Speed Twin ST2 - a twin-engined kit build

[Roger Bird]

Sorry about the delay in replying Tim, been away. The pics will be no problem. The only problem is when. A few months agao I was at a loss as to what to build next, I could find very little of interest. Now I have several projects ready to go. It's a bit like busses, none show up and then all of a sudden they all turn up at once.

Next in the pipeline is a 'Warbirds Replica P51', followed by a Tiger Moth and then hopefully your little beauty. That will still leave a few more sitting on the shelves all ready to go including a 'Warbird Replicas Spitfire' and a Tucano. I do like being busy.

[Jose L. G.]

Hi. Congrats on your "model". Really a cool model.

Yesterday I logged in "Modelflying" for checking the contens of the new issue. Found your model and checked the videos and the building log.

What a great surprise!, I found in my letter box the magazine and could`t resist from separating the plan . Really I`m going to built it, perhaps a little bigger (With your permission, of course).

Thaks for this cute model.

José Luis G.

Spain

[Tim Hooper]

Jose,

Be my guest to re-scale the ST to any size you like! Be sure to keep us posted though, OK?

tim

[simon burch]

Tim,
This one is on my list, but I'm very tempted to add retracts, I think it would look super smooth in flight even though not scale. Not tried these electric retract units, but I'm guess there wouldn't be much work to get a set in.
Like the sound of a slightly larger version as well.....so many great plans to choose from.
Cheers,
Simon

Edited By simon burch on 26/06/2012 23:51:23

[David Ashby - Moderator]

We're having a Laser/CNC kit produced, more news on this soon.

[Tim Hooper]

Posted by David Ashby - RCME on 03/07/2012 10:37:21:

We're having a Laser/CNC kit produced, more news on this soon.

*Big, inane grin*

tim

[Stephen Jones]

Hi Tim ,

Lovely model with a Lovely large cockpit area , any reason why you made it out of foam .

And if there is going to be a cnc kit surely it crys out for a clear cockpit .

[Jose L. G.]

Decissions!, Decissions!.

This weekend I`ve been studying the plan. I've decided to re-scale to 1/5 (About 61.4 inches wingspan).

Really you can re-scale using a ruler and pencil/calculator because the plane lines are straight, except the wing profile . The increase factor is 40% (To pass from 1/7 to 1/5). Really I`m going to use 44% (About 1/5 scale at 63"-160 centimeters).

This change permits me using the stock of balsa I have.

The sides of the fuse will be 3 mm (1/8".

I`m going for a transparent canopy with some detail ( I have a vacuum box).

The cowls/nacelles will be of fiberglass (Foam plug and lost method or a final mould?)

Perhaps retracts with oleos.

Decissions!....

Probably this week I'll go to the printing shop for enlarging and draw the new ribs in Compufoil.

 

Cheers.

José Luis G.

Hi Tim, did you prefer a new thread, separe of your build log?.

Thanks for this fine model.

 

 

 

 

Edited By JOSE LUIS GUERRERO on 04/07/2012 11:04:13

[Tim Hooper]

Steve, I used foam for simplicity as I couldn't easily source a ready made item.
Jose, it's probably better if you start your own thread. You'll get more response that way.
Right-ho, I'm off on my hols for a week or so, so i won't be logging on so frequently.
Tim

[JP2]

Hi Tim

Already cutting ribs etc, BUT, searched the web and cannot find turing 2826/10 1400kw motors! help please. Idon't mind plugs, just want the motors.

Must fit retracts having seen these photos

Any suggestions?

John

Edited By Steve Hargreaves - Moderator on 06/07/2012 09:28:17

[Steve Hargreaves - Moderator]

John I don't think the full size Speed Twin has retracts......thats what makes it a nice simple model.

I think Tim got his motors from ebay but you can source them from here..... currently OOS but I'm sure they'll have some in soon....

[Roger Bird]

John, the motors are available (at the time of writing) at electriflite.co.uk and are currently priced at £11-65 each. Just search for D2826-10 and it will go straight to it. Hope this helps.

[JP2]

Doing some research on this current "in build", there appears to be two versions of G-STDL with quite different engine nacelles. www.airliners.net has an almost 1930's look about it!

JP

[Simon Chaddock]

John

Th initial version had iinverted 4 cylider inline LOM (Walter Mikron) engines.

After a prop failure these were replaced with Lycoming flat 4s hence the change in nacelle designs.

[Roy Holmes]

Hi Tim

What do you suggest re cooling, I can't see any exits. Great model have started building!

[Rex Ashwell]

Hi Tim,

I've also started building, just my second scratch build (the first was a Guppy glider) so I'm having to keep referring to your excellent plans and everything I can read in this forum. I've learnt a lot already on this build, but it is slow going when you have limited experience so I expect it will be quite a while before I finish the model.

I'm also interested in where you have placed cooling outlets and also what type of hinges you used on flying controls, particularly ailerons. I have your specified Turnigy motors but intend to use them with 8 x 4 contra-rotating props so I'll let you know how that works out. Static tests show around 180 watts on each motor using a battery at storage charge so there is plenty of power available.

I've posted a few photos to show you how far I've got at this stage. I'd like to press on a bit quicker but it's mid winter here in New Zealand so there are days when the shed doesn't seem appealing. Thanks for a nice design, I couldn't resist from the moment I received my magazine.

[Concorde Speedbird]

Will this plane take IC power?

CS

[Tim Hooper]

Roy,

The clearance holes for the motor shafts are generously sized, and there seems to be a through flow of air which exits out of the undercarriage ports in the lower cowl.

Rex,

I've used hairy CA hinges for the tail surfaces, whilst the ailerons are hinged on the prototype with nothing more than Sellotape! I didn't specify all the details in the build or magazine article as I never intended the Speedtwin to be a beginners model. Having said that, I'll do my best to answer any questions you amy come up with. My designs are not engraved in stone, and there are always choices to make based on the personal experience of the individual builder.

You've certainly made astonishing progress in less than a month, and your ST2 looks great!

CS, A propeller doesn't care what makes it rotate - whether it's electric, ic or a hamster in a wheel! Mind you, you'd have to make substantial changes to go the ic route - fuel tanks, throttle linkages etc. I'm guessing a pair of .07 or .10 glo motors would do the business, but I'm no expert on ic matters.

tim

[Concorde Speedbird]

Maybe it needs blowing up to 60" span. A future project for me, it looks lovely.

Starting to try and design my own plane, 60" low wing Sport plane to keep things simple. Any tips? You can PM me if you want to avoid clogging up the Speedtwin thread.

CS

[Rex Ashwell]

Hi Tim,

Thanks for the information. I'm not a total beginner, having built free flight and control line models in the distant past, but many new techniques and new materials have become commonplace since then. I actually used sellotape hinges on my Guppy glider and they have been very successful, but I wouldn't have thought to use that method on an aerobatic power model. You will see from the wing construction photo I posted that I set small reinforcing blocks in place to use pin hinges in the ailerons and I'll probably stay with that idea.

Cutting out the ailerons after gluing the top sheeting was a bit of a trick, even though I had cut through the corners on the bottom surface to give me lines to work to. Is there a trick to this, as I think that in future I would cut the ailerons free before top sheeting and cover finish them seperately. I think this would also allow more positive gluing of the rear spar in the aileron cut-out. My 18g servos were a bit too deep to fit where you specified so I've moved them forward a little but I don't imagine that will make much difference.

I think I'm progressing at a reasonable pace although I can see the Olympics slowing things significantly. The fuselage is essentially complete with just the nose block and canopy to make, so next on the list are the tail feathers and then the nacelles, which look like they may tax my meager skills a bit. I've posted a couple more photos.

[Tim Hooper]

Rex,

Re the aileron postions; I put pin pricks through the lower sheeting after the spars ahve been added but before the top skin is added.

Don't forget that on a model such as this which features some built-in washout, the ailerons do have a slight, intentional, twist in them as a consequence. That wouldn't be present if you skinned them as separate items, and they might not fit the wing profile perfectly.

I'll go and check your photos, although you're more than welcome to post them directly into this thread!

tim

[Rex Ashwell]

Hi Tim,

You are correct (of course), I didn't think about washout affecting the ailerons but there is a slight twist to them so I will have to bear that in mind in future.

I've got a few more questions as the build advances and I'd be happy if you could answer as this is a good opportunity for me to learn a bit more about design philosophy. I've finished building the tail feathers, which are quite straightforward, but I wondered why the rudder and elevators were skinned with sheet and not just film covered - was this because the full size aircraft is skinned or is this just the way you prefer?

I'm currently planking the upper nacelles and finding it quite tricky, and I'm slowly losing my fingerprints to CA glue! It occurred to me that it might have been easier to fill between the formers with foam, sand to shape then use light weight glass or possibly brown paper. What are your thoughts as I may yet do the lower nacelles this way? What kind of filler do you use after planking? The result so far doesn't look too bad but there are a few narrow grooves to fill.

I'm also thinking about making fibreglass nacelle fronts as they are both identical and could be made in a simple mould, or another possibility is to form them from plastic using the plastic bottle/heat shrink method, which I'm also intending to use to make a canopy. I've used this method for canopies in the past and it works quite well.

Not far from the point where I have to decide on a colour scheme and I'm a bit uncertain which way to go here. I really like the original colour scheme which you used, but I'm a bit dubious about my ability to actually do it. What are the difficulties? I noted that you used the lighter colour first and then applied the darker colour.

I'll post a few more photos when I've got something worth showing.

Rex

[Tim Hooper]

Rex,

Good point about the tail surfaces. The sole reason that I sheeted them was to make it easier to cover them in fairly random blotches of Solarfilm (without huge overlaps). I'd certainly leave the fixed tailplane and fin as sheeted items in the interests of torsional rigidity.

I'm with you on the nacelles in that there's no reason at all not to use foam! It's that I happen to sort of perversely enjoy planking with balsa. Yeah, I know......

I'm glad that you're going to go for a blown canopy. I tend to shy away from moulding - it's something I've little experience of - so I like to keep a design destined for publication as simple as possible.

No matter what colour schem you plump for, if you use film then you're going to be dealing with lots of itty-bitty bits anyway. The psuedo-camo scheme actually made life easier - no straight lines to try to maintain over all those compound curves!

How about glasscloth and paint?

tim

[Rex Ashwell]

Hi Tim,

Hmmm, that is perverse. Perhaps with a bit more practice I'll enjoy planking as well, but at this stage I'm finding it tricky.

I understand your reasoning with covering the flying controls and appreciate the torsion box principle, and I've already built those parts per the plan. My original idea was to build strictly to the plan, although I was always thinking about a clear canopy even though that means finding a suitable pilot.

I like the suggestion about glass cloth and paint but i'm a bit cautious about a possible weight penalty. Any ideas there?

This is a pin together assembly to show how far I've progressed - it's nice to give yourself a bit of encouragement along the way, although there is still a lot to do. Next on the list will be the canopy I think.

Rex

[Jim 15256]

Very Nice !