Jump to content
Alibabaj

Pitbull 2

Recommended Posts

Alibabaj

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

Share this post


Link to post
Share on other sites
Baldyslapnut

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

Happy  Landings

 

Greg

 

Share this post


Link to post
Share on other sites
Les
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 .

Share this post


Link to post
Share on other sites
Baldyslapnut

Cheers Les.

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

Regards

 

Greg

Share this post


Link to post
Share on other sites
Les
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.

Share this post


Link to post
Share on other sites
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. 

 

 

Share this post


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.

Share this post


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.

Share this post


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.

Share this post


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. 

 

Share this post


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.

Share this post


Link to post
Share on other sites
f3fisa
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.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • 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.