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X-Models PrismaRay Build Thread

Started by GP, April 11, 2012, 00:04:45 am

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No chance I'm afraid, I haven't even started the wings yet.

My fancy-schmancy Emcotec German wing connectors arrived today.  Instead of the usual 9-pin D connector or Multiplex green connector, I decided to try what is claimed to be the very best. 

They seem good but I'm not sure they're worth twenty quid per wing.  The advantage is they're easy to solder up and they clip together totally securely - they will never, ever accidentally come apart in the air.  The disadvantage is they're hard to unclip.  I can see myself cursing them at going-home time. 

The wing side is fixed to the wing.  You solder your leads onto those easy-solder bits you can see in the second photo.  Then heat shrink and a cable tie go over the tab bits and make it all it rock-solid.  The fuse side has to be loose so they can come out of the plane so you can wrestle them apart when it comes time to take the wings off.  Overall, they're good and I recommend them.  But I guess it is a bit debatable whether they're worth the money or the trouble of bringing them in from Germany.  They did arrive fast though.   Here's the link (go to this shop, which is actually Emcotec direct, and click on General Accessories, and you'll see the Emcotec Wing Connectors):


By the way I notice in my April 29 post I recommended the Hitec HS-485 servo, but I meant the Hitec HS-985 servo.  The 985 is a top of the range analogue servo with massive torque and accuracy.  The 485 is a much more modest one.  So anyone building a PrismaRay, please don't fit a 485 on my recommendation!  It's a beefy 985 I'm using.


I decided to use a proper Graupner wing retainer system.  Not easily available in the UK.  But Modelmaniacs claimed to have it in stock (£25).  I ordered it, and sure enough, it arrived fast.  Well done Modelmaniacs. 

It's a great wing retainer system.  A metal tube with spring-loaded release rings connects to the "nipple bits" which go in the wing.  To release, just pull the retainer rings (which will be inside the fuse) and the wing bits spring out.  The central tubular bit can be adjusted over a wide range of fuse widths.  For me this is perfect: strong, easy to connect, easy to disconnect.  If you have a high-performance model that needs wings connected strongly, I recommend this Graupner wing retainer system. (However for lower-performance planes maybe the old rubber band system is good enough, and it "gives" in a crash.)



Well, I've been fitting wing servos and connectors to the fuse etc.  It's taking longer than it should.  Just getting the wing/fuse connectors to align takes care.  This plane is completely unfinished in that respect - it's up to the builder to sort everything out.  The fuse around the wing area is reinforced with carbon/kevlar mat and it's a nightmare to cut neatly.  That kevlar would rather ignite than cut!

A tip for anyone else building this plane: sort out all your fuse hole cutting etc before you fit the innards.  I fitted all the gear first and then started cutting the wing connector holes etc, and that means all the innards get subjected to a lot of vibration and dust.

Never mind, it's coming along well and and it's going to be a rock solid, reliable plane.

By the way: I wonder why the wings are kevlar and the body is glass (with carbon and kevlar reinforcement).  Kevlar costs more and is harder to work than glass, so X-Models must have had a reason for making the wings out of kevlar.  Kevlar never breaks, but the epoxy around it does, which means a crashed Kevlar plane is still in one piece but it goes all soft and floppy.  That's actually very hard to fix.  The kevlar wing skins are easy to ding too - I've started putting foam under the wings while I'm working on them, because I noticed I was getting various minor dings in the wings just while building it.

By the way 2: the wing construction is quite impressive: the wings are totally hollow except for two carbon spars.  There are no ribs at all.  This is truly a hollow moulded plane.


I weighed my PrismaRay, and it's 5.9kg.  That's lighter than I expected.  The 5.9kg is with the carbon wing joiner.  With the steel joiner it is 6.5kg, so still a little less than I expected.  This is the first time I've ever built a plane that came out lighter than the manufacturer claims!  I haven't done a lightweight build either, I've used quite beefy kit in there.  Should fly well in a wide range of conditions.


I've done the wings now.  Used the horns supplied with the plane.  Actually I think South Coast Sailplanes add them, rather than X-Models.  They're little brass bolts that go into brass keepers.  I've used them before and I like them.  The advantages are strength, easy fitting, height adjustable.  The disadvantage is you get a little brass bit showing on top of the control surface.  But I don't mind that.

I used the servo covers that came with the plane, although they're much too high really.  The rod is only a few millimetres about the wing surface, but the covers are extra-high.  Maybe X-Models thought people might want to fit huge long servo arms like on 3-D power planes, but I couldn't see any reason to do that.

The various bits that go from the wing to the fuse (joiner, servo plugs, retainer) were a bit of a pain to fit, partly because the end of the wing that sits against the fuse is not at 90 degrees.  It slopes to match the fuse, which means plugs etc have to come out at an angle.  Actually other builders might be better engineers than me and might have no trouble building this plane, but for me it's been the longest build I've done to date.



Virtually ready to maiden ... I can't shake the feeling I've forgotten something crucial, but once I get over that feeling it will be ready to maiden...

paul w

Quote from: GP on June 18, 2012, 16:06:11 pm
once I get over that feeling it will be ready to maiden...

When Gary?
Goodwind Slope Soaring     blogtastic hill side adventures



I wanna be there!

I have just switched the last of my fleet over to 2.4, which just happens to be the Big Fox so I think she needs to make friends with Prisma....

I'm back from the Dark Side - I like gliders!


Is this wing a typical x models non wiper wing?
problem with the brass horns is that you cannot get the hole over hinge line which is normally advisable for good geometry.
Saying that I am not sure if I am a good enough pilot to tell the difference, but it may help to get better throws.
I keep saying I will replace these brass horns for g10 horns on my blade, but now that it is flying i just fly it. But I do tape up the flaps to remove that little bit of slop it has.


Yep, no wipers.  The gap is tiny though, so I've decided to fly it as is.  I'm not sure whether X-Models intend builders to add wipers or not.  If it seems a problem I can always add wipers later.

Regarding the horn over the hinge line issue, personally I don't mind if the horns are not quite over the hinge since it seems to make no difference in reality.  However in this case, it was possible to have the aileron horns over the hinge line so I did.  The hinge line is not directly under the gap, so don't be put off by the fact that the horn isn't near the gap.  Hard to photograph, but here's a shot showing how I filled epoxy around the horn inside the aileron, with two bits of foam to hold the epoxy in place:


Simon, I don't want to fly this with your big fox, it'll make this PrismaRay look all petite and pathetic!!

Actually it was you flying your big fox, and especially your slightly smaller Swift, that made me decide to get this PrismaRay.  You were really putting the Swift through its paces, plenty of g forces, and I thought "Why am I flying tenth-hand planes with tender wing joiners etc that I have to nurse through the air?  Time to invest in a proper plane that I can put some g forces on without having to worry about bits flying off."


Nice philosophy GP. Got a steel joiner?
Get the fox and the prisma doing synchronised flybys and let us see the vid!


Good idea, we'll try to do a synchronised vid.  The fox is a big 18kg beast, so maybe if I fly closer to the camera than the fox, we can get them to look the same size!


I'm sure the performance of your Prismaray will be awesome Gary - and you'll certainly get to fly it more than my Fox! (Although I hope to get over the fear factor at some point!)

I'm back from the Dark Side - I like gliders!


Some random bits of advice for anyone else building a PrismaRay:

Protect your work surface with foam sheet or something, those kevlar wings ding quite easily (you'll probably need to think about protection during transport too, some nice wing bags or something.)

Consider having both tail servos in the tail (it will raise the plane's overall weight by 150 grams or so due to the extra nose weight required, but it is probably worth it to have really solid connections and avoid a pull-pull rudder setup which requires finesse to get right, probably always has a tiny bit more slop, and risks entangling with wing servo leads etc).

You'll need plenty of weight in the nose so you may as well build the nose strong.

Maybe build the wings and connections into the fuse first, then do the fuse innards once that's all sorted.

Remember the PrismaRay is not meant to have flaps going way down, they're meant to be semi-flaps, so do the flap linkages a bit more like aileron linkages, including more up travel than usual for flaps (apparently the Stingray and PrismaRay behave badly if the flaps go down too far.  X-Models have designed the flap hinges so they can't go anywhere near 90 degrees down, so don't try to re-engineer that).

Be patient, it will all take longer than you think.

If I have any control throw advice etc following flight testing I'll post it.


The X Models PrismaRay has flown.  I took advantage of the longest day of the year yesterday to maiden it at Beachy Head.  Flew very nicely.  It's fast, its aerobatic, it seems like it will make quite a good thermaller.  Wings possibly a bit flexier than I expected, but no more so than large scale ASW-20s and Nimbuses etc.

I've got the c of g at the rear edge of the wing joiner (so 8mm behind the recommended "centre of the wing joiner") and that is good for a maiden.  Still a bit nose heavy, but a good safe starting point.  I reckon I'll gradually remove another 100g or so of nose weight to get the c of g a few mm behind the wing joiner.  I've got quite large throws, and it seems to need it.  When crow braking is applied, the plane balloons dramatically, almost beyond the ability of down elevator to control it.  So for anyone else making a PrismaRay, make sure you have plenty of elevator movement.

I did two flights, both landings were a bit heavy.  The first time, I landed a bit too fast, just because I didn't want to tip stall it.  But that was fine, it just slid along the ground a bit.  The second time, I tucked the crow brakes while it was still about 4 feet off the deck, and it dropped rather heavily.  So I think the landings require some accuracy: medium speed, crow only turned off when the plane is inches about the ground.

Thanks to Simon for launching and Eric for photography.



Very nice! Great pics.

Looks beautiful. At first I thought the extended wings might not look in keeping, but it all comes together nicely!


By the way, I forgot to mention the sound.  It's generally a quiet plane (kevlar wings are bound to be quieter than carbon ones I guess) but when you do a fast roll, it makes the most impressive sound I have ever heard a glider make.  Yes, I realise sound is wasted energy, but in this case it's worth it!  It's hard to describe ... but if aliens ever visit earth in their UFOs and do twinkle rolls, this is what they will sound like.


Cliffhanger, I just saw your video on Vimeo of Andy B's Wings and More Stingray flying at Rhosilli, very nice.  I'd love to see one of those Wings and More Stingrays in action ... all carbon, thin HQ aerofoil, the price of a small car ... it doesn't get much more exotic than that.


Quote from: GP on June 22, 2012, 15:57:31 pm
...but when you do a fast roll, it makes the most impressive sound I have ever heard a glider make. ...
Same with my X-models Blade: that's why I haven't retro-fitted aileron/flap wipers, as that would smooth out the airflow  :-\
Cheers, Geoff


Quote from: geoffers on June 22, 2012, 19:10:34 pm
Same with my X-models Blade: that's why I haven't retro-fitted aileron/flap wipers, as that would smooth out the airflow  :-\

One of our guys has a glider that's pretty quiet even at speed, but has airbrakes which squeal like an American car chase when you put them out. He likes to sneakily fly behind everyone then shoot back out in front with a screech, making us all jump.

Doing what you like is Freedom
Liking what you do is Happiness


I flew the PrismaRay again, and from that experience here is some more advice for any other PrismaRay builders:

(1)  It flies more impressively with a bit of weight.  So I have to be honest and admit that I wasted time making a lightweight carbon/alloy wing joiner.  The heavy steel wing joiner is fine.

(2)  You might want to consider building in a bit of ballast capability.  The main thing preventing me adding a ballast box on the c of g is the wires from the pull-pull rudder.  So I recommend building both tail servos in the tail.  Then you have a nice clear fuse and it makes fitting everything that bit easier. 

(3)  The analogue servos I've used seem a good choice and are more than man enough even in a severe blow.  The Hitec HS-985MG I used for the elevator is a particularly impressive servo and I'll certinly be buying that one again in applications where I can justify its cost.

(4)  The plane is good natured, it doesn't seem to have any nasty habits so far.  I have the c of g a few mm behind the wing joiner and it's still safely slightly nose heavy.  The Stingray pilots who have the c of g on the joiner must be flying the Stingray pretty nose heavy.  I'm increasing my crow brake throws slightly, the mild crow brake setup doesn't do much.  I flew at a blowy hill with a small difficult landing area, so I had to plonk the PrismaRay down a bit, and it takes that fine, it's a sturdy plane.


Quote from: GP on July 11, 2012, 14:25:57 pm
... so I had to plonk the PrismaRay down a bit, and it takes that fine, it's a sturdy plane.

Yep - the X-Models planes certainly are well built, and will take a good plonking  ^-^ : much better than the egshell which RcRcm models seem to be constructed from.... :''
Cheers, Geoff


Quote from: GP on June 22, 2012, 17:08:45 pm
Cliffhanger, I just saw your video on Vimeo of Andy B's Wings and More Stingray flying at Rhosilli, very nice.  I'd love to see one of those Wings and More Stingrays in action ... all carbon, thin HQ aerofoil, the price of a small car ... it doesn't get much more exotic than that.
That was previously my plane.  It has a propriatory WaM airfoil, not an HQ.
Chris van Schoor


Has anyone else got an X-Models PrismaRay?

This model has such a low profile on the internet I'm thinking maybe there are very few of them about?

When I bought mine there were some supply problems but a new manufacturer was meant to be starting production soon.  Maybe that didn't happen?


Has anyone mounted a small turbine on one of these by any chance as I think it would make a good platform for one?


You're right, a turbine would be great.


I flew the PrismaRay in 40mph wind yesterday, it flew great.  Paul the master filmmaker took video, so I'll be able to post a video link soon.


Here is a short video of the Prismaray, thanks to Paul for filming it:




Norman Carter

Hi, this is a question for GP.

The Graupner wing joiner you are using is much better than the Graupner/Tangent plastic retainers that are as good a chocolate tea pots. Modelmaniacs don't list it now and the Graupner website has no size info (probably linked to their bankruptcy woes). Logic RC will be importing Graupner stuff, but what size retainer did you get and what is the fus size of the model at the wing root? I know, question after question.....

Are you a fellow ESSA member?

Norman C


Thanks for your message.  It may not be possible to get them any more with Graupner bankrupt, but I guess there might be old stock somewhere.   

They came in two sizes, and my tip is to get the bigger one, because it's just the smaller one with an extra length of tube and extra threaded bit.  In other words the big one is just the small one with two centre bits.  I have them in two planes, the Prismaray which is about 6 inches across the gap between the wings, and a Paritech model which is about 10 inches, and I used the larger size in both.  You just screw the threads in and out, or even saw down the tube if you need it to fit a narrow fuse, to get whatever size you need.

It works well but requires accurate installation (a couple of millimetres too short and it might seem to be clipped but actually it can slip loose - a couple of mm too long and there will be a gap between the wings and the fuse).

Norman Carter

Thanks, Gliders have both sizes in stock, thanks for the info.

Norman C


Ha! I just discovered this thread, I completely forgot I'd written it. Just an update to say the Prismaray is still going strong six years later. I flew it last weekend, it flies nicely, all the components etc I fitted in it have proven to work well, no problems.



Hello Gary,
I've also just found this thread for the first time, only 6 years since you maidened at Beachy Head . . . . . and I'd forgotten that I'd taken the photos for you that day!
I'm not old, I've just been young for a very long time!