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Das Liddle Stik

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Geoff S24/04/2020 16:05:24
3818 forum posts
49 photos

I've been getting regular emails from Aerofred.com about various free plans and last week there was one which included a 3D printed Das Liddle Stik. After looking at it I decided to go the other way and build an electrically powered version in balsa as a means of aleviating the lockdown lassitude. I'd got most of the stuff in stock anyway.

It's a 46" ws high wing smaller version of the Ugly Stik and seems ideally suited to a 2200 3S powered model.

I downloaded the plan as a pdf and discovered (after ordering a full size plan ) that Adobe Reader has the option of printing to 100% on several sheets of A4. It's a bit of a fiddle joining them together but 15 sheets and some Selotape have resulted in a useable plan. The size is surprisingly accurate.

I'm building it without dihedral but toying with the idea of some washout. How much and is it worth the trouble?

I have a copy of the original article and there's a mention that aileron movements of over 1/8" (3mm in English) result in rapid rolls. This seems a bit hairy to my old fingers but I've been unable to find recommendations for any control throws. There is mention of using mechanical means of aileron differential but no indication of how much. I'll be using separate servos so that's not an issue but the deflections are - elevator as well. Has anyone any experience? That +/- 3mm on aileron makes me apprehensive.

Anyway it's just a quick rough and ready build which I probably won't be able to fly until next year as things stand right now.

Geoff

Edited By Geoff S on 24/04/2020 16:06:45

Stuphedd24/04/2020 19:54:51
722 forum posts
376 photos

May 1968. R/C Modeler plan and article , my first multi propo aircraft. , taught me a lot !

on the plan it shows angled bevels driving the airerons , , looks like 60 degree ones , so the up aileron will go more than the down one , I cannot remember the throws ,

But dont use washout as its a symetrical wing

cheers

Geoff S24/04/2020 20:55:49
3818 forum posts
49 photos

Oddly enough, although it looks symetrical, the wing is actually not so. I've cut a 3mm ply template to cut the ribs and if you draw round it and then turn it over, it doesn't quite fit. I checked to make sure so that I need to indicate which way up the ribs are when I cut them out. However, I'll not bother with washout as you suggest, thanks.

I'll do my usual aileron differential of 50% down compared with up programmed in.

Geoff

Phil Green25/04/2020 01:48:12
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1657 forum posts
344 photos

My first propo power model, though I had a slide-on nose-block and slope-soared it too!

The original was definitely fully symmetrical. No washout, no differential and throws - 'plenty' is always my preference with propo.

With the OS19 shown it was badly underpowered, with a Merco 35 it was just right.   IIRC I used spruce spars and L/E.

A brilliant model, you'll love it !

 

5.jpg

 

ustik2.jpg

Edited By Phil Green on 25/04/2020 09:56:24

Nigel R25/04/2020 07:13:45
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4159 forum posts
698 photos

No washout or dihedral needed. Build it as one panel and eliminate the joining stage too. I'd make the section symmetric while you're there 😀

Ps 3mm sounds small for aileron throw to me. If you build light for modern radio and electric power it will fly slower than the original and need a bit more throw all round. I doubt differential will be necessary. 

Edited By Nigel R on 25/04/2020 07:15:56

Edited By Nigel R on 25/04/2020 07:16:50

Geoff S25/04/2020 14:55:32
3818 forum posts
49 photos

Here's the rib template cut by sticking on a cutout from a copy of the original drawing.

rib template.jpg

As you can see it's not exactly symetrical - close, but not quite. Plus the bottom main spar is shown at an odd angle which I intend to adjust. I'm also thinking about putting capping strips on and fitting the t/e 1.5mm sheeting to the top and bottom of the ribs rather than in a rebate. So it will be a bit thicker in section.

I've ordered 48" spruce spars 1/4x1/4 and 1/8x 1/8 and some 3/16 balsa which I lacked in stock so I can't build the wing yet. It will be built flat in one piece with no need to join and so should be easy.

I don't think electric will make it any lighter than glow because it will stil need to balance in the same place. The only way to make it lighter is if I can reduce weight at the back which won't be that easy. It will be a tail-dragger.

thanks for the advice. Now we've had our 4 mile daily walk I'll do a bit

Geoff

kc25/04/2020 17:45:31
6709 forum posts
173 photos

The lower spar slot is angled so that the spar fits flat on the board and does not project into the wing covering film. The spar web is supposed to fit between the ribs, but it might be easier to angle top spar too so that the webbing sits flat on the back of both spars.

A feature of the design of the Liddle Stik, Ugly Stik also the Bingo etc is the lack of LE sheeting which reduces weight and material cost.   Therefore cap strips are not used as there is no thickness for the cap strips to make up.  If the TE were not in rebates then the ribs would not sit flat on the board as designed.

An electric model could well have the nose extended an inch or so to help balance as the weight in an electric is a long way back due to the length of the Lipo. In a glow model the weight is right at the front- crankshaft & bearing etc, so even if the weight of Lipo and motor are the same as a glow engine the balance is different.

Edited By kc on 25/04/2020 17:50:32

Edited By kc on 25/04/2020 17:55:07

Geoff S25/04/2020 21:02:05
3818 forum posts
49 photos

The reason I wanted to align the spar location was to make fitting the interspar webs easier. As drawn, it would be difficult to get them to glue properly (assuming the grain was vertical as is usual with webs). I think I'll realign the top spar as you suggest. I was thinking of adding cap strips to the whole rib right to the l/e; the front part would need to be with the grain at 90deg to allow it to bend. However these are just musings and I'll probably build the wing as per the drawing as a first attempt (apart from the spar angle adjustment) though I may add some sheeting to the top centre where the wing bands go.

You're probably right about the desirabilty of making the nose longer but I've already made the uselage sides so I'll have to rely on pushing the battery as far forward as possible and keeping the tail light. I'll also mount the mini servos as fa forward as possible. I'll use 3mm carbon tube for push rods.

I'll probably rename it as Das LockDown Stik laugh

Geoff

kc26/04/2020 11:08:06
6709 forum posts
173 photos

Capstrips are usually cut with grain along the length, while LE sheeting has the grain spanwise which helps the bend around to LE. So I doubt you could get full length capstrips to bend easily right around to the LE unless they were cross grain.

The whole point about the Liddle Stik and the Ugly Stik is the wing uses a minimum of parts - saving weight, money and most importantly time. Adding capstrips etc goes against this idea!

On reading the article it says the spar webs are fitted BEFORE the top spar and this seems likely to get a good joint without too much fitting. Making a simple template to cut web to height might help get a good fit. It is probable that a firm fitting to the ribs alone would make the webbing worthwhile even if the joint to spar is poor. So maybe fitting the webs as each rib is inserted would work well and ensure ribs are vertical ( if the webs are cut square!) However the article does say some models were built without webs.

A joint to extend balsa sides would be perfectly OK if it occurred over the ply doubler.

kc26/04/2020 11:58:23
6709 forum posts
173 photos

Geoff, you might be interested in my Rapido which is shown in another thread today. Really a 50 inch electric Liddle Stik with Ugly Stik style features removed!

Geoff S03/05/2020 14:39:19
3818 forum posts
49 photos

I've just about completed the wing.

Here are the ribs - most are 3/32" but the tip ribs and the 3 at the centre are 3/16".

ribs.jpg

You'll see I marked each rib to indicate the top surface. Superficially, they look symetrical but the bottom surface is flat from the spar location to the trailing edge which makes building easy. It's more obvious with a complete wing because it won't sit flat on the board when inverted whe the slight curve at the top allows it to rock. Also you can see that I've made the spar locating slots straight so that the interspar webs fit properly (see the rib template earlier to see how the original drawing sets the spars at an angle to each other).

The wing on my magnetic board during the build.

wing 1.jpg

The complete wing which weighs about 250 grams including servos (12gm 2kgcm torque metal geared from 4max). The ailerons are hinged with Blenderm tape as well as (ultimately) the film covering. I made the scalloped t/e with sandpaper wrapped round a piece of cardboard tube. Not perfect but it's a bit of the model's quirkyness I thought amusing.

wing 2.jpg

Geoff

kc03/05/2020 17:07:19
6709 forum posts
173 photos

Geoff, how did you actually use Blenderm tape? Does it work just sticking it on in the obvious way?

 

Elsewhere you mentioned building a bipe version. Check out the 4-40 Bipe for a similar wing construction - mostly no LE sheeting - but the section is different, probably too much drag with 2 very thick airfoils. Frankly the best flying small bipe is the Acrobits, I flew my Renegade bipe ( R Clarke design ) and then tried a friends Acrobits. Acrobits was better than the very good Renegade.   People in my club reckon the Pasadena Special is the best small bipe.  Very simple build.

Edited By kc on 03/05/2020 17:09:28

Edited By kc on 03/05/2020 17:20:01

PatMc03/05/2020 17:59:43
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4481 forum posts
548 photos
Posted by Geoff S on 03/05/2020 14:39:19:

You'll see I marked each rib to indicate the top surface. Superficially, they look symetrical but the bottom surface is flat from the spar location to the trailing edge which makes building easy. It's more obvious with a complete wing because it won't sit flat on the board when inverted whe the slight curve at the top allows it to rock. Also you can see that I've made the spar locating slots straight so that the interspar webs fit properly (see the rib template earlier to see how the original drawing sets the spars at an angle to each other).

The wing on my magnetic board during the build.

Geoff, IIRC the odd angle of bottom spar is because the flat section extends from the front of the spar to the TE in order to allow the wing to be pinned down over that area during building. The designer having decided that the slight asymmetry introduced would have no effect on performance.

Geoff S03/05/2020 20:08:00
3818 forum posts
49 photos

kc: I applied some MD Covering adhesive (Balsalock replacement) to the ailerons and wing t/e. The ailerons are top hinged so it was just a matter of sticking the tape in place at the top and then turning the wing ove rand folding back the ailerons to apply the tape on the bottom surfaces. I put the heat sensitive adhesive on to help adhesion when I do the covering. Not sure if it will work but I'll keep an eye on it. I don't think it will fail suddenly so there should be warning if the tape or the covering is causing problems.

It's just that the ailerons are made from solid 1/8" sheet which is very thin to slot for normal hinges so Iopted for a tape/film combo.

I like biplanes a lot and have a few in my collection though some have been grounded for some time.

Pat: The flat bottom section of the rib shape certainly makes building straight forward. The ribs sit firmly on the board and the rest follows. The adjustment of the spar angles is quite small to get them in line and has no effect on the build except to make the shear webs fit properly. I think the shear webs were an after thought so the need to make the spars the same angle didn't exist.

Geoff

Geoff S06/05/2020 18:07:36
3818 forum posts
49 photos

Making some progress. The wing is more or less complete except for covering though I'm toying with the idea of glueing some location tabs on the centre ribs so that the wing seats accurately each time it's banded on. They'll be weak enough to break in the event it's needed

I had a bit of an issue with the fuselage formers being too wide for the side pieces to sit properly (or at all) on the 3" wide 1/8" ply base. Not sure if it was because the drawings of the formers didn't take account of the 1/32" ply doublers on the 1/8" balsa sides or if I chose the wrong side of the 1mm thick lines on the drawings but all came out OK in the end as I found out before any glue. I just needed to make them 1/16" narrower.

The formers and side pieces

fuselage 1.jpg

I laminated the balsa formers with either 1/32" ply (the 3/16" ones) or 1/64" ply ( the 1/8" ones at the back) so I could cut large holes to make passage of the push rods easier. There seemed to be no weight penalty and I ended up with slightly stiffer formers.

The base is made up of 1/8" ply at the front glued edge on to 1/8" balsa at the back. Not convinced about the integrity of the butt joint but I'll see how it goes. I may add a small reinforcing part over the joint in either 1/32" ply or 1/16" balsa.

The tail components.

tail 1.jpg

I've persisted with the wavy trailing edge. It takes almost no time to do and it's typical of the model.

Dry assembly of the fuselage components less the base panel. The SLEC fuselage jig is a real help and I think essential. I've even built a boat hull on it

fuselage 2.jpg

Geoff

FlyinBrian06/05/2020 18:20:29
677 forum posts
4 photos

Super building work Geoff

In my formative rc years I had an original Ugly Stick (HP 61 powered) and a Middle stick (HP 40 powered) both were great fun and taught me a lot. Fantastic bang for buck ratio you will love it.

One of my club mates could build a Middle Stick ready to cover in a couple of evenings.

Phil Green06/05/2020 20:45:42
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1657 forum posts
344 photos

Have you though about colours yet? remember that all Ugly Stiks have to be red, like Kawasakis have to be green and KTMs have to be orange smiley

Edited By Phil Green on 06/05/2020 20:46:04

Geoff S06/05/2020 20:46:45
3818 forum posts
49 photos

Thanks, Brian.

This is a genuine Lockdown model A bit of an impulse build really as I had most of the components in stock except for the spruce spars and I did a bit of restock at SLEC. I don't think I could have managed it in a couple of evenings but then, I'm trying to stretch it out a bit as it's not likely to be flown for some time.

Geoff

PS the fuselage is glued up now and I'm waiting for the aliphatic to set properly. Fingers crossed tea

Edited By Geoff S on 06/05/2020 20:48:57

Geoff S06/05/2020 20:55:21
3818 forum posts
49 photos
Posted by Phil Green on 06/05/2020 20:45:42:

Have you though about colours yet? remember that all Ugly Stiks have to be red, like Kawasakis have to be green and KTMs have to be orange smiley

Edited By Phil Green on 06/05/2020 20:46:04

Well all BMWs should be black with white lining and have two horizontal cylinders although I did once see a beautiful BMW/Steib outfit that was white with black lining ridden an equally beautiful woman

I'll use what film I have in stock which does include red but I have a roll of black/white check which will certainly appear somewhere.

Geoff

Geoff S20/05/2020 17:04:01
3818 forum posts
49 photos

I've got the Liddle Stik ready to test fly. It's currently plain and undecorated but I have some ideas to correct that. It'll be a bit fanciful

complete 1.jpg

 

complete 2.jpg

It weighs almost exactly 3lbs ready to fly which is a bit heavier than I'd hoped (that applies to just about every thing I've ever built!). What did surprise me is that it balances just slightly in front of the point in the plan. I'll probably test fly it like that because the recommended CoG is quite far back (about 30%).

The motor is a Turnigy SK3 3536 1050 rpm/volt and the esc is an Emax 30 amp (with a 40 amp burst - whatever that is). The motor is ex-Fugly (rip) but I've no idea where the esc came from but it's what I had in stock. When I tested about 2 years ago it consumed 270 watts at 25 amps with 10x6 prop. All I have is a 13x4 HK electric prop cut down to 10.5 and rebalanced. That draws 30 amps. I have a couple of APCe 10x6 on order from Airtek.

The wing loading is around 1lb/square foot so it's very lightly loaded and shouldn't need much power to fly reasonably well.

Here you can see how I moved everything as far forward as possible.

installation 1.jpg

The receiver and antennae are held in some 3D printed supports I came across on eBay. They're very neat. The receiver box is held with a couple of screws into the 3mm ply fuselage bottom and the antennae supports ar hot glued in position. The Corona (appropriate name!) servos are as far forward as I could get then and the pushrods are 3mm carbon tubes with 2mm threaded steel rod epoxied in place.

There's just enough space to accommodate comfortably a Graphene 3S 2200 mAH LiPo. The esc is fitted below the removable LiPo shelf. The motor is currently mounted about 12mm forward of the firewall and will probably be moved back to get the balance nearer to spec assuming the test flight goes according to plan.

installation2.jpg

The underside of the wing and tail plane is chequered (I'm trying to use up the roll). The undercarriage is the remains of my first Riot which was flown so much it wore out.

Test flight soon, I hope.

Geoff

 

Edited By Geoff S on 20/05/2020 17:18:30

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