Trampoline Replacement

[Peter Verralls]

Replacing Trampoline and Bimini Netting
We replaced our trampoline while in the Rio Dulce, Guatemala in 2012. We decided to got for a Dyneema net to get long life, maximum strength, minimum stretch, and minimum wave resistance.
We were very pleased with the results.
We purchased from
Richard Leng
Sunrise Yacht Products
6544 44th St N Unit 1205
Pinellas Park FL 33781
Mailto: info@multihullnets.com
Website: www.multihullnets.com
Phone: 727 526 9288 Fax: 727 528 0351


Richard had several drawings for Switch 51 trampoline's, so maybe there is more than one configuration. We made measurements and he used his closest drawing. For both the bow trampolines and the bimini trampoline we measured the size of the aperture, then Richard produced a drawing 70mm smaller to allow a 70mm gap to lashing the tramp to the edges. He also calculated the length of Dyneema rope to use as the lashing material.
The attachments below are the drawings we used.

The dispatch time was six weeks from approving the drawing.
For those considering the Rio Dulce as a make and mend location:-
The delivery time to Fronteras, Rio Dulce, that is almost to the boat, was 10 days via Aeropost.
http://amchamguate.com/en/aeropost-de-guatemala-sa
We opened an Aeropost account with Jim at Pama Meats, Fronteras.
Jim +502-4530-3478
We needed to obtain a NIT card from Raul in Livingston, because the value was over $1,000 landed. A NIT is a Tributary Identification Number. The NIT is a personal identification number a shipper must obtain from the Finance Ministry in Guatemala or Superintendencia de Administration Tributaria (SAT).


Trampoline Photo Zia.jpg

Trampoline Drawing Zia.pdf

Bimini Zia.pdf

[sigmasailor]

What is on the outside perimeter of the netting to allow the line to attach the net to the boat? I assume there are some kind of eyes on the boat side. I'm interested in how the netting was reinforced.

[Talbot]

Dyeneema has great strength, and I am sure will give you a nice tight tramp.

One of the problems with this material is it\s known UV degradation. What are they using to reduce this, and what life have they given for the material?

[colemj]

Dyneema has excellent UV properties - no need for any treatment at all.

Mark

[Talbot]

Dyneema has excellent UV properties - no need for any treatment at all.

Mark

I suggest you do more research. If Dyneema was that good there would be no need for the UV coverings being used when the material is used for Standing Rigging. It has not been available long enough for long term results, but i understand that synthetic rigging lifetime has been reduced to 5-8 years following experience in the tropics.

[tamicatana]

Easy enough to paint the nets with net paint, which is a latex coating, also available from Sunrise.

You can get Dyneema netting cheaper, although not made up, from Net Systems www.net-sys.com

[Peter Verralls]

Dyneema and UV Exposure
My experience is that the material changes colour, indicating a change, probably degradation of the outside of the rope, but that then protects the inside and the rate of degradation slows up considerably. Dyneema usually offers so much overkill in terms of strength some initial degradation is tolerable.

From http://www.multihullnets.com/Product/tech/techuv.aspx
Graph showing effects of UV exposure
Note that coated Dyneema stands up well


From http://www.colligomarine.com/docs/misc/DynexDuxFAQ.pdf
Q: “I have heard that Dynex Dux will deteriorate in the sun very quickly due to UV degradation. How often will I have to change my standing rigging due to UV exposure? “
A: “The base fibre for Dynex Dux is Dyneema SK-75. It is widely known as the best synthetic fibre for UV resistance. Having said that, we like to work with real numbers, so we are doing an ongoing UV study on our boat in Western Mexico (where it rains about 3 days a year).
In addition, a study was completed by the University of Aukland several years ago
that showed some initial UV damage occurs externally, causing the outer layers to become relatively opaque to UV, and then the rate of damage decreased.
With the data we have today, we can easily predict a life of 5 years or more for UV
exposure. This compares to an 8 year recommended replacement interval for steel.
We also believe, as new data comes in, that the life expectancy will go up.”

[Peter Verralls]

Talbot
Can you quote your sources regarding the need for coverings and the reduction in working life. I have not seen any mention of this.
Wire is rapidly disappearing from trawlers, tugs, oil support vessels. I do not see any of them going back to wire from Dyneema and its variants. These guys want reliability and value for money.
http://www.colligomarine.com/docs/ne...Jan%202009.pdf
http://www.colligomarine.com/docs/newsletters/Jun%202010.pdf
http://www.colligomarine.com/docs/newsletters/June%202009.pdf

[Peter Verralls]

Sigma Sailor
Hope this photo answers your question
Trampoline Lacing.jpg

[Peter]

Sigma Sailor
Hope this photo answers your question
Trampoline Lacing.jpg

Many people do but lacing trampolines like this is dangerous. One failure in the lacing line and it will unravel allowing someone to fall through. Although more difficult to tension it is much safer to have a locking knot (clove hitch) every 2 or 3 loops.

[colemj]

I suggest you do more research. If Dyneema was that good there would be no need for the UV coverings being used when the material is used for Standing Rigging. It has not been available long enough for long term results, but i understand that synthetic rigging lifetime has been reduced to 5-8 years following experience in the tropics.

I will make that same suggestion for you. Dyneema has much more UV resistance than polyester and nylon (the other common netting materials). Just do a google search for "dyneema uv resistance" and you will find pages of technical information - none of them describing it as uv-fragile.

Anecdotally, we have a length of 3/16" dyneema in use as a chain stopper that has spent the past 5 years in the equatorial tropics continually exposed to sun (it sits on the foredeck) taking full snatch loads when we anchor. No problems at all.

Mark

[sigmasailor]

Sigma Sailor
Hope this photo answers your question
Trampoline Lacing.jpg

Peter, partly; yes. What did you use on the edge of the netting and how did you attach it to the netting? looks like a thicker line with the netting wrapped around it?

[Peter Verralls]

Sigma, the tramp was delivered made up, as in the photo. We did nothing except lace it. There is a thicker rope around the border, which is "parcelled" in some way and we just laced it to the boat.


Peter, yes you are right regarding safety but we put additional independent security lashings that would allow the tramp to go slack but not allow a person to fall through. These lashings perform two functions, they keep the netting secured to the boat and they prevent the original continuous lashing from running. A failure of the continuous lashing would not be fatal.
The tramps appear quite difficult to secure, at first sight. We did several experiments. Now, having done the two front tramps and the bimini tramp we are quite good at it! First we would make individual lashings at the four corners and halfway down the sides. This allowed us to stretch the netting out and roughly centralise it. Then we put the continuous lashing on and then progressively tensioned it up, keeping the squares of the netting square and the runs straight and the tramp centred. Once tensioned we would remove the original single lashings and then put on the security lashings. The tramp will feel very solid at this stage, but a few weeks in the hot sun and some activity on it will cause it to slacken. Dyneema is either bar tight or slack, there is no stretch. But heat and activity will cause it to reform slightly. Even so, when slack it is tighter than the original tramp, but we chose to retention it a second time.

[colemj]

and the bimini tramp

What is a "bimini tramp"??

Mark

[georgetheleo]

Sigma, the tramp was delivered made up, as in the photo. We did nothing except lace it. There is a thicker rope around the border, which is "parcelled" in some way and we just laced it to the boat.


Peter, yes you are right regarding safety but we put additional independent security lashings that would allow the tramp to go slack but not allow a person to fall through. These lashings perform two functions, they keep the netting secured to the boat and they prevent the original continuous lashing from running. A failure of the continuous lashing would not be fatal.
The tramps appear quite difficult to secure, at first sight. We did several experiments. Now, having done the two front tramps and the bimini tramp we are quite good at it! First we would make individual lashings at the four corners and halfway down the sides. This allowed us to stretch the netting out and roughly centralise it. Then we put the continuous lashing on and then progressively tensioned it up, keeping the squares of the netting square and the runs straight and the tramp centred. Once tensioned we would remove the original single lashings and then put on the security lashings. The tramp will feel very solid at this stage, but a few weeks in the hot sun and some activity on it will cause it to slacken. Dyneema is either bar tight or slack, there is no stretch. But heat and activity will cause it to reform slightly. Even so, when slack it is tighter than the original tramp, but we chose to retention it a second time.

An easier wat that Iused was to buy a package of cable ties 18 inches long from Uline for $22, then position net and put a cable tie at every fastening point. Then draw net evenly till it gets tight all around. Then tie in permanent ties.Then remove cable ties. Your done.

[Peter Verralls]

George, nice idea, but my temporary lashings are reusable, earth friendly! But your idea is fast and you would probably use more ties and so get a better placement.

Mark, a bimini tramp sounds odd. The bimini on my Switch 51 consists of an aluminium frame with the top covered in Sumbrella. We need to walk on the bimini to zip up the stack pack, tidy the sail, access the topping lift, etc. The Sumbrella is not strong enough to walk on. So the aluminium frame is strung with a trampoline, over which the Sumbrella is fitted. That way the Sumbrella does not take body weight.
I'll see if I have a photo to attach.
The photo's show the lacing with the first temporary lashings in place. Cable ties might do a better job, see Georges idea in an earlier post. Then the temporary ties are removed, and the continuous lacing tensioned up. Those that have had Hobie cats will be familiar with the techniques. We used the anchor chain snubber. A length of rope with a chain hook attached to the end. I stand above the lashing, hook the chain hook through the lashing and pull. Lorie then pinches the downstream lashing as it passes over and through the net, I release the hook, move op one lacing, pull hard and Lorie pinches the next loop on the lacing. And so we we work our way around. The shape of the squares on the netting and the line of of the squares give a good indication of how even the tension is.



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[georgetheleo]

That Bimini Tram is way cool btw-any photos of captain Lorie?

[sigmasailor]

Sigma, the tramp was delivered made up, as in the photo. We did nothing except lace it. There is a thicker rope around the border, which is "parcelled" in some way and we just laced it to the boat.


Peter, yes you are right regarding safety but we put additional independent security lashings that would allow the tramp to go slack but not allow a person to fall through. These lashings perform two functions, they keep the netting secured to the boat and they prevent the original continuous lashing from running. A failure of the continuous lashing would not be fatal.
The tramps appear quite difficult to secure, at first sight. We did several experiments. Now, having done the two front tramps and the bimini tramp we are quite good at it! First we would make individual lashings at the four corners and halfway down the sides. This allowed us to stretch the netting out and roughly centralise it. Then we put the continuous lashing on and then progressively tensioned it up, keeping the squares of the netting square and the runs straight and the tramp centred. Once tensioned we would remove the original single lashings and then put on the security lashings. The tramp will feel very solid at this stage, but a few weeks in the hot sun and some activity on it will cause it to slacken. Dyneema is either bar tight or slack, there is no stretch. But heat and activity will cause it to reform slightly. Even so, when slack it is tighter than the original tramp, but we chose to retention it a second time.

Thanks Peter; I assisted in replacing a tramp once and found it difficult to keep things square and central. Next time I will get myself some strong Tyraps to pre tension it before lashing it. We used a system where a SS steel tube was woven through the meshes of the netting; the lashing than goes around the tube rather than the netting itself. I do like the idea of inserting some safety lashes in case the continuous one fails.

[catsoon]

For what its worth- we are 4 years in to our Dyneema net trampline on our Athena 38. It seems to be holding up really well so far and shows now signs of degradation.

We just bought the raw netting and put a 5/8" nylon around the edges that we wrapped with dyneema line, and then attached the tramp with 1/4 nylon with a few extra safety lashings as you have done.

I think they are a pretty decent way to go- I wish I knew someone could "make one up" for me!

CHRIS

[D&D]

FWIW we'll chirp in here re our nets and their knotting. We recently had to redo the nets and in that process learned quite a bit...

For a start we learned the material in our nets is Dyneema Ultra Cross Knotless...and that material is rated 'High' for all of UV resistance, strength, non-stretchability and water evacuation. We already knew, however, from the past 3 years that our nets were great in all conditions, from safety in big seas to relaxing on beautiful cruising moments. So we began the process reluctant to change our nets...and ended the process even more so. We would certainly recommend ultra cross knotless netting.

Then as for securing, our first attempt (or more accurately the attempt by the 'professional' commissioned to do the job) was a farce...nowhere near as tight as the original and done with a continuous line with (as Peter noted already) all the risks of that approach. So we re-did the job pretty much ourselves...

We started with cable ties every other tie point. Then we began single knotting every tie point so that each was snug against the metal attachment points; as that process progressed the cable ties were gradually removed and, of course, replaced with individual knotting. Finally we ran a continuous line around the secured perimeter, but with the line returning to the nets between each of the individual knots, thus providing additional lateral strength to the knots and spreading the load onto twice as many points on the net. All the securing lines were also dyneema.

All-in-all it was a slow and tedious job, tough on the hands as well. Our knots were perhaps not as pretty as those of the tradesmen who put the nets on in the first place, but the nets are now again every bit as tight as they were originally...and we look forward to another few (?!) years of enjoying them ahead.

tramp knotting close-up (2).jpg

tramp knotting, new (9).jpg