[secant0give]

I’ve been doing some work on getting the new fuse ready.

These NTM 28-30-3000 motors are pretty grunty little units, The specs say they are rated at 755W and I reckon that, seeing how hard these planes fly, this is pretty close to true.
Dynamite is designed to go flat chat from seconds after launching until the 2 minuet timer alarm sounds, by which time the Lipos are pretty much at 3.75V per cell. That means there’s going to be a substantial amount of heat generated.
I wanted to force as much air coming in through the front of the plane as possible to go through the motor in an attempt to take this heat away. Air poring through a fuselage creates drag so I wanted the best cooling value for this drag. In a search for such value I read a few articles where people have cut holes in the pointy ends of spinners to let the air flow through the spinner and hopefully into the motor. It might seem like the go but looking closely at this there are problems. The spinner is rotating and any air entering it will also begin to rotate helped in this rotation by the hub of the propeller and the roots of the blades. With the Dynamites motor running at close to 40,000 rpm that rotating air will, due to centripetal force, want to fly out sideways as soon as it exits the back plate of the spinner. The spinner will act like a pump throwing air out at some high angle to the slipstream and this will, not only, steal power from the motor, but may add heaps of unwanted drag by upsetting the air-flow around the front of the fuse.

I thought the best way to try and get air to cool the motor was to have the front section of the motor surrounded by a reasonably close fitting duct where for a distance of about 20mm aft of the nose, there is only about 1mm clearance between the duct and the rotating bell of the motor. This 1mm annulus presents less projected area than vents in the motor so I would hope that more than half the air coming into the fuse would go right through the motors windings and help to keep it cool. You can see form the photo the duct is just made from a piece or PVC water pipe thinned down a little on the lathe.


One thing I found a bit tricky with the original Balsa fuse was getting the motor mount bulkhead at just the right angle.
I wanted Zero down thrust and zero side thrust. But it’s just as hard to get that, as any particular combination of angles. There is nowhere to measure it from, to get a reference angle, particularly with regards to down thrust. The plan is to use a long piece of rod with holes drilled and tapped in one end at the same spacing as the holes in the back of the moter. The rod should be long enough to stick out the through the nose and allow me to measure at what angle it is, in reference to the nice flat table top. I'll set the fuse up so the table top is parrellel to the cord line of the wing. That way I should be able to set up the thrust angle nicely. Well that’s the plan You can see the aluminium rod in the picture I’ll just bolt that to the "motor mount bulkhead" line up the rod and glue the bulkhead in place then I can unbolt the rod and my bulkhead will be in the the right place and set at the right angle as well.........hopefully

   

[smuzz]

I've been thinking about incidence measurement lately too (having time on my hand ... that's the singular, on purpose).

I've decided I'm going to buy some low-power laser pointers from eBay and make some jigs and mounts for those so that I can attach them to the model and point them at the wall of my shed which will be five metres away. This will give me some distance along the alignments to help improve accuracy - or, as you say, that's the plan

[secant0give]

That sounds like a good idea with the Laser pointers. You'll have to take care making the jigs but once you have them you'll get the use from them

[secant0give]

Here's a couple of close up Pics of the front of the fuse and the air duct around the motor.
It must work reasonably well because the prototype use to land with the motor dead cold after 2 mins is of absolutely flat stick flying, I measured the static current draw at just over 50A, It makes me think I might be able to push the motor just a little bit harder.



   

   

[secant0give]

Here’s the motor mount bulkhead bolted on to the Aluminium rod.
I had to turn the rod down a bit so I could get it in and out of the fuselage without unbolting the motor mount bulkhead every time.
Turning it down also made it a fair bit lighter and easier to handle while trial fitting to line things up.

   

Here it is being trial fitted to the fuse.

   

The wing mount bulk head is temporerally tacked into the fuse with CA, it will be permanently bonded in with a fillet of epoxy bog later. It's important to scuff up the surface of moulded parts before bonding. I think this joint will be under some considerable stress and I don't want a failure of the wing mount because it won't end well !!

   

The dowels have been carved away so they will fit up to the bottom surface of the wing. They, with the ply plate will become one with the underside of the wing courtesy of some more epoxy bog.

   

[secant0give]

Since everything is set up off the wing, or more precisely, from the cord line of the wing.
I reckon it'd be best to put the wing in place, on the fuse, first.

   

So it's some cling wrap down then plug in the wing mount plate. The cling wrap is so thin that it happily goes in between the dowels and dowel holes without making them overly tight.


Then it's mix some resin, and keeping some resin aside, mix up a bog of micro-light and microfiber fillers from West Systems. Paint enough unfilled resin on the wing and on the wing mount plate to make it wet. This greatly helps the adhesion of the bog, especially as I make the bog a slightly dry mix to keep it light. Of course the wing was scuffed up in the area where it was to be bonded, prior to painting on the unfilled resin. Then a generious amount of bog was placed on the wing mount plate and then the wing was placed on top ligned up and weighted down while the whole lot cured.
Here it is the following day after the epoxy had cured.

   

   

And here it is after a bit of a trim and clean up with the Dremmel. It doesn’t have to be beautiful just strong, accurately placed and reasonably light. 


   

You can see in this last pic that, the wing mount plate and dowels are bonded onto both top and bottom of the wing with a fillet of epoxy bog. I can’t see it falling off in a hurry

[secant0give]

A slight diversion from the new Dynamite.

I fitted a new wing to the old Dynamite fusealage, which has been repaired and checked over and looks servicable once again. The main damage to it was that the motor mount bulkhead had broken away. The bulkhead has now been bonded back in and the wing fitted using the old wing mounting plate that was recovered after being torn from the original wing diring the midair.

I was missing flying it, so it'll will be good to have it back in the air again!!

   

[secant0give]

The servos have been mounted
The wires are run along a shallow groove in the underside if the wing that is covered over with a thin strip of 3M book binding tape
   

The servo fairing have been trimmed to the right size but won't be glued on unroll after the test flight to make sure the linkages are right

The servos I'm going to use are
541BBs from electric wingman
Also available from HK as turnigy 541BB

   

[secant0give]

I've been doing a little more on the Dynamites this afternoon.
Putting together the aileron control horns.

These are made from 1mm ply, drilled first then shaped all together by putting them on the drill bit, using the linkage hole to keep them lined up. This way it's easy to shape them together and get them the same size.

Balsa gussets on zapped on either side of the ply hornes give them a decent footprint. The linkages are adjusted on the threaded pushrods until the clevis pin is directly over the aileron hinge, the ailerons are scuffed up with 180 grit paper where the horns will be placed. With the radio on and servos and trims centered the ailerons are held in the neutral position by hand and the horns are zapped to the prepared surface of the aileron. This way they should all centre exactly.

Here's a pic showing how the horns are made & here's a link to those thin servos from HK http://www.hobbyking.com/hobbyking/store...09Sec.html

   

[secant0give]

It's ready to go tipping the scales @ 432g with No batteries and 587g with 4S 1300 45-90 nanotechs.

Hopefully it flies well, I've expended all of my Graupner props for it. But I've got a a couple of 4.75X4.75 APC carbons ready to try out so that's what's mounted on it at the moment.
It's also got the top wing fairing in place, I've never flow in with that before. It should be much more slippery as the new wing has a very smooth finish, noticeably better than the old one, It's lighter than it's ever been and it's fully faired too.
I decided to take the risk and put the aileron linkage/servo fairings on as well.

   

   

[secant0give]

I had 4 flights with it on Sunday and it flew really well. It's hard to say if it's going faster, I didn't get any video of it to do a Doppler shift analysis. It takes a few flights to get one of these trimmed out just right as they don't fly for very long and the trim is slightly different at full peg to what it is at half throttle. I'm not overly keen on taking my thumb off the sticks at full pace to trim it. I'd rather back off, then add a few clicks of trim, then power up again and that takes a bit more time.

I did a bit more work on the new Glass fuse version today. I put it up on our nice flat cast Iron marking out table and double checked the incidence angle between wing and horizontal stab. I'd machined this carefully on the plug and I wanted to check that it was still correct in the moulded part, it turned out to be pretty dam close. The wing saddle is a very slightly different shape to the actual wings aerofoil but it didn't make any noticeable difference to the incidence, nothing that I could reasonably measure anyway.

So with it all looking nice and straight I prepped the surfaces and bonded the horizontal tail to the fuse with a small amount of epoxy and micro-fibre filler. I can probably put the vertical fin on tomorrow

[wingtipper]

WHAT A SLICK LOOKING SPEED DEMON !!!!

[secant0give]

This is the speed controller I used.

http://hobbyking.com/hobbyking/store/uh_...duct=20556

I chose it because it fits nicely, because it has a decent heat sink, it's reasonably light for a 55A ESC (53g) and it cost only $23.50 from HKs AU Warehouse. I did do a quick modification to it. I cut away the heat shrink to allow air flow through the fins of the heat sink from front to back. You can see from the two photos showing the front and back of a modified and an unmodified ESC.

241 & 242
   

   


I have the ESC mounted on a removable shelf. This keeps it up high, so there is space underneath for more lipos or telemetry sensors. The top hatch could also be provided with an NACA type air inlet for greater cooling of the ESC. The air would come in and blow straight through the ESC's heat sink.
The removable shelf is made form 1.5mm ply and sits on the two 1.5mm ply rails bonded to the inner sides of the fuse. These ply rails should also add some back up to prevent the motor mount bulkhead from moving aft in the event of a heavy landing.

244 & 245

   

   

Currently the cooling is provided by air flow through the top hole in the motor mount bulkhead and over the top of the bulkhead itself. Some air should flow out of that hole and pretty much get blown onto the end of the ESC’s heat sink you can see how it sits in relation to the bulkhead from photo below.

243
   

[secant0give]

The elevator servo, A HXT 500 is mounted in a tray inside the fuse just behind the Trailing edge of the wing. 246
   
The servo is connected to the elevator control horn by a ridged push rod. In the past I’d made these from spruce but having run out this one is a ply balsa ply sandwich. It’s very ridged much more so than a length of 2-56 steel push rod wire and about ½ the weight as well. 247
   
The last pic shows the z-bend at the servo control horn end. The wire was tapered down on the bench grinder till the end fits the control horn nice and neat then the z-bend was put in. The other end was ground to a point and bent at 90 degrees to push into the timber before it’s bound with thread and bonded with CA. When grinding these thin rods I always grind them so the axis of the rod is tangential to the grinding wheel. What this does is make sure that all the scratch marks, from grinding, run length wise along the tapered wire. If the scratch marks go around the wire it makes it much weaker and it will often break when being bent. I really like to make my own push rods that way I can get the fit of the rod or clevice pin nice and neat in the controll horn. It's improtant to reduce slackness as much as possible in the control linkages of quick little machines like this. It helps in any model actually 248
   
For safety reasons, it’s a very good idea to remove any tool rest from the bench grinder before doing this!! Whenever grinding something thin like wire, always make sure that you hold it so it can pull out of your hands if it snags on the wheel and won’t drag your hand into the machine.

[secant0give]

Here's a Pic of the new fuse with the motor mounted. Using that Jig I turned to locate the motor mount plate in the fuse payed off as the motor lines up beautifully.

Instead of shortening the screws I just used some extra washers on them, they are 10mm cap screws, the ideal length would have been 7.5 mm. It worked out well that way as they stuck out far enough that I could get a decent grip on them to start them in the threads and wind them in all the way to finger tight. It can be a bit fiddley getting those screws in the back of the motor. They need to be locktited in as well. If they aren't they will come loose guaranteed !!
   

The servo/linkage fairings are trimmed and fitted then bonded on with CA

   

The front hatch and the hatch that covers the elevator servo are held in place with 3M book binding tape, which sticks like the proverbial!!

The radio gear is all in and it's just about ready for a test flight

   

[gbanger]

Jason
I noticed a few posts back that you need a couple of Cam speed props.
I have two 4.5 x 4.5 Cam speed props if you need them.
Let me know
Gazz

[secant0give]

Jason
I noticed a few posts back that you need a couple of Cam speed props.
I have two 4.5 x 4.5 Cam speed props if you need them.
Let me know
Gazz

Thanks for the offer Gazz but I was after the 4.7x4.7
Although the 4.5x4.5 still works pretty good
I have a few APC props in the 4.7 pitch that I can use till I get some more Graupners from Peter pine

[secant0give]

I just fitted the battery, checked the C of G and put it on the scales.
Flying weight of the all glass Dynamite is 619g which is not bad considering it is using the heaviest of the Vac bagged wings.
The Original model with the old wing and balsa fuse weighed 624g and now with the lightest of the new wings it weighs 587g.
There is quite some scope for making the moulded fuse lighter. If I lay it up in Kevlar I'll use two layers of 1.7 Oz Kevlar cloth for the whole fuse and a 3rd layer, from the C of G forward. That should make it a lot lighter that the first moulded fuse, which used the same number of layers but in 4 Oz glass cloth. The cloth component will be less than half the weight for yet greater strength. The first fuse was also a bit of a wet lay up I'm sure I can improve on that. A nice dry layup will help, weight wise as well.

I really couldn't tell much of a difference between the Original balsa fuse and the new wing and how it flew with the old wing.
I'm hoping to notice more of a difference with the New moulded fuse. It should be slipperier as it's narrower and quite a bit more nicely shaped as well, than the original balsa fuse.

[secant0give]

Here's some video of flight testing on Sunday.
It's going a bit quicker with the moulded fuse not much change from 250 now. I noticed it's more slippery expecially trying to bleed off speed landing.

http://www.youtube.com/watch?v=Q2xKuOq6cFk

http://www.youtube.com/watch?v=15m-Ll7ZcZw

[wingtipper]

LOL . YOU DA MAN . HAHAHAHAH . that has definately evolved in speed and flying characteristics . it does seem more slippery , not that ive seen it live but it's evident on the vids in sight and sound .

[secant0give]

hey Thanx 'tipper

I've put some legs on the mould to make it a little easier to lay up a few more fuses. They are just cut from 19mm thick ply wood and bonded on the outside of the mould with a bog of epoxy and microfiber filler.

   


I also made a pattern for making a template to cut the cloth to size before it's layed in the mould. This way I can cut all the layers together and lay them up in one go. It should reduce the time it takes to mould a fuse. Doing the first one was a bit of a lengthy affair.

Here's what the cloth will look like in the flat

   

[secant0give]

The pattern was made of hand towel that I held to the shape of the mould with plasticine and traced around the edge.
I used the pattern to cut out these templates.

   

All the layers of cloth were put down on the table on top of a sheet of bakeing paper and the ends taped down. then the cloth was wet out with resin and blotted with dunny roll then glad wrap put on the top
then the templates put on top of that and cut around using an exacto knife. The bakeing paper was peeled off the back. Then the cloth was ligned up and pressed into the mould. once in place the glad wrap was peeled of the inside. this made things a lot quicker and easier !!

Here's GRP Fuse no2 and the hatch and wing fairing to suite

   

here's the wing for it that I prepared earlier, of course these all need a bit of a trim as they are just out of the mould

   

[secant0give]

Ranjit takes the Dynamite for a fly while I aim the camera
http://youtu.be/8NDp2inZ7Ic

[secant0give]

A bit of work on the new Fuse and a bit of a repair on the first moulded fuse.

The latter got damaged when I gave it less than great hand launch. Not much damage mainly the wing mount bulkhead and a broken prop.

Hopefully I'll have it ready to go for the weekend and set up on the Taranis as well !!

   

[secant0give]

Here it is all set up on the Taranis with switchable spoilerons to slow it down a bit for landing and even a warning sound to announce that they are active and nice slow 2 second fade in after the switch is activated....................How nice it this radio!!!!!

All repairs done and ready to go again

   

[secant0give]

It flew very well at Marulin for a couple of flights then then both the Motor and esc failed, the moment was marked by a thin whisp of smoke eminating from the "rear air hole".
Fortunatly the ESC's internal BEC remained able to power the reciever and servos and I glided it in deadstick without damage.

Both the motor and ESC have been replaced, this time it's using a Castle Cremations lite ice 75A instead of the turnigy trust 55. I'll replace the ESC in the other one, the original dynamite airframe with a YEP ESC probably an 80A. I might go back to the Graupner prop too, becaused it used a little less power than the current APC


A bit more tinkering on the next air frame too
I've done the cad work for cutting them and Karl has put a few sets on the CNC

Here's a couple of pics

   

below is all the plywood parts for 1 Dynamite airframe, including controll horns

[wingtipper]

very impressive .

[secant0give]

Thanks 'tipper !!

Here's some in flight data from the Castle Cremations ESC.
It's from the one flight I had with it yesterday at McCoy Field
For this flight Dynamite is using a slightly cut down APC carbon 4.75X4.5 prop, measured prop dia is 4.470"

   

[secant0give]

Got this little machine out the other day for a bit of a blast around the sky.

I must say, you certainly know your alive when your at the sticks of this one.

Chris your mate down south was interested in putting something like this together

Here's a bit of a thread on it's development and some info on how it was put together. I still have all the moulds for it and a couple of semi finished wings. It will take me a little while to get around to laying up another fuse but if he's in a hurry for some serious speed. He might try one of these (link below) with the same power system as I used in the Dyna-mite. all the motor servo and esc details can be found by looking through the tread. I have two Dyna-mites both use the NTM 28-36-3000KV 755 W motor, one is using a castle cremations 70 A esc and the other I think is currently using a YEP 60 A ESC. I gave up on the Turnigy Trust ESC after it failed leaving a thin white smoky line it its wake one afternoon down at Marulan fortunately the on-board BEC was still alive and provided enough power for the control link after the motor drive part of the board was completely fried. This does not always happen I've had ESC's fail and all the lights go out with the inevitable result.

http://www.hobbyking.com/hobbyking/store..._ARF_.html

This plane from HK has almost exactly the same wing span. The Dynamite has a slightly wider cord so probably has just a little more wing area but seriously I don't think there'd be much in it at all. I'm not sure what section it's using but I do know the Dynamite uses a very thing MH areofoil section which makes it little wafty to fly at low speed but super solid when it's powering along at speed. details of the section are also in the thread.

Be warned tho' these things make a Rare Bear fun fighter look passé and fly close to a hundred klics faster.

The Battery I'm using is 1300 4S 45-90 Nanotech and that flies it just long enough to do the pylon course and land which is about 90 seconds flank speed and a little whizzing around at 1/4 throttle to line up for the strip. It probably flies happily for 3 or 4 mins if you only use 1/4 or 1/3 throttle. 1/4 throttle is adequate for take off and it's quite fast even at 1/3 throttle. Too much throttle applied too quickly creates a very nasty torque roll and left Yaw which you want to avoid by opening the throttle slowly when flying slow. (there is no rudder to counter the yaw so a little caution in this department is required) You can set the spool up on the YEP controller to accro extra soft and that helps a lot

Dual rates on this machine are a must and you must use them it's simply dangerous to fly at high speed with high rates and at low speed there is simply not enough throws for proper control.