XP5 build log

[chris gibbs]

I've now received my XP5 and should be able to start building it in a few weeks time after I come back from an impending business trip.

The kit comprises of;

Wing;

R wing panel 1 3/4oz (51g) and L wing panel 1 3/4oz (52g). Made by Phil Barnes this wing really is beautifully made. Using the same kevlar with carbon D-box construction as previous XP's this wing has a new 3 panel planform design giving a far higher aspect ratio with a more eliptical shape. The Drela wing section appears to be thinned towards the tips as the outer panel is very shallow in thickness compared to other DLG wings I've seen. The tips are reinforced with additional carbon. My existing two XP's have proved to be very durable with hardly a mark on their wings after over 100 hours flying on each, this wing should be as durable if not more. The wing has dihedral already sanded in the roots as well as servo wells and wiring channels pre-cut.


Fuselage;

The fuselage at 1 1/2oz (44g) is a new sleek design, far lighter and smaller than the previous XP fus. It still has a very generous cockpit area for servos, Rx, battery etc but the wing saddle and pod have been vastly improved on. The tailboom although lighter (?) feels as stiff, if not stiffer. The fus comes fitted with carbon tail pushrods. This new fus is carbon fibre construction but also uses kevlar in the layup in some areas.


Tailset;

With a total of 1/2oz (14g) for the tailset. The horizontal stab is the same as the XP4.5, but the fin/rudder is a new high-aspect ratio design with a swept back rudder.


Bag of bits;

At 3/8oz (12g) this contains the carbon tail mount, which I know from experience offers a very strong and reliable method of mounting the horizontal stab. carbon rods and wood horns, as well as glass bandage for wing joining.


This all adds up to a total weight of approx 5 7/8oz (173g)

To this I'll be adding a Shulze 535 Rx, a 450mAH Lipo battery, a Goddo LipoPal regulator, 4 x SD100 (D4.7) servos and a switchjack wiring harness, plus in-wing aerial. this should all add up to approx an additional 2 1/4 oz or so... that's a total of approx 8oz excluding glues etc. I'm aiming for around 8 1/2 oz AUW for the first flight.

More to follow.

[Mikehlg]

It's a good looking model Chris, I hope you'll gimme a go with it

M

[richard]

Looks very nice

The xp4.5 and xp5 are no longer made by Phil Barnes. Shane Spickler is doing them now. I think 52 grams is the lightest commercial wing panel I've heard of. I'm even more impressed that they are managing this with the carbon skin.

[Smiffy]

My ill fated XP-5 wing panels weigh 52.6 and 53.6 grammes, the lightest panel on the taboo was 53.3.

Paul

[chris gibbs]

The xp4.5 and xp5 are no longer made by Phil Barnes. Shane Spickler is doing them now

You are incorrect with your statement here Richard 

XP4 = Phil, XP4.5 = Shane, XP5 some Shane, some Phil

Mine are deffo Phil and are a work of genius 

[richard]

Your right... I am incorrect.

Now I'm very jealous.

[chris gibbs]

Building tip No1....

Don't epoxy the wings together nicely, all wedged up on a flat table to give the correct 6" Dihedral and then after 5 hours listen to your wifes' moans to clear the kitchen table...

Although the epoxy has gone hard, it hasn't cured, the result being after leaning the wing against a wall overnight,  a lovely 10" of dihederal 

Out with a hacksaw blade, epoxy and lets start again....

AGGHHHHH!

[chris gibbs]

Ok, after the 'unfortunate' start of the wing joining, things are back on track.

Using a 12" hacksaw blade I carefully cut the wing panels apart again  and rejoined them at the correct 6" dihedral. All is now well  .

Using a drill I then drilled the wing seat bolt holes through the wing and fus and tapped the holes, re-inforcing the tapped threads with thin CA. (I've used 6mm plastic bolts rather than the american threaded ones that came with the kit as I know I can easily get 6mm spares in UK). I then drilled a 10mm countersink hole, for each bolt,  in the top of the wing, so that the head of each of the bolts is flush with the top wing skin when tightened up.

Word of warning regarding drilling the rear wing bolt. The wooden block to hold this bolt hole sits right on top of the carbon boom inside the pod. You need to be really careful when you drill (and tap) this hole so that the depth is correct and you don't end up drilling through the carbon boom as well as the wooden block. Although I'm not using the supplied carbon pushrods/tubes for rudder/elev (I'm using teflon tube and thin steel wire rods) it will also be very easy to damage the ones already glued into the pod that are supplied with the model by inadvertantly drilling the rear wing bolt hole a few mm's or so too deep.

The XP5 has a very differently shaped fin to the previous XP models and I think I prefer this one. In addition to the differing shape and larger size, the rudder hinge line is raked back by approx 20 degrees. I shaped the LE on the vertical stab fin and half slotted the boom and half slotted the fin and joined the two with thick CA, making sure the fin was vertical to the wing span, by turning the model inverted on a table top so that the model was supported by the wingtips and then using a set square to get a 90 degree alignment. I then re-inforced the fin/boom join with a patch of .7oz glass either side of the fin and a few turns of kevlar thread CA'd to the boom in front of the fin. (I had thoroughly sanded the boom with 400 grade wet and dry to remove all excess epoxy prior to this).

Onto the horizontal stab, again putting the model inverted on a table, resting on it's wingtips I used a ruler to ensure the horizontal stab was parallel to the main wing span, before CA'ing the carbon tail mount to the boom.

I then fitted the first of the radio gear. Using a LipoPal regulator from Goddo, I attached this with tape to the front of a E-tec 450mAH LiPo pack. This was then fitted into the pod, so that the LiPoPal was mounted right in the nose of the pod with the battery pack behind it. Thin CA was then fed in to hold the battery pack firmly in place. Using a 2.5mm switchcraft switch jack I wired this all together. With the jack acting both as an on/off switch (using a 2.5mm plug) and as a charging jack. The Shulze 535 Rx fits neatly on top of the battery pack, sliding into the nose section, but with the glitch counter LED still visable.

I then epoxied in the rudder/elevator servos (D4.7's or SD100's) using 5min epoxy and microballoons.

Next I need to fit the wing servos, make up the wing wiring harness and fit the control rods plus balance/trim and we should be ready for a first test flight.

You can see from the piccies below the XP5 sort of looks 'right, so I've high hopes it should fly reallty well.

The current AUW is 7 3/4oz so I've high hopes it should end up being under 8.5oz.

[chris gibbs]

She's finished at last 

AUW is a bit more than I was hoping for at 8 7/8 oz (see note later) but I'm delighted with the end result.

Managed to give the model a quick test fly for the first time on Saturday and the difference between this and my XP4's is dramatic. I don't know whether it's the lower AUW, the thinner wing section, the new wing planform or tail or a combination of all, but this model really handles very smoothly like it's on rails and seems to float on a lot, lot ,more than my XP4's. It reminds me in a way of the few times I've had a go with a Taboo.

The model flew straight and true from the first hand lauch with three/four clicks of up trim needed for a sensible cruise speed.

I hope to be able to give the model some proper hand launches tonight/tomorrow, weather permitting and get the C of G setup properly, I'll report back what the performance is like Vs my XP4's

Note on AUW - an extra 1/2 oz ain't going to make too much difference, but having to cut and then rejoin the wings after my first bodged wing join attempt probably didn't help things too much. Another point worth noting is that I placed the LE of the wing approx 1/8" on front of the wing pylon front edge (similar to my XP4's) whereas some XP5 builders seem to be placing the wing LE just behind the wing pylon front edge in an attempt to give a slightly longer moment arm to the nose, to help shift the C of G forward. I didn't fancy the idea of this both from a cosmetic viewpoint and also a wing incidence point of view. I think I may have the C of G a tad too far forward at the moment, I'll check that with some dive tests on the next test  flight session.

[chris gibbs]

Few more detail piccies of the XP5.

Weather is not condusive to doing some flight testing today.. mayby later in the week.

[chris gibbs]

Finally got to do half an hours flying over lunchtime, very pleased with results. 

I've trimmed the model with the C of G as far back as I dare, so that it 'just' (and I mean just) pulls out of a 30 deg - 45 deg dive from around 140 feet. This (to me) gives very smooth handling, with good lift indication. If you are building an XP5 I'd suggest starting closer to 4" from wing TE and move the C of G backwards slowly to around 3 7/8" or so. My balance point for my model is approx 3 3/4" inches in front of the wing trailing edge.

The wing and tail incidence is spot on at this balance point and with the wing LE positioned approx 1/8" in front of the wing mount, with a central tail trim to achieve level flight.

To get this balance point, my XP5 was initially a bit nose heavy, so I moved the RAM2 altimeter I've fitted to a new position (see text below) and also moved the Shulze 535 Rx rearwards by approx 1". This is using SD100 servos (D4.7), a schulze 535 Rx, an e-tec 450mAH battery pack and LipoPal regulator, a RAM2 and a 3.5mm switched socket in the pod. the model now balances perfectly without any nose or tail weight. The photo below gives the final internal pod layout. I've glued a small square of foam to the underside of the canopy which securely holds the Rx in place when the hatch is fitted.

I ended up fitting the RAM2 altimeter inside the rear of the pod (it's a very tight fit but it just fits in there), with the download 3.5mm minijack mounted through the top of the pod (if you look at the photo below, you can see the minijack socket just behind the hatch). This means I can easily plug a laptop or Palm PDA into the XP5 to download data, without  having to untape and remove the hatch.

The weather at lunchtime was flat calm at aprox 16 deg C and quite humid. Quite a good trimming day, but not so good for launching /    Launch wise I could only manage approx 120ft in the no wind conditions, which is probably what I'd normally do with my XP4. I'll report back on what launches are like in a 10 mph wind comprared to my XP4's (which I can normally throw to approx 145ft).

The model flies very smoothly, has a good speed range and indicates lift well. I got away in lift right from my very first gentle throw. In flight it seems to be giving a higher flight performance than my XP5's. In saying that the XP4's also fly well too and the limitation is definately me the pilot, rather than the models 

You can see from the RAM2 trace below that I it climbs quite well (162ft/min on the 2nd flight) and the rapid trip back down to ground gave it the high speed 'flutter of death' test which it passed.

If you do build a XP5 remember the tail/rudder hinge line is meant to be swept back by approx 20deg. Denny draws a line on the tail to line it up with the boom, but otherwise just eyeball this when slotting the fin/boom.

One worry I had was using SD100 servos (D4.7's) as I've had some issues with them in the past, but touch wood they seem to be doing well, so far.

A final re-weigh confirmed the final AUW at 250g which is approx 8.8oz

[mitch]

Nice thread Chris, good job on a nice plane

I am impressed with the flying weight you achieved, 250g. It looks like you did not really try to achieve this as you still have the rx case on etc, and as you say you could have got it lighter

I built my latest Taboo to 242g, and I really tried to keep the weight on this model down. My other GT which is built more like your XP weighs 262g
Is the wing on your XP smaller in area than the GT? or is it comparable and every thing else is just made that much lighter?

I'm not a light plane fetishist (honest ) but it is always easier to make a light plane heavy when you need to.

[chris gibbs]

With a two competitions and some flying under my belt with the XP5, I've made a few changes.

The first is I moved the C of G forward by adding a couple of grams more in the nose.  I also had a session with setting the control throws and flight modes etc (something I didn't have time to do before properly) and found a few 'suprises' with my TX settings in terms of aileron diff and expo settings. It is now set up with 1:1 aileron diff amd no expo on any surface except the elevator, which has approx 25% expo set.

Secondly, although I really like the design of the new XP5 pod, the rear of the wing seat area finishes a couple of inches short of the wing TE with a flat end and looks like it could be a source of drag. After seeing Phil Barnes had added a balsa fillet in this area on his XP5, I decided to go one better  and using some carbon sheeting I have made by laminating 2 x 3oz layers of carbon cloth and a layer of 1oz glass cloth. I made a carbon fibre fairing, which is fixed with Cyano to the pod/boom. The end result looks like it might do the job of making the model less draggy in this area and is a very light addition.

I also found out that I had damaged the RAM2 altimeter when fitting it in the pod (my launches were all ending up showing approx 110ft  ). So I've replaced it with a 'how high' altimeter as per my XP4's - I'll report back what launch height I'm really getting when the weather next allows.

Pictures below show the XP5 wing seat area, before and after - with and without the new fairing added.