richbran

Here are some more tips. Those are my choices, if You do not like it, don't use them.

My preference for fitting the gears is not using wood screws but regular M4, with a countersink nut in the wood. One the forward side of the gear You can get to the underside of the gear beams, for the back side You have to open up the main rib as shown so You can enter and put the nut where it belongs. I had once a bad experience with wood screws when the model got beside the RWY and one gear was ripped off. because the heads of the screws sheared off.
Now one can say this is a safety feature, because they will break before the gear beams do, but I have all my models nowadays fitted with M4.



We fly off concrete runways, the surface is VERY rough. We normally put skids under tips and other parts of the model which are likely to get in contact with the ground if things do not develop like You wished!
This time, more or less by accident I found red duct tape which is about the same colour as the red tips.
I stuck a few layers on the first part from the tip.
To protect the tail boom underside against full stall landings with a low tail, I glued some 3mm aluminium (aluminum ) skids (no picture)



My fuel system was checked with overpressure air so I knew it would not leak, anyhow, I normally drill some 4mm holes near formers where fuel would most likely accumulate in case a leak would develop. (no pics)

The engine "bay" i painted that (horrendous expensive) fire protection stuff. It does not look nice (very rough, like sand) but it works perfect. Its colour is white.

DenisFerrari

..

richbran

For the time being (need better weather than this continuous rain!), until more flights are made, the last few tips.
In one of the messages David commented about the base plate of the tank. I concluded that the base plate's holding power is limited, due to the weight of a fuel tank.
So in between the skin and the plate I glued a few scrap plywood pieces, with foaming wood glue (yellow suff that foames like PUR, but has great bonding power, I use it a LOT!). So there is way more area the plate is fixed to the structure and will not break that soon under stress. Leave some parts open to pass the straps.
Of course it will not hold in a crash, a full tank being the heaviest part of a jet, has incredible inertia!

When ready I covered the base plate and the former that makes contact with the front of the tank, with padding material (white in pic) to prevent "chafing" to the underside of a tank.
Jets are basically not prone to vibration damage from the engine, but over the years I discovered that during take off and landings (especially on concrete) it rattles like hell, loosens all screws and chafes anything that is not fixed properly.
In the aviation industry chafing is a serious sleeping monster that can produce nasty damage, not right away, but after 15, 20 or more years. A chafed wire connection somewhere You cannot reach easily can get trouble shooting mechanics looking for ages to find.

BTW the tank holds 4300 grams of fuel and with a SG of 0.8 that amounts to 5.4 litres.

I normally consider the fuel that is in the hopper (STD hopper 125cc/100 grams) as non-useable, but I include that in the Empty weight and for the balance check. Whenever You land with a (partially) emptied hopper, You seriously have to reconsider Your timer setting or flying style! Even for my 160 that 5,4 litres is some comfortable 10 minutes of flying time, with room to spare, ideally for training. For lower powered engines a partly filled tank is a serious option. (or maybe the supplier could offer two versions?)

Finally I removed the Velcro style of fixing the tank, could not find anything at the normal DIY stores but internet shopped through some tie wrap suppliers and found heavy duty long tie wraps. You need about 70cm lengths to have a comfortable use.

A last word about the project. I normally add up all that I stick into a model (but keep FAR away from my spouse...) and even while its a relatively "cheap" model, costs still soar at the end.
If I subtract the cost of the Weatronic equipment (525 euros due to the large 12-22 receiver plus optional patch antenna's), the Unilight LED system (235 euros), FESTO parts (180 euros) and the jettronic etelctronic valves, the (new) price is still a 5000 euros.
Jets will never become very cheap, and basically that is a good thing, You will always think of that second hand car that is flying around You and You'd better be careful with that.
It is a big safety driver, to not cut corners during building, and not during flying.

One picture shows the metal skids at the bottom of the tailbooms

richbran

2nd flight
Today I made a (partly) successful flight myself.
Before the flight I cycled the gear twice, and refilled the air, the flight went according to the book, until it was time to lower the gear....and nothing happened. Tried a few cycles plus G-force but nothing showed underneath.
So decided to make a wheels up landing on grass, after I discarded the idea of using the main hard surface runway. The grass was not really short. plus not very even, which posed some risk.
Came in very low and flat because I did not want to use the speed brake, which surely would have been damaged.in the process.
Made a nice landing, and it slid to a stop.
Inspection(also later in my house) revealed NO damage! Not even scratches!

Tried all evening to figure out what happened and in the end the Jettronics unit wasn't responding anymore! It is the 2nd time these units fail on me, I am going to replace it for an Ultra Precision UP8 plus servo, that brand has never let me down

.

aquaskiman

My Feedback: (46)

here is a pic of mine

richbran

Third flight last week I had a problem with the electronic brake valve, causing the brakes to lock up after landing. I discarded the unit and put a mechanical valve in (UP6).

Contrary to a terrible forecast we had a beautiful day today, I scored 3 more flights with some 12 landings, got more and more confident and widened the (my) flight envelope. I like the plane more and more, till now it posed no real surprises.

Stalls and spins (easy recovery), outside loops plus some "knife edge". However that last one did show some peculiar behaviour. Of course it is basically a trainer and no hotshot acro plane.
What I noticed is that with a 90 degree bank and maximum rudder the Xcal the bank angle INCREASES instead of rolling back, what one might expect with single fuselage planes. Normally You will have to feed in some counter aileron to keep it at 90 degrees. Here I had to give aileron INTO the same direction as I did the rudder. It is a bit off the ordinary, interesting aerodynamics.

The other fact was the floating tendency upon landing. I really had to aim well before the landing spot, as it floats a long time, notwithstanding an almost 90 degree airbrake (flap if You will) setting, combined with UP aileron (crow mixing).
This behaviour might stem from a few personal choices, like I use a WREN 160 which is on the highest end of allowable power,. These engines have a residual idle thrust that is in line with their max power.
Plus my flying style is more aerodynamic than just firewalling and rocketing around. That means that after some 10 minutes of flight that compromises general flying at reduced power with some full power bursts, but also with touch and goes, I still end up with half a full tank! That does not help deceleration neither. I will reduce this by slowly maximizing my fuel levels before take off.

All of the (landing) lights now were in full swing, a very nice added fun factor.

In all we had a great day! And NOTHING to adjust, repair, modify or whatever (OK, its is drying at the moment, got a few drops of rain at the end of the day.....

richbran

Today's the base's activities provided a slot time of about 1,5 hours, so together with my son we had a dash to the field and made ONE flight of 45 minutes! (with two refuellings with running engine) Some 15 touch and goes.
My son did the knife edge as well and he said that with modest rudder values, it behaved as expected. Only with the rudders at the stops, it rolls into the bank.
Once again, nothing to worry about, and possibly normal for twin boom planes,
He too confirmed a long flare time, but as stated before, most likely cause is the high residual thrust of the 160

Dave Wilshere

Its fine with a JetCat P-180RX, but as I have said before top end power is not everything important about turbines!

I have added a mix to split the rudders at full flap, 20mm out on both rudders adds pure drag, I've done this on some Jets Munt powered std Xcaliburs.
It was never a knife edge machine, but you should try a Rookie or Harpoon in the KE with lots of rudder! It really flips on its back...

Dave

richbran

Internet is great, thanks Dave for the tip on the rudders as brakes. Stupid I did not think of it, as I know that with F18 carrier launches the (angled) rudders kick in with a toe-in displacement to create a pitch UP moment at full aft stick.

I still need to get used to the possibilities a twin boom setup offers!

I use Weatronic as my control system and have an almost unlimited way to program the flight controls, the rudders are already on separate "channels", so feeding in some offset with full flap is a no brainer.
As I have already flown in the ELEV correction needed with the flap settings (minimal btw), the added toe-out settings can be flown in next time.

As I told my son yesterday, I like planes that are basically sound but with some tweaking can be improved even more. I once bought an Angel S50 that flew great right out of the box, I fly it seldom, I have no feelings with that plane.

Yup, high end power is not all bells and whistles. The in flight structural failure of my ELAN XL still haunts me during flying with the Xcal, I still don't fly it flat out level, only during climbing manoeuvres I firewall it.
Not again a cloud of balsa snippets in the air for me!

Dave Wilshere

Its easy on a 'basic' JR XG11 or XG-14 too :-)

Dave Wilshere

Not flown the Plus since the end of last year (the Mini Xcalibur is so easy to grab and go!) but the weather was OK today so decided to blow the cobwebs off it. Built as stock, and now 10 months old, it continues to be 100% reliable, I have not touched it with a tool since before the first flight.
Longest flight today messing with the low power slow passes...14 minutes and still 1 1/2" of fuel in the tank!

We even had a how low can you go comp! This is not the lowest it sat on this pass, there was no shadow at one point, its so lightly loaded,its easy :-)

DenisFerrari

wow..wow..and wow.

aquaskiman

My Feedback: (46)

Does any one know what covering matches the white and red on the thunderbirds trim. I had a dead stick and scraped one of my wing tips. Thanks George

richbran

Btw flew mine at a great place, Tortosa in Spain where I was towing gliders as well (but not with the Xcal...). Good field of about 180 m asphalt, recently re-covered. Both sides long overruns. Just trees around, no housing.

I still don't have the correct attitude and thus speed on final in my fingers, ending up a little too hot and flaring too long. About every flight I do fly some some low speed flying at a safe height and I am astonished how slow it can get with a good nose UP attitude. But I don't dare to fly that attitude yet on final.
One good remedy it to shorten the final part, where it is difficult to estimate the actual speed. So turning in early and seeing the base leg speed is a better clue. Drag builds up quickly however when getting slow, increasing the rate-of-sink. I tend to increase power there though, instead of raising the nose to get the speed down.

lionherz

Hello Dave, how did you mount the turbine to the tray there is no place to drill 90° to the tray nor to drive the mounts 90°
But in the picture it looks like the mounts are 90° to the tray .
Did you mount it on the wood then glued the wood to the tray ?
Would be nice to hear your KNOW HOW.
I am just mounting the xcalibur plus
Thanks
Elmar Germany

Dave Wilshere

Elmar

You mean the spacers between the rails and turbine strap? On post #135 you can see, yes I screwed the strap to the blocks, then glued the blocks down. I used M4 socket head screws so I can remove with a ball driver if ever needed

Dave

lionherz

Hello Dave thanks !
But did you use captive nuts on the other side of the blocks or screwed the m4 direct into the wood blocks without the contering nut on the other side (will this be strong enough)
In thread #135 you wrote: '' when its dry, I'll drill through with longer screws into the bearers''
But thats the problem !? Because of not able to drill 90° ?!
Will it be ok to drill and Screw only within the blocks (perhaps with flat nut on the other side) . AND THEN GLUE ALL TOGETHER TO THE BEARER (''bearer is the fixed wood within the fuselage to mount the turbine to i hope???!!)

Sorry for the boaring question on this topic - but there is only one chance to do it the right way ....
Thanks
Elmar

Dave Wilshere

No problem asking as many questions as you like.

I do not use T nuts (spike nuts) at all, just tap the wood with a sharp tap. Turbines don't vibrate like internal combustion engines, the thrust is all in shear, so really even 2.9mm self tapping screws into wood is enough. The wooden blocks can just be epoxied onto the rails and again this is enough. I used Hysol 9462.

But I did make the front screws go through into the main rails. The two front holes line up pretty well with the canopy slots, so I Dremel a 7mm hole in the slot area to allow a straight drill onto the hole and through to the rails. I did this as a shear fix on the block, its not 100% needed.

Dave

aquaskiman

My Feedback: (46)

Dave do you know what covering will match

Dave Wilshere

Its their own covering, but I know people have found a match in the Oracover range. I guess we will see if the various distributors can see if they can get film packs from the factory, they are always going to be needed

Dave

aquaskiman

My Feedback: (46)

Thanks Dave The ultracote (oracover) red is an almost perfect match the white is a little off but not bad

Dave Wilshere

I think there are three Whites in the Oracover range!
I asked Oracover for a catalogue at the Nuremberg Toy fair this year and he wanted $25 for it...
I only wanted it for references like this on matching covering for people.

RENO

My Feedback: (17)

David,
will silicon spray on the wing tube damage such. Having a tough time getting wings on in the proper manner. Sanded the tube with 1800 paper.Right wing is within 18mm of being seated.Thinking of using CA on the fuselage wing tube junction.
Skeet

Dave Wilshere

1800 will just polish it! I used 240! The tube is usually a nice fit through the fuse and wing, its the clamp that is tight, so I heavily rotated the last 2" wrapped in the wet n dry paper.
You can use silicon spray, but obviously the wing needs to grip. Sanding is the best option.

Dave

RENO

My Feedback: (17)

Dave,
Thank you!!
Skeet