Contact   Imprint   Advertising   Guidelines

Kite Tech Tips: Brummel Splice

forum for kitesurfers


OzBungy
Very Frequent Poster
Posts: 2070
Joined: Fri Oct 21, 2005 11:35 am

Re: Kite Tech Tips: Brummel Splice

Postby OzBungy » Wed May 02, 2018 9:59 am

In the paragliding world the manufacturers recommend 5kg for thin bridle lines, and 10kg for thick main lines.

In reality, when you stretch the line it gives quite easily at first then stops stretching. You can get an idea of what that tension is. I used to use a fishing spring balance. Later I used dumb bells. Bottles of water are good because you can calibrate them if you want two weights to compare two lines.

It's not a matter of stretching the lines so they stay stretched. You want to load them under tension so you can measure them accurately.

For bridle making I use a long wooden plank with a nail in one end and a steel ruler to measure. I could mark lengths and bang in extra nails to mark the length.

For flying lines I attach one end the front gate and compare the ends. That's why I am so keen on having adjustable splices. There is no other way to make matching 25m lines.

OzBungy
Very Frequent Poster
Posts: 2070
Joined: Fri Oct 21, 2005 11:35 am

Re: Kite Tech Tips: Brummel Splice

Postby OzBungy » Wed May 02, 2018 10:10 am

foilholio wrote:
Wed May 02, 2018 5:41 am
...

It is possible to make accurate spliced lengths without adjustments. You need to prestretch the line, then use accurate pen makes, using the edge of the pen mark. ...
It might be possible to mark lines to make two the same length (ie. follow the same procedure exactly). I don't think it is possible to mark the lines and expect them to finish at a specific length. The simple act of splicing consumes 10-20mm of length and that is variable. Every element of the splice (the loops, bury, taper, thickness of the line, the smoothing of the bury) consumes length. I have not once been able to pre-mark a splice and have it end up at a specific length. I have been able to get to within 10mm, but that's pretty poor.

The concept of pre-stretching is mistaken. If you stretch Dyneema line it will retract within 15 minutes. I have proved this by measuring paraglider bridle lines using a laser measuring system.

What you need to do is to measure under tension so that any slack in the braid is taken up and you are measuring under the conditions the line will be used in.

The simplest technique yields the most precise result. Straight eye splice. Measure and/or compare under tension. Hand sew or pin and machine sew to lock. Simple. Certainly use a brummel splice for the non-adjusted ends if you want. And it makes sense to do it so it doesn't introduce twists.

foilholio
Very Frequent Poster
Posts: 2391
Joined: Sun Aug 23, 2015 3:20 am
Kiting since: 1337
Local Beach: Ventura Beach
Favorite Beaches: Tarifa
Style: Airstyle
Gear: Foils
Brand Affiliation: None

Re: Kite Tech Tips: Brummel Splice

Postby foilholio » Wed May 02, 2018 12:25 pm

You are confusing measuring under constant tension and removing shrink. You can restretch ( remove shrink) a line and it will hold its new length for a lot longer than 15mins. No need to use a laser, I have seen 20cm come out of bridles, this is not nano-meter stuff.
OzBungy wrote:
Wed May 02, 2018 10:10 am
I don't think it is possible to mark the lines and expect them to finish at a specific length.
It is possible and I have done it many times.
OzBungy wrote:
Wed May 02, 2018 10:10 am
The simple act of splicing consumes 10-20mm of length and that is variable.
The process is as variable as much as you control the variables. It is very controllable as line is very consistent in manufacture.
OzBungy wrote:
Wed May 02, 2018 10:10 am
The concept of pre-stretching is mistaken.
I have found it necessary to achieve consistent results. I don't think it is mistaken at all, when dealing with line in a varied state of shrink prestretching is a must if you want to avoid fucking around with it later or having things go out of symmetry.
OzBungy wrote:
Wed May 02, 2018 10:10 am
If you stretch Dyneema line it will retract within 15 minutes. I have proved this by measuring paraglider bridle lines using a laser measuring system.
The results are so large and glaringly the opposite you could use your hand to measure them.
OzBungy wrote:
Wed May 02, 2018 10:10 am
The simplest technique yields the most precise result.
It's not a matter of simplicity but what process achieves what result.

foilholio
Very Frequent Poster
Posts: 2391
Joined: Sun Aug 23, 2015 3:20 am
Kiting since: 1337
Local Beach: Ventura Beach
Favorite Beaches: Tarifa
Style: Airstyle
Gear: Foils
Brand Affiliation: None

Re: Kite Tech Tips: Brummel Splice

Postby foilholio » Wed May 02, 2018 1:25 pm

jannik wrote:
Wed May 02, 2018 7:51 am
foilholio wrote:
Wed May 02, 2018 5:41 am
...Can't emphasize stretching lines before you do stuff with them enough....
With how much weight and for how long do you stretch? I'm about to make new lines.
As much as possible without damaging it. That said I have had good results with as low as 20kg on thin bridles. Flying lines 100-200kg +. Shock loading the line seems sufficient, a second or more is enough. You are trying to consistently get the weave tight. You will see the line change to become tighter and more stiff. Trick is to get measurements done while it is like that and avoid handling it too much, each time you kink it you'll shorten it a bit ( not permanently, but if you stretch the line again your measurement will be out).

Don't forget if you are making matching lines, say two front lines you need to have matching prestretch and measuring forces. Measuring under tension is very important too. All not hard to do. I wrote a thread about it, I can go looking for it if you want.

User avatar
PugetSoundKiter
Medium Poster
Posts: 100
Joined: Sat Feb 20, 2016 5:53 pm
Kiting since: 2009
Style: Wake TT, Strapless Surfboard, Landboard
Gear: Cabrinha, Ocean Rodeo, Slingshot, Naish, North, Pansh, Ozone, HQ, Peter Lynn
Brand Affiliation: None

Re: Kite Tech Tips: Brummel Splice

Postby PugetSoundKiter » Fri May 04, 2018 5:59 am

- tape fid on rope
- 3 times thru
- bury
- stitch
- cut
- repeat
:hah:
AmsteelFid.jpg
AmsteelFid.jpg (4.45 KiB) Viewed 3384 times

OzBungy
Very Frequent Poster
Posts: 2070
Joined: Fri Oct 21, 2005 11:35 am

Re: Kite Tech Tips: Brummel Splice

Postby OzBungy » Sat May 05, 2018 12:54 am

Sorry, running the line back and forth through does absolutely nothing useful. If you hold the rope around the buried section and pull the loop the bury pulls straight out.

Back and forth does make a little bit of a splice, similar to doing a bury, but it doesn't lock anything ... and it looks ugly.

You can try taping the end if you don't a have a splicing tool. It works on thicker lines. A splicing tool (bent bit of wire) or a guitar string is much easier to use.

OzBungy
Very Frequent Poster
Posts: 2070
Joined: Fri Oct 21, 2005 11:35 am

Re: Kite Tech Tips: Brummel Splice

Postby OzBungy » Sat May 05, 2018 3:54 am

I just did a Brummel splice experiment where I measured a 50cm length of 2mm Dyneema under 5kg tension. The measuring device was a length of timber (a fence post) with a nail to attach the loop to, and the 50cm length marked with a steel rule.

The actual Brummel splice bit can be measured accurately and does not consume any length. So far so good.

The trouble comes when you do the bury. It increases the thickness of the line over the buried portion and that consumes 2cm of length, so my 50cm bridle line becomes 48cm. The bury was about 16cm long so the consumption is about 12%.

Increasing the tension to 10kg made no difference to the final length.

It is possible to do a few test splices and work out the length consumption of the bury, but I was only able to get to about 1cm of repeatable accuracy.

Compare that with a straight splice where you can easily adjust it and get to better than 5mm accuracy every time.

There's other problems with Brummels. Pushing the splicing tool across the line takes a little bit of effort to make sure you go through the middle. If it's off centre, or you've shredded the fibres then you've introduced damage.

During the second step where you pull the loop through, you're pulling 4 thickness of line through the hole in one thickness. A straight splice at most requires two thicknesses being pulled down the length of the line.

My feeling is that the rigid lock of a Brummel takes away the natural flex and stretch of the line. That rigid lock and the holes in the line just seem wrong to me. A straight splice has only the bury and a few stitches to stop it slipping when not under tension. It seem much less invasive and damaging to the line. As I've mentioned before, it's the only one you can do in situ when repairing kite bridles.

Absolutely use Brummel splices in thick rope where you have strength to spare. Yes do Brummel splices in the dead end of lines where accuracy is not important. Always do straight splices with some hand or machine lock stitches where accuracy matters.

PS And always try stuff out for yourself and make sure you understand what's happening. Just because it's posted on the internet doesn't mean it's true.

foilholio
Very Frequent Poster
Posts: 2391
Joined: Sun Aug 23, 2015 3:20 am
Kiting since: 1337
Local Beach: Ventura Beach
Favorite Beaches: Tarifa
Style: Airstyle
Gear: Foils
Brand Affiliation: None

Re: Kite Tech Tips: Brummel Splice

Postby foilholio » Sun May 06, 2018 2:59 am

With regard to prestretching, 2mm Dyneema has a break strain of about 500kg, 5kg or 10kg will do nothing to this except help measure. You would need to prestretch with 400-450kg, in reality I have had good results with 100-200kg. Without prestretching you will find your obsessing for mm precision going to shit after a short while and then needing adjustment.

It is quite easy to measure the consumption from the splice with the first one made by using a pen mark at a known measurement a bit further up the line, then when you make the second splice you just add that much extra. When bridles for things like foils are made they don't continuously go back and forward adjusting things, they have lengths they cut, marks for splices and that''s it.

Oh and you need to apply a lot of force to set splices fully, I would say similar to prestretching.

Stitching will weaken the line, it's best placed only near the loop end so the tail nearer the line end is undamaged. In reality it doesn't matter as it is only a minor reduction in strength and the line will most like fail from damage else where.

User avatar
lovethepirk
Very Frequent Poster
Posts: 550
Joined: Sun May 10, 2015 7:04 am
Kiting since: 2015
Style: Learning to tack on the hydrofoil
Gear: Delta Race Hydrofoil w/ Slingshot Space Pickle Board, 12m Switchblade, 9m Switchblade, 142x42 SS Misfit
Brand Affiliation: None
Location: Naples, FL

Re: Kite Tech Tips: Brummel Splice

Postby lovethepirk » Sun May 06, 2018 3:17 am

OzBungy wrote:
Sat May 05, 2018 3:54 am
Compare that with a straight splice where you can easily adjust it and get to better than 5mm accuracy every time.
I created a small spreadsheet of each diameter line I use that I am looking for accuracy on and how much the line shrinks due to the brummel bury, ie. the 7/64"(2.78mm) dyneema(pigtails), the 1/8"(3.18mm)dyneema(beefier pigtails) and then the flying lines I use. When you handle a straight bury, even after pulling it tight I've seen it work loose 1mm which is greater than the deviation I have with my brummels.

Also, when making center lines and steering lines, you can have poor accuracy and make that up with your pigtail accuracy. For instance, my center line pigtails larks head to the small diameter center flying lines then I just knot them off on the other end to exactly where they need to be. For the pigtails on the steering lines, you have to be crazy accurate with your pen marks and exactly where you work your magic....after enough practice it is very accurate on length. BUT....remember your last course of action to dial in the steering line lengths is adjusting your knots coming out of your bar ends....so in theory if you build your bar correctly, you can fine tune any goofy mishap you may make with the brummel losing accuracy.

I just had to rebuild my switchblade bridle from pulley wear and used the 1/8" (3.18) dyneema and dialed in my brummels carefully and the deviation was almost unnoticeable.

Also, one trick I use that may or may not be helpful is once I have the brummel lock done I don't pull the living shit out of it before the tail bury, I don't loosen it per say, but I try to make the tail bury carry the load, vs having a crazy tight brummel lock before burying the tail. Maybe meaningless, but I am looking for the tail to carry the load, vs a weak tail bury causing the lock to carry the load. I'm also using 60x bury lengths, I'm working on a bar now with a wichard quick release and may need to use a much smaller bury for a certain area that I'm concerned about, but everyone here hasn't seemed to have problems with those small burys on the thicker dyneema lines.

foilholio
Very Frequent Poster
Posts: 2391
Joined: Sun Aug 23, 2015 3:20 am
Kiting since: 1337
Local Beach: Ventura Beach
Favorite Beaches: Tarifa
Style: Airstyle
Gear: Foils
Brand Affiliation: None

Re: Kite Tech Tips: Brummel Splice

Postby foilholio » Sun May 06, 2018 1:39 pm

Ideally the lock shouldn't have any tension on it at all.


Return to “Kitesurfing”

Who is online

Users browsing this forum: picekjeas, Tony and 20 guests

cron