Hobie 18 forward trampoline

Attention all engineers here! I'm a new sailor with an 18, WITHOUT wings. Wish I knew better when I bought it, but hey, I was just boat hungry for the first time. I'm looking to plan an island hopping adventure in the Keys with a friend, and I'm worried that putting my friend, myself, and all our gear on a single trampoline will make things quite uncomfortable. I started playing with the idea of rigging up a two-ish feet long structure from pvc with some sort of tramp material stretched between it, attach it some way across the hulls, just in front of the mast. It'll be used strictly for keeping luggage out of the way due to the lack of wings. Has anyone done this before or have any ideas?

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-Andrew
1982 Hobie 18

What kind of weight are you figuring on? I've had up to ~725 lbs (5 young adults & 1 child) on my H18 before, and honestly, it was very nearly a submarine. 550-600 lbs (4 young adults) is a heavy load for the H18. Design load is probably ~285-350 lbs, with a "max" of 500-600 lbs. It's sailable, but you're going to be going ~12-13 mph where you could be going ~16 mph.

The other concern is trim - the ideal waterline for an H18 goes from about halfway up the bow to the very bottom of the transom at the stern (on the leeward hull), with the windward hull just kissing the water surface, which is only possible at the design load. You have to shift your body weight (and that of your crew) forward and aft, inboard and outboard, as the wind gusts and lulls to maintain that trim and heel attitude. If you add significant weight forward, you'll have to shift the weight of yourself and your crew aft to keep the bows from digging too deep, which will probably sink the transoms down to the point that they'll drag deeper in the water and add drag to the hull.

But the short answer is yes, it's perfectly doable if it's positioned close to the mast and the weight is kept down. The H18 is a two person boat, but 3-4 is doable. It'll be a "dog" by catamaran standards, but still twice as fast as a monohull or dingy of similar size. I've seen people rig up a cooler in front of the mast. As long as you don't interfere with the mast rotation, spread out the weight on the decks a little and don't put too much weight too far forward, you'll be fine. You won't be able to do much in light winds, and you'll have to be careful in heavy winds (the forward driving force on your sails also tends to push "down" on your bows).

Aside from those considerations, a long distance(ish) adventure on a Hobie sounds like an awesome way to improve your sailing skills and understanding of the boat, and have a blast doing it! Some of the most fun I've had sailing was while I was exploring groups of islands in the St. Lawrence River, and I hope it's a blast for you!

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Mike

'79 H18 standard 'Rocketman II' sail #14921 RIP
'78 H18 (unnamed) sail #14921
'08 H16 sail #114312
'97 H21SC sail #238

Like I said, it would just be me and my friend. I'm a little over a buck and a half and my friend is about 160-170. I've taken him out on it before, it has done fine. The luggage I would be bringing is probably two small duffel bags, an ice chest, and a tent, at least that's what I can think of right now. It would probably be around 80-100 pounds of stuff depending on how much beer we pack
I'm definitely looking forward to making this trip myself. Still not sure when exactly I'm going to plan to take it, but I've heard to go around spring and fall. If the summer runs smoothly, I might squeeze it into next fall.

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-Andrew
1982 Hobie 18

I think PVC is definitely NOT the material to use. It's heavy and much too flexible to support the weight you're planning on carrying (unless you use a very large diameter). I would try to source some aluminum tubing. A bottom section of a windsurfing mast might also be a good option (carbon fiber, about 2.5" diameter). You definitely don't want your gear flopping around or at risk of being lost. Figuring out how you can safely and securely connect this bar to the hulls is going to be your biggest challenge.

Also keep in mind that there is quite a bit of storage space inside the hulls. Back in the '80s, two guys sailed a H18 across the Atlantic and most of their gear was stored inside the hulls. So maybe with some clever packing you can get away with just using the hull space for storage.

Anyway, if you go with the rack idea, I think you need to make sure it's fairly robust. In wind and waves, it's going to take a beating being located in front of the mast.

sm

For a forward tramp setup on your boat, try using an old Hobie 18 boom (cut to fit) with some fabricated stainless steel pcs. (offsetting Z's") similar to a Hobie 21SC bow attachment setup.

This should be strong enough and more compatible than pvc.

Somehow fasten a pair of Hobie 18 tramp track along the deck lip?

Now rivet a series of eye straps along the face of the forward crossbar.

With all this on the boat, design a net style forward tramp to suit your needs and find someone to fabricate it.

Good luck!

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Bill 404 21SE

Can someone find the link to the Arctic Expedition, the two guys who sailed the NorthWest passage back in the early 80's, using Magnum wings?

Then there were the Brazilians who made a custom carbon fibre H18 and sailed around Cape Horn, then north up the coast of Argentina....about two years ago.
Again, with wings and not tramps.

I suggest you shop your heart out for wings..... or try fabricating your own. For safety reasons, putting extra weight forward is not a great idea.

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2015 H16, with spin,
SOLD 1989 Hobie SX18 Sail # 1947 "In Theory..."
'Only two things are infinite, the universe, and human stupidity. But I'm not sure about the former.'

Already made one earlier this year. Used some wood to raise up the pvc to match the height of the front beam and keep it out of the water. I drilled new .5" holes in the lip of the hull to hold the new beam down. Tied that cargo net out of some para rope. The hardest thing is getting it to mount to the front beam. As you can see I used a length of rope and I used the gromets in the tramp for the hiking straps and lacing to hold it.

The PVC is strong enough I can add my whole weight to the center (170lbs) and it bends but doesnt break. I wouldnt want to bounce on it. But for cargo in dry bags it works perfect.

As far as weight forward of the mast it's a non issue. We mostly load it heavy to take our camping gear out and drop it off on an island before going out in the ocean when we usually might have 30lbs of rope / water / food / life jackets etc. The beam itself and net I'd guess weighs like 5-7lbs. I never take it off. I got a video of us with 600lbs of crew in some chop with a decent amount of stuff in the forward cargo area and it's not having any problems.

https://www.youtube.com/watch?v=MUBvk9RvPfo

That arctic expedition was featured in the National Geographic magazine so that ought to make it possible to search for and find. I had that issue once. If you are seaching make sure you use the words northwest passage like the previous poster mentioned...with all the warming someone just might be able to make that whole journey on a hobie without dragging the boat across ice fields. It was an awesome undertaking!!!

yep, came up right away http://www.helmdesign.com/polar-01.html will get you on track..... ABSOLUTELY A MUST READ FOR ANY 18 OWNER!!

Great story on the NW Passage on a Hobie 18. The wings are great, get some if you can. I have seen them for sale on this forum from time to time.

TAMUmpower that's really awesome! I hope you don't have the design copyrighted

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-Andrew
1982 Hobie 18

Go for it. Sailing with a clean trampoline is so much nicer. I might get bored one day and replace the wood risers with some custom fiberglass ones. Who knows

There was a Dutch guy modifying his H18 for a longer adventure in the mediterranean, around Morocco.
He mounted a H18-boom at the front with a full trampolin connected to the hulls.
Unfortunately i can´t find his page again and i have tried for hours!! Maybe some other here could help. It was really well described with many pics. It could maybe have come from thebeachcats.com

One thing you really have to be careful of there is too much weight too far forward. The H18 was never designed for a forward tramp. Sure you can make one, and use it in light-moderate air with moderate weight and little chop, but anything more and you're asking for trouble. The H18 doesn't have the forward volume (or buoyancy distribution) of a Hobie Getaway or Hobie 21SC. These boats were designed with extra volume forward to account for the additional weight of more people up forward. The forward buoyancy on the H18 is there to resist the "head over heals" tendency of the boat when a gust hits your sails.

The center of effort of your sail plan is generally assumed to be about 1/3 the way up your mast or so. When you've got a driving force of several hundred pounds or more, centered on a point ~10' up the mast, it tends to push your bows down. The extra buoyancy in the bows from the flared hull design and large "freeboard" & rocker is intended to counteract this force. Load up with some gear or an extra person up forward, and you've reduced the boat's ability to resist it. Take a wave over your new "forward crossbar" and the boat may pitchpole. Doesn't mean you can't or shouldn't do it, but it's advisable to take it all into consideration. Wings are a more advisable modification because they add space but don't appreciably affect the fore & aft trim of the boat (unless you overload them as well).

These images might help with some build ideas but i'd tend to agree that the H18 isn't built for too much weight to sit forward of the mast. I actually have a front spreader bar for my H18 which attaches at the bridal joins. I don't believe it's a genuine Hobie add on but its made well, in black anno and does a good job of keep the hulls together.

The first (unloved) one I think was spotted somewhere near Sydney and the 2nd two are from a recent ad here in Australia.

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2007 Hobie 16 - 'Slingshot'
1996 Hobie 18 - 'Onrails'
Hobie Bravo - 'Hobie Bites'