Hull already built - what’s the best way to attach the trampolines?

[Chotu]

Well, this is not what I was hoping to hear.

Good thread though. I’m going to need a bit of time to figure this out.

Maybe this is a can to kick down the road and just run without trampolines at first to move the boat, adding them on next haul out.

[MicHughV]

Chotu,

One Papillon has provided an excellent link, worthy of your time and attention. I looked thru' it....very informative.

You have several options regarding the tramp material, but at the end of the day, you might want to consider getting a pro to design and install it.

It will be an investment, but it will be dollars well spent.

Good luck, I will keep an eye out for future tramp threads from you.

[GRIT]

I'm sure you'd be fine with 5200. My only issue is the extrusion in post 8
will induce peel if it's mounted with the bolt rope on top. If mounted with the bolt rope on bottom, I'd bet big bucks you'll be fine.

I don't see why folks don't think it would be strong enough. It must be many times stronger than bolted saddles, like the ones in the photo earlier in this thread.

I'm assuming you're planning to have that extrusion the full length of each side.

I'd have a bolt on each end to help prevent peel at the ends, and hold it in place while the adhesive cures. And a few spacers to be sure you have enough thickness to have full strength in the adhesive. Maybe 2mm or so.


Cheers.
Paul.

[Tupaia]

Originally Posted by GRIT

I'm sure you'd be fine with 5200. My only issue is the extrusion in post 8
will induce peel if it's mounted with the bolt rope on top. If mounted with the bolt rope on bottom, I'd bet big bucks you'll be fine.

I don't see why folks don't think it would be strong enough. It must be many times stronger than bolted saddles, like the ones in the photo earlier in this thread.

I'm assuming you're planning to have that extrusion the full length of each side.

I'd have a bolt on each end to help prevent peel at the ends, and hold it in place while the adhesive cures. And a few spacers to be sure you have enough thickness to have full strength in the adhesive. Maybe 2mm or so.


Cheers.
Paul.

I would agree with GRIT but suggest if your go this route to source a double flanged extrusion.

[Chotu]

Originally Posted by Tupaia

I would agree with GRIT but suggest if your go this route to source a double flanged extrusion.
Attachment 250965

EXACTLY what I was thinking.

Nice, huge bonding area. The trampoline fabric/rope would probably fail before a 5200(4200) bond with that much surface area.

Hull is not flat where I need to do this so it will take some figuring out.

[Tupaia]

Originally Posted by Chotu

.

Hull is not flat where I need to do this so it will take some figuring out.

Now you mention it...

How un-flat?

[Chotu]

Originally Posted by Tupaia

Now you mention it...

How un-flat?

Well, no boat is a perfect slab side except those Kelsall flat panel ones.

It’s not too bad. I’ll get it sorted.

[blubaju]

Originally Posted by Chotu

Looks like I’m getting a mast section forward with track. I’ll have a composite walkway centerline.

That leaves attaching the trampoline to the hull.

The hull is glass/corecell/glass.

I don’t want to open up the laminate and go through all that work. Can I use and adhesive like 5200 to put some track on there to hold the trampolines?

Do you know of some common and effective ways trampolines are typically held in place where they meet the hull?

Tennis racket style, by suggestion of our designer:
20mm tube, laminated on, 6mm rope on a 5mm solid stainless bar (blue rope is NOT my boat)

This would not work out nice for the beam and catwalk, and I try to avoid metal wherever possible, I laminated a flat epoxy bar and laminated that to hull, catwalk and beam.

I used 6mm black Polyesterrope, made in Germany, now 12 years old and still good to my surprise. Black rope has best UV resistance and gives best vision. I had white netting on my other cat and this is no good idea if you want to see below at night. Think, once Covid restrictions are gone I will replace it.

I know, laminating you do not like, I would not trust my life on paint.

We have a carbon fibre mast and Harken track, the track is glued on only, but wet sanded with epoxy and directly glued. The trick is, do not give the Aluminum any time to start oxydation! Using wet epoxy instead of water for sanding is a new experience, I tell you!

[Sand crab]

You can buy the track and the glides here in St. Pete, Fla:
https://multihullnets.com/Prices/Sup...chmentHdw.aspx
And get your nets there too. There is a single flange for mounting on top of the deck and a double flange for mounting on the side of the hull. The single flange has the groove rotated 90 degrees from the double flange. Can you glue on the top? Or if you have to maybe drilling and the filling would be easier that way?
Another poster gave a link to various acrylics and epoxies used for construction. Obviously you would use an acrylic if you needed it for something. Be careful because some of these have a grit like fine sand mixed in. That's great for setting anchor bolts in concrete but not so great for overdrilling and then filling and then fine drilling for your screws. Ask me how I know. Also some of these set up in less than a minute so you better be ready.

[Breaking Waves]

Originally Posted by Chotu

5200(4200) bond

can't you use plexus (or a similar two-part methacrylate)? Seems much more suited to this application than 5200.

[tamicatana]

I have to ask:

Why didn’t you build trampoline accommodations when you built the hull to begin with?

[Benz]

If you could find those flanged track slides in a composite material...the Gunboats get them somewhere...you'd have a far better adhesion to your glass hull than trying to bond aluminum.
Why not buy pultruded vinylester tubing from McMaster, slit one side on a table saw with a diamond or grit blade, and glue the other to the hull with vinylester and cabosil? Make a nice, big, pretty fillet, put some peel-ply over it to cure, fair, paint, and voila! Composite track.

[Redreuben]

The only method I would have faith in on a composite build is to glass the track on.
But you can’t use epoxy so your screwed.
Anyway, bond on a tube with filled resin then glass over it with double bias, you can then cut a slot it it length ways for a bolt rope or cut vertical slots in it and install a rod. Choose appropriate tube size to allow fixing around rod.

[Rotten Ricky]

Originally Posted by Chotu

Well, no boat is a perfect slab side except those Kelsall flat panel ones.

It’s not too bad. I’ll get it sorted.

Chotu,

What is the shape of the chine like where the deck meet the topsides? And do you have to have the strip attached to the topsides or could it be along the deck surface? If it is a big radius then this might not help you.

I went through the same issue but my chine is a fairly tight radius of about 3/4" (epoxy/glass over wood) so I looked for a way that I did not have to put dozens of fasteners through into the core. So in my case I made some 3" wide strips of polyester/glass about 1/4" thick to match the slight curvature of the chine - like about 3" over 6 ft. All along the outboard edge (close to the net) I drilled 1/2" holes every 1.5" - leaving a good half inch of material between the edge and the hole. These are very strong as there was a very high glass to resin ratio, most of it roving. Not all the holes are used, but I have the pick of them for the best fit.

I am sure the strips could be attached with 5200 or similar, but in my case I epoxied the strips along the deck surface so that half of the strip was used to glue to the deck while the other half hangs out over the chine. I held the strips hard to the deck with screws that I later removed before fairing. 3/8" line could then be passed through the holes (carefully radiused) at convenient points to lash the netting to the hull.

The glass strips are very strong and in this manner no fasteners pass into the hull. Being subjected to a horizontal shearing force it will never come off - whereas by attaching an alternative anything to the hull the tramp tension just wants to tear the attaching system off at 90 degrees to the hull. This does not appeal to me.

A couple of other points should be considered. This puts the net at the same level as the decks so there is less of a tripping hazard, particularly as the net tends to sag even more when stepped on. I also deliberately did not try to fair the strip into the deck, but left it so it leaves a slight 1/4" high lip where it attached to the deck. This has proved to be invaluable in providing grip along the chine for deck shoes, thus preventing slipping onto the net from the camber of the deck, especially if the deck is heeling.

It is also better looking than I expected especially as it emphasizes the curve of the chine. It is incredibly strong, durable and as it required no fancy aluminum extrusion or special parts, it cost next to nothing.

Hope this helps. Stay safe in these crazy times!

Cheers, RR.

[Chotu]

Some brilliant ideas in the last set of posts!

Thank you, all! Who would have thought this was commercially available too? Nice link to the nearby shop.

The deck level flange bonding seems to be the smartest way to do this, putting the load in sheer. Then drilling out the holes in the material to tie the net to.

That’s the way I’m going to do this.

I really like the added benefit of having the net at deck level making it easier to use. Way less of a struggle to go forward that way.

Great thread!