Broken luff track?

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GER170
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Re: Broken luff track?

Postby GER170 » Wed Mar 06, 2013 10:58 pm

Jon,
can you make any statement about the age of the track?
Who did it belong to?
Was the track broken on the mast it came off?
GER495

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GER170
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Re: Broken luff track?

Postby GER170 » Wed Mar 06, 2013 10:58 pm

Hi Iver

Sorry but I have no idea on age for the track.

Looking at the photos you have posted most of the tracks I have replaced are the same as the track on the left and the track on the right looks to be a stronger design bigger triangles and less unsupported material please note I am not a engineer.

Cheers Jon
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Re: Broken luff track?

Postby Rick » Wed Mar 06, 2013 11:07 pm

GER170 wrote:I have now three pieces of track
1) Given to me by Jon Simpson 4/3/2013, from a broken mast (sail number unknown)
2) Given to me by Jon Simpson 4/3/2013, source unknown (sail number unknown)
3) Track purchased direct at Ovington Boats 27/10/2010 as spare track

Up front, I can already say that there are two different geometries!

More details to follow.

If anybody else could upload pictures of their intact/broken track that would be great!


Do we know which geometry is current?
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Re: Broken luff track?

Postby GER170 » Wed Mar 06, 2013 11:16 pm

Jon, I totally agree with you that the track with the round track looks stronger.

Some specs of the tracks

1)
shape: round sail track
weight/m = 219g (including some glue, guestimate 10g, hence approx. net weight of 210g/m)
Width = 29.5mm

2)
shape: round sail track
weight/m = 216g (including some glue, guestimate 10g, hence approx. net weight of 210g/m)
Width = 29.5mm

3)
shape: square sail track
weight/m = 172g
Width = 27mm

The weight /m difference between the round and square sail track is therefore (210-172)/210 = 18%

Note, the two tracks are not really compatible. Put end to end, they look the photo below.
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Re: Broken luff track?

Postby Rick » Thu Mar 07, 2013 12:14 pm

paul manning wrote:Unless its an optical illusion, the one on the left (narrower footprint) is the old spec.


Well that is most interesting ... typically we had few (none?) failures with the old track.

That may be due to the change in geometry or material???

If the new one is bigger perhaps it is getting more pinched between the batten pockets and mast than the old one.
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Re: Broken luff track?

Postby GER170 » Fri Aug 16, 2013 6:38 pm

At our company we have many an analysis of the three track pieces.

This analysis has confirmed that sample #3 has a filler content of 20% while samples #1 and #2 have filler contents of 12%.

A higher filler content usually lead to greater brittleness.

As a recap, sample #3 is the square bottomed section and has an 18% lower weight/m.

Hence, the square bottomed section not only appears to be weaker but more brittle.

Sail track as per sample #1 and #2 seem to be the favourable choice.


@Chris Turner: could Selden confirm which section they use now and why they have changed it over the years?
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Re: Broken luff track?

Postby paul manning » Fri Aug 16, 2013 7:42 pm

Iver

You are a complete Geek! Well done :D :D

I expect the change was commercially driven but these details will certainly support our concerns if it transpires they tie up with what we see with the tracks...
Paul Manning
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Re: Broken luff track?

Postby Rick » Fri Aug 16, 2013 10:21 pm

Is there an end photo so we can see a cross section of the 3 tracks samples?
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Re: Broken luff track?

Postby Old Git » Fri Aug 16, 2013 11:22 pm

My experience is that broken tracks have little to do with the mast, but a great deal to do with variability on the main sails. The mast track breakages are caused by the track being compressed and crushed by the batten pocket reinforcement and the distance between the reinforcement and the bolt rope varies from sail to sail. This is also effected by the batten tension, but the amount of tension you can apply varies in proportion to the distance between bolt rope and reinforcement.

Presumably the wider mast track may also have the effect of closing the gap detrimentally.

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Re: Broken luff track?

Postby GER170 » Fri Aug 16, 2013 11:26 pm

An end on Photo is on Page 3
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Re: Broken luff track?

Postby Rick » Sat Aug 17, 2013 8:54 am

GER170 wrote:An end on Photo is on Page 3

There are only 2 in that photo and they are not labeled.
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Re: Broken luff track?

Postby Bruce » Sun Aug 18, 2013 10:49 pm

Nice work Iver.

As the track is plastic and looks a bit like a drainage channel, can't you just get ACO to make us up some new super strong "specialist drainage channels"? :D
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Re: Broken luff track?

Postby GER170 » Sun Aug 18, 2013 11:02 pm

Regarding the shape of tracks #1-3
GER170 wrote:
Some specs of the tracks

1)
shape: round sail track
weight/m = 219g (including some glue, guestimate 10g, hence approx. net weight of 210g/m)
Width = 29.5mm

2)
shape: round sail track
weight/m = 216g (including some glue, guestimate 10g, hence approx. net weight of 210g/m)
Width = 29.5mm

3)
shape: square sail track
weight/m = 172g
Width = 27mm
GER495

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Re: Broken luff track?

Postby DangerBoy » Thu Oct 24, 2013 1:50 pm

Any updates on this?

I have broken a track section again at the weekend and its getting really annoying to keep losing valuable sailing days as I have to repair track.
Mark

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Re: Broken luff track?

Postby Rick » Thu Oct 24, 2013 6:33 pm

DangerBoy wrote:Any updates on this?

I have broken a track section again at the weekend and its getting really annoying to keep losing valuable sailing days as I have to repair track.


http://www.mustoskiff.com/sub-pages/selden-mast-updates.htm

This was also run on Facebook and as an eNews article :wink:
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