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Pitbull 2


Graeme_M

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12 minutes ago, Alibabaj said:

Looks superb Les, can’t wait for mine to arrive.

G

Thanks G

Bloody he'll it's going to be a tight fit up front.

John said he's going to cast us some nose wait and send me mine which is very kind of him.

As soon as I get mine I'll shoehorn the battery and receiver in and get the first flight.

The build quality is excellent and putting aside  my bit of a wait Baudis has done it again with a beautiful looking plane. 

 

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2 hours ago, Les said:

Thanks G

Bloody he'll it's going to be a tight fit up front.

John said he's going to cast us some nose wait and send me mine which is very kind of him.

 

 

Yes it’s very tight.

Looking at John’s last weekend, with a bit of careful positioning and his custom nose weight, should give a tight but tidy install.

Espen shared some pictures of his instal on Facebook, and he managed to squeeze in a Jeti 9 channel receiver!

G

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Greg Dakin

Yes, really nice machine Les - well worth the wait. Looking forward to seeing the PB2 on the F3F course!!!!

Cheers,

Greg

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Fitted the lead cone for the nose  that John very kindly made for me this evening. 

It fits perfectly and giving just the right amount of space to allow battery and receiver to go in.👌

Just the maiden now 

20171213_212748.jpg

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oipigface

Now that you've all read the secret of perfect cast lead nose weight in the latest BMFA News, I thought I might add a couple more observations about my experience with the alginate method since I wrote the article. My first attempt in a real nose was my Pitbull 2. It was a doddle. For one thing, there is already quite a large hole in the nose, which Daniel has identified in this thread as giving access for the ballooning of the fuselage interior. This means not only that the problem of air bubbles that I mention in the article is solved, but also that the finished plug can be freed simply by shoving a piece of wood through the hole and pushing. I think there may have been some release agent inside the nose, because the plug came out really easily.

I thought it would be interesting to see how uniform the casts were, so I've made a couple more. Les reports that his fits perfectly, so presumably the mould hasn't degraded very much by use, and furthermore, it is a testimony to the uniformity of Baudis's building both inside the fus and out. Here's a photo of Les's nose - let me rephrase that - here's a photo of the weight that I sent to Les.

IMG_1294.thumb.JPG.94d4cea8fff47c53befa0bca61c4a05c.JPG

As you can see it is in 2 parts; one is about 130g the other about 30g. This is so that the CG can be varied between about 104mm (which is where the centre of a Pitbull 2 ballast tube is) and 107mm. Fine adjustment between these positions can be achieved with wheel balance weights. If a CG further back is needed, it is a comparatively simple job to take an extra slice off the weight if you have access to a band saw. The main difficulty is securing the workpiece while the cut is being made. I tried several methods of doing this, some of which ended in 160g of lead flying around the workshop. I finally managed a safe way of doing it with a large pair of pincers. Just hold the piece firmly between the jaws of the pincers and the saw will easily cut a neat slice as long as you don't try to rush it. The noseweight in my own Pitbull 2 I sliced with a hacksaw while holding the cast lead in a vice. This worked OK, but took much longer for a less neat result than the bandsaw method.

By the way, when it came out of the mould the rear end of this weight wasn't very neat, so I just filed it back a little. It wound up a little under the target 160g.

 

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oipigface

If you are going to get ballast made for a Pitbull 2 be more careful than I was. I went off to a local precision milling firm with the diagram from Baudis that Graeme reproduced in a post earlier in this thread. Being good at precision milling, they made exactly what I asked for. (Half a millimetre less, please.) The result is shown in the picture. It fits the peculiar double taper perfectly, but the length given on the diagram (238mm) is too great!

I'll have to do all the calculations again. The total here weighs 746g, but cutting the pieces to the right length will reduce that to around 600g. I think I will need another two pieces to make up the 900g or so that I was looking for.

IMG_0862.JPG

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oipigface

I'll do the calculations again. The local guy charged me £25 a piece which would be OK if they were the right shape! As it is I'm going to have to trim them to length. I've got both tungsten and brass to go in the wing boxes.

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oipigface

Haven't got around to thinking about ballast again, but I did take the beast off to Whitesheet yesterday. On the NW slope in 10ms with 500g on board, it seemed ballistic to me! It was really cold, though, so I didn't fly for any more than an hour.

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Good to hear your getting some stick time on your new Pitbull John. Hopefully the weather gods will be kind to us again in a few weeks time for rd 3 of the Southern Winter lg, we'l see then just how ballistic it is :frantics:

  Stu.

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oipigface

As you know, Gromit, flying a course is a different experience from just hooning about!

Anyway, for those who are interested, I've figured out the following (I hope without any errors!)

I've got four pieces of brass (density 8.45g/cm3), which weigh 746g. These are made up to the design provided by Baudis, which has an error. They give the length as 238mm. It should be 191mm, I reckon. ( I asked the guy who did the milling for me to knock .5mm off both dimensions of the section, to give a little wiggle room.)

Apart from the length, these fit rather well. There may be a little more than 0.5mm to spare at the outer ends of the joiner, but the pieces are easy to fit and remove. I have decided to cut 47mm off the fat ends of the pieces I've got, which will leave me with 550g. The maximum permissible auw is 4.682kg. Filling the wing ballast tubes with tungsten leaves me 834g short of this, so if I get two more pieces made up, I'll have just 12g to spare. At £30 a throw, this doesn't seem cheap, but then these will probably fit other joiners as well.

I've calculated the correct dimensions for the ballast. These numbers have the 0.5mm knocked off. Baudis' original dimensions were (H x W in mm): Fat end 13.72x9.82; Thin end 6.74x8.30. Reducing the length to 191mm by cutting off the fat end gives a reduced section 12.34 x 9.52. I haven't checked these figures against the actual pieces, but I shall, and let you all know if they are wrong!

While I could cut the thin ends, this runs the risk that they would be too much of a tight fit. 6 pieces are so close to the max anyway, that it seems pointless to save a few grammes.

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Been trying to get a cleaner installation and with the 18650 cells it was looking a little messy. 

So I've replaced the 2cell 18650 with a 1600mha 2 cell LIFe and some black rape to strengthen the front,not that its weak defore everyone ask.

This gives me 5mm more space for the receiver and magnetic switch.

Well happy😉

20171217_214615.jpg

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Well the few flights out of the way and very please.

Couple more hours to fine tune the snapflap and I think she's done besides removing some weight from the nose to take the CG back a little. 

 

20171223_133116.jpg

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2 hours ago, Skip said:

WooHoo!!! good stuff!

Looking forward to seeing it go mate.

Will be great to see you back on the slope Skip👍

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  • 1 month later...

Just had feedback from Pavel at Baudis, my PB2 should be in the post Tues 30th everything crossed for a Friday delivery😀

G

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  • 2 weeks later...
2 hours ago, drewetm said:

Well G, don't keep us in suspense. Got any pics??

 

Unfortunately not, it was shipped today now expecting it Thursday 

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