Hobbie 18

Hi,
I am looking at using hobbie 18 hulls as amas (outer floats) on a sailing trimaran.
Does anybody know the fully immersed buoyancy of a single hobbie 18 hull??

 

Set the hull on blocks.
Fill with water.
Drain into bucket.
Count the buckets......

 

A guess

You may damage the boat if you fill it with water on land so be careful.

As a guess the Hobie 18 weighs about 120kg. It can carry two big blokes fine - say another 200kg. And there is still some deck above the water. My guess is around 400 litres.

Your trimaran idea has been done quite a few times. If you use the rig from the 18 and a surf boat type main hull the boat performs quite well. I sailed on my mates surfboat/Hobie 18 tri and I was impressed with the performance - nice cruising speeds - 7-8 knots in 9 knots of breeze on a reach

cheers

Phil

 

Thanks for the comments guys.
Phil, was your mates hobbie surf boat tri a "predator" design or one that he put together himself?

 

Just a surf boat

My friend got a surf boat hull and then fixed it up with some Hobie 18 hulls and rig. It is a great idea. I saw one before that was cruising around the Whitsundays.

My mate wants to sell it if you want a head start.

cheers

Phil

 

Thanks for the offer Phil, but not at this stage.

 

i wonder if using a hull with a transom is such a good idea. it is going to be much more heavily loaded than the cat mode and a deeply immersed transom is not a good feature for speed.

the h16 is better in this regard, and asymmetric hulls are more useful on a tri than a cat, as well.

 

That true Bill, but they don't have enough bouyancy.

 

Hi Phil

Probably not ready to buy yet because I have to sell my catamaran (see www.mainproject.info) but I'm interested in your mate's surfboat/Hobie Tri. Please give me contact info so I can get more info and some pictures

Cheers

Alan

 

Hobie 16 or 18

The only people who can really say whether the Hobie 16 or 18 would be best would have sailed with both. Dick Newick did design a great boat called a Tremilino which was a dory hull with Hobie 16 floats. If Newick thought it was good then it can't be bad. I saw one in the early 90s in Pittwater. The guy used to have a mould but as the boat was flat panel it would be better top build it out of ply or foam.

In the end Newick designed bigger floats for the tremilino. I have sailed the surf boat with the 18 floats and would definitely go this way. It is true that the float sterns are larger but this may not be such a bad thing. The floats themselves are much more buoyant and I didn't find the immersion of the floats transoms to cause much drag. The idea of the pin ended float was a big thing in the 70s and 80s. Floats now seem to carry their volume much further aft on most modern tris. The decks are also much higher which will reduce drag greatly compared to if you put the crossbeams straight onto the 16s deck.

 

Phil

Are you going to be in Sydney on the week of December 21? If so, I'd like to get your comments on a proposed hybrid with Hobie 18 amas and a completely new main hull based on the Catri 24. Using published info on the latter, (I asked permission to do so), I have lofted the lines and produced a table of offsets, also a 1:20 balsa model. I think this will be a knockout as a cruising Tri and later, I'll share this development with others on the forum, but a bit of local comment from someone with your experience would be very helpful. You can call me on 0418 230562

Cheers

Alan

 

if you are assembling a small tri from the spare parts bin, the trem site should be an early stop. they've tried a lot of combinations:

http://groups.yahoo.com/group/tremolino/

 

Hi Bill

Thanks for that - though the link is broken, I think I have already looked at most of the Tremolino material as well as the Dix threefold-six and Kismet 23/24 options. Another contender might be the Trinardo - lovely design that will work with Hobie 8 Amas and this may yet be the selected option.

However, what I like about the Catri 24 is the superb hull shape - beautiful entry lines, a knuckle hull where the wetted area is low but the interior space is huge, relative to overall length and for a cruising boat, that matters to me. The speed is of far less consequence as I shall never race it. 6 Oz glass/epoxy over 9mm WRC will not be as light as the foam original, but stronger and again, as a cruiser, that matters.

The scale balsa model is nearing completion - used to "prove" the offset table I developed.

The offer to catch up with anyone in Sydney on Christmas week stands - maybe on the catamaran in the Lane Cove river for a beer?

Cheers

Alan

 

If you plan to have a folding system, try to place the struts higher than the chine to avoid excessive spray. Streamlining the struts is not enough to reduce the spray.

Good luck,
Luiz S

 

Hobie 18/Catri-style composite

Thanks Luiz, I agree. They will not be "constant camber", but they will be set high enough to avoid impact except in extreme cases.

For interest, I'm attaching some pictures of the scale model. You will see the beams are set into the sheer, well above the chine, where they provide maximum lateral strength too, while not interfering with the internal layout. The beams will fold upwards - not shown in the pictures, but they allow the amas to vitually touch in the centre above the main hull

Comments from all welcome

Cheers

Alan