New Attempt at Old Idea, or ... a new live for your Hobie 18.
A friendly “Hello” to everybody
Live is funny and its interesting how ideas come out of nowhere.
We had regatta the last weekend and there was a little tri sailing on our racecourse beside the other tri’s that overtook us one after the other. Iam still forced to sail on a mooonoooomaran, so there are a lot of people sitting on 34’ of boat. My skipper has a broken toe, so he was at the helm instead of me and I had time to watch that trimaran. After the race I walked to the other side of the habour to have a closer look. It was a Tricat 22 daysailor wich looked interesting and a little “retro” with its strong curve in the sheer. Beside the tri there was a old Hobie 18. Hmmm, “Hobie 18 is retro too” I thought ... “or just old???? ...old????? ....... Cheap!!!! Old boats like the Hobie 18 are going away for 1500€ on Ebay, complete with trailer. You just have to find a good one.”
Suddenly there was some electric activity under my hair…...
Why not pick up the Hobie 18 and give it a mainhull to make cheap trimaran. Like Dick Newick did it with the Tremolino and the Hobie 16. The Idea was ( and is) somewhat ingenius. If you have (or can get) a Hobie 18 in good used condition it would be the cheapest possibility to go sailing and cruising on a multihull. Exept for the beams you can use every piece of the cat’s equipment for the tri, so you just have to build (and pay) the mainhull and new beams, nothing else what is expensive!
Today I looked for a good sailplan of the 18 and found one. I scaled it up to 1:20 scale and started freeship. Hmmm, how to make it??? I wanted a retro look to match the 18’s lines and as few material as possible. So, the best way to design it is like Newick or Greene did it in the 1980’s. Small and low hull, curved sheerline , big cabin with (short) wings placed direct on the uninterrupted sheer, same place where the beams will be. Of course it has my favoured modern sharpie hull with flared sides for simple, fast and cheap construction as well as good hydrodramatics.
And here it is ... the first sketch of the new trimaran’s mainhull with the H18 amas in place . LOA/LWL 6.4m (21’), BWL 0.65m (2’2’‘), Ratio 10:1, Hull draft 0.21m (8’‘).
A rough calculation for the needed basic material made it clear ... this boat will be really cheap!!!!!! 4 and / or 6mm plywood, marine grade Okume .... 10 sheets !!!!!!!, stringers will be nordic fir (or what you have in your area that is light and cheap). Following my experience you will need around 30kg of epoxy. (West 105 or similar). Two more sheets of 4mm ply for the interior ... some paint, consumables, bits and pieces ....thats it!
My next task will be to find an Hobie 18 that I can measure, so that the final design of the mainhull can be done to match the Hobie lines and numbers.
So far for now, Iam open for comments! And NO! , I will not build this boat, this a is a design project!!!!! But if somebody is interested in the design and wants to build it, feel free to contact me and we will see if I can speed up the design process.
Greetings from the North Sea Coast, Michel
Nice sketch. The concept is rather appealing; I think your design is very worthwhile to do. There is a company putting out a production hull (not plans) for this sort of conversion. If you haven’t seen it maybe you could use it for inspiration though it doesn’t look like you need any more of that.
http://www.predatortri.com/
Thanks Adam for the compliments,
and many thanks for the link of Predator. I really missed this. But its quite heavy with a bare wheight of 500 kg.
I expekt to get a wheight of 300-350kg for the bare boat, ready to sail, 180kg for the Hobie 18 and mainhull 120-170 kg . Max payload 200kg. Enough for two sailors and a little cruising gear. Displ. is (so far) 550 kg with the mainhull carrying 480kg.
Construction of my hull will be 6mm ply all over. I considered to make the hull sides from 4mm, but I think this is to fragile. Better to have 6mm and therefore the sheeting glass lighter (4oz). This also gives you a little quality tolerance if you can find a good underlaymant plywood in 6mm with 5plies of veneer.
Meanwhile I found the Strike Design of Richard Woods, but in my eyes it looks very “boxy”.
But it makes sence to make the boat comatible to all kinds of beachcats. As you all know from my postings I have strong feelings for harmonic lines and simple plywood construction. I would modify the hulls profile and of course the beam mountings to match the style and the balance of the beachcat. A modern one like Nacra or Mystere would get a mainhull with a modern styling. Its quite simple done without changing the basic design and hydrodynamics.
Best Regards, Michel
A slightly larger version of this idea was Derek Kelsall’s Typhoon based on the Tornado
A friendly “Hello” to everybody
Live is funny and its interesting how ideas come out of nowhere.
We had regatta the last weekend and there was a little tri sailing on our racecourse beside the other tri’s that overtook us one after the other. Iam still forced to sail on a mooonoooomaran, so there are a lot of people sitting on 34’ of boat. My skipper has a broken toe, so he was at the helm instead of me and I had time to watch that trimaran. After the race I walked to the other side of the habour to have a closer look. It was a Tricat 22 daysailor wich looked interesting and a little “retro” with its strong curve in the sheer. Beside the tri there was a old Hobie 18. Hmmm, “Hobie 18 is retro too” I thought ... “or just old???? ...old????? ....... Cheap!!!! Old boats like the Hobie 18 are going away for 1500€ on Ebay, complete with trailer. You just have to find a good one.”
Suddenly there was some electric activity under my hair…...
Why not pick up the Hobie 18 and give it a mainhull to make cheap trimaran. Like Dick Newick did it with the Tremolino and the Hobie 16. The Idea was ( and is) somewhat ingenius. If you have (or can get) a Hobie 18 in good used condition it would be the cheapest possibility to go sailing and cruising on a multihull. Exept for the beams you can use every piece of the cat’s equipment for the tri, so you just have to build (and pay) the mainhull and new beams, nothing else what is expensive!
Today I looked for a good sailplan of the 18 and found one. I scaled it up to 1:20 scale and started freeship. Hmmm, how to make it??? I wanted a retro look to match the 18’s lines and as few material as possible. So, the best way to design it is like Newick or Greene did it in the 1980’s. Small and low hull, curved sheerline , big cabin with (short) wings placed direct on the uninterrupted sheer, same place where the beams will be. Of course it has my favoured modern sharpie hull with flared sides for simple, fast and cheap construction as well as good hydrodramatics.
And here it is ... the first sketch of the new trimaran’s mainhull with the H18 amas in place . LOA/LWL 6.4m (21’), BWL 0.65m (2’2’‘), Ratio 10:1, Hull draft 0.21m (8’‘).
A rough calculation for the needed basic material made it clear ... this boat will be really cheap!!!!!! 4 and / or 6mm plywood, marine grade Okume .... 10 sheets !!!!!!!, stringers will be nordic fir (or what you have in your area that is light and cheap). Following my experience you will need around 30kg of epoxy. (West 105 or similar). Two more sheets of 4mm ply for the interior ... some paint, consumables, bits and pieces ....thats it!
My next task will be to find an Hobie 18 that I can measure, so that the final design of the mainhull can be done to match the Hobie lines.So far for now, Iam open for comments! And NO! , I will not build this boat, this a is a design project!!!!! But if somebody is interested in the design and wants to build it, feel free to contact me and we will see if I can speed up the design process.
Greetings from the North Sea Coast, Michel
Michael,I really like it, and that’s not just because I own an old H18!
Dan
Michel, I like it too. Converting a beach cat to a tri is a classic design exercise, and using the Hobie 18 hulls, with the springy sheer gives an attractive result. Hope you continue.
Michel, I like it too. Converting a beach cat to a tri is a classic design exercise, and using the Hobie 18 hulls, with the springy sheer gives an attractive result. Hope you continue.
I will continue, this is a interesting design project.
Dan has offered his help with measuring his H18. Maybe he will build one. At least this is the fastest and cheapest way to get a simple cruising tri.
Meanwhile I was searching the net to get more informations about beachcat / trimaran conversions and found a lot of it. Most interesting are the videos from golden oldies multihulls, where you can see a lot of Tremolinos sailing in a lot of wind. Despite the fact that they have low volume H16 Amas, they can be pressed pretty hard to sail quite fast. Remember that these boats are quite heavy due to their big and strong mainhull.
I learned that their longitudual stability comes from the Mainhull alone and the Ama ist just for transverse stability. This would be perfect as the flat bottom of the sharpie hull has a lot of long. stability.
When the design continues I think I will give the bow more “upsping” to make it look more radical.
.
A slightly larger version of this idea was Derek Kelsall’s Typhoon based on the Tornado
Yes I know the Typhoon, the green one is called “Monster” and a video of the rebuild can be found on youtube. It has legthened mainhull and amas. Must be 8.5m long or more.
But look at the wheight in the advertising ... it has 600kg all up, thats quite heavy!!!
Michel