Catamaran tender to replace rib?

I've had cat dinghies,
they were pretty ok but crummy to row into chop for distance,
the first I had was in alu, the seat/tunnel & hull bottoms where out of 2mm checker sheet, the topsides & tunnel in 2mm sheet, transon & "bow transom" in 4mm plate, there was a tube gunnel & corner braces, also 90 degree folds formed seats & bouyancey fore & aft & a U set of folds formed a thwart also, it was a very tuff little boat. The topsides where 2400 long plus the tube gunnel & some camber cut to the top of the bow transom made it come in about 2500 long overall. Every one would borrow it, I put some rocker/ rise in the buttocks to sweeten up the run aft for oar power, rowed ok but hard work should have left it strait for power use because it did squat a bit much under power. Up the coast a couple of people took templates cos it was a good thing, would hoist aboard our 10 m cat & sit on the tramp fwd good, back in sydney another bloke wanted it but priced up a copy- came in at 3-4.5 k to have someone fabricate- so he bought a sheet punt for around 1k.
I also had tooling for a "Lamoore" style glass cat dinghy about 2.4m, was great for using up overs of glass & resin, they used to come in about 38-40kg, sold the mold because there was too much labour to make a good rate on.
What Mr Efficiency has said has truth but not absolute, the cat dinghy you could stand in one hull no prob, would take all our stores for two of us & tote water etc from the wharf & all that but like ll cats theres more structure/complication for the capacity.
if your looking for something to hang behind the cat maybe a utilty skiff like http://jwboatdesigns.co.nz/plans/trover/index.htm this but built light(mebe foam S) & around a size/length to suit might be handy, thats the style I'm thinking of for mine, I reckon the well for the outboard would be cool for while hoisting to davits between the hulls with some nice D rubber, might also be possible to have a detachable bow & stern module...

Jeff.

 

Being able to sail and row can be a great safety feature.

I remember talking to a chap who had anchored of some interesting small islands, and thought about taking his outboard powered inflatable tender, over to them.

With an offshore wind off the islands, and being by himself, and having to have total faith in his small outboard, he decided to cancel the trip, and came back and built a tender that could sail as well as row for his next trip.

 

PuddleCat

Roger Mann has designed, built and sailed a series of simple small and useful catamarans with asymmetric hulls. The smallest is a 8/9ft "puddlecat" which can be sailed, rowed and paddled - but displacement might be too low for your purpose: http://s1263.photobucket.com/user/rogermannorg/library/PuddleCat 8 or 9 footer?sort=3&page=1

 

Here is a photo I took a couple of days ago of a typical dinghy dock. How do you think an outrigger would cope? Apart from anything else, how do you board one from the bow?

I have yet to meet a cruiser who does not carry heavy loads in his dinghy at some time

Richard Woods of Woods Designs

www.sailingcatamarans.com

 

Well the more designs I see first the more ideas I have to design my own. Seems like a good small project. Call this research.

Thanks all. I only have 2 min to check this thread right now and will go through all the replies when I have time.

 

Sorry Richard w - i'm not selling something - merely making suggestions according to what the poster asked......
If what he asked for was what the average cruiser used then your product would be perfect.
That and - it says to replace RIB - all i see in your pic is ......

 

For a catamaran dinghy check the Unicat design at the following site.

http://www.brettmarinedesign.com/designs.htm

 

Put two "sit on top" kayaks together. Could be made to sail, small outboard, row, paddle, fin propulsion, good load carrying, Separate into kayaks when you want to.

 

A scaled down version of Tom Kane's rectangular plan boat in a recent thread would make a good tender imo.

 

We actually have had to use a larger Livingston to carry bigger groups-rowing I might add. It did the job. for the size it wasn't too heavy. There is more drag towing than I expected, however it did track straight. If you ever bottom a cat dinghy with a bridgedeck/tunnel the load carrying does increase with the drag. 5 full size adults don't bottom out a 10- 12 footer. While the hulls seem designed to plane the ones I see powering seem to wallow rather skim but do run above hull speed. As a low cost alternative they have some good points.

 

My inflatable has become a deflatable and I am just exploring options. The cat tender was just an idea and it does not have to be a cat.

MR E, The Shoinning designs linked easily pass my weight and load needs and I am sure will be very stable, perhaps you were thinking of something smaller?. Usually the load will be 2 people a 25kg outboard, fuel and a backpack. That is all I would take on longer exploration trips, and under this load condition it would need to perform well. Yes it is true that I will carry large loads at times, but performance only needs to be good enough to get to the main boat at slow speeds as this situation will not occur often (re provisioning etc).

Re nesting tender. I actually like the idea of an efficient rowing and sailing tender. The prob is it would have poor performance with a 10hp outboard and not be very stable. However it would be pretty perfect for the electric outboard with good speed with little power consumed. How heavy would a decent sized one be? Perhaps I might be able to run 2 tenders rather than go for compromised all in one design?

Re inflatable cat tender. These look like a lot of fun but they look very wet and still have the downside of being in(de)flatable.

RW, I like your duo design. Very light and should be good with the airbags. Looks like a good muti purpose craft. How much weight would you really save with the helium in a RIB?

Re outrigger. Thats kind of cool too, and could be a candidate if I run 2 tenders but as pointed out would be a poor primary.

Waikikin. Your cat dingies are exactly what I had in mind. Got any pics? How is rowing compared to a rib?

The puddlecat looks a little small and does not do it for me aesthetically. The brett marine designs are interesting too.

 

Seen these, dunno the weight. http://www.gumtree.com.au/s-ad/cron...drift-catamaran-hull-dinghy-3meter/1005878446
on mine the alu was a one off, pretty much scribed & cut it out one Sat morning to get the max out of 2400 x 1200 sheets, then tacked up the skin, over the next couple of weeks at end of days fun I'd weld out & fit-install seats gunnel etc.
i'd have to dig for pics & scan, the glass ones may have been similar to a markham rather than lamoore, I got the mold for 250 from a dinghy builder, built 3 boats out of the tail end of a 44 of resin b4 it went out of spec & sold the mold for 400
Jeff.
Jeff.

like this http://www.boatdesign.net/gallery/showphoto.php/photo/11471/ppuser/12438

 

Helium is less than 15% the density of air, so you can easily work out how much "buoyancy" it will give you

A more useful idea maybe to have a big nesting dinghy. Say 16ft long. Use the aft half as a pram dinghy say 10ft x 4ft for moving your big loads at slow speed, and bolt on the front pointed bit when you want to go fast. I did that once about 30 years ago, and only used a small outboard to move 4 people at 8 knots

I consider a 25hp outboard to be a big engine, especially on a dinghy. It's as big as the biggest engine I have ever owned, and that was a single main engine on my Skoota 20 powercat. My Skoota 28 has twin 20's for 16 knot speed.

So how fast do you want to go? How heavy a dinghy would you accept?

Richard Woods

 

http://www.leeroysramblings.com/johnson_E-FD_15_18hp.html

Older Evinrudes and Johnsons sold the same motor under various HP ratings according to url above. Wonder how many MFGs do that today? If you knew which motors were detuned for a lower horsepower, you could save some money buying the lower rated engine, and tune them up to their max output. Maybe?

 

Some interesting craft there in those links. I brought up this one from within your link
https://www.youtube.com/watch?v=4L11v9FCP08

I'll have to seek out a few more videos/ info from this outfit.