Depron Tyro

[Colin Leighfield]

This is a somewhat more sophisticated approach than I have achieved with my Barn(Shed)stormer fuselage Chris, but I'm getting there! I will be copying your wing technique and looking carefully at how you are doing the tail. I might deviate slightly on that, but probably not by much. Learning all of the time. Thank you for going to all of this trouble.

[Chris Bott - Moderator]

Good i'nit Colin?

Lots of techniques here that I certainly hadn't figured go into a depron model.

[Colin Leighfield]

It's called "intelligent design" Chris, which explains why I haven't got there yet!

[Steve Hargreaves - Moderator]

Really enjoying this build Chris.....can't wait to see it finished....

[Chris - Depron]

Hi Thanks everyone for the comments and feedback. Here goes start of the sprint to the finish now if left alone for a while.

[Chris - Depron]

If I had thought about keeping the tail sq earlier i could have had a rib in the middle this could have also acted as locating point you mat wish to do that Colin if you've not gone past that point.

Once I was happy that the tail was attached to the fuselage sides square and level, I applied the tail top skin this had been cut to size and shape. During the dry fit, I also created a light crease to facilitate the change in angle by running the back edge of a scalpel across the surface you can just about see it in the pic below.

In the pic above the two slots one for the fin and the other is for the rudder servo control arm to pass through. You cannot see from this picture but there is a fine cut from the fin slot to the end of the panel. This was so that the panel drops over the fin and under the rudder.

Next up was to glue the black longerons on the top of the fuselage and the two fine strips either side of the fin.

Not sure if i mentioned this previously but my normal gluing process is to run glue along the surface to be stuck too, a thin long bead. I then place the part to be placed on top of the glues areas so that there is a trace left and remove it again. Then touch up the glue (add a small bead) then lightly squeegee so a nice thin coat is produced. The trace of glue on the underside fuselage tail top indicates the area that will be adhered too, so I use this as a guide to add a bead of glue and again sqeegee into a thin area. (This is technique on the wing surfaces coat the ribs and spar mark the wing surfaces and assembly).

 

Again it is imperative to ensure everything is square as this will stick very quickly if you've left this thin glue line a short while.

I just noticed that I forgot to mention I cut two small holes to pass through the rib. This rib is actually an addition to the original design. I positioned this so that it was at the point at which the fin merges into the tail skin this appeared to offer the greatest support and amount of leverage to hold the fin and tail in place.

Here you can see how the top surface was over size and this was trimmed back to the fuselage sides by wiping a very fine long knife blade along the surface.

Edited By Chris - Depron on 18/05/2014 20:49:03

[Chris - Depron]

I then looked to working on the other end and the mounting of the motor. I used a piece of light ply and and used bolts and nuts to angle the thrust down and to one the right to match the angles on the original drawing the largish hole in the middle at the back was to ensure that the shaft did not foul against the mounting plate.

Here you can see the motor in place (tou can see that the 2mm sides glued to the shaped sides). You might be also able to notice that I removed some material from the 6mm Depron bulkhead to allow the bolt heads to be recessed into the surface. The ply motor plate and the bulk head were coated with Araldite and stuck together the excess exuded around the edges of the plate and thus bounded them to the fuselage sides.

As this was a long curing Aradite I clamped the it all together and left it 24hrs

[Chris - Depron]

As I'm useless at juggling plane and transmitter I prefer to have an undercarriage to avoid hand launches.

So my attention turned to adding an undercarriage - You can see the notches i created in the 6mm sides to support a Depron mounting plate, these are hidden by the 2mm fuselage skins.

I created two rectangular ply plates and drilled through them so that the dowels would be parallel when fitted. I used these for the same reason as the wing mounts to hold firm ans stop the dowels pulling free especially if stressed on a landing.

Next insert the second dowel

Then the Undercarriage support plate was added here you can see the notches and tabs that hold this plate in place which also assist in securing in place (initially during the dry fit)

Next I added a thin ply plate again to add physical strength without to much weight (These next few pictures are from the dry fit as the plate is over size).

This plate was trimmed back to fit to the fuselage sides so as to stop the rubber bands cutting into the Depron.

I then placed the Undercarriage on the ply plate and secured it with rubber bands (not shown here) so as to mark the required position of the backstop.

I next glued the backstop in place with UHU-por to the ply plate and then when i mixed Araldite for the motor i used some for the backstop as as to ensure it was going to stay in place.  Ending up with a result something like below (this is the dry fit). 

 

 

Edited By Chris - Depron on 18/05/2014 21:20:12

[Chris - Depron]

As all the radio gear is in time to check everything - power up and centered the servos. Then glued in place the elevator and rudder horns made from ply waste.

I noted that that the wing security bands had started to cut into the trailing edges of the wing so I added two small ply strips to protect the edges.

So as good as ready to go. sorry about pic quality

Just the motor cover to glue into place as I can see here that the securing pins are still in place.

I will try to find pics of the battery cover construction as this section is missing.

Edited By Chris - Depron on 18/05/2014 23:45:10

[Colin Leighfield]

There's no doubt that it's a Tyro Chris, can't mistake that! Thank you for the tip about the fin. I've been working this evening on the removable hatches, haven't got as far as wing and tail yet, but I should get there soon.

Are you going to coat yours with anything, or leaving it in the raw?

[Chris Bott - Moderator]

Chris, I recon you must have been really good with those cardboard models on the back of weetabix boxes as a lad?

[Chris - Depron]

Hi Chris Strange you should say that about weetabix I was wondering if any of the designs still exist? My recollection was the kings and queens of England and yes i did make them.

The other thing I wondered if they repeated them as retro boxes and than other than us oldies going down memory lane would youngsters make them with the zeal we did? - hassling mum to get a head we didn't have.

(PS. I think it was Kellogs Cornflake boxes)

[Chris - Depron]

Hi Yes thinking about covering - At present the plan is to leave it as virgin Depron for the RCM&E event.

I have used Acrylic paints and iron on film previously to cover Depron, but I'm experimenting at present with another idea / covering / finishing process.

If this works I will attempt it on the Tyro - The plan is to use the original David Boddington scheme of Orange, White and Black.

If there are any other covering ideas i'm all ears.

[Chris - Depron]

Just to show the finished undercarriage held in place

[Chris - Depron]

Another part of the under carriage is of course the rear skid. This was created with a piece of wire bent to create cross and lateral support. This was secured in place to the plywood skin by fine strands of copper wire twisted to hold the piano wire securely.

This assembly was then Araldited to the lower tail skin

[Chris Bott - Moderator]

Looking good Chris.

By the way, this is the sort of thing I was remembering. Good old google!

[Chris - Depron]

Last component the battery cover (sorry I obviously have mislaid some pictures during the build).

I first created a rectangle in 3mm Depron with tabs and slots in the corners this was made to be a tight fit when inserted into the fuselage. The edge was shaped to match and be flush with the top surface of the Fuselage.

Below you can see the tab corners - the bottom edge is starting to show some damage from the battery wires

The rear black strip is made from black insulation tape this to facilitate as a tab to pull the cover up.

Top view - you can see how the covering was made to fit across the fuselage sides so that they finish flush with the outer sides. The fold was again created by lightly scoring the top surface to create a clean fold.

Whilst this covers the battery it of course doesn't hold it in place this was achieved with a velcro tie and a 6mm V shaped wedge to stop the battery sliding forward . This was chosen in case I use a different battery at some point I can the just create a new V wedge.

Here you can see I had to notch the tops if the V legs so that they didn't foul the battery cover when it is pressed down.

So there she is all ready for her maiden flight.

But first of all Chris Bott kindly came over and tested the power consumption - Full throttle she hits 80 Watts on a 7 x 4" prop with an all up weight of 1lb 1oz or approx. 482 grams - not sure what weight she turns in at with a traditional build, always interested to hear. So confident she had plenty of go and CG is right on the centre spar off she went the next time we had a good calm day and last week was it. Off to load more pics back soon!

[Colin Leighfield]

Congratulations Chris. That really does show what can be done with Depron. I have no doubt that you are below half the weight of a traditional Tyro with a 1.5 cc diesel and single channel radio, can't fail to fly well.

[Chris - Depron]

Hi Chris - Dam you found my secret - the only problem is as a kid I always expected a better finish that I got and I never ended up with it looking like the box lid or adverts - That's not changed too!

[Chris - Depron]

So the nerve wrecking day arrived and my Tyro turned up with its excellent baby brother the Mini Tyro built by Chris Bott

As I'm as rusty as heck at flying and I would not trust myself with a maiden flight. CB fortunately volunteered do the honors. Using our freshly mowed strip (thanks guys) it makes take off's so much easier.

Off she trotted sitting pretty with a little down trim

First flyby showing off her ribs and spars

After putting it through some loops and rolls Chris gave it a thumbs up. So it was in for finals.

Maybe not - around again

and down in one piece - Phew! Thanks Chris you made it seem so easy!

Then I was made to have a go - I'm glad to say it survived that trial too and I'm now waiting for the RCM&E funfly or we may see you this Bank holiday weekend if your coming to Greenacres MAC - May Fun Fly don't forget your BMFA Insurance card! Check out the details at www.greanacresmac.co.uk - traders and campers are welcome.

I hope you all enjoyed my story.

PS: If I cover the Tyro I'll create a follow up - Hope to see you soon.

[john stones 1 - Moderator]

Well done lads

John

[Danny Fenton]

Well done Chris, great ending to an excellent build blog
Cheers
Danny

[Chris Bott - Moderator]

Great stuff Chris.

I have to say that it was one of the easiest maidens ever.

After all the usual checks and double checks and in a fairly gentle breeze, I was a little concerned that with all that dihedral and a tiny rudder, we might suffer some ground looping.

Surprise surprise, then, that she tracked straight across the width of the strip, into wind, and was gently off about half way across. Adding more power then lifted the nose, so a little down trim was added and that was it with trimming.

She's so light that a lovely slow, gentle fly around is a nice relaxing way to fly. Elevator hardly needs to be touched and rudder just guides her around the sky. A few clicks more power and she gains height, a few clicks less and she gently looses height, just lovely.

Open her up and she climes at a heck of a rate, or blasts around quite quickly with aeros thrown in too.

The first approach was overshot, because Tyro floats on a bit, so round again and down for a very gentle touchdown indeed.

A total success, very well done Chris D

.

[Chris Bott - Moderator]

PS - Little brother Tyro weighs 320g and I thought that was lightly built. So 482g for the big one is just excellent.

[Chris - Depron]

A final BIG thanks to Chris and Danny for the kick in the rear to do this and encouragement through out. Plus of course the proving of the pudding by Chris and the generous donation of the motor and esc by Danny (I owe you a pint or 2). I'm sure he did this so I couldn't back out or procrastinate any further! but thanks again both.

At some point I'll enjoy flying her but I'll keep her in one piece for the time being

Now to the next project! Decisions, Decisions, Decisions!