web tramp or net
From the pics it is difficult to tell how big the tramps are going to be.
The cons of webbing tramps are as follows:
1. High labor cost (each intersection will need to be stitched to prevent the straps from sliding around).
2. Relatively low open area
3. High windage potential, depends on your boat design whether or not it will have an adverse effect.
4. spacing between webbing with either be small creating very little open area, or large making it prone to catching toes, heels etc. and a little difficult to walk on.
5.They are heavy and more difficult to tension, especially if the alignment and sewing isn't right on, you may have an intersection where there is a pucker or high tension.
6. Lots of thread to degrade by UV, unless you use teflon thread. (see #1 labor intensive to make).
7. Personally, I don't care for the look, to me they are not as graceful looking but that is subjective.
1. They are pretty durable, meaning you can throw things on them like anchors and probably won't tear them, or little chance of falling through them if you land on the tramp really hard, even when nearly worn out.
2. They are more comfortable to lay on and walk on if you keep away from the holes. Considering this, if you use 2" webbing, and alternate your design with a 2" space, you will still have 2" holes which is big enough to catch toes in and make it hard to walk on. And you have approximately a 50%-75% or more blockage from waves and wind (not good).
Aside from that, if you expect to encounter some serious wave force, I would not go the webbing route. For the same cost as webbing, you can get spectra netting. (both are expensive options) Find some photos of Playstation and study the tramps, that is spectra. Unfortunately, spectra is very slippery, gets strung like a tennis racquet, and is almost like a cheeze grater when you fall on it. It is very light, nearly stretch free and has very low windage. (wave forces are more destructive). I did several boats in spectra, and don't miss working with that material.
For 1/4 the cost of webbing or spectra, you can go with nets. I would go with a small (1"-1.5" more or less square) mesh(there is a term the netting manufacturers use but it does not make sense as they measure the opening of a net with the netting stretched closed (no grid pattern, essentially if you are thinking a 1"x1" square net, it will be called out as a 2" size by the net guys)).
The difficult thing is to find a big twine and small square knotless net. Typically, you fiind big twine (1/4" or larger) it will have a big opening(2" square or larger) or really fine twine and small square grid.
FYI, the knot in a knotted net will reduce the strength of the strand used to make the net by something like 40%. Knots are painful to walk on too. They also stretch much more after initial tensioning.
Netting can be fabricated with a heavy rope edge woven into it by some marine suppliers. Some French cats come this way new from the factory.
The cost of netting is sold by the pound, not sq. ft. or any other method we can understand, but netting is pretty inexpensive in the scheme of things.
Also, netting routinely comes treated with UV protection and most black netting actually started out white, it is the UV coating bath they run it through that colors it. Most net suppliers know the treatment by the industry name, I can't remember it, I used to sell it by my company's trade name.
There is more to the story, but I am getting a little long winded.
Nevermind about the length of your wind. I too am building a cat and am eating up your posts! Thanks for all the great info.
That's great info Bryan, thanks very much. We were actually thinking of sewing the webbing together ourselves, which might be a lot of work, but probably wouldnt seem like too much trouble compared to building the boat!
I'm still a fair way off needing tramps just now, but I will start keeping my ear to the ground regarding knotless netting. I've walked on knotted net tramps and didn't like them much. (But it was quite a thin twine). There are fishing trawlers based here so I might start asking questions there too.
Multihullnets.com recently started selling a new net they call "Offshore". I have a sample of this and it looks like the perfect combination (compromise?) among strength, openess and comfort.
multihullnets, product, open
I used to compete with Sunrise Yacht products, so I am familiar with the material, the offshore net is the material that is used on corsair tris mostly. It is also available from several other sources in raw form like Bainbridge (not cheap, but available in small quantities). This netting has mixed reviews. It is small opening for easy walking/laying, cannot be tensioned too tightly or tightly enough, depending on your expectations (ask me how I know this) is a knitted material that abrades pretty easy. This is one of the common complaints from the Corsair owners, especially before the tramps came coated with the UV coating. I am not that comfortable using this material if there is going to be heavy loading (lots of people).
I even experimented with this " öffshore " net on Hobie cats, but didn't to that well because it is too stretchy.
Just to toot my own horn, I used to routinely beat Sunrise's pricing on everything and customer feedback said quality was as good or better. I even forced them to start selling the UV coating as a DIY product. Prior to that, they would only sell you a tramp.
If there is enough interest, I may dig up all my old sources for netting materials and post it. Most of the sources are either the mill or wholesale suppliers with minimum purchase quantities.
Also, I can give suggestions for how to mount the nets for best load distribution if there is any interest. Being an engineer, I always was thinking about distributing the loads in more effective ways.
One big question I would always ask customers is if they were getting nets for safety purposes (blue water) or for deck extension (as in a day sailer, or dive boat). Most of the time, you can have one or the other but not really both.
Also sewing machines: Any " walking foot" type machine is the only way to go. Sailrite makes portable ones, but you can purchase full size commercial machines for less (or you can rent commercial machines for about $50/month). Industrial sewing is much different than homeowner sewing, just a caveat. The heavier the machine the better. I have machines that have sewn through 1/8 masonite and even sheet metal (all by accident and not damage!) Most of the webbing made tramps seem to have the joints sewn by machines that do nothing but a box stitch. Very specialize, but much quicker. I have sources that make webbing tramps if anyone is interested.
Personally, If I were replacing the nets on an offshore boat, I would go with open netting for the passage, and a fine mesh (like the trampolines or beach cats) for hanging around. That fine beach cat mesh will last for 10 years, I have old tramps to prove it. The downside is time changing out, and almost guaranteed blisters on your hands. There are some tricks to making tramps "quick on-quick off" relatively speaking.
I once tried to do the open nets with a mesh overly for the conditions just described (passage making vs hanging around), and it was a disaster.
This is the manufacturer of the net coating.
1969 Rutgers Univ. Blvd.
Lakewood, NJ, 08701
Sunrise has changed their website. I don't see the product listed, but the colors they show as being available is this Flexguard product. Most net makers use black and white.
West coast netting was another net source. I believe they made the nets for the Dennis Conner's boat.
Redden-net.com is another netting source.
The material is guaranteed to last five years, and the material duplicates the trampolines that I have on my Privilege 39 Catamaran.
You can visit their store online and look through their catalogue. They have a big mail order business and have instructional videos on how to make things, although I don't know if they have a specific DVD on how to make trampolines.
tramp building tips
There seems to be a fair amount of interest in DIY for tramps
1. Hot knife everything. Everything you use will be sythetic, so hot knife everything, no exceptions. You won't regret this.
2. Don't buy an expensive hot knife, get a hot knife replacement blade (Engle brand comes to mind) for about $25, then go to Sears or Home Depot and get a cheap soldering gun (250watt). I got one with a light on it, which was quite useful, again $25. I would use a gun for a couple of years of daily use. It also works as a soldering gun if you need it to.
3. Hot hole punch all grommet holes. I use a handheld soldering iron 70watt and use a hole burner die sized for the grommet. This is a hard to find item, but it makes sure your holes are fused when you make them. This will add to the durability and you don't have to pound anything to get a hole. the soldering iron runs about $35-40, the die about $25 for the small brass/copper die. Despite the fragility of the dies and the high cost, I never went without it. Some cheap fabricators don't burn their holes, they just punch them out, leaving loose frayed edges, that over time will unravel and may also let the grommit wallow around, and then pull out. Most awning fabricators don't burn their holes in sunbrella. Burning the holes is good insurance that the item will hold up over time.
4. Always use rolled rim spur grommets. We used nickel plated rolled rim grommets exclusively. They didn't tarnish up anywhere in anywhere near the same time as plain brass, no green oxidation either. There are about two different grommet manufacturers, Stimson seems to be the brand I use. Avoid stainless steel grommets, while they sound better, when we tried to incorporate them into any project, we had about a 50% failure rate from the hard material, and they were 5 times more expensive
5. Grommet setting dies are not the same for plain grommets and rolled rim grommets (even the hole size for the same " #5" is different between plain grommets and rolled rim. If you use the incorrect setter, you will damage the grommet and never get a good set. Cheap setters usually work as well as expensive setters when new. The expensive setters just last longer.
6. Don't bother spending money on a bench top lever arm setter (or a hand held snap type setter for grommets) unless you plan on setting thousands of grommets. The hammer driven grommet setters also are better for use in tight locations and easily fit into a small took kit.
7. Always use a plastic dead blow hammer, it works better all around.
8. Use a walking foot sewing machine that can handle large thread (#138 thread). Always use polyester thread, or if you spring for it, teflon thread, but teflon thread is more difficult to work with.
9. The vinyl that you may want to use for the edging is truck tarp vinyl, some brands are "road star" , but most manufacturers have the equivalent. If there is a Keyston Brothers supply house near you, you can get the vinyl and lots of sunbrella and other general fabrication supplies (no netting though) from them.
10. Never use nylon for tramp material. Nylon has two features that you are not interested in 1. nylon stretches and does not rebound quickly, once walked on, it will look saggy, and won't return to its shape 2. nylon is hydrophyllic (it absorbs water). Use polyester or something that does not stretch as much or hold water. While nylon is initially stronger, it loses its strength much quicker from UV breakdown than polyester. Don't confuse polyproplyne with polyester. Polypro is the inexpensive webbing used everywhere. It has its uses.
11. If at all possible bolt-rope attach at least one of your edges. This creates a uniform load on the material and the object is is attaching to. This design eliminates grommets, which are not necessarily the best attachment method. Most bolt rope extrusions are 1/2" diameter. It looks the neatest and most finished as well.
12. The next best alternative is to use sail slug-slides in a track. this allows the tramp to shrink and grow without distorting the tramp and the mounting point. It also makes for a quick removal tramp. Just loosen and slide the slug slides from the track, reinstallation is equally as easy.
13. Always design a tramp so you can tension it in two directions, this sounds obvious, but trying to make something fit between two hulls without being able to tension it (which I have seen) isnt going to work.
14. If applying a border to the edge of the tramp, keep in mind that the net or mesh will probably stretch more than the stitched up border, so pre stretch the border when sewing it on (it may actually take on a slight pucker and wrinkled look when not under tension. This is an area where trial and error and experience help.
15 If you are going to use an open net, the best design is to have a rope border whipped/laced into the edges. This isnt as nice looking, but it will be the easiest to tesion up and maintain.
This is just stuff off the top of my head. I hope it helps. If there are any specific questions, I will try to address them.
Thanks for sharing your expertise - a very well-written tutorial (clear, complete, yet concise).
could we merely punch a slightly undersized hole, then seal the perimeter edges with a pencil iron?
Thanks and regards,
hot hole punch
You can punch the hole and then sear it, but you risk making the hole oversized or oblong. One of the key things about grommets staying in place is to have a snug hole where the grommet cannot wallow around. This is also very tedious, but in a pinch and with care, you can replicate the effects of the hot hole punch.
I will look into my old business documents to see where I used to purchase the hot hole punches.
My tramp looks like a cargo net, made with 1" webbing. The perimiter of the tramp has loops sewn into the ends of each strap. A 1" SS tube is inserted thru the loops on each side (4). The tubes attach to the boat with rope lashings, which are pulled tight to tension the tramp. If I used the newer type material should I use the same method of attachment, or what would you suggest?
One design method to eliminate a sewn loop at each end of the webbing is to do a diagonal weave. What I mean is that if you follow a run of webbing from the beginning, at a starting point, vector off the at a 45 deg angle when th webbing hits a tensioning rod make a 90, then continue until it hits the next tensioning rod all the way around. With 90 deg turns, the end most likely will not meet up with the beginning, but you eliminated individual looping and splices and cuts. Try plotting out the design on paper making a 90 every time you hit an edge and you will see what I mean.
If you have edges that are not square, this design won't work as well, but still reduces the cuts and loops you would need to do .
How it is mounted to the boat is often another story. Over time some of the lashing points get damaged or pull out and a new method of attaching to the boat needs to be installed. This is where I would recommend either a bolt rope or a sail track (slug slide) mounting. The continuous extrusion distributes the load much better than individual anchor points.
Q for Bryan or others
OK, having little salt water experience with catamarans, and no bluewater experience at all, I'm having trouble understanding what the problem is with having a fine-mesh tramp on a big cat. I believe you know what you're talking about, I'm just asking for a little education. :confused: Thanks!
Another question. When using nets or other materials for tramps on big cats, is it possible to handle some of the tensioning issues by using a "bias cut"? That's one of the things about my fine-mesh Hobie tramp that makes it work so well. Let me explain. The standard Hobie tramp is vinyl, in 3 pieces: left, right, and back. The left and right are laced together in the middle, and both are laced to the back piece. With the bias-cut mesh replacement, the mesh is cut at 45-degree angles to the weave, and it is in one piece. It is laced only to the back rail, with sliding D-ring slugs. When you tension it against the back rail, the bias cut causes the tension to be directed against the sides in a big "V", rather than just pulling directly across from the back to the front. Of course, the tramp must be cut and sewn carefully so that its initial un-tensioned fit is pretty close, and then a fairly small amount of stretch applied by that back rail lacing really brings it up tight, and it stays that way. The left, right, and front edges are all done with sewn-in "rope rail", as with the Hobie original. Is that attachment method viable on a big cat?
By the way, for the racers here, I am aware that this tramp makes my boat illegal in class racing, and I'm OK with that. :)
This topic has been very interesting and very informative. Thanks to all!
I'm quite familiar with the bias cut tramps, in fact we used to do a "single piece reverse H-18" , which is the bias cut but the lacing strip is at the front not the rear. No sheets dragging in the water. This was a pretty popular design. You are correct that a pretty close tolerance is required, but the rear corners had to be either cut out diagonally or left to pucker (not good looking). Most H-18's are not the same width at the front as the back, so tolerance was even more important. I must have measured 50 of them and everyone was slightly different.
A mesh net will not let a strong wave pass through. It will capture the wave and the forces will be transferred to the boat, usually in undesirable ways. You have a lot of water hitting the mesh with a strong intensity in a fraction of a second, the mesh can't let it pass. Open netting obviously lets nearly all of the wave force pass through. The wave forces and the wind forces are all captured by the mesh. Tri owners are more concerned about the mesh tramps catching air.
I did tramps on a boat being delivered to Hawaii from San Diego who insisted on the mesh because it was friendler to day sailer tourists,(and the CG would not let the boat go unless it had tramps on it) and they hit some heavy waves during delivery; the waves ended up tearing up the bows on this boat. The tramps tore up the aluminum structural member in the center that the tramp was attached to and ripped up the mounting rails on each hull. The mesh tramps held up.
Considering that Hobie class tramps traditionally had always been solid plastic, a mesh tramp was a vast improvement over the solid wing you create when flying a hull. From what I understand, most fleets ignore the tramp rule, since Hobie also makes a mesh tramp, but it is all sonic welded, rather than stitched. The only difference now being thread or no thread. But you are right, everybody's tramp except Hobie's is illegal.
PS: "gator81" are you a UF alumni?
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