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Scram

Strega 2 Build

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Scram

Strega 2 Build

Getting going with the build has been slow due to the amount of thinking time I need.

 

However I decided an insurance policy was needed to start with on the basis that if I build a fuselage jig, hopefully, I will never need it.

 

So I started with a base made from 22mm flooring chipboard and then I had to think about how to align wings and tail of the fuz is broken as this must be more difficult with a V-tail.  So I decided a support using the wing joiner would provide alignment at that end and use the shape of the fuz at the tail.  I also decided to make the jig for the Vampire as well, on the same base.  Again this is difficult because it really needed the fuz in upside down because of how it is kitted out.  This left only a little tail surface to align with bit it will have to do.

 

IMG_2976_zps48bf476c.jpg

 

The fuselages I prepared with a layer of packing tape in each place of support which got two layers of furnisher polish, before dobs of body filler were applied to the base and the fus pushed in.

 

IMG_2978_zps7fb6d717.jpg

 

Will it come out??  That base is heavy ...........

 

IMG_2979_zpse1196b84.jpg

 

................ phew!! 

 

IMG_2981_zps6d82d49b.jpg

 

A bit of squeezing and manipulation at each point got it out.

 

Both fuselages how they would need to be set for repairs

 

IMG_2989_zpsd5cecc46.jpg

 

............... hopefully never to be needed

 

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Scram

Strega Fuselage.

Adam sent me a radio tray for fitting out the fuselage and this caused lots of head scratching on how to get it in and get the nose weight in but first I made the cutouts for the tail servos. 

 

In the end, I made a plug to get the inside nose shape using shopping carrier bag liner and a sand/cement mix to get the internal shape.  I assembled the plane with most bits in and put some cocktail sticks under the wings at 100mm and loaded the nose with lead weights to get an approx mass needed  ~ 240g to balance the CoG.

 

I then made a mould for pouring lead into again using a sand/cement mix with the polythene wrapped cement plug stuck in.  When almost dry I pulled the plug out and stuck the resulting mould in the airing cupboard to cure and dry out.  Left it there for a couple of days and went to pour in about 300g of molten lead.  I’ve mentioned this before!!  The mould was not dry and molten lead sprayed out as residual water vaporised.  Luckily it all missed me but I had to re-do the cast, this time after making darn sure the mould was dry.

 

I had to fettle the plug then to get it to go right to the front of the nose, then cut it back to just over 200g to give me a balancing allowance. 

 

IMG_2990_zps704c0058.jpg

 

Stuck it in with epoxy.  I had to cut the front off the radio tray and move the battery back a bit.  I tried to use Adams method to glue in the radio tray but got in a right mess as syringe and epoxy do not get on and the long snake tube extension would not stay on.  I chucked it all in the bin, just saving enough epoxy to locate and secure the tray.  When dry, then I ran CA into the sides of the tray to fix it to the fuz before mixing epoxy and microfibers to fillet and secure it the full length and to glue in the ballast tube.

 

IMG_2996_zpsc27d950c.jpg

 

The ballast tube had a cut-out for introducing weights and I drilled a hole and epoxied on a 3mm Tee nut underneath for securing the last weight.  The front of the tube was supported on a block of hard balsa previously glued in to get the height right and this was generously epoxied  to secure the front of the tube ................ nearly a big mistake.

 

Having got the tray installed I then looked at getting the pushrods for the tails cut and fitted but when I put the tails on and looked in the back end, I could see that there was a longer moment arm on one elevator horn.  These are bits of ally angle glued in but one was fitter off resulting in this:

 

IMG_2997_zps9ffc14be.jpg

 

I gripped the elevator with pipe grips and cardboard so that I could bend the arm down with pliers without straining the joint.

 

IMG_2998_zpsdb50ad9a.jpg

 

.............. that’s better.

 

Pushrods went in OK and the 7mm servo arms just fitted with a little gap between the servos thus ensuring ballast will go in and no kinks in the pushrods ................ though there is a good curve in the carbon tubes!!

 

Last job was to fit the wing wiring and this is where I nearly came unstuck with the ballast tube front fixing ................. I left very little space for the wiring.  I’m using the old wiring from my broken Wiz so it’s already made up but there was no way I could get the leads with plugs on down beside the tube from the greenie plug positions and through the small apertures left at the front end of the tube.    :huh:  So I removed the greenie plugs and used a long thin weight to drop 2 threads through each greenie position, over the tube and down the opposite side and out through the aperture beside the front of the tube.  I could then pull just the cables back through and out so’s I could re-solder the greenies back on.  Fuselage finished.

 

On to the wings later.

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Big Bear

Great thread thanks. I shall be following this as I have acquired one too

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Gromit

Nice work scram, keep this detailed build thread of yours coming please :thumbsup:

 

  Stu.

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Scram

On to the wings...............

 

A couple of things first.  I thought I would need a bunch of clevises for this plane so I bought 2 packs of Multiplex 2mm clevises.  Much to my surprise, the plane came with a pack of clevises and threaded rods for the pushrods.  However, these clevises I rejected on 3 counts:

 

a)  the arms were way out of parallel

B)  the pins were loose  :(

c)  the pins were only 1.5mm dia whilst the holes in the horns were 1.6mm.  Does metal to metal rattling still cause interference on 2.4 GHz?  (ally elevator horns)

 

However, when I came to fitting the Multiplex clevises, I find most of the pins are really a bit rough machined when looked at closely and have a burr making the end larger than 1.6mm

 

IMG_3003_zps3e84e918.jpg

 

I have had to file this burr off each one, fiddly.

 

Secondly, I was standing the wings on end, resting on the incidence pins (6mm carbon rod).  On one, it was not glued and had no inside stop so it pushed in and nothing I could do would stop it disappearing inside the wing – grrrr 

 

IMG_2972_zps53c8ca9b.jpg

 

Had to fit a bit of 6mm tube with 4mm rod glued inside to make it solid rod.  The battery I made by opening out a square 4 format pack.  Required no re-soldering, just re-shrink wrap.

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Scram

I debated long and hard with myself how much I would spend on this plane, which servo’s and kit to use.  I decided on S3150’s for the wings and servo mounts instead of my usual gluing them in.  I got mounts and outer support bearings from T9.  There’s no way I will spend £25 a throw on these outer support kits!!   However, when I looked at fitting the T9 supports, it was clear that the support bearing/pin arrangement, designed to allow the servo to be removed leaving the bearing in place was not to my liking.  The bearing would be so far under the wing skin, there’s no way I could ensure alignment.  I felt this would make for dubious long term operation. 

 

IMG_2992a_zps731d8a34.jpg

 

So I determined to improve this with my own bearing blocks.  The brass horn securing screw with an extension is 2.5mm dia rather than 3mm as I expected but I was able to find suitable 2.5 x 8 x 4mm bearings at Simply Bearings. I bought 4 and some 6mm thick Tufnol sheet.  I cut 2 strips of Tufnol ~ 5mm wide and put them face to face making a 12mm deep sandwich which I bolted together at suitable intervals with M2.5 socket head screws and then bored through the centre line in 4 places with an 8mm drill.  Cut into 4, this then made 4 bearing blocks with removable tops.  I cut the end off the support shaft leaving the 2.5mm shaft to go into the support bearing.

 

IMG_3004_zps98f96613.jpg

 

IMG_3005_zps134c8c96.jpg

 

The bottoms of the bearing blocks prove to be about flush with the wing skins but this is not terribly important as epoxy glue securing it will take up any difference.  These will be installed at the same time as the servo frames.

 

Horns for the flaps and ailerons on one wing were installed earlier

 

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but ........ maybe I should take more notice of Tom and Mike ‘cos when it came to fitting the clevis to the horn, there was not much room inside the moulded shroud.  The horn pin would be better being further forward and this would require a jig to position it.  Measuring the length of the horn is impossible though, I find, so I will make the rods a suitable equal length and suck-it-and-see how the throws go.  This is essentially following Mike's Easy Flap Install instructs.

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isoaritfirst

Looking good jerry. The fs4 wing servos Are installed complete with end bearings which simply slide into a fairly thin wing rib that is fixed to both top and bottom wing skins. Bearing slips in and out. As servo is installed. Very simple, also rib position is very accurately installed during construction so servo position is dictated by the rib.

I would copy the idea on any future installs. Rib positioning with its bearing hole would be very easily located by butting up yo main spar.

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mark_r

Enjoying reading this thread - always interesting to get different perspectives on some of this stuff. Thanks!

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Scram

Instead of using the ball bearing, I could possibly just have drilled a hole in the Tufnol as this material is used for plain bearings.

 

Final instalments later .................

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Big Bear

What the advantage of using the bearing method over the traditional method?

Cheers

Adam

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isoaritfirst

What the advantage of using the bearing method over the traditional method?

Cheers

Adam[/quote

It reduces float in the servo output shaft, should make the linkages better and servo last longer. But servos these days are very good if you pay decent money, so advantage is possibly hard to see. Of course if you keep your models for many years and fly then a lot, or if you use cheap servos then their advantage may be more noticeable.

Lots of things you can do to make a good strong linkage before you need to add end bearings. But then again it could be argued they are simple enough so why not.

The other reason for using them is that head stresses have increased as the

Servo arms have become shorter.

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Scram

I would add that using the servo mounts (as I am) increases the flexibility of the servo location and adding the bearing support will counteract this.

 

The supports I've made come in at just 4.9g each including the brass bit so do not add much to the o/a plane weight.

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isoaritfirst

Not sure that that is quite right Jerry, yes it will restrict flexibility of servo positioning, but that is a benefit. It makes for two identical aileron/ flap servo pairs, provided the ribs are correctly fitted.

 

The only down side is that the bearing hole within the rib needs to be at the right height from the wing skin to match the servo used. Thats no problem if making yourself, but if factory fitted for a 10mm servo then you are restricted to a 10mm servo.

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Scram

Mike,

 

I was not commenting on your method of providing the support bearing or locating the servo, but observing that the fact of the support bearing would decrease the defection (maybe) or flexibility of the servo mounted other than stuck to the skin.

 

My choice of the word "location" could be ambiguous  :blink:

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Scram

Back to the fuselage for a question.

 

I need a method/location to get the Rx whiskers out into the air.

 

IMG_3006_zpsdfbc7b3f.jpg

 

There's quite a bit of carbon about, strips down the sides of the fus in the canopy area and full lining behind the canopy.  There is also quite a lot in the wings, though not full carbon.

 

I think maybe it needs one whisker high, above the wings and one low below the wing line.

 

Else, would it be OK to poke both out at about 90° to each other, through holes in the canopy, maybe with 1" of snake outer for protection.  Seems to me this may screen both antenna when the plane is high and going away from the Tx??  I have a Hall effect switch so canopy will need removing only once per session.

 

I'm wary of drilling holes in the fuselage if this is not necessary.

 

Any suggestions?  Thanks

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isoaritfirst

Leave them inside. Poking out they are likely to get fractured, either by handling or possibly just by waving around at 150 mph ☺

Tape one along the canopy edge with a bit of diamond tape wrapped from inside to out. The other position either across or vertically , sometimes I use a little piece of EPP jammed in and melt a small hole through for the antenna.

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thermaldoctor

Or have them outside and protect with heatshrink tubing

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stewartg

This is 2.4 friendly I would try a range test from all angles with one aerial horizontal and one vertically in a plastic tube poking into the canopy void before I drilled any holes

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isoaritfirst

Not put one outside yet in "loads of models"

 

and before you all  jump on that statement - I still have them all, or they were sold, still in one piece.

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Phil.Taylor

 

However, when I came to fitting the Multiplex clevises, I find most of the pins are really a bit rough machined when looked at closely and have a burr making the end larger than 1.6mm

 

 

I have had to file this burr off each one, fiddly.

 

 

thanks for taking a close look at those MPX clevises

you've solved a mystery for me - as to why I've often had problems getting them into and out of the metal horns !

I standardised on MPX 2.5mm clevises a couple of years ago after having various problems with cheap-n-nasty ones

I've just looked at an aileron linkage that happens to be on my desk - same "burrs" as you've got

I'll still use them, but now I know to do a bit of filing to make them nice before fitting them

 

Phil.

 

Phil.

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