High Performance MPX Foil/Self-righting Trimaran-The Test Model

I don't buy that Doug.
Spectra creeps? sure, when it's under 90% of design load for days and weeks on end. That's why we do lashings, they are easy to adjust any time and they are light. If understand correctly, you wanted to do some kind of connection that is easy to undo, and then re-do, when you rig and de-rig the boat. so essentially every time you use the boat, you simply tie the line and get the tension you want. Simple as that.

I will put together an illustration later of some knots that are dead easy to tie and untie in this application.

Plus, why blow money on Dyneema for this? Nylon whipping twine is more than adequate for the job at hand. It's just a keeper line, it doesn't even have to be under a ****-ton of tension to do its job. It's holding the amas on so they don't float away right. do you have shrouds attached to the ama's? If so, unless you lose the rig, the amas are not going anywhere anyhow.

you know that we use lashings instead of turnbuckles on our C-cat shrouds right? We use string for everything we possibly can for the reasons stated, it's light, it's strong, it's soft, it's dead easy to repair, it's easy to pack in the spares case. I even always keep three 4 to 6 foot long sections of line in my pocket on the boat at all times, on ANY boat I ever sail on, just in case, The lines are simply three different diameters for different uses. That and an Exacto knife is on hand at all times. On the C-cat we have less that 3 pounds of metal on the boat, in large part because of our dedication to line instead of eyes, blocks etc. every single member of the team is expected to be able to bang off a Dyneema eye splice, because we just use it so often. whats more, it's easy to do lots of slip splices, which are adjustable, or lock splices, which are "locked". And so on and on and on. to that extent, we have even perfected splicing line less that 2 mm in diameter.

 

MPX Test Model

Thanks, Magnus. I already have the spectra and also dacron. I used 150lb spectra for the shrouds and a bowsie for adjustment-thought I'd try it anyway. Knots all set with CA.
I'm still thinking-I'll look at the knots you suggest and then decide.

PS- the white line in this picture is the shroud "chainplate" and the shroud is attached near the end of the main hull forward crosstube.

 

OK, so first up is my all purpose nylon twine. a few thousand feet of heavy nylon sewing thread I picked up for hand sewing leather for a few bucks. Dirt cheap, I use it for everything, it has less creep than dyneema fishing line which is kind of useless I have learned. That's the first photo.

So I wind it three or four times around the carbon tube, pull it as tight as I am able, then tie a reef knot in it.

does it loosen when I do that? yep, sure does, I don't care, it makes no difference. If I cared, I would have someone put their finger on the knot while I tie it, but alas, it doesn't make a huge difference.

Then a dab of CA on it, to just place it. The reality is that it should tighten up like a Chinese finger cuff anyhow and then it won't want to slide around on the carbon tube.

Then in the tail of that line, bend in a loop and then simply tie a hitch (granny knot) with the loop. Keep it neat, and pull it tight to set the knot. Try to do it closer to the lashing on the tube.

Now do exactly the same on the other side. On the first side, I left a long tail on the knot (String is cheap remember). On the second side, I trimmed down the tail to only an inch or two.

Now feed my long tail into the opposite loop, then back to the first loop, then pull it tight. Voila, everything is bone tight now.

Next I simply tie it off with another loop hitch. Eg. make a loop and then tie a simple hitch with that against the last loop you went through. This will set the tension. If you want it safe and sound, tie the loop in a few more hitches around the whole assembly. these last knots you don't need to wail on them, they are just to make sure it doesn't all come apart at high speed.

to undo it, simply undo those last hitches, then when you are down to the last hitch, like your shoelaces, you should be able to simply pull on the tail and the whole thing will undo itself and release the tension. all your lines are still attached to the boat and as fast as you can tie your shoes, you can lash the boat back together.

Total weight a fraction of a gram. achievable tension, 10's of pounds no problem. First time I did it without shooting photos, it took me 62 seconds without rushing. Cost, less than a penny, perhaps more with the 2 daps of CA.

 

MPX Test Model

Thanks a lot , Magnus. Much appreciate the effort and the original suggestion! See the sketch below-easily adjustable and attached/removed--unless somebody points out a problem with it(that I agree with) that's final:
PS- may use a loop in the center to keep the line close to the tubes.....
click-

 

looking better.

Another thing, when we use Dyneema etc, we pre-stretch everything we plan on using if it is going to be a long line and under a lot of load. We have a hydraulic we use for this. We set up between two trees or anything line that, lay out the line, tie knots in either end, or pop in a quick splice, then load it up, with a load cell on it, and leave it there for a while. Then release it, then do it again a few times. Rob takes it up to about 90% of rated working load. this cuts out a lot of creep issues later. Keep in mind water and sun affect the creep characteristics as well on many modern fibers.

likewise, we test all sorts of splices and stuff to destruction when trying new line or new systems, before they go on the boat, if they are mission critical, like a shroud.

 

Some instances of lashings and other rope work on the boats.
Shrouds, forestays, and the trampoline at the back of the boat are the big highly loaded ones.

In other photos you can see how we try to use deck loops instead of metal eyelets to fasten things down. Obviously the local laminate has to be up to the job. for the loads

In the last shot you can see the strops we have made up with carbon bonding pads on the end, they glue down to the deck. those strops are lashed to the side of the trampoline, to keep the sides tight. With the PDB tramp, life is very nice and stiff.

Lashings are great on the tramp because we would wind them tighter every three or four sails as well, as the tramp would stretch a wee bit.

finally, all of our racing shrouds are essentially lashings as well. They are just PBO filament wound in a loop many times, then wrapped in plastic and a rubber coating, with a single reef know keeping it all in place.

 

MPX Test Model

Interesting stuff ,Magnus. Do you use CA on the C's to hold knots or in other ways on spectra/Dyneema or what-have-you? I've never used Spectra for shrouds before-I'm interested to see how its going to work. Especially interested if the bowsie ,with the line around it to make it harder to move, will work and stay put as a shroud adjuster. Spectra is a bit "slippery", as you know. All knots are "set" using cyano... In past model experience I learned that cyano doesn't like water-a guy in Orlando-and I've heard of others-lost a bulb that was glued with it. I don't think it will be a problem on this boat.

 

generally we do not use it. CA is after all water soluble given enough time, so it should not be relied upon. On some very small splices inside the wing, where it is generally dry, we may lock a splice with it. If we really want some loop locked in place, we just do a lock splice.

What you may see we use generously is electrical tape. AKA Vinyl tape, or we just call it E-tape. So we'll tie off a lashing, then throw in an extra knot or two, then wrap the knots in tape.

We use E-tape because it's stretchy, it comes off clean for the most part, it seems to grow on trees and be readily available. Taping up lashings keeps them from ever getting untied for any reason, it also cleans it up, so a sheet or something cannot get hung up no the knot and it's more aero when we're done.

We treat E-tape like water, always have two rolls on board, don't be shy about using it, and if in doubt, put one more wrap on. We order it by the case. (it's the cheapest tape we use save for painters tape)

 

MPX Test Model

I've got Her Majesty set up on the work table to add the"super lube" grease to the plug-in joints and to add the retaining lines to each cross arm. I really appreciate the help in thinking about how to do the retainer with particular thanks to Magnus, Hoyt and Eric!
The greased joints work so much better-much easier to assemble! Now they're waterproof as well(I hope). Maybe I'll drill a hole in the lowest point of both crossarms just in case.

click--

 

...


I see from googling 'weather Cape Canaveral',
that you have something like 4mph wind at the moment?

Go outside and check?

 

====================
12-15, gusts to 20. Their anemometer must be blanketed....... Thats about 12 miles north of here.

 

...

Oh shoot.

It was easier to launch the Space Shuttle, they were happy with anything under 15 knots.

Thursday and Friday might be OK, according to Windguru .

tick, tick, tick.

 

MPX Test Model

---------------------------
Forcast for here now is 7mph, and its way above that. The next time it's forcast to be below 10 is Saturday and thats it for the following week. But forcasts around here are not reliable. Need it light to rig it the first time and light for the first sail. In the many big boats I've designed, built and sailed the first time I always did it in light air, but many times all that meant was getting to the water early- by 10 the wind would start to pick and by 1 it would be 10-15. Perfect test "regime"!

 

Doug is perhaps lucky. a week ago I was in FLA and had I been any closer I was going to drive down there and ambush him with a video camera and have him do a walkthrough of his project. then I was going to sit in his living room drinking weak American beer until the boat went sailing.

Unfortunately I was not prepared to drive 6 hours either way to pull the mission off given my not too long holiday time available. (I was in Destin up on the pan handle).

Had I been in Orlando, woooah, I would have been there in a shot with an electric cow prod to push Doug into the water holding his craft kicking and screaming.

 

==========================
Funny how many people think Destin, Ft. Walton and Pensacola are in Florida! I grew up in all three places and I guarantee you they are in Alabama.
Most people don't realize how long the drives can be in this state....
But I can't believe you came down here and didn't just hop right over-whats 6(8) hours one way to a Canadian?!