Multiplex Arriba

[Gary B]

A bumper edition today, might split it into two posts!

The tailplanes and ailerons have been tissue covered, doped and sanded ready for primer. The wings still need more work.

I bent the rudder clevis threaded end trying to lever it off the ball link (no need for them) so I de-soldered it to fit a new one with a marvellous slop free MP Jet clevis. 

I looked at the elevator wire end and noticed two threaded ends had been soldered together (novel!) then noticed that the rear one had been slotted to crimp onto the wire (see photos).

Ye Gods! I'm really glad I looked closely at that, replaced as the rudder wire with a new end and clevis. 

Some piccies of the clevises.

 

[Gary B]

Running out of jobs so I looked at making new fuselage formers to support a servo tray.

I have a profile gauge which gives an approximate guide to the shapes needed, transferred onto card and tweaked here and there to get a good fit.

Transferred the card shapes on to 3 mm ply and they fitted very well, the servo tray is too wide to fit easily so I split it into two halves.

I can see that I will probably have to lower the height of the formers but it's a good start. 

Not sure what will happen at the front, possibly two ply sides and another former to create a battery box.

The battery in the photo is a 4S 3,300 mAh used for a ducted fan jet, might be too big. 

Nothing will be glued in/finalised until I have a new motor and ESC, the plan is to get the CG in the correct range without adding any noseweight (or tail weight!) .

 

[Gary B]

Not much progress recently but a bright ray of sunshine today.

I went back through this thread and had another look at the instructions, there are a few diagrams but I guess that there was a plan sheet originally. It's dawned on me that the elevator and rudder servos were originally supposed to be further rear with the receiver on a removable ply plate (mounted to rails). This would leave the whole cockpit area clear for the battery box (must have weighed a ton stuffed full of torch batteries). This would explain why the original snake outers stop in line with the centre section hatch, the elevator snake has been extended with an extra length.

A couple of weeks ago I e-mailed a few companies that might possibly have the brass airbrake screws (the originals have badly chewed heads). I got a reply from a member of staff at Florian Schambeck saying that sadly they did not stock them but that he thought he might have some at home. Today I received eight brand new brass screws, what are the chances?!!

Herr Werner  Schröder, danke sehr! 

The hold up now (not that there is a deadline) is the prep for paint, the wing undersurface is still lumpy despite hours of sanding. I've used glazing putty on a glassed Xtra Wot wing to fill microscopic but visible rough areas, it works well but the brown colour means more white paint has to be used to cover it.  I'm saving up for this product, looks just the ticket.   

Some piccies: The new screws, the Xtra Wot wing with glazing putty and the almost finished article (yep, I know it's not a glider!).

 

[Gary B]

For sanity reasons I have reached the end of sanding!

I had achieved a mostly smooth surface on the wings but there were still hollows and visible patches of glass cloth weave that would have taken an awful lot more sanding to get rid of.

The answer was to use a glazing putty or stopper. 3M do an acrylic filler but it's £25 a tube if you can get hold of it, I was tidying the garage and moved a small tub of Polyfiilla, a light went on.

My worry with Polyfilla was that I thought that it was basically plaster and water, brittle when set and would fall out. Looking at the manufacturer's safety data sheet (MSDS) it is mostly synthetic with epoxy and plasticiser as ingredients.   Spread very thinly with a credit card it can be wet sanded. 

Have masked everything up for painting now, the airbrakes are used as blanks with some cereal packet card wedged in to seal the bays. The tailplane main pivot hole was filled with a kebab skewer and the drive slots filled with clean fuel tubing.   The wing blade boxes were filled with lolly sticks.  Although the fuselage hatch cover was in perfect condition (original gel coat) I will paint that as well because there is more than one shade of white and it might look odd being a slightly different colour.

[Gary B]

Thought I would share a tool tip that I just discovered.

I have a battery Dremel which has been invaluable and I was thinking of upgrading to a mains powered one with a few attachments.

Dremel produce a shaper/router table but all I really wanted to do was sand the inside of concave shapes or the cutouts in the middle of formers.

It does require a pillar drill then all that has to be done to convert it to a table drum sander is fit a Dremel rubber mandrel with a cylinder into the chuck and raise the table until the tool is halfway through the centre hole (the pictures should explain it).  

It doesn't move up and down like a bobbin sander but then neither does the Dremel table. 

 

[Gary B]

I've gone a step further with this idea and bought a set of larger diameter sanding drums (up to 50 mm).

The Arriba parts have been primed, sanded, touch of filler on one wing and primed, sanded again. My camera is not over happy with the whiteness!

Might be able to apply the gloss coat later this week. 

To pass the time I am building a balsa Centi-Phase fuselage.

     Gary

 

[Marc RC pilot]

Looking fantastic Gary! Great work 

[Flyingscot]

The arriba was originally an electric  all balsa glider designed by Colin  Sparrow. This was when electric meant brushed geared. I bought the plan but never built it but may do now.   Love a good build!

   regards

          Bob

[Gary B]

Welcome Bob.

There's not much wood in this Arriba.

I think it means 'up' in Spanish, the cartoon mouse Speedy Gonzales was always saying it.

[Darren_O]

I have a set of wings for sale for an arriba if you need a spare set?

[Gary B]

I did see them just now on FB.  No fuselage?

Mine are ok, just need a top coat of paint.

 Cheers

     Gary

[Darren_O]

No fuse, I'd keep them if I had one:)  Price would be greatly reduced if you want them. I'd just like to think they were going to be used rather than left rot.

[Gary B]

They would be handy to have but you're quite a long way from me.

I will have a look at the instructions and see if the wing joiner blades and incidence pins are factory installed (might have been done in a jig).

[Gary B]

According to the instructions the blades and pins are fitted by the builder, I guess any misfit could be sorted.

My wings are quite heavy, are yours film covered?

The DG600 I have has similar wings with alternative tip options.

[Darren_O]

Film covered, don't think they're glassed. I'll have a closer look tomorrow after work.

[Gary B]

Cool, just the distance that is the problem, could look into a courier.

Have a play with the airbrakes, they can be fixed if broken but it's fiddly!

[Gary B]

Some recent progress:

The white paintwork is done apart from the lower surface of both ailerons.

It feels quite heavy but I weighed it all minus fuselage electrics and it is just under 2.7 kg, the instructions give a flying weight of 3.5 kg, it should be well under that.

Threw it together in the kitchen for some inspiration, it will probably need some kind of colour trim and I'm debating getting the original graphics copied (I don't particularly like them!).

  Gary

 

 

[Gary B]

...three years later!

Successful test flight today, some minor snags to sort out but it's home in one piece which is the main thing.

Finished off the front end with a new prop/hub and spinner, a 4S 3300 Lipo plus 100 grammes of lead put the CG at 105 mm (recommended 95-110).

On rigging the wings they have the classic Multiplex rock back and forth, the fuselage is protected at the front by a dowel compression strut but there is nothing at the rear, stressing the wings rearward opened an existing tiny crack in the fuselage. It's weaker than usual here because of the hole for the radio receiver, I trimmed a ply plate to fit and glued it in. At the flying field the wings did the usual 'attempted self-removal' after landing, I might try a second clamp on the joiner box.

The wing loading is around 19 oz sq ft, plenty of power available for the launch and climb. Took a while to trim out for straight flight, appeared to need aileron and rudder trim, although the wings weigh the same there could be a tip/root imbalance. Saw some odd behaviour at times, a wing would drop then it would immediately recover to straight flight, even rolling slightly the other way. 

It was behaving quite nose heavy and I removed all the nose weight in stages.

On the last launch I could see that the tailplane was no longer in line with the wings for some reason so I flew a careful circuit and landing, the tail bellcrank plastic supports have come loose, shouldn't be too difficult to fix and strengthen.

It does need some colour, I have packed the box with all my Multiplex stickers and German flags etc so deep in the loft that I can't get to it, lol!!

1 and 2. Adding a ply plate for fuselage crush protection.

3. Front end, treated it to a new spinner and blades, used the original outrunner which is unidentifiable (all markings worn off). Also changed the HobbyKing speed controller for a Jeti 70A Advance Pro SB.

4 and 5. At the flying field today.