Jump to content

Pitbull 2


Graeme_M

Recommended Posts

Graeme_M

Also maidened mine yesterday in far from ideal conditions. 40+ mph, 1.5kg onboard, 45deg crossed, launching by myself😬. Discretion being the better part of valour, perhaps I should have waited but I chucked it off anyway. Despite the conditions it went very well, and got on step very quick.

G

  • Like 5
Link to post
Share on other sites
  • Replies 257
  • Created
  • Last Reply

Top Posters In This Topic

  • Les

    47

  • oipigface

    43

  • Graeme_M

    38

  • satinet

    19

Top Posters In This Topic

Popular Posts

Completed a successful maiden today on Whitesheet  First of course the obligatory “just in case” picture  Started empty with CG at 104, wind was light but ok, so I chucked it off. As y

Delivered at last😁  

I've been a bit quiet because my phone has buttons and the internet connection at home has had problems. Whether or not it has been fixed permanently, I don't know.  Anyway, Baudis has had a long

Posted Images

Baldyslapnut

Does anyone know if the Pitbull 2 wing joiner is the same dimension as the Pitbull 1 wing joiner please?

Happy  Landings

 

Greg

 

Link to post
Share on other sites
57 minutes ago, Baldyslapnut said:

Does anyone know if the Pitbull 2 wing joiner is the same dimension as the Pitbull 1 wing joiner please?

Happy  Landings

 

Greg

 

The PB2 has a shorter wing joiner Greg.

Around 15mm so you can't swop wings .

Link to post
Share on other sites
Baldyslapnut

Cheers Les.

A Pitbull 2 joiner would go in  a Pitbull 1 though.

Regards

 

Greg

Link to post
Share on other sites
1 hour ago, Baldyslapnut said:

Cheers Les.

A Pitbull 2 joiner would go in  a Pitbull 1 though.

Regards

 

Greg

Yes but it's just a bit shorter.

You can't swop wings from 1 to 2 though.

Link to post
Share on other sites
  • 3 weeks later...
oipigface

Ballast again! 

I’ve been getting my new PB2 ready for its maiden, and succeeded in getting the CG to the recommended 97mm without use of joiner ballast. In order to get my green PB2 to that point I always relied on 540g of ballast in the front joiner. With the new one, noting that the moment of the front joiner is about 1/10th of the moment of the nose, I reckoned that if I could squeeze 54g of lead in the front, I would have a plane that would fly in light winds. I already have the nose in front of the battery full of lead, but there was a space which looked possible on top of the battery, just in front of the aperture in the inner nose. 

I used dental alginate (see BMFA News about a year ago) to make a plaster-of-Paris mould. Alginate is easy to trim with a sharp knife, so where the liquid had flowed in down the sides of the battery, I flattened the bottom of the casting off before I made the mould. I also trimmed off a little lip on the top so that the finished lead casting would slip easily into the nose. This produced a 56g casting, which was a little big. (Not sure why, but it is partly to do with the shape of the lip around the aperture.) I worked at it, removing about 2mm material from each side, and a small amount from the top.  I was left with 46g which fits neatly on top of the battery, and butts up to the bigger nose weight. (See photo.)

This left adequate room for a couple of 5g wheel balance weights on top of the battery, which is where most of the wires go as well. The weights are under the tape in the photo. Measured CG is now 97.1mm, which will do as a starting point.

Remaining jobs: tape up the servo covers, and fling it off!

1EFBCA42-FD4E-4B1E-9EC6-9A810208D719.thumb.jpeg.9fb4e58f0cfc484c9b84ec0065fbee21.jpeg

P.S. If you’ve got one of my PB2 noseweights, and you are thinking you would like one of these additional ones, then you are going to have to make it yourself. This piece is a complicated shape, and I had to destroy the mould to free the lead casting. If you’ld like a couple of spoonfuls of alginate, I can probably help you. 

 

 

Link to post
Share on other sites
Stefan Bertschi

I struggled with setting the cg on one of my freestylers too. I solved the issue, not with refined craftsmanship like John, but with throwing money on the issue. The solution for me was 'Tungsten Putty' which is a kind of plasticine mixed with tungsten. Normally used for fishing but also very handy for balancing a plane.

Link to post
Share on other sites
oipigface

I did think of mixing tungsten swarf with molten lead to cast a new noseweight, but since I couldn’t find my stock of tungsten swarf, I made the extra little piece to fit over the battery.

Link to post
Share on other sites
satinet

Isn't the density similar to lead? (Edit: Of putty)

I found molten lead poured in to the nose to be the most space efficient method down the years. 

Nose in a tub of water. Only works for sealed noses obviously.

Link to post
Share on other sites
isoaritfirst

B5657618-C970-4664-8C20-683158E0A33C.thumb.jpeg.2a848372558da7a355c808f12f83a8c8.jpeg

i used the nose weight that John gave me. Together with a 2100 life battery. The battery is a very snug fit and needed reworking and it’s Mylar cover removing as well as around 1mm removing from the fuselage reveals. 

There is plenty of room left in the nose for more lead. Originally balanced at 97 without problem. 

 

Link to post
Share on other sites
oipigface
11 minutes ago, satinet said:

Isn't the density similar to lead?

I found molten lead poured in to the nose to be the most space efficient method down the years. 

Nose in a tub of water. Only works for sealed noses obviously.

I’ve never done this for safety reasons. The PB2 has a hole about 5mm diameter in the nose, but this could be effectively sealed with tape. Lead is about 11.3g/cm3, tungsten about 19.3. So a mixture could reduce the volume of a casting of a given weight substantially.

Link to post
Share on other sites
2 hours ago, oipigface said:

 Lead is about 11.3g/cm3, tungsten about 19.3. So a mixture could reduce the volume of a casting of a given weight substantially.

Tungsten putty has a density of 10g/cm3.

David.

Link to post
Share on other sites
  • 1 year later...
oipigface

I don’t know if any of you have looked carefully at the pushrods in your Pitbull 2. They are square!!

So now that I’ve broken one, I need to know where I can source 1.5mm square CF rod. I’ve tried Google. Robotbirds have some but only in 750mm lengths. I need about 1100mm. The other usual suspects only have larger sections.
I can probably get it from Baudis, but that would be pricey. Another alternative would be to sleeve the breaks, but the rods run very close to the inside surface of the fus, and I’m not sure that could be done without causing binding.

Link to post
Share on other sites
oipigface
11 hours ago, Andy_B said:

and you cant use the conventional round ones because John ?

I don’t know what shape the outers are. 

Link to post
Share on other sites
wookman

If you can fit 1.5mm square snakes in the tubes then can you not fit dia 1.5mm in the same tubes? They would be equally well supported and have less friction. Not to mention being much easier to source.

  • Like 1
Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Who's Online   16 Members, 0 Anonymous, 39 Guests (See full list)

    • Mark Evans
    • dave l
    • heli_bee
    • Redbird
    • Peter
    • Graham Lorimer
    • Mick Barnett
    • PeterT
    • John Minchell
    • JFreeman
    • pete beadle
    • Andy_B
    • sorry
    • abbof3f
    • StraightEdge
    • AndyS



×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.