DH Tiger Moth 1400mm

[Bob Smitham]

A 20% off Bangood coupon and a few loyalty points meant this kit was mine for £60.

**LINK**

Iv'e been bashing foam board for a while.The constant "one day I will do a balsa build" thoughts are now reality.

It's my first balsa kit so it will be a slow one.And I will mostly be following Tim Hoopers build ( huge thanks Tim)on RCME.

**LINK**

The kit is hardly scale but with help from thread above and one one a German forum.I can hopefully get reasonable results.

First job was a build board and this version of the kit comes with scale plans for the wings(when HobbyKing sold this kit these were not included).

Wing tips require reversing from the original and extra ribs and cap strips adding(agian following Tims build).I must admit the thought of cutting 80 or so of these was hardly thrilling.An hour or so on CAD and a 3D printed alternative was decided upon.

Each process research and testing of bending,stripping,gluing the wood has had me leaving the shed at 3am .Wonderful way to forget the troubles of the world.Lost in forums,and building an extensive folder of pictures of scale and real Moths.

For a little variety from the wings I moved on to the tale section.All reasonably straight forward.A few strips to add a curved rib on the flat surfaces.And the 3D printer was called in to print a "hinge lining upper tool".After my initial failure at lining the opposite cuts.

Probably not an ideal first kit.But why make it easy on yourself.And after a week it's progressing really well and I'm now hooked.

The 3D printer is justifying it's place in the shed.A few balsa working tools helping to keep the costs down.

Over the coming months expect a multitude of questions as this progresses.Oh and just to make it harder on my self I'm going gas.As If I hadn't bitten off more than I can chew with this build.

[Martian]

I will enjoy following g along

[David Hall 9]

Nice 3D printed tools... I need a strip cutter, can you share the file or location for this?...

[Bob Smitham]

Posted by David Hall 9 on 20/02/2020 17:21:09:

Nice 3D printed tools... I need a strip cutter, can you share the file or location for this?...

Yep it's this one on thingyverse. Will take a 9mm or scalpel blade.

**LINK**

[Bob Smitham]

Things are moving along.The fuse is dry assembled and looking true.I remember pulling my tape measure out before ordering and thinking 1400mm yeah no problem.I now however think I need a bigger shed.

I have spent some time researching the dark arts of the glow engine(sad to see so many engine companies folding).I must have watched a few dozen ebay auctions to gauge used prices.£50 upwards seemed to be the going rate for 46 ish size.I was hoping to find an engine with adjustment for the muffler to avoid hacking the cowl.How ever the ones i watched were Enya four strokes and out of my budget.

I put a bid in for £35 on an Irvine 46 and to my surprise won.

Looks unabused and has compression so fingers crossed.

The carbine struts with the kit are to be kind functional but not very pretty.So I'm working on using 6mm aluminum tube to give them a more scale look.

A question or two concerning the engine if anyone can help.

1 Best position for the fuel tank and size of tank ?

2 Will the engine need mounting at an angle has I have seen on some builds.

3 Best fuel (a bewildering amount of options Iv'e noticed)

4 Does any one know of an alternative muffler for this engine that will be less conspicuous .

Before I get back on the wing assembly I had a little play on F360 CAD and drew a quick sketch to see if a instrument panel would look ok.

I think with a little re-scaling and some more detail adding it may turn out ok.But the instrument faces will probably be better printed on paper and adding to the blank panel with some PET bottle plastic as a cover.

Loads of stuff to do so I will get cracking.

 

Edited By Bob Smitham on 21/02/2020 12:32:22

[alan p]

Just Engines stock a good range of alternative exhausts

[Denis Watkins]

I have 2 Moths this size and to be inconspicuous, both motors are mounted Inverted.

The Yellow SLEC tanks are laid directly onto a new 3mm ply floor with thin insulation

Therefore placing the main fuel feed just below carb height

2 different motors

The 4 stroke has a flexipipe to the silencer slung outside under the tank area

And the 2 stroke has a pitts silencer attached to the motor pointing down through the cowl

[Jon H]

I dont wish to be negative but a 46 2s is rather excessive for a little tiggie.

I had a fractionally smaller 52 inch tiger moth many years ago and it was very happy on a 30 4 stroke at around half throttle.

And before everyone says it, no, you cant always throttle back and even if you do, just touching the throttle makes the thing accelerate like mad and generally make it unpleasant to fly.

If at all possible i would look for something smaller and/or, 4 stroke. Its a shame saito 45's are so rare these days as that would be ideal.

[Denis Watkins]

Apologies, I did not type in the motor sizes

Old OS 40 4 stroke

OS 35 2 sroke

[Jon H]

Posted by Denis Watkins on 21/02/2020 14:50:45:

Apologies, I did not type in the motor sizes

Old OS 40 4 stroke

OS 35 2 sroke

Ah ok. I just saw the irvine sat there on the bench

Of you two you mention, the OS 40 fs would get my vote

[Bob Smitham]

Thanks for the feed back fella's all taken on board.And Dennis,Alan P. I'm off googling your suggestions now.As for the engine size Jon-Laser I did choose the one of the many build instructions this much used and re-branded kit recommends is a large envelope of 6.5-10 CC ! I was thinking lower end 2 stroke upper 4(a throw back to my days of silly fast 2stroke motor bikes) .And Is'nt assumption the mother of all cock ups eh.. Not a big problem I'm sure it will recoup it's price on fleabay and my flying skills are probably 12 months short of ever considering flying this build.The cheap entry price and technical challenges are all part of the attraction.Plus the Tiger Moth is a beauty of a flying machine.

Obviously 2 or 4 stroke will give wildly different fuel consumption, A 10oz/275 ml tank will fit comfortably in the upper nose section(20z at a pusht he lower subdivide of the front fuse and also keeping Tim's 2cm below carb recommendations.Oh and the power to weight ratio and I imagine a half empty tank of heavy liquid sloshing around.

So to stop waffling on would a 10oz tank with a smaller say 40 engine be a optimal choice ?

[Denis Watkins]

Have just noticed on Bangood, Bob, that this model could come out at 6lb which is ballpark .46 power

So hang on to the Irvine until you can weigh the airworthy model

You 10oz tank will provide good flight time for a 40, and Laser 5% comes recommended for fuel

Keep asking

[Bob Smitham]

Well things are progressing after a fashion.

Things Iv'e learned up to now.

Blasa can be like cutting soft metal or butter dependent on the the grain .And yes I know it's wood and all wood works this way. But the window between easy and hard is a little narrower with Balsa.

You can't have too many clamps of varying sizes shapes.And even then elastic bands paper clips books and 1/2 full 2 litre gloss paint tins all serve their purpose.

Don't measure twice cut once.Measure thrice and cut once.

Phatic glue is a wonder of science.

Never measure fuel tanks or any other item for a build late at night after a few pints of bitter before hitting the online shopping button.

Wonder why you didn't just build the "sports scale" kit and not add embelishments.

Just like huge Government infrastructure projects.A build will at least double the original cost estimate.

Don't spend longer on a section of the build than your limited attention span can cope with.

Google is your friend.

I can't work out how to rotate uploaded pictures to the forum album.

And finally the scale builders deserve all the praise they get.If like met the last attempt you made at anything remotely touching on this art was a 1/72 Spitfire Airfix kit. You will know where I'm coming from.

The structure is 90% completed,Just a bit more strutting to be added and the aileron hinging.

Now as for my admission on the scale front.

Well this is my third attempt.Each one improving slightly. A few more primer filler coats to remove the 3D print layers.And an improvement on the home printed from tinterweb images for the instruments.But progress has been made in each one.So I expect it will be ok on my sixth attempt.

I blame you lot on here for me practically living in the shed the past two weeks.And spending more than is prudent on as my darling Wife says"on daft bloody model planes"

And for that I thank you.

 

Edited By Bob Smitham on 28/02/2020 20:52:13

Edited By Bob Smitham on 28/02/2020 21:24:33

[Tim Hooper]

This looks great, Bob!

Thanks for the mention. I really enjoyed building my Tiggie, and I appreciate the way you've refined it even further - especially in the use of 3D printing for the riblets and dash board.

I'll be following this thread with interest.

Tim

[Bob Smitham]

Posted by Tim Hooper on 28/02/2020 21:09:14:

This looks great, Bob!

Thanks for the mention. I really enjoyed building my Tiggie, and I appreciate the way you've refined it even further - especially in the use of 3D printing for the riblets and dash board.

I'll be following this thread with interest.

Tim

It was your build that inspired me Tim .I'm just attempting to learn as I go and hopefully end up with something half as good.

[Bob Smitham]

Been busy of late and what time I have had has been spent bogged down on working out a way to replace the flat carbon upper wing to fuse struts.After attempts at hammering a flat edge on each end of some 6mm aluminum tubing.Then bending and drilling cutting slots for the cross members with a dremmel I nearly gave up. Beyond my skills too keep all angles and flattened ends true on the X & Y axis.

Several hours CAD and prints tested to breaking point finally paid off, ish.Still not sure if it was worth the time and effort to replaced the supplied probably much stronger supplied struts.

(note a small example of failed attempts in the pic)

Original and the 6mm ali version on the model.

I really must work out how to rotate pictures .They are correctly orientated on my phone and PC.

I picked up some fuel the other day so my first dabble in the world of glow engines began.Well lets say it was a success well kinda sorta.

A Heath Robinson pocket size (great for the flying field) engine test bench was knocked together.This utilises a kitchen chair my Mrs has been mithering me to take to the tip for months,an old bread board and an ancient huge adjustable bench PSU with a centre tap transformer as a glow plug starter.

Lots of half starts and splutters followed.My first mistake having the fuel tank too high.This caused a siphon effect and flooded the engine.My second mistake was tuning the engine over to clear the flood and having the carb spit a stream of fuel in my eye.The cheap glow plug starter soon gave up the fight and my meter shown it was down to 1v hence the old bench supply was brought out of retirement.Several more attempts and she kicked in to life.It was getting on a bit by this time so didn't want to upset the neighbours any more than I had.Another day of tinkering will be needed as the engine cut out with quick throttle changes and needed a lot of fine adjustments to keep running.But all in all I'm happy the ebay engine started up.

[Denis Watkins]

Bob, you have no pressure pipe to your tank

This accounts for the half starts and splutters

This is not a huge problem,

But get the tank much nearer to the motor, always just behind.

Shorten the carb feed pipe and join up the silencer pressure nipple

To the tank breather

[Ron Gray]

The rotating photos is annoying and in my experience usually happens when you take landscape not portrait shots. To overcome the problem I just edit the photos, a simple re-size is enough, then save and then the upload keeps the orientation correct.

Edited By Ron Gray on 07/03/2020 07:49:33

[Andy48]

Wow! A good old Farnell power supply still going strong. It was 50 years ago I left their factory.

[Bob Smitham]

Thanks Dennis .I sorted the plumbing out and the Irvine is running fine now(arnt theses little buggers loud).

And Andy yes I have two a 12v 10amp and 30v 2amp .After being in a workshop with daily use for twenty plus years and sitting in my damp shed for three years.They still power up when I dig them out once in a blue moon.They will outlive me I'm sure, quality bit of kit.Just wish they weren't so big.

PS Thanks Ron Think I have sussed the picture orientation .Oddly enough I have to use MS paint and rotate 90o for them to save to the forum album in the correct orientation.Maybe it's an Iphone/Microsoft thing.

[Bob Smitham]

A quick update on the moth build.

Still haven't finished the wings .I'm finding the learning curve steep and slow, but what's the rush.The tank and support struts are assembled with some corrugated foam giving a not too far from scale look.A few 3D printed details added.A quick blast of undercoat has revealed a few rough areas that require a bit of work .

I then moved on to the under carriage .The one supplied with the kit is huge.So some wire bending with the help of a chefs torch a little balsa whittling were required.The areofoils helping cover some of the ugly soldering and wire that is holding it together.The 3D printer continues to earn it's keep with some hubs printed.These really were a pain on the CAD package to design .

I will be applying the same rules to this build as I do my home D.I.Y jobs"it will be reet once it's painted".

I will need to be able to strip this plane down for storage( the sheds getting a bit cramped)So a system is needed for the wing struts.Tim's method on his build looked the most straight forward.But after my torrid time with the under carriage I'd had enough of piano wire for one week.

The supplied struts were sandwiched between two strips of balsa to give a little bit more shape.I then applied the rigging as per the instructions.This involved a single line threaded from the lower wing crossing the struts and then to the top.This was pulling the wings in all kinds of wonderful contortions.The piano was reluctantly used for the cross between the struts.The rigging now just holding the wings to the fuse rather than actively altering any wing physics.I have some small clevis pins and R clips on order for reasonable faff free removal of the struts

A couple of carbon tubes are on order with the internal diameter of the exiting wing supports.I intend cutting and epoxying the existing ones in each wing and the fuel tank.I will then be using the narrower tubes to hold everything in place.

Next job will be servos and the long cable runs for the rudder and elevator.For this part of the build I will be following a thread of this kit build on a German forum.All wonderfully explained and precise in a very Germanic way .

Once again it's my first build in balsa and using a glow engine.So don't be shy about shouting out any weak points or areas for improvement.

Cheers.

[Dale Bradly]

You're doing a great job, I've wondered what this kit would be like to build.

[Manish Chandrayan]

Love that tank work, but please tell us what's that big bulbous thing under slung at the rear left of the tank ?

[Cuban8]

Posted by Manish Chandrayan on 20/03/2020 08:40:13:

Love that tank work, but please tell us what's that big bulbous thing under slung at the rear left of the tank ?

A drain sump to collect water, I believe.

[Bob Smitham]

Posted by Cuban8 on 20/03/2020 09:13:07:

Posted by Manish Chandrayan on 20/03/2020 08:40:13:

Love that tank work, but please tell us what's that big bulbous thing under slung at the rear left of the tank ?

A drain sump to collect water, I believe.

It is and it does need scaling down a few percent .It's not easy to get an idea of the scale until it comes off the print bed and put on the model.I have a small pile of wheel hubs that were a little to small or large.And re scaling in Cura then reduced the the depth of the concave inner surface meaning the hub sat clear of the wheel rim.It was then back to the CAD sketches and pretty much starting again.

But isn't that one of the pleasures of a build the wide range of information and skills you learn.I didn't have a clue what a "Venturi" was called or its function until last week.No doubt these will take a few prints and edits to get right ish.