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Samba Prestige 2pk build


thermaldoctor
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thermaldoctor

As many will know the new Prestige 2pk is the very latest model from Samba. It is also their first model exclusively dedicated for F5j and not an F3j model made lighter for F5j. The overall concept and  goal in both classes though is actually similar but go about it in different ways so we are now seeing purposely designed models for F5j that are now fitting the task noticeably better than previous cross-over type models.

And the Prestige is most definitely one of the new breed. At the very first 2019 F5j WC in Trnava there were one or two models that just looked a bit better and a bit more comfortable and not struggling against other models in the slot over a week of very different conditions and the Prestige was one of them.

With the many different proprietry Philip Kolb designed airfoils and planforms running through the rudder, elevator and main wing it is arguably the most aerodynamically sophisticated f5j model available at present and definitely one of the top choices if you are after the very best in performance that current technology and aerodynamics has to offer. 

But this is not without its compromises.. 

The Prestige 2pk uses Rohacell solid core wing technology for the ultimate in light weight, strength and stiffness from such thin low drag wing sections but it is prone to denting more easily than conventional hollow moulded technology. It also means you have to bore your own holes in the  Rohacell cores for pushrods and aileron servo wires (centre panel comes completely done with wiring for you) but for anyone with proper traditional modelling skills it will be a breeze.

The fuselage is super skinny to offset the drag of the prop compared to a pure glider fuselage and although there are performance gains to be had, it makes installation very tight and a pig compared to traditional older fashioned layouts but once done and the swearing is over it is very neat very slick.

Here is a pic of my final fuselage installation. Read next time how we got there....

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PeteMitchell

Wing dents can usually be removed using a damp/wet paper towel laid over the dent area, and carefull use of a covering heat iron.

The iron needs to be hot enough to  cause the damp paper to steam. The steam expands the foam and returns the surface to undented condition.

If the dent is in a painted area the steam can cause the cloth weave to show through the paint.  And if the dent is a  'sharp' one, caused by   i.e. a heavy tool being dropped on the surface,

the dent will probably never be fully removed. So dont do that!

 

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  • 3 weeks later...
thermaldoctor

The Prestige fuselage comes with pre-moulded in servo trays intended for the MKS 6100 servo format. Unless very close to these dimensions servos will not fit without some major surgery. But there are one or two others that will fit from KST, Bluebird. Not wishing to fit these brand of servo i elected for some major surgery. But there was another reason going for major surgery - my first Prestige to put together is a windy lay up one with 4s 1kw set up. So I figured flying forward at full power into  a strong headwind will give quite a high airspeed plus possibly quite turbulent conditions. Therefore I did not want to run small 9g servos on the large rudder and elevator surfaces. It would be like ramping a Fiat 500 down the motorway at 100mph. So i fitted larger 12mm servos with bigger stronger gears and nearly twice the torque.

The major surgery involved cutting out the existing servo trays (but leaving the two ledges each end) and fitting my own from 1mm carbon. It was self inflicted pain but the end result is worth it. But I wouldn't suggest people going down this route unless they really wanted to.  My normal and light Prestiges will use the Kingmax 0309W's which are 8mm 3kg items and should be fine and will fit with only minor effort.

Below is a good look inside the fuselage that not many will ever see as here we have it without the pre-moulded trays and all cut out.  You can see the Textreme spread tow carbon on the fuselage floor and on the left hand side just under the ledge is the carbon ballast box bonded in place.

As it comes the carbon pushrods need the threaded couplers glueing on and clevises fitted in place. For me this was much easier than normal as I did it before I glued my servo plate in so had easy access . As I would not necessarily suggest people go down the route I did I would refer you to Ali at Flighcomps video on how do a conventional fuselage servo install. I have also put together a conventional Prestige together for a customer and Ali's method works well.

A good suggestion thanks to Martin Gilbert for at least the rudder is to pull the end of the pushrod forward clear of the fuselage and fit your coupler/clevis/horn first. Then push it back in place, line it up with the servo, and then chop the pushrod and  fit the rudder ball link last of all. You can also do this for the elevator but will need to chop off the pre-glued elevator ball link and then fit another once you have done the servo end and lined it up. There is plenty of length on the pushrods to do this.

 

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The servos I wanted to fit were 12mm 5kg items. But being meant for vertical fuselage mounting I needed a way of fitting them flat to a horizontal surface. I opted to cut some 1mm thick carbon angle from Easy Composites and after roughening up and degreasing both surfaces thoroughly I used thick slower setting cyano to make up chassis mounting type holes. I did this for one side of each servo and then for the other side of each servo i used the same 1mm carbon angle bonded to each fuselage ledge with screw holes drilled on  the vertical faces to bolt the servos to

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thermaldoctor

The end result worked out like this and for me was well worth it for 1KW dedicated windy weather model. But as mentioned quite a major effort and perhaps way over kill but I am happy with it.

The receiver sits in a pre-moulded bathtub set into the rear of the fuselage. I like this idea very much but it has been poorly executed if you don't have a receiver that will fit. Space is quite tight for some receivers (mine are Multiplex) so be prepared to get the heatshrink out to get it to fit. I have seen a number of receivers fit perfectly however, so just like for the servos it seems to have been designed around the most popular sizes. I have seen JR, FrSky, and Futaba fit just fine.  What you will need to do for all receivers however is cut out the front face of the receiver bathtub to allow for the connectors. At the rear you need to make provisions for the aerials.

The wiring loom comes pre-done for you and all you will need to do is cut out the rectangular hollow moulding into the fuselage and glue in the connector. To do this I plugged it into the wing (the wing one comes ready fitted in the mould) and then bolted the wing to make sure it all lined up and making sure to use a smearing of grease to stop gluing the wing on.

 

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The rudder comes as a separate moulding and is designed to be de-mountable for easy storage and transportation. As standard it is simply a friction push-fit on and retained with a single screw on the bottom. Further rotation is prevented by taping the fuse/fin joint. The engineer in me was not comfortable with this, particularly for a windy weather model facing strong crosswinds and 1KW of prop wash so I decided to line the fin up an bolt in place. Then use a pillar drill to drill vertically through the fuse and fin at the joint. Then use a carbon rod glued into the fuselage projecting just enough to locate the two slots made in the fin. This worked perfectly and put my mind at rest but again...maybe overkill. Would you need to do this? Probably not I think I am the only pilot to have done this but it certainly cant do any harm. I won't be doing it for my normal and Light versions it was just for the windy model.

The screw now is there just to stop the fin falling off. All rotation is now taken care of by the rod and slots. With regards to the screw I had to open out the hole in the bottom of the fin to allow the fin to sit perfectly vertical. As it was the fin was at an angle which was unacceptable. I have spoken to Samba about this and all future models will come perfectly jigged.

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thermaldoctor

At the back end more material was needed to be taken off the pylon part of the elevator slot to allow full down elevator. As it came it had just enough down elevator but i dremelled it out further to allow the elevator to just touch the top of the fuselage ie absolute maximum. I like to have enough down elevator for full brake compensation and then also a further as near to full travel movement to nose the model over onto the spot if needed. While i was there I also widened the slot to make sure the elevator rod could swing freely at maximum travels without catching the sides.

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In this picture you will also note a tailplane seating. This is not standard. As it comes the tailplane seats on top the slim pylon and again the engineer in me rejected this because of any lateral loads will only be spread over a very narrow seating area. Although the tailplane is quite hard at the mounting points the idea came from the Osprey 2 which has a nice wide 20mm tailplane saddle that works really well and gives very firm support for any lateral loads applied to the tailplane. So the idea was transferred to the Prestige with great success and perfect for a windy weather model that will be experiencing a lot of turbulence and prop wash. Again is this totally necessary? Probably not but it cant do any harm and i feel much happier having done it. Most likely i will not bother doing it on my standard and light version.

As it came my tailplane was slightly out of alignment and it needed small work with a file to align. This was unnacceptable but speaking to Samba this is now fully corrected. 

To finish the rear  end off the rudder slot needs opening out to allow full and free movement, the ball end bonding on, and job done. 

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PeteMitchell

My one is a standard setup, more or less as recommended by Samba.

Jeti R7 fits perfect 🙂 

PrestigeServos.jpg

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Pretty standard install on my fuselage - Frsky X8R receivers fits fairly easily with the case removed. Altimeter is pushed down the boom.

servos.jpg

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Disappointing  finish around the canopy opening though. You would normally expect better attention to detail from Samba..

canopy.jpg

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  • 2 weeks later...
thermaldoctor

Right, to the wing. Straight away you need to decide if you want to fit an IDS system or a conventional horn and clevis set up. I decided on a normal clevis and horn set up. G10 horns are supplied by Samba if you choose traditional linkages. An IDS system will need to be bought on top of the kit price if you choose the IDS route. The Prestige comes as standard without any pre-determined control surface linkage set up so is a blank canvas to do what you want.

Whatever set up you choose first job is to make up pushrod tunnels in the solid Rohacell cores. I started by screwing the servos (with horns fitted)  into their frames and test fitting them into the moulded in  servo bays. The moulded in servo bays are a nice touch.  Then I rotated the servo horns to rest on the back edge of the servo bay and marked with a pen. This would then of course be the point at which a tunnel needed to be made. I measured these points back to a reference point (on flaps it was the centre moulding line and on the ailerons it was the end rib). I then translated these same measurements back up the false TE of each panel and marked again with a pen. This would then give exact exit points for the pushrods.

Now with exact entry and exit reference points to start making each tunnel it starts to become less about measurement and more about feel. I drilled one small hole at each entry point and 1 small hole at each exit point. The idea being to connect the two up to make an accurate tunnel. I used a sharpened up 2mm carbon rod and very carefully pushed and rotated it from the back of the wing through to the servo bay. At all times i monitored that each angle was somewhere near correct. The most important angle not to get wrong is the vertical one through the wing thickness  otherwise you risk marking or worst case punching through the upper or lower skins. The key here is to start out with a small diameter. A bit like using a centre punch or drilling a smaller pilot hole when drilling a larger hole.

The pic below shows an initial 2mm tunnel already accurately made with a screwdriver poking through for reference. Once done I then gradually opened up each tunnel with a series of round files ending up with a 6mm file. I made the mistake on the first tunnel by trying to open it out too quickly and assumed the rohacell foam would naturally guide everything down the pre-formed hole. It does't and I marked the lower surface from the inside. So you still have to be careful and eyeball the angles of the file but here is where patiently and progressively opening each tunnel out will pay dividends. Another way would be to get a smaller round file in place and then work a larger diameter out by filing.

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I found for the ailerons a slot in the upper surface of approx 16mm long was needed to clear the clevises. The tunnel need only go half way down the false TE to get full down aileron movement. For flaps the hole needs to go right down to the bottom of the false TE to get full brake movement (watch the hinge) and only upper surface slots of approx 5mm long to clear the clevises.

While at it i measured each centre point of the exit hole to give me a horn location. I then offset this one way by 1mm to allow for the asymmetrical clevis.

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thermaldoctor

Just as for the the pushrod tunnels i started off each control horn slot smaller in width and carefully opened up with a flat file to get a nice friction fit horn which really helps when setting them in place when glueing. The initial slots were made with a brand new scalpel blade. Needless to say as you file (or if you choose to cut the final slots with a scalpel) keep the slots perfectly upright and at 90 degrees to the hinge.

 

 

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I made sure each control horn slot had the rohacell carefully removed right to the bottom so as to expose the lower wing skin. As each Samba supplied G10 horn is computer cut they are perfectly matching pairs so by sitting them down perfectly onto each lower wing skin it would ensure each pair of L and R clevis holes would be at an identical height above the hinge line. This turned out to work perfectly and it means you only have to concentrate on matching each pair so they each sit over the hinge line point.

Speaking of the hinge line reference point, it is useful to know that top line of the aileron face is 1mm behind the hinge line and the top line of the flap face is 3mm behind the hinge line. Thus you aileron horn clevis holes need to project 1mm forward and your flap horn clevis holes 3mm forward.

For the ailerons it means you need to dremel out a small clearance along the width of aileron face to allow the clevis to spring open and closed unhindered. For the flaps this wasn't necessary. The pic below shows the aileron dremelling needed.

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So it is now ready to glue the horns in. I like to drill a series of small 1mm holes in each horn and thoroughly scuff up both sides to help bonding. I also used a good quality slow setting epoxy resin with carbon powder in to give a really tough rock hard bond. Using a spatula to paste the epoxy carbon mix into the holes before fixing in place gives me peace of mind the horn will never ever get ripped out of its slot.

 

Slot masked off, horn drilled and roughened up and ready for bonding. I found a clevis fitted into each flap horn and then carefully pushed up against the flap facing gave the perfect 3mm forward projection of the clevis pick up point. With a smearing of grease on the clevis and only a light application of the epoxy carbon mix nearer the clevis hole I found this worked perfectly and I managed to get both flaps moving identically with only a minimum of electronic curve trimming between L and R.

For the ailerons i pushed through a 1.6mm 2 inch long piano wire and eyeballed to ensure straight and parallel. Then fitted each horn and used 2 small squares of 0.8mm ply each side against the aileron faces to act as shims to push the piano wire up to. I didn't get a pic of this sorry.

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thermaldoctor

An example of a completed traditional horn installation....

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For the tip panels you need to make another tunnel only this time to facilitate the aileron servo plug/wiring. Same method as before. Could have been done at the factory but I guess different servos and/or different servo layouts will have different hole positions required in the servo bay. But with the centre panel having the wiring already in place, the hole in the aileron end rib can only be in one location.

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As this one is a windy model I wanted to fit a bigger more manly servo than a tiddly 10 grammer on the ailerons. I found with a bit of trimming of the lugs width ways and then the bottom lug filed totally away I could fit my beloved Kingmax CLS0612W servo. These are identical in size to the KST X10 mini so it shows it possible to get a bigger servo in there if you want to. You can see below how the servo and servo  frames have to be cut and trimmed in order to make this happen. This is not possible if you are fitting IDS or wanting a ballraced servo frame however as the aileron servo bays are simply not big enough.

 

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thermaldoctor

Final aileron servo installation. Not much room to spare but fits a treat..

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No such problem on the flaps fitting a ballraced support frame but be aware the bottom lug will still need to be cut off to allow enough of a gap between the bottom of the servo and the bottom wall of the servo bay to be able to pull the servo back enough and out of the bearing. If you didn't want a ballraced servo frame (and to be honest with the smaller chord flap of the Prestige and the quality of the Kingmax CLS0612W gearbox you don't really need to) then you can have a normal basic servo frame and keep the bottom lug of the servo intact for a proper 3 screw set up.  For my next Prestiges I wont be bothering with a ballraced frame and will use justa  basic green plastic one.

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Marc RC pilot

I must say  thermaldoctor, your attention to detail/skill/precision/ high tolerances in your work is quite amazing sir (and great quality close-up pics)! 👌 Outstanding and something to aspire to.  

Thanks for sharing  

I am resuming the position:

:popcorn:

 

PS btw I noticed your very short Kingmax wing servo lead; is that how they come? Does make sense 

 

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thermaldoctor
On 20/07/2020 at 18:05, Marc RC pilot said:

I must say  thermaldoctor, your attention to detail/skill/precision/ high tolerances in your work is quite amazing sir (and great quality close-up pics)! 👌 Outstanding and something to aspire to.  

Thanks for sharing  

I am resuming the position:

:popcorn:

 

PS btw I noticed your very short Kingmax wing servo lead; is that how they come? Does make sense 

 

Thank you for the kind words Marc.

To confirm, both the Kingmax CLS0612W (KST X10 mini size) and CLS0911W (KST X10 size) come with nice short 50mm servo leads for wing mounting.

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If anyone is wondering about the numbers, the first two digits are the torque figures and the last two digits are the operating speed. The CLS bit stands for coreless. 

The W bit is supposed to stand for Waterproof. But i haven't tested this out and neither do i think they are fully waterproof either. There are no O rings on the case joints and the cable grommets do not have any extra rubber around them like proper fully waterproof servos do. They do seem splash proof though 

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