[secant0give]

A pic of the quickly made mould and a couple of untrimmed servo fairings.

   

[gbanger]

Your attention to detail never ceases to amase me Jason... nice work mate!!!
PS: Don't throw those mounds away, HK might sponsor you in thier R&D devision.:

[secant0give]

Here it is with a little more done
The wing is covered in the usual racing colours
   

[gbanger]

That inverted construction must be a little awkward mate!
Lookin' sleek and fast!

[secant0give]

Thanks Gazz.
I put the motor and ESC in it and mounted the prop. I did this before covering as the Iron on film goes over the ESC hatch and holds it down. If I need to access the ESC I will just cut the covering and to replace it I'll Iron on some more. Needless to say it helps to know that the motor is going the right way before sealing things in.

I ran it up on a 1300 4S nanotech and with the 3000 Kv motor driving a 4.5X4.5 prop she fairly howls !!
In fact it's very nice, with no sign of vibration or anything nasy. Just good clean revs and shifting lots of air!!

I'm starting to think this will be a lot quicker than a RareBear.

If it can get to 45000 rpm and it should go close, then the pitch speed is 308 Kph

Allowing for some slippage and losses I'll be very pleased if it does between 250 & 270 in a straight line.


   

[smuzz]

Oh yes - a 3000kV motor on 4S! ... you'd need a fair bit of space to open the taps on this one mate.

[secant0give]

Oh yes - a 3000kV motor on 4S! ... you'd need a fair bit of space to open the taps on this one mate.

Yep I reckon around an isosceles triangle with a base of 40m and a length of about 145. Well that's the plan

I hope it turns well.

[gbanger]

Jason I run my prop driven Skyfun on a Scorpion 2221-8 at 3600kv on 4S spinning a Graupner Cam 4.5 x 4.5 speed prop... and we all know how that tears up the sky, full throttle theoretical on that is 54000rpm ... I haven't flown it since Steve tried to chop his launch fingers off .... note to self: remove digit from rear end and build bungy launcher

[wingtipper]

struth . these things will put a rarebear at the back of the field in no time at all .

[secant0give]

Jason I run my prop driven Skyfun on a Scorpion 2221-8 at 3600kv on 4S spinning a Graupner Cam 4.5 x 4.5 speed prop... and we all know how that tears up the sky, full throttle theoretical on that is 54000rpm ... I haven't flown it since Steve tried to chop his launch fingers off .... note to self: remove digit from rear end and build bungy launcher

Gazz if you just put a tow hook on it I'll bring my launcher down to the field that will get it flying no probs at all !!

I do remember how that thing went!! The day that we had 3 or 4 of them in the air at the same time doing laps of the field. Fewwwwwwww!!! My one isn't slow and you went past me like I was just putting allong.

The other trouble with those rear mounted props is that they make a lot of noise. I think it's because the prop blade is close to the TE of the wing. Having a few of them in the air at one time made a fair bit of a din. Samste's one wasn't too bad because he had a much larger prop and it wasn't reving so hard. that was a big improvement noise wise but more dangerious to hand launch

having the prop on the front does reduce the noise a hell of a lot just listen to how quiet those RareBears are, especially once the motor has been potted, then they are not noisy at all. Mind you they are only doing around 22,000 rpm

Another thing with those fun jets is they loose heaps of speed in a tight turn I noticed this with my one. But they are AWSOME fun to fly !! Mine still needs some repair after the canopy came loose and went into the prop while it was doing 220 odd clicks. I need to pull my finger out and fix that too

[secant0give]

Here it is the Dynamite ready for a test flight. It still needs the fairings for the servos put on and the fairing for the top of the wing but these can be done later. I want to make sure the travels and linkages are set to best effect before I mount the fairings. To change the linkages I’ll have to cut them off so I want to get it all sorted before hand.

Wonder if I can make the field this evening 

Here’s a pic
   

[gbanger]

Looks good mate, well done... I hope the maiden goes without issue and at a speed that causes blurred vision.

[wingtipper]

with that tail i'm guessing 3D is out !

[Flying fisho]

Well done Jason, another pocket rocket to cut holes in the sky. You made need to start another class at Pylon. I think it will kick ass against the Rare Bears

[secant0give]

It would be great to race it against similar planes and there are a few similar models amongst the NSWpylon crowd. There are Bandits, which are about the same size and very quick, there are also the pylon racers from HK like the pistol and the "Electric fiberglass pylon racer"
Links are here:

http://www.hobbyking.com/hobbyking/store...duct=24547

http://www.hobbyking.com/hobbyking/store...duct=28853

I'm sure there are a few of these kicking around, anyway they are not deer to get in the air if you wanted something a bit more pacey than a rarebear but not quite as wild or as expensive as an F5D.

Rumour has it that Adrian was doing a small run of composite racers of a similar size. I saw the plugs he made a while back and they looked really nice!! Hopefully I'll get to see a finished machine in the flesh on the weekend. Perhaps one of those, a bandit and the Dynamite may all get airborne at the same time for a bit of fun

But the main reason I wanted the Dynamites, was to have something a bit quicker to practice with 'cause if I practice with something faster. The Rare Bear and the Viper should seem slow and that will make it easier for me to fly them well ......................that's the theory

It would be certainly fun to get a 3 or 4 models like this going for the next willows cup day!!

[gbanger]

I like your theory Jason ... it does make a lot of sense.
Any reason will do as far as I am concerned just as long as we break the sound barrier

[secant0give]

Well the test flight didn't quite go as planned
I hand launched it, Jag was on the sticks and Claudio manned the camera.

We can safely discount pilot error and radio failure. So I'm not entirely sure what happened

I suspect that that tail is either not big enough or it's positioned too low relative to the wing.
I did change the position of the wing, I raised them up about 10-12 mm from the original plan so I had enough room in the fuse for Bigger lipos, wires, plugs etc.

I'm thinking that it Yawed and pitched up and the tail got in the down wash of the wing and it was all over. Jag did well seeing the end was neigh early on and backed off the power immediately which minimised the damage. It was an unintended and rather unexpected result.

Any other theories as to what happened would be most welcome here's the video slowed down and zoomed in a bit, It all starts off OK but then comes unstuck, you can see it spins more than rolls. It's quite unusual. Nice Camera work Claudio !!

http://www.youtube.com/watch?v=1xiIoK3I1CY&feature=youtu.be

[kizza42]

Talking out my ass here:

I was gonna say p-factor but the spin is opposite to the prop going off the previous pics, Its probably in effect till about 6 seconds into the video. After that it looks like a flat spin (with a large amount of forward thrust)

I've had simulated planes do this and its usually a lack of vertical stab.
The Center of Pressure is too close to the CoG and any yawing moment can't be nullified. You get similar handling from those Easystar shaped FPV planes that have all their fuselage (Vertical surface) ahead of the CoG and not much behind due to the boom -> tail construction, they get away with it because they have thrust blown surface from the rear mounted props.

My theory is that at ~7 seconds the AoA came up and the vertical stab was completely stalled, the adverse yaw from ailerons kicked things off and it was all over from there. I'd be keen to see the same flight but with a ventral stabiliser as well, F16 style.

I reckon the horizontal stabs are ok.

Of course this all goes out the window if the pilot was trying to push nose down from the get go!

--Edit--
It's a rainy day! If you can furnish me with some plans I'll try and model the DynaMite in X-plane and see what it reckons!

[Flying fisho]

Sorry to see that after so much effort & attention to detail, that it met it's demise in such a short time.
Here comes my sixpence worth.
It's possible that the co-rotational vortex created by inequality of the hydrosonic confibulators, caused uncontrolable spiral axioms.
Try equalising the hydrosonic confibulators with 13 deg left agnoromial to counter the co-rotational vortex

[smuzz]

--Edit--
It's a rainy day! If you can furnish me with some plans I'll try and model the DynaMite in X-plane and see what it reckons!

Now that's a great idea - very interesting. It would be fantastic if similar characteristics could be observed in the simulated model!

[wingtipper]

too me it looks like stall torque roll . looking at the pic of the plane the wing looks too far back , is this in the plan design ? i had a different theory , i since deleted and re edited this post after re looking at the pics . thrust line error , did you put side thrust in there ?
ive never seen a high wing plane with the wing that far back . give some good right side thrust and give it another go , it looks a little tail heavy in flight also . . i reckon some attention to these areas and one you get it right this thing will haul .

[gbanger]

I don't know shit... but simply looking at the airframe I'd agree and believe the tailplane and most importantly the Vertical stab are way too small.

[secant0give]

Talking out my ass here:

I was gonna say p-factor but the spin is opposite to the prop going off the previous pics, Its probably in effect till about 6 seconds into the video. After that it looks like a flat spin (with a large amount of forward thrust)

I've had simulated planes do this and its usually a lack of vertical stab.
The Center of Pressure is too close to the CoG and any yawing moment can't be nullified. You get similar handling from those Easystar shaped FPV planes that have all their fuselage (Vertical surface) ahead of the CoG and not much behind due to the boom -> tail construction, they get away with it because they have thrust blown surface from the rear mounted props.

My theory is that at ~7 seconds the AoA came up and the vertical stab was completely stalled, the adverse yaw from ailerons kicked things off and it was all over from there. I'd be keen to see the same flight but with a ventral stabiliser as well, F16 style.

I reckon the horizontal stabs are ok.

Of course this all goes out the window if the pilot was trying to push nose down from the get go!

--Edit--
It's a rainy day! If you can furnish me with some plans I'll try and model the DynaMite in X-plane and see what it reckons!

Interesting Ideas Kizza, I would be very interested to see the results of a simulation. Unfortunately the plans are on paper and at work so I couldn't send them over to you to tinker with. Also there are some slight differences from the original plan, The height of the wing in relation to the tail and the fuse is also taller forward of the wing than the original plan by about 12mm. Aft of the wing it is pretty much as per plan. Having more lateral area in front of the C of G, as it does, would add to the problem you describe.

Jag wasn't holding down elevator on it he said he gave it a touch of up initially and got straight off it he said it rolled to the left and he gave it a bit of right aileron and then it just spun uncontrollably so he backed off. You can hear from the clip the throttle remains constant so it wasn't torque from slamming the throttle wide open either.

I agree it does look like a flat spin with heaps of thrust. Take off was with only half throttle but that was more than enough to get it under way. When I put the meter on it she was drawing around 50A at full peg and using about 800W for it's 600 grams

Thanks for your insights !!

I've uploaded the video again at actual speed so you can see how fast it all happened

http://youtu.be/rA2U3nDAksQ

[kizza42]

Once the rough fuse outline and wing dimensions are in X-plane, its a doddle to move the wings/stab sections around. Too easy... makes me wish building model planes were that simple!

Instead of modelling the Dyna-Mite I spent the day designing a cargo carrying Single Stage to Orbit Spaceplane so the day wasn't a total loss

       

[secant0give]

It’s been established that it was, not tail heavy, it was not pilot error, it was not radio failure. It was not incorrect incidence, the throttle wasn’t opened up suddenly, control rates were set reasonably for this type of model.

Kieran It could be that the fin is too small. I.e. the Centre of lateral area is too far forward. Here’s a couple of Pics showing the changes I made from the original plan.
You can see that I moved the wing back slightly as well as made the fuse bigger at the front. The design was probably already pretty close to the money with having the minimum sized fin. Which makes sense from a drag reduction point of view, after all it is a pylon model.
I’ve enlarged the lateral area in front of the C of G by quite a bit by making the fuse taller and moving the wing back a little so I could get the ESC in up front.

   

The Wing is also a little bigger in span, than the original design, which doesn’t help with Lateral Stability.

   

The other thing I don’t like is that the tail is just a little lower than the wing. I don’t like the idea of the tail being in the down wash of the wing. Even tho’ the insidence angle is zero the wake of the wing can have the air flowing
At a slightly different angle and this may upset things in Pitch ?? The original design had the wing and tail in line. I had moved the wing up, by probably just the wrong amount.

   

The model survived with out too much damage so I guess the next step is surgial removal of the tail group and repositioning it higher, further back and the enlargenment of the fin.

[secant0give]

Some progress, hopefully in the right direction

   

[secant0give]

Here it is almost ready for another test flight
   

[kizza42]

Any way you can really blend the ramp here into the tail and remove as much horizontal surface as possible, it'll be draggy and possibly give a tendency to pitch up

   

[secant0give]

Yes I probably should do that and I did think about that top face causing a pitching moment but that was about the easiest way to get the tail group to its new position. I was going to fix it in the next revision
Perhaps I can shape up a couple of peices of Depron on either side of the fin to fair it in a bit without putting too much weight up the back of the bus

Thanks Kizza

[secant0give]

Something like this ?

It ended up easier to fair it out with Balsa
and it didn't change the C of G much.