building new amas/floats from recycled beachcat hulls

Thanks SolGato, that's a really good idea I hadn't seen or thought of.

 

You’re welcome.

Don’t know what it will get you, but I have owned a handful of classic Hobie Cats and know that the flange is pretty thick.

I tried to find the photo album of a Farrier Tramp owner who documented their modifications to pass along for reference, but unfortunately I can’t find it.

On the Tramp the hull to deck joint is just sandwiched with glue and stapled together with a rub rail slipped over it.

I think the main reason the Hobie’s have a nice curved thick flange is so you can hike out and stand on/against it when flying a hull. Was much easier and comfortable to do this on my old Hobie Cats than on my newer super slippery roto-molded smooth plastic models. Easier to right as well. On my new boats I often slip off a few times before getting my footing right.

Otherwise for your project, I don’t see why you couldn’t cut it off completely and glass it over smooth.

 

I guess it will remove 3 to 5 kgs from each amas, I'll weigh the offcuts, but any weight loss is going to help.

 

Sounds worthwhile. IMO being a little heavy up there isn’t the worst thing. I’ve sailed with a good amount of water in my amas and it actually smoothed out the ride in rougher conditions on a small boat that otherwise got tossed around pretty good. Lots of older designs have smaller displacement low volume hulls that probably came in over weight when all was said and done. I guess it all depends on where and how you like to sail.

For example sailing a Classic Hobie feels like you are sailing through the water with their relatively heavy low volume big rocker hulls, and the boat even when flying a hull feels planted and stays pointed well.

In comparison, my new high volume lightweight HDPE hulls feel like they are riding on top of the water. They bounce around a lot and require a lot more input to stay pointed, although their built in low aspect keels do an excellent job when they remain in the water considering what little wetted surface they provide.

Anyway, I know high volume hulls on Trimarans are the new norm and that later versions of the Tremolino (that is what you are building these for? Looks like a main Trem hull in background) adopted this philosophy with well proven results, but the original design worked pretty damn good.

I almost bought a project Tremolino a few years back just because I felt bad that it had been sitting in disrepair. Unfortunately a number of the original corner castings were cracked and unrepairable, and the trailer was a disaster. I thought perhaps the corner castings were borrowed from a Hobie as well, but when I compared them to my stash of parts, I realized they were specialized.

 

Good to hear that weight had some benefits, it's building in extra safety factors that I get distracted with, I'll be sailing solo mostly and want to explore the coast, sometimes overnight stops and 3 day runs. My level of experience means I can sail for 3 hour stints going at 10 + knots comfortably. My logic is that if I don't scare myself getting into conditions I can't manage this will be a long term pastime, but it's been more theory than practise now for 2 Covid years, my balance is out.

I really enjoy design and don't mind the work... time permitting,..
I know the local weather and waters well, the trem needs a little adjusting to help me , it is a very forgiving craft to sail already and I enjoy quick relaxed sailing. Surfing, camping,exploring, I don't need to carry much weight and the seating is very comfortable.
There are so many good ideas and insights on this forum I have forgotten more than I've learned. Thanks for the insight SolGato.

 

I hear ya. Yes, it’s easy to get distracted and wrapped up in doing what’s best.

You’re so far into it (I can appreciate the work) that it’s my opinion that you should carry on and make the best out of what you are working with as I believe any good designer should rise to the challenge of making the best out of what they have, later taking what they’ve learned and applying it to designs that may follow.

Most of the boats I’ve built use hulls that were either given to me, salvaged or were within project budget (aka cheap). I prefer to spend my time battling the rest of the design elements.

For your planned use, I think you’ll be okay if you continue to be mindful about weight and take every opportunity you have to reduce it.

If however your plans were to load the boat up with your family, travel in unfamiliar waters, set speed records, or be able to leave the sail plan up and take an 8 hour nap, I’d be preaching for an extra margin of safety.

You’ll get this done and back in the water to enjoy, and eventually you will meet the design limits of your modifications and the boat and either be happy, or long for more or maybe even less.

I’ve had quite a few conversations with owners of faster, modern, more complicated multihulls that get to a point where they really miss the simplicity of their first boat and say they would be happy with a slower less exhilarating sailing experience if it meant a little more space, a less stressful sailing experience, easier maintenance and rigging, etc..

One thing I considered doing with the Tremolino project I thought about buying, was using my Hobie Getaway hulls on it for Amas, mainly because its original Hobie hulls had delam issues, and spent some time wondering what results that would produce.

One Farrier Tramp owner has modified his with Super Cat (if I’m not mistaken) hulls for Amas and a twin rudders setup. I think he might have also modified the transom. His goal being more speed of course.

 

Thanks for the insight SolGato, Being an easy to use low maintenance boat with simple affordable parts that is effectively a micro cruiser with good pointing ability is the main part of my SOR. I gave up on trying to entice my wife onboard a few years ago. I want to get back to sailing along on a sound boat being surprised by the dopey grin on my face. I remember you discussing that Trem and toying with the idea of Getaway hulls now.

 

The pivot point was intended to be 6ft from the ground, the boom being a factor

The crank handle was an add on you can stick on a model without building the complexity, but it could just turn blocks etc.
The pivot point is interesting because it could also allow for the beams to slide up and down for trailering, berth s etc.

The arms need to be higher from the waterline and have less windage but there are limits to making a quick model and I am mainly interested in the folding mechanism.

Aluminium mast wont bend that much I don't think but a couple of cut and welds might work , the beams would need to be doubled up alongside for them to have much hope of lifting that weight.

I'm chasing weight down the rabbit hole by extending the bows and stripping any excess from the amas/floats. ha doomed, it's a cruiser not a racer but still.

The boat has to be attractive enough to be in keeping with it's roots.

 

Could you point out the design decisions for each of the features shown in the model above.
I don't quite know what to think about what I see.

For example, why does the ama folding pivot need to be at 6' above the ground?
How much beam would you have and how much beam reduction would you get?
More to come.

 

The two main reasons are so that a 20ft beam could be achieved simply, 7ft for the seat area, 6ft for each beam after the axis /pivot point, 19 ft, so close. The angle of the float/amas and its own beam will add more width.

Even though that much beam requires a lot more strength in the beams the risk of beam capsize is less.

The 2nd is so that folded the amas are close to the same depth as the centre hull/aka for trailering the beams will only need to slide up the axis point a few feet or less.

Scaled this model is too wide in the seating area by about 18"/450mm I think.

Explanations will be a little obscured until I'm using the correct terminology, apologies to those that find it annoying.

 

So are you trying to reduce the beam for trailering by pivoting the ama/crossarm?
How will you "slide (the beams) up the axis point a few feet?

 

The model just lashes the intersection together , if a fibreglass mould was fabricated instead the top half[cap] of the section of the pivot could be loosened by backing off the4[?] bolts that hold it down each side of the beam, so 16 for the four points. Stopping the sliding from jamming would be an issue , marking rings could be painted on the beams to indicate it sliding evenly.

If the fabricated pivot sections extend each side of the longitudinal "axel" they will be assisting the areas with the most load.
The blocks of foam on the "cabin" tops are only there to assist the model, beam end strap latches would be a likely locate and secure mechanism.

 

how about some sketches on how these points would be built.
Sounds extremely difficult to "slide" the outer beams up the inner beam pivot points.
Are you going to do this while the boat is on a trailer?

 

On the trailer would require winching, My guess is that the floats would be partially open position entering and leaving the water. I haven't put as much time into this aspect because it only became evident to me when the model was built. The scaling isn't exact at all, one possibility is raising the landing height of the centre hull on the trailer, but that has its own issues.

 

KISS. do you want to sail or fix s**t.