks for that help to Bruce Matthews, Andy Kunz and Cherokee Flyer for their wisdom and experience, not to mention going well out of their way to share their time and even spend a real effort to help me. People in the RC hobby really do extend a helping hand, and their friendship, and I appreciate it very much.

I'm not ready to post picture yet, I'll prepare the first pieces and get something worth seeing before I do. If you saw my other logs they were very detailed, I'm going to try not to do that so much this time. I tend to throw it all in there but I'll be experimenting and learning this time so I'd prefer to just use the results of that rather than meticulously log ever tiny decision, error and change. This build is to take me from my current beginner/intermediate level to the next stage, and I will still have a long way to go after that. I look forward to trying these new (to me) techniques, and trying that fantastic Saito twin engine on an interesting model. If you have questions or contributions please go for it, all welcome.

Basic spec's:
Modified Das Ugly Stik
Scaling factor (on plans below) - 1-1/6 (116.7%)
Wingspan - 70" / 1.78m (between outermost ribs, not counting wing tips)
Chord - 16" / 406mm (inc. control surfaces)
Wing area - 1120 in^2 / 72.26 dm^2
Target weight - 3.2 - 3.6kg/ 7 - 8lb (target / maximum)
Wing loading (target) - 14.5 - 16.5 oz / ft^2
Powerplant - Saito 130TD, 21.3cc / 1.30 ci, dual glow plug ignition. 1.3kg / 46 oz.
Construction time - 0 to 50 years.
Sign up now
to remove ads between posts
Apr 25, 2018, 12:31 PM
What could possibly go wrong?
Thread OP

Design


I came up with the spec's in post #1 basically by starting with only the weight of the engine and knowing I wanted an Ugly Stik to fly it in. I got some good advice and settled on the wing loadings you can see, and I had to work out what I think the model will weigh. I know the weight of the engine, but for the rest I had to use intuition. Anyway, I've tried to go for strength-to-weight first and foremost, that's why the trussed rear fuselage and moulded LE, D-tube wing. There will also be cap strips on that wing, TE sheets and upper and lower spars with sheer webs. I'll probably go for built-up ailerons, and I'll probably think about whether I'm going to abandon that and just make them from solid sheet... don't know yet but I hope I stick it out for built up. I'm definitely planning on some kind of built-up fin, rudder, tail-plane and elevator. The type of trussed rear structure I want to do is explained in this series of articles (this is the 2nd of 3 pages, links forward and back on the page http://www.airfieldmodels.com/inform...e_sides/03.htm

I'm showing some sketches here posted for me by Bruce Matthews, I'm very grateful for these. You can see he started with a full truss fuselage for his own Das Ugly Stik design, mine will be a hybrid of that and a central torsion box. That box will be lightened with cut-out, so that it LOOKS like truss but will just be flat ply. There will be top and bottom pieces on the box, but at least the tops will be mostly cut away to save weight and give access. I'll add a partial height bulkhead at about 1/2 chord under the wing as that's a pretty big box for a radio bay under that 16" chord. I really want it to be stiff and strong in there, as the engine's heavy, torquey and I hope to give this model a good ol' fling around.

I've also added an early sketch I made of the "strong box" at the core of the model. Other designs often tend to 3 strong areas for firewall, wing saddle and landing gear, then tied together almost ad hoc with doublers and whatever, but I'm going for an integrated way to make all these strong and stiffen the model completely. I think it can be done in an efficient way. OK so the "truss look ply" sides are really more for show than effect, but hey, they do look kinda cool don't they? (thanks Bruce Matthews - your idea!) But I think they will function the right way. The fan or sunburst of struts supporting the landing gear plate on Bruce's sketch is to spread the shock of landing and the load of the model's weight on the ground to where the structure is strong - I think that's worth doing in my version too. I want to remove plenty of weight from the basic ply box, and what remains should be only enough to do the job where it's needed and not much more.

If you've seen the difference between an Ultra Stik and a Das Ugly Stik the main visible cue is the triangular fin vs. the DUS rounded fin, I'm going with the triangular type. The Ultra Stik is not in public domain so I can't post the plans (haven't got em anyway) but I'll find a photo. I'm going to try and end up with about the same ratio of fin/rudder area and the same kind of shape. I'd like to make the tailplane a "real" built up wing with ribs, a spar and sheet it with thin balsa but maybe it'll just be a diagonal truss type, but it won't be a flat plate of sheet balsa. Neither will the fin or either control surface.

So I think the general design concept is clear - as strong and light as possible at a slightly expanded scale, for a particular engine with its own demands. More modern engines of this type are lighter but I think this one will have decent output. I want the total loading to be modest and the structure to be stiff, to not distort overly in flight and stand up to a real workout. Looking forward to starting.
Apr 25, 2018, 12:42 PM
What could possibly go wrong?
Thread OP

Moulded sheet balsa LE


I mentioned the moulded sheet balsa LE, similar to the skin on a foam wing. Many of you will have seen this, see post #1 for a description if not. I made a prototype to see if it will work, and it does. It meant I had to make a mandrel (former, plug etc) to wrap it around once soaked, it's not as much work as it looks but still significant. And I'm going to have to make another one! One sheet isn't enough, each wing panel will need 3 sheets joined edge to edge to make a single piece wrapping from top to bottom spars over the LE, and my mandrel is nowhere near deep enough for that. But, this did prove the concept and give me some valuable experience. I'll know how to go about it next time.
Last edited by BernardW; Apr 26, 2018 at 02:05 PM. Reason: Missing photo caption
Apr 25, 2018, 02:20 PM
Registered User
Hey Bernard ! How is everything down under ? Welcome back and good luck with the new airplane ! Mike
Apr 25, 2018, 02:36 PM
What could possibly go wrong?
Thread OP
Hi Mike, all's well, I started with a new employer late last year (concert and production crewing agency) and that went GREAT, after a difficult year with nowhere near enough work. But the season has kinda wound up now approaching our winter, however I'm much better set up with new contacts and training to get through it this time. I think I won't have it quite so bad this winter, though it'll be lean. That's why it's time to have a build going!

Haven't been able to get much flying in and I've GOT to get out there!! This is the best time of year, conditions are sweet. Little wind, just enough to land better. Pleasant and cool, just enough cloud to take the edge off the sun, real nice. We had one of the mildest summers on record, that suits me! I am not a hot weather person, and that's a problem if you live here. But outside summer really the climate here's very agreeable.

Yep this will be my most ambitious project, lots of new tricks. Biggest powerplant and my first multi, I hope the first of many. This will give me a chance to try all sorts of things I've wanted to do like the Warren truss, and I've got a special interest in the moulded LE, that's from Andy Kunz. I'm doing it the broke person's way, it's one more nudge towards setting myself up to make foam wing cores. The time has come, I need them. Not only do I want foam wings but that would be MUCH easier than building half a wing just as a former to make a skin for another wing!! AND I'm going to have to do it all over again... but I learned how to do it, it worked and it'll work better for the real thing. While work was going great guns I upgraded my radio gear, this plane will get a Hitec Maxima 9 receiver in it and their D-series servos (got a couple still to buy), that's good stuff and I will need that for a model of this size and power. I plan to start learning pattern on it so it's got to have capable controls. I don't really know what to expect from this engine but it's a 1.30ci twin, and Saitos always have plenty of poke. It'll be fun and the airframe's designed to match it.

If I get just a few more good weeks I'm going to grab a used compressor and a spray gun and look into a fabric finish of some kind with paint... THAT would be icing on the cake! I'm hoping this structure will have some wiggle room in weight to play with, such as for a nice finish. But I think it's going to be a long slow build at the rate I do them. Well the only way forward's to get on with it so gung ho! See ya soon and thanks for checking in
Apr 25, 2018, 03:26 PM
AndyKunz's Avatar
Your excitement is contagious, Bernard!

Andy
Apr 25, 2018, 06:58 PM
Registered User
Bernard, this will be a fun build to watch.... Kinda' a high tech approach on a classic design. That leading edge idea is really cool, as are the other new concepts you are building into this airplane ! I am sure the 3 Pros you mentioned will be cheering you on from the land up over ! I should stock up on some extra popcorn next time I go to the grocery !! Have fun ! Mike
Apr 26, 2018, 02:02 PM
What could possibly go wrong?
Thread OP
Well, I did say I wasn't the quickest builder. I am working on it though. I spent some time transferring the basic fuselage layout sketches to plywood at the final scale and it turns out it will have to be a bit different for my application - Bruce's drawings were for a smaller Stik and it doesn't really work as drawn for my model's size. Remember that the chord is 16", that makes the compartment under the wing relatively long and low, at least by the standards I've used so far. So I'm making sure it's right before I commit to cutting wood. I want to see some alternatives on paper first.

If you saw the photos of the mandrel I used to mould a test LE sheet, that has to be done again too. That mandrel was only big enough to mould a single 4" wide sheet and I'm going to need to join 2 of those and a 3" piece, so I need a mandrel deep enough to mould the whole skin. That one already has its problems and if I try to extend it that will just make it worse, so best to build a new one. I made a cutting template and new ribs for it from that and will have the mandrel finished in a day or two. I think this time I'm going to shape a LE out of rectangular balsa stock instead of a dowel. It will be a lot like a conventional wing from the spar forward, and just as much work, before even using it to mould the actual skin. But the result will be worth it and hopefully I can use it again. I would much prefer to make it in foam, exactly like a foam wing core, so ASAP I want to built a foam cutter. I wish I had that now. Meanwhile I know this way does work, it's just extra time and effort. I'll get photos when there's more to show.
Apr 26, 2018, 03:34 PM
Registered User
Bernard, it looks like you have a winner there. Never too many stiks; they''re such great flyers. The Great Planes Giant Big Stick has an 80.5" span and mine weighs about 14 pounds, about 21 oz/sq ft. Your plane isn't much smaller including the wingtips but at a projected weight of 8 pounds it will float! Very cool.
Apr 26, 2018, 03:57 PM
Registered User
Cherokee Flyer's Avatar
Iíll be riding along and watching.

L.
Apr 26, 2018, 06:05 PM
What could possibly go wrong?
Thread OP
Welcome David and Cherokee Flyer, glad to have you here. There's one of that particular Great Planes versions for sale at one of the hobby stores near me, not what you call super cheap but looks like a nice plane. If it hits my target weight that modest wing loading should make it agile.. I think it's realistic - starting with the standard Ugly Stik this one's larger but there's plenty of scope to save weight. I chose the rear structure to save weight overall, and the birch ply might be heavy but I can cut out a lot of it too. It's all about strength-to-weight. I don't know if I'm working today or not yet but if not I'll spend some time on it and hopefully finalise a plan for that front section.
Apr 26, 2018, 09:22 PM
Mumbling in the corner.
flyboy2610's Avatar
Quote:
Originally Posted by BernardW
I also plan to use flaps, probably a 3-servo wing (rather than 4, I'll get to that) like an Ultra Stik. So it will be a hybrid both in design and construction.
Hi, Bernard! I'm looking forward to following your build. You always do quality work.
As you may recall, I'm putting flaps on my Great Planes PT-60, and also using 3 servos in the wing: one for each aileron and one to drive the flaps. Here's how I made the pushrod for the flaps: https://www.rcgroups.com/forums/show...&postcount=175
I'm hoping someday to actually finish this plane!
Apr 27, 2018, 09:39 AM
What could possibly go wrong?
Thread OP
Time to make a decision and get that ply cut. I might have to abandon that attractive but more complicated truss-like layout for the ply sheet. My original idea was in the sketch called "Strong Box" below, then Bruce contributed those cool hybrid ideas cutting diagonals into the ply. Maybe what I'll do is only keep the Vee supporting the landing gear base plate, and just have open space ahead and behind it until the verticals for the bulkhead behind the fuel tank and at the rear of the gondola (box). I want to have a bulkhead at about half chord, around half way along the compartment under the wing to split it in two, and that's about a good spot for the LG support too so I could have a vertical inside the Vee, or just a solid triangle of wood with cut-aways either side to lighten the ply. In the sketches below the Vee section would be much narrower than this, those sketches are all based on a smaller version of the Skik with truss construction, and I altered it for a larger ply gondola up front. Anyway I'll make a decision and mark it all out ready to take it to where I keep my scroll saw tomorrow but I think I'm tending to the 2nd version below.

If anyone sees a problem with this let me know... I would think that this structure in 1/8" ply and a layer of medium 1/8" balsa over that would be plenty for this model at this size and weight, but if you have seen any reason why it wouldn't be I'd appreciate hearing your experience.
Apr 27, 2018, 11:32 AM
What could possibly go wrong?
Thread OP
Just did some measurements from the plans I started with (post #1). On the side view the engine thrust line is exactly half-way up the firewall... I'd have thought it'd be referenced to the airfoil centre line, the firewall to me seems a little arbitrary. it's only the dimensions it is to fit around the tank, so that doesn't give any specific relationship to the camber line... does it matter greatly? I measured it thinking there must be some relationship between that line, the wing and the max. height of the fuselage but I guess not. I really thought I'd find it was half way between the fuselage floor and the wing centreline... OK so this is one of those silly pedantic details that stumps me because I have no idea whether I can safely ignore it or should it follow some rule of thumb which I don't know... hmmm. If anyone's thumb has some rules for me I'm all ears, thumbs, left feet etc, but I'll ask around. I hate getting stuck on stuff like this, if I can't find a reason to set it to any particular value I'm going to make it equal to exactly "whatever".
Apr 27, 2018, 12:44 PM
AMA 46133
SeismicCWave's Avatar
Quote:
Originally Posted by BernardW
Just did some measurements from the plans I started with (post #1). On the side view the engine thrust line is exactly half-way up the firewall... I'd have thought it'd be referenced to the airfoil centre line, the firewall to me seems a little arbitrary. it's only the dimensions it is to fit around the tank, so that doesn't give any specific relationship to the camber line... does it matter greatly? I measured it thinking there must be some relationship between that line, the wing and the max. height of the fuselage but I guess not. I really thought I'd find it was half way between the fuselage floor and the wing centreline... OK so this is one of those silly pedantic details that stumps me because I have no idea whether I can safely ignore it or should it follow some rule of thumb which I don't know... hmmm. If anyone's thumb has some rules for me I'm all ears, thumbs, left feet etc, but I'll ask around. I hate getting stuck on stuff like this, if I can't find a reason to set it to any particular value I'm going to make it equal to exactly "whatever".
There are as many "Ugly Sticks" in this world as there are modelers. I just looked at three and there are differences in the thrust line of the engine. According to the plans you are using (drawn by Guy Fuller) the engine thrust line is exactly in the middle of the "finished" firewall. That is the firewall with the top and bottom sheeting in place. The top sheet is thicker than the bottom sheet so the thrust line is really slightly higher in the actual firewall itself.

Then if you look at the other plans. The one from RCM has the same thrust line like yours.
https://outerzone.co.uk/plan_files_0...939_oz6801.pdf

However the plans from Grid Leaks published back in the 60's shown the thrust line considerable higher on the firewall.
https://outerzone.co.uk/plan_files_0...aks_oz5175.pdf

Jensen kitted the Ugly Stick and the plan followed the Grid Leaks plan with the engine mount higher than the center line on the firewall.
https://outerzone.co.uk/plan_files_0...sen_oz1253.pdf

I personally do not think that the 1/4" or so of thrust line is going to make ANY difference at all in the performance of the aircraft.

However to give you a peace of mind and feel like you are more in control I suggest using an engine mount that you can adjust. One engine mount came to my mind. The Great Planes mount is adjustable with the mounting bolt holes slotted in the back. If you don't stretch the engine mount all the way to the maximum you can actually slide the mount up and down 1/4" or more on the firewall if you mount the engine sideways.

However I am not sure what kind of engine mount you plan to use with your Saito.

For practical reason I would say forget about the camber of the airfoil. It is a flat line since the foil is fully symmetrical. To throw in a bit of a monkey wrench. If you look closely at the plans from Grid Leaks the wing looked like that is a slight positive wing incidence.


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Build Log 90" Das Box Fly Bipe (scratch build) AA5BY Balsa Builders 466 Oct 07, 2019 10:30 PM
Discussion Das Mini Stik build bobbyblank 1/2A Planes 43 Jul 10, 2019 09:17 AM
Build Log Das Ugl-E-Stik Build thread pmjass Foamies (Kits) 374 Oct 31, 2018 09:36 AM
Discussion Das Ugly Stick - Modified Scratch **neons** Foamies (Scratchbuilt) 1 Jun 22, 2008 10:57 PM