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Gary B

Multiplex Arriba

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Gary B

Continuing my quest to collect dusty old Multiplex gliders I managed to obtain an Arriba last week.

As a bit of non-news the Multiplex Flamingo I restored last year still hasn't flown!

Along with the Arriba came an unbuilt kit of an MPX Astra, I will start a separate thread on that.

I hadn't heard of the Arriba, it is an ELG version of the Schampus apparently (which I had vaguely heard of).

The Arriba is 3.4 metre span and appears to use the wings from the DG600 of the same era (or it could be the other way around!).

The model is in flyable condition but as usual I will give it a birthday. The wings are glassed but could do with a repaint, the fuselage gel coat is very good but I'm not a fan of the purple trim colour.

The original tailplanes (fitted in the photos) have been driven over by accident, they are actually ok apart from some spanwise cracks. A spare tailplane was provided.

The spinner is a little bit over in diameter, looking at it  I was thinking about removing the motor and flying it as a pure glider, dunno.

 Cheers

    Gary

 

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pete beadle

Hi Gary

Well found for this beauty too.....

According to the MPX Building Instructions the Arriba was produced to be an electric assist aircraft from the outset, so my vote would be to leave it as such:thumbsup:

As usual I completely agree with you that this isn't going to be a Class A rebuild but just a "neatening-up" job and, yes, I totally agree the painted trim is a must to improve/replace as one of the first things to do......

Oddly, I seem to remember, in the darker recesses of my tiny mind that I had always thought the Arriba was a flying wing design........where that comes from I don't know, but the name Carrera seems to be where I originally saw that name.......good luck with the research on this, and attached please find the destructions for the MPX Arriba.....English version from page 28 if that helps you......:yes::)

Onward and upward Gary

Regards

Pete

BARCS1702

MPX Arriba building instructions Eng p28.pdf

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Gary B

Thanks Pete,

 Both this and the Astra came with hard copy instructions, it seems to be a bit random exactly which instructions Multiplex have in their archive, they don't have the Astra.

Tempted to try them for the airbrakes I'm looking for but I e-mailed them a while ago (about graphics I think) and they said all they have in the back rooms are cobwebs!

The Cortina was the flying wing, my first car, a Mk III estate that would have made a good glider carrier. 

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Gary B

Been a few months since I looked at this glider and I've built and flown an Airsail Voltimer.

I had removed the rudder by pulling out the hinge pin and started on that today. The paint surface finish was quite 'lumpy', when I started sanding there was a distinctive smell, household Dulux gloss, nice.

The rudder just needs priming and painting now.

Fuselage next, this has also been painted but doesn't have any major repairs (that I can see).  remnants of purple paint were removed from the NACA air inlets with a Dremel and a fine burr.

Wanting to preserve and reuse the original graphics I managed to carefully peel them off using a hairdryer to soften the adhesive.

An odd problem at the fin was servo mount screws being used for the all moving tailplane bellcrank . The left side screws were correct and original, there didn't appear to be any reason why dome head screws were being used on the right (and the two screws on the right were different to each other!).  The main problem (apart from being untidy) is that the tailplane half is held off causing a gap and possibly catching on the screws. Removed  them by heating with a soldering iron to melt the epoxy they were inserted with.

Lastly, a look at the wings. they appear to be glassed and painted in Dulux, the ailerons  are covered in Solarfilm and are very tatty.

One wing had a graphic which I was able to remove intact and some white Solartrim covering a glued in servo. The other wing has no hole so some surgery has happened here.

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Rudder, sanded smooth, dents filled.

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Fuselage fits nicely in my CentiPhase jig.

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Gary B

Photos continued:

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Gary B

Uninspiring weather (no model flying or motorbike riding) so 'll tinker with this some more.

I was hoping that the tail bellcrank screws would be listed in the instructions, they are  but it just says 'Brass screws'.

Luckily I have a Multiplex kit from the same era which I guessed uses the same screws, they are quite special, M2 x 5 with a stepped and flat top. I can only guess that the builder lost two of the four screws during the original build, I cant see any other reason why they would be disturbed.

Two pairs of tailplanes were supplied with the glider, the original set have the Dulux finish and have hairline cracks where they were run over by the previous owner's car. They look repairable but weigh 126 g. The other set were bought as replacements and are covered with film (probably Solarfilm by the bubbling), they weigh 96 g.

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pete beadle

Hi Gary

Glad to see you are persevering with the Arriba

One thing you don't have to worry about with MPX kits are the metric threads.....on most of my really old English/British kits they are often really odd old threads, BSF, AF, Whitworth and such, something I first found out when trying to get a 2mm threaded metal clevis onto a bicycle spoke pushrod on a "Golden Oldie" UK kit once - no names, no pack drill.......

My mate Dave used to swear by Brolac and even Woolworths paint, he swore that the Woolies "Pillar Box Red", alledgedly containing polyurethane, was even fuel proof!:yes:

One thing I did get in the habit of, with MPX tailplanes was to cut large circles out of the foam veneer ones, usually two per tailplane half, and this usually made a BIG difference when adding the necessary noseweight to get the CG right......never had a structural failure........that was usually reserved for the tailplane bellcrank bearings and or the connectors on the end(s) of the AMT pushrod wires which I usually replaced with helicopter ball ends - MUCH better:)

Keep it up!

Regards

Pete 

BARCS1702

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Gary B

Hi Pete,

 The tailplanes are foam/veneer according to the instructions, I will have a go at stripping the covering off the newer, lighter pair, if it is Solarfilm it might be a painful process. I think my Fiesta and Flamingo tails are built up with balsa.

I've searched Google.de and eBay.de for the special brass screws, even uploaded a photo to Google to search for similar items, no matching results.

Might be able to make some from Futaba servo mount screws (one of the removed screws was exactly this) by grinding the heads down and cutting a slot.

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pete beadle

Hi Gary

I've always found that removing Solarfilm should be a two man job, one to direct the heat gun at low temp ahead of t'other, with a blunt scalpel levering the edges up, and then removing the biggest area of Solarfim possible at one go........IMHO too much heat is fatal, the "heat gunner" should practice heating the area JUST ahead of the scalpel and where the colour of the film changes, showing him where to go next.......it's just a case of getting the adhesive to soften JUST enough

Have you tried West London Models for these screws? They look like they ought to be an MPX part.....www.westlondonmodels.com - good luck:yes:

Regards

Pete

BARCS1702

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Gary B

The Solarfilm is coming off, leaving a good surface.  Pigment remnants can be lifted with Wildthing colour tape (other brands are available) and heat, it is possible to lift veneer splinters with this method.

I spread talcum powder on any adhesive/pigment left behind which makes it a bit easier to sand off. I'm told that Profilm/Oracover come cleanly off with heat.

I did make two replacement bellcrank mount screws and checked that they were not fouling the mechanism, it seems to have more down than up travel which I will sort out when I replace the elevator servo.

As there was some gel coat chipping around  the stab hinge tube  I blanked the hole with a kebab skewer and added filler. I discovered that one of the stab hinges was carbon rod, will be replaced with wire. The other set of wires are firmly glued into one half,  I guess it is more difficult to lose them this way.

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Gary B

Removing Solarflm from the ailerons has been an endurance test.

Two half days spent on them so far, the wrinkled film on these did not want to come off with heat so it has been all mechanical, scraping with a new scalpel bladed, a new single edge razor blade, a power sander, various grades of wet and dry (240 seems to work the best) and some tests with solvent removers (aware that the ailerons are foam cored as they are cut from the wing).

The most effective tool, if a bit brutal, is my David razor plane. Set on the smallest possible cut it takes a small amount of wood off and the film with it. The lower surface is slightly undercambered so it doesn't work particularly well there.

If the ailerons end up undersize then I will skin them with 1/32" balsa which will tidy them up nicely.   

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Gary B

Last week I sprayed the rudder, a thin coat of acrylic white primer rubbed back then acrylic Audi Laser Red (left over from a Phase 6 build), that's one part finished. I have no idea what the base finish of the rudder was, could have been paint directly on to balsa but it rubbed back nicely and is good now.

Still sanding tailplanes and ailerons, just about done.

I spent a short while in the garden today, a bit blowy and possible to end up with large parts on the floor.

Fuselage: Removed the servos and rubbed back wet with 180 grit first then 500.  I wasn't sure if it was painted or gel coat but in one spot it is clear that it has been painted and the original gel coat underneath is still there.  Quite a good paint job then by whoever did it and not Dulux as seen on the wings and tails.  No existing repairs anywhere and just some small spots of filler needed.

I developed Tennis Elbow (lateral epicondylitis) in my right arm about a year ago, most likely caused by rubbing down old Multiplex gliders, the treatment is not to rub down old Multiplex gliders!

As I stood back and looked at the fuselage with the fin vertical I could see that the servo tray was nowhere near horizontal and that the battery supports were similarly at a jaunty angle but the other way.  I think I will pop all of these out and see if I can improve it. The Arriba instructions show a ply box structure for the battery, plenty of room in there for one.

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Gary B

More piccies:

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Gary B

A short break then another burst of enthusiasm on the wings.

The finish is quite lumpy but mostly only on the bottom surface, sanding the top surface (wet) revealed a yellowed layer of paint below.

I am very cautious about sanding glassed veneered wings wet as I had a disaster once, the finish on these (resin) appears to be waterproof, using the minimum water possible for the job.

The airbrake caps have chips of thick paint missing, they can be dismantled by removing the brass screws, these are the same screws that are used on the tailplane bellcrank, learning all the time!

Getting there.

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Gary B

In the garden again, almost pleasant.

Removed the airbrake blade from the opposite wing, raising it with a servo tester it was sticking. The cap strip was fouling the wing skin and the screws were too tight, backed the screws off, trimmed the cap strip, fixed.

Next job I had to do was tidy up the right aileron servo bay. Cutting a circle of wing skin out was the easiest way. 

The servo is a Hitec HS-81, the gears are good, it must have been a replacement to leave such a mess behind, the wing skin is 1 mm thick so I made a 1/16" (1.6 mm) disk of balsa to plug the hole. In theory (!) I should only have to sand off 0.6 mm of balsa to level it with the skin. 

I trimmed the spare plastic off the end of the servo horn before fitting the disk and worked the servo during gluing to make sure there was no restriction.

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Gary B

Some spots of rain so in to the shed for a bit then finish for the day.

The paint on the airbrake cap strips was so thick that they weren't flush when closed, I decided to sand almost all of it off.

When I'm sanding something like this I tape the paper to a piece of shelving or directly on the worktop and sand the part all at once, it avoids the lumps and bumps that can creep in when using a block freehand.

Servo bay cover was sanded down then brushed with sanding sealer (about five or six coats, sanding between).

More wet sanding of the wings, I've taught myself to sand left handed to ease the RSI.  Although the photo shows a blotchy surface it is nearly smooth now, something must have gone astray at the glassing stage, I know my early efforts weren't  wonderful.

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Gary B

Couldn't do much today as we had visitors.

Very pleasant in the garden, light wind and milky sunshine.

I ran the motor up on a home made test stand (ply with holes in it!), it didn't sound too happy, possibly bearings and while removing the prop the shaft started to pull through (there are grub screws at the rear end). Any identification has rubbed off of it and the rotating part was munching through the wires. Weighs 195 g out of interest. Motor screws are M3 and appear to be 19 mm between centres.

The propeller has also seen better days, the spinner is slightly oversize at 42 mm, needs to be 40 mm.

Last little engineering triumph for the day was to modify my Centi-Phase/Hi-Phase fuselage jig to hold the Arriba fuselage firmly.

I added two wooden side plates and drilled a hole in each to take an 8 mm steel rod (the wing joiner from my Multi-Phase, RIP). 

The steel rod passes through the holes for the anti-crush dowel (wings try to swing forward on landing and crush the fuselage), a Velcro strap secures the tail, nice and solid now leaving both hands free for surgery.

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Gary B

Well, I'm really glad that I decided to remove the servo tray and battery mounts, they fell out without a fight.

A sheet of lead under the motor came out just using a fingernail.

Surplus blobs of epoxy were removed from other places so now I have a totally blank canvas. The ply plate for the receiver seems fairly well attached, it only has to carry 10 g, left well alone.

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Gary B

Been having trouble posting, Austin is looking into it.

More wing sanding, there is no end!

Is it me or does the former look like a surprised cat in this diagram?!

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Steve J

I do like a refurb topic. Thanks for posting.

Steve 

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