Razor Build thread

[richard]

7th April 2007

Got my hands on a new Razor DLG, supplied in the UK by http://www.acemodel.co.uk . The quality of the moldings on this model are seriously impressive and easily competes with the finish of high-end DLG\'s approching twice the price.

A collection of pictures to give you an idea.....

Check out the reflection on the surface of the wing! The finish is awsome.

8.5g for the fin+rudder.. this is a good weight for a commercial offering, and it\'s plenty strong enough to take some knocks too. Take a look at the way it mounts... it just slots on the the boom with no messing.

More pics tomorrow when I have time

[richard]

8th April 2007

Spent the day flying, so no progress.... however I do have some more pictures and weights : -

Here is the tailplane and mounting assembly. The v-mount is sturdy, and the included spring means you can easily opt for push/pull or spring/pull.
Some detail of the spring mount

10 grams for the tailplane, v-mount and spring

Time to measure all the weights to get an indication of final target

Wing 130.5g
Tailplane+mount 10g
Rudder 8.5g
Boom 16.5g
Pod 29g
TOTAL 194.5

This means that sub 10oz should be easily possible with lightweight SD100/D4.7\'s, let\'s see if it\'s possible if we upgrade to some quality 9gram servo\'s

4x9g = 36g
shulze w/o case = 9g
KAN 400mAh pack 32g
switchjack = 3g

This leaves me with approx 9g to play with for control runs, launch peg, leads and glue.... not to mention noseweight

Time to order the gear, and play around with some configurations to balance.

[richard]

9th April 2007


Following the airframe weigh-in, I was keen to see what kind of configuration will get the model balancing close to the desired position. Weighing out some screws and nails to equal the weight of batteries, servo\'s etc, it is possible to get some sort of indication of what layout and equipment will get things well balanced.

This balancing session confirms that the model would need a fair bit of noseweight with wing mounted aileron servo\'s, however 4x9gram JR/Graupners mounted in the fuselage should see things balancing up nicely. Time to order 2x Graupner C261 and 2x Graupner DS281 for the ailerons (these are essentially the same servo, except the DS281 is digital, meaning it has better holding power to resist flutter)

I\'m glad to be using these servo\'s as I feel they give the best performance, although they are a bit fatter and heavier than some of the other options.

Tomorrow I want to play around with various pushrod solutions for the ailerons to see what is possible

Here are a couple more pictures....

Pod and boom junction
Pod and boom pushed together. I left a millimetre extra simply as its a good tight fit and I did not want to have to twist too hard to part them after the picture was taken. This push fit is flawless and does not require any jig or measurement.

[richard]

11th April 2007

Servo\'s should hopefully be here by the weekend, to be going on with I needed to drill out the wing for 2x4M wing-bolts.

The fuz comes with the nuts already installed (as part of the molding process). Having this job done for you is a huge timesaver and gives a better quality result than I can make myself. Having said this, if the manufacturer\'s tolerences are not good you will end up with a mis-aligned wing.

I put my faith in the manufacturer and used a drill-press to open out the recessed \'dimples\' in the wing, the placement was apsolutely spot-on.

As mentioned on in the last blog entry, some time needs to be taken to work out the best way to drive the ailerons. With the side-mounted hatch, it will no be practical to have a symmetrical left-right layout as all servos will need thier arms exposed to the side mounted hatch, so both the left and right ailerons will have to be driven by servo\'s with there output shafts on the LH side of the fuz.

I cannot see that it will be possible to use a straight pushrod due to the angles involved, so a rigid snake-type installation seems the only option. Reading the info by \'Mseid\' on RCGroups (http://www.rcgroups.com/forums/showthread.php?t=639293) has helped me make up my mind that this is the correct method. At the moment I plan to use either .5mm or 1mm carbon rod, supported by aluminium tube with the same inner diameter, that should keep things under 1.5g for each side. The aluminium tube should get rid of slop, yet allow us to gave a curve in the control run.

http://www.freeflightsupplies.co.uk for the carbon rod.

Drilling the wing... just centre the press in the dimples and go!
This gives a perfect fit for the bolts. The wing sits nicely on the pylon with no need for an epoxy/microballoon \"splooge\".
From the top
carbon rod and alu tube

[richard]

15th April 2007

As promised the servo\'s arrived with the Saturday morning post, just as I was leaving for the Twywell F3K comp. With the amazing weather this weekend the build took a bit of a back seat, but I have made progress with the aileron pushrod/snake and also got a better idea of the layout up-front.

The alu tube/carbon rod combination looks good. What you can see is the left-over pushrods from a written off TabooGT which I have used just to test there is not too much friction using this method. The finished rods will be neater. The good news is that these do seem to fit the requirements.

Moving on to the servo placement. My initial worry was the amount of space available in the pod, however on finding out that the servo\'s will fit in the pod sideways all problems are solved. In this proposed configuration the front two sevo\'s also sit higher than the in-line back two, which will help keep the contol runs clear of one another.

[richard]

28th April 2007

Unfortunately the Razor build had to take a back seat for a couple of weeks due to work and competition outings, I have now had the chance to install the servo\'s and get a better indication of what the final weight is to going to be.

I install the servo\'s simply by using a 15min epoxy +microballoon mix, this is much easier and lighter than using servo trays and they snap out of the bond easy enough if there is ever a need to change them. A picture is worth a thousand words so here is how I place them (notice the angle of the servos to give the runs more room)

Putting the battery (now going to be an e-tec 450mAh 2S Lipo) and the rx (shulze 5.35 w/o case) in place here\'s how the pod tips the scales....

We will need a lipo regulator(4grams) and switchjack (3grams) but this still leaves us on track for our <10oz build !

[richard]

06th May 2007

Yet again work has got in the way of the important things! I need to get this model finished this week, ready for trimming and as a back-up model for the German Open.

Next job is to connect the ailerons to the servo\'s, pictures again to explain this.

(NOTE - BOTH THE HORN AND PUSHROD ARE SCRAPS JUST IN PLACE FOR MEASURING)

Lets try and make some pushrod material with some 1/16 balsa and carbon

Now test everything fits....

[richard]

8th May 2007

Good progress with the Razor, I have finished the installation of the aileron control runs using the method described. I am really pleased with the result I have got from this, as it has given a totally slop free system with exactly the right throws (see pictures). This means that I do not need to cut ugly holes in those beautiful wings!

Full Aileron .........

Full flap (landing)

Next job is the tail surfaces

[richard]

13th May 2007

Getting towards the final stages of the build now.

As previously mentioned I will be using spring return method for both the rudder and elevator as I want the initial build to be as close to what is suggested by the manufacturer. This method is seen in quite a lot of European models (I used it on my Aspirin). The difficulties I find is getting some zero-stretch line to use, I have tried a couple of options from a fishing tackle shop (spiderwire) but it is too stretchy. I have some high quality kite line on order which will hopefully fix the issue.

In the meantime I have made up some of my own lines with the threads from some 1oz kevlar cloth, I soaked a small amount of kitchen paper in CA and rub this once down the length of the 3 theads to bond them together and stop fraying, it will do as a temporary solution but will fray too quickly to use long term

If I am not satisfied with the spring return method, I will change to use .5mm carbon pushrods in etched teflon tube bonded along the length of the boom.

I have had a couple of questions about the details of the linkages so here are a few pictures.

Kevlar threads secured by servo horn screw. This is only temporary for the first few test flights, kevlar will cut plastic so a better long term solution will be used (similar to the rudder horn pics later)

Elevator Pull line

Yet more use of the alu tube, this time to route the rudder pull line......

A lot of questions about this. A piano-wire torsion bar for the rudder spring return. Use alu tube (again) to retain and spread the load of the wire on the fin and rudder surfaces........

[richard]

close up of the pushrod termination for the aileron, use heatshrink tube over the carbon and piano wire join, wick in a couple of drops of CA and shrink the tube.....

The servo end... same type of connection. Using some more of the alu tube in the horn. ...

A blurry pic of the aileron pushrod exit........

The rudder horn with .... guess what - more of the alu tube!!!!!

[richard]

the actual linkage installed on the rudder...

a couple of pics of the cells im using... these are fairly standard and easy to source

[richard]

21th May 2007

I received the kite line and it has transformed the spring pull systems on both surfaces. Instead of the \"spongy\" feel when the spring tensions the pull-line there is now a very solid stop and the resulting movement from the surfaces is very precise and centers as well as with a pushrod.

The batterypack was made from the 4xKAN 400mAh cells. The best configuration of this is 2x 2 cells in-line. This will enable any small rx to slide in alongside the battery and give plenty of room in the front of the fuz.

Finally the launch blade. On the Razor, the positioning of this is a dream as the wingtip is shaped in such a way that there is no worry about catching the webbing of your fingers on the traising edge. I simply followed the line of the spar to the mid-point of the carbon tip-doubler and placed the peg there. This is both the best position in terms on strength and also feels very natural in the hand.

So off to a the field for some initial test flights.........

With all of my DLG\'s I never bother to balance them before the first few flights. Instead I just take a selection of coins and some insulation tape and make fairly crude adjustments by taping coins to the exterior of the fuzelage to get things on track. I find that starting with a forward CG and working backwards can end up settling with a CG that is too conservative so I never add noseweight before I have flown the model.

The first few javelin launches confirmed my suspicions, the CG was quite a way back from neutral as the model was quite difficult to get tracking correctly. Tapeing a £1 coin to the nose seemed to get things a much more on-track. At this point I had only spot tacked the stab-mount and rudder in place, just in case something needed changing. The resulting javelin launched test flight confirmed all was looking ok, so I returned home to make up a lead 10g weight for inside the nose, and to properly secure the tail surfaces.

By the evening the wind had died down nicely, so after a couple more javelin launches to check things were looking ok, it was time to discus launch..

The Razor feels nice and solid, it is a very stiff model and gave me plenty of confidence. The first couple of launches were as gentle as possible, just so I could get a feel for my elevator presets. The time for the first 50% power launch had arrived.

This launch (and all thereafter) gave one big suprise..... the Razor is virtually silent as it leaves your hand, much quieter than any other DLG I have owned. I think that with some practice and careful trimming of the presets this model will give very competitive launch heights.

I played around with the flap settings and the model seemed to respond very well, I did not find that the various flap settings had a huge affect on sink-rate, but the difference in cruise speed between them was very noticable.

The \"long-wheelbase\" of this model (Approx 7\" longer than a GT or Aspirin) seems to make the model steadier in the turn and does not demand the co-ordinated rudder&aileron of the shorter wheelbase models.

This model will be joining my Aspirin and TabooGT for my trip to the German F3K Open event this coming weekend. I should get the chance for plenty of trimming flights on the Thursday and Friday before the competition but I suspect that I will stick with the other two models for this comp, as I am much more familiar with them. However I do plan on flying the Razor in the next couple of UK competitions so a real judgement can be made on its performance so far everything looks very promising!

Because of the rush to get ready for the trip, I have not had a chance to get the final AUW, but will publish it as soon as I get a chance. I expect with the noseweight we might creep up towards 10.25oz total.

The Kite Line

[richard]

RAZOR - Bullet proof!

02th June 2007

I have had a reasonable amount of stick time with the Razor now and have really been geting to grips with it, today saw pretty much zero wind conditions so I though it would be fun to put the model through it\'s paces on the slope!

Once at the top of Ivinghoe Beacon I had quite a few flights while all other models were being launched only to land 30 seconds later 50ft down the face of the slope... no such problems with the Razor! The wind was shifting all the time pointing to each bubble of lift that came through, and it was possible to hook up with this lift and easily spec out the model on just about every flight.

After a short break I went for another throw, switched on and checked the surfaces were moving... I gave it one of my more powerful launches off the steep slope, but as soon as it left my hand I had no control.. the model just did a slow nose over and headed rapidly towards the bottom of the slope at terminal velocity, disappearing from site over the brow of the hill. Radio failure.

I knew before I even started to walk down the slope that the model was a certain write off, there is not a crunchie model I have seen that would not be consigned to the dustbin after this.

I found the model behind a bush with its nose buried into the VERY hard chalk rock.... but the amazing thing was the boom was still upright, the tail feathers attached and the wing still firmly together mounted on the fuz.

After a minute or two\'s effort I managed to prize the fuz from the ground and inspect the damage..... which is

- A cracked pod just in front of the canopy (an easy fix)
- Some very minor creases to the underside of the wing, the spar seems 100% in-tact. All easily fixed by injecting thin CA
- A snapped pushrod.

Who knows what went wrong to cause the radio failure, as all was working when I reached the model. The main thing is that this model is unbelievably strong and will be flying again within a week.

The launch position

a vertical dive to nose in just short of the road

The damage

The lack of damage!!!!

[sj]

Thanks Richard for a great build report and all the help through pm's.

My Razor is together now and had a test glide ready for me to take the plunge and launch properly.

Just to be different I've bolted mine together so that I can take it apart for transport or if I want to change the set up.

sj

[sj]

With a bit of luck her's a picture of the tail.