Please help me with my first RIB purchase and set-up

cabo35kk · 13 July 2010, 02:35

Have always carried an inflatable on my swimstep. Currently have an 8 and 1/2 foot Achilles air floor with a 3.5 Tohatsu. Time to step up for the family and get something that can pull a wakeboard, explore, etc... Will need to tow it behind my boat (Cabo 35 flybridge) and would like to be able to do 20kts or so in decent sea conditions with the tender in tow.

I am currently looking at a Nautica RIB Sport 12 with a helm, folding seat, the usual. Boat weights around low 300s w/o outboard. Dealer says to go with a Yamaha 25hp 4-stroke or a Tohotsu 30 4-stroke. Says a Yamaha F40 is overkill and probably too much weight. From those I have talked to, seems like a 25 will be sluggish with more than one or two folks on board, and that 40hp would be ideal. Have seen many RIBs around the harbor in the 12 foot size range with 40's, but maybe the motor is too heavy for this particular boat.

Would appreciate any comments or insights as to the foregoing, other options in the 11-12 foot range, issues with towing behind my boat, and anticipated performance with various hp options. Thank you in advance.

njensen · 13 July 2010, 09:44

too be sure i would go for 40HP for waterski. 25 is not enough for adults on waterski.

Nasher · 13 July 2010, 10:20

I think a 40HP 4-stroke would possibly be too heavy, and that a 25HP will not get a wakeboard 'over the hump' easily if you have some passengers as well.

When I was a skinny, spotty 14yr old, my Father had a Force4 Flatacraft with a Chrysler 35HP (2-Stroke) on the back, it just about managed to get me up out of the water on a pair of skis, but it took a while and some serious hanging on. We found that anyone larger it just didn't have the grunt to get out the water unless they were really experianced. We did used to swap props for skiing which helped.

The ideal would appear to be a lighter 35-40HP 2-stroke, but I'm not sure how much lighter 2-strokes are these days, or even how easy they are to come by in the States now.

I'd be a bit worried about towing a tender any distance at 20knts in anything but a flat sea, unless some serious modifications were carried out to the bow, or a very efficient bridle was devised to spread the loads around the boat. It's still going to crash about a bit though.

Nasher.

cabo35kk · 13 July 2010, 16:10

Nasher - Thank you. We will add two additional pad eyes on each side of the bow and construct a 3 point harness to connect to the bow of the tender.

Jizm · 13 July 2010, 18:29

I had an Avon supersort 3.4 with a Yam 25 on it, rated for 18hp. Performed very well and towed toys no problems..

RIBRyda · 14 July 2010, 07:52

Quote:

Originally Posted by Nasher

I'd be a bit worried about towing a tender any distance at 20knts in anything but a flat sea, unless some serious modifications were carried out to the bow, or a very efficient bridle was devised to spread the loads around the boat.

Just to back this up - we're in the middle of building a 10.5m cabin boat specially designed to be towed (up to 60 miles offshore for up to 48 hours transit unattended) - the entire bow area has been designed specifically to take big stainless re-inforcement both internally and externally to cope with the stresses - I realise that this is a bit more extreme, but don't underestimate the forces on the towed craft and be very careful with the length of the tow-line so that you don't end up turning the tender into a submarine in anything other than a flat calm!

9D280 · 14 July 2010, 10:11

Which is maybe why they are suggesting a smaller / lighter engine on it. Not so much for the tender's use, but more so it survives the tow.

Not sure what your Cabo's transom area loos like, but would fitting a set of davits or some clever half davit with one toob of the tendder on the swim step & the outboard one suaspended be an option?

cabo35kk · 14 July 2010, 23:00

The only way to davit a boat of this size (500lbs+) effectively is to put a hoist system on the transom and swimstep that would severely impair fishability - can't do that! The small easily removed tilt-up davit systems seem to cap out at handling a boat in the low 300 lbs. Thus, towing seems to be the only realistic option.

The additional 2 pad-eyes will have backing plates, and the bridle they intend to make will connect to the middle and side eyes, with a bit of slack on the side cables when the boat is straight so that when the boat starts to drift to one side or the other, tension will be placed on the applicable side cable which in theory should pull the boat straight again. Does this sound workable?

Ribryda - when you say be careful about the length of tow line, are you suggesting it should be longer or shorter? Please explain. I had planned on buying 150 feet of 7/16 New England Dinghy Tow Rope (which floats) and then playing with different lengths to see where it works best. Some say you need a lot of distance (up to 150 feet), while many others say something closer to 60-70 feet works best???? Any other suggestions for best tow line? Thanks.

RIBRyda · 15 July 2010, 07:08

The biggest problem you have is that individual towing setups will all have their own characteristics. Thus what works for one won't necessarily work for another.
In terms of the cable I would always tend to ensure that any cable you use doesn't have too much stretch in it, and also bear in mind that even with a light boat on tow if it suddenly gets caught in a wave and swamped you could have a snatch force on the towline of several tonnes.
The length of the towline is definitely something you will have to experiment with; the reason I mention it is that if the tow-boat is cruising at a speed which creates a following wave, obviously you don't want the tender anywhere near it - with a big towboat you could well find yourself simply dragging your tender through the middle of your own wash, with inevitable consequences - the chances are that with a tight towline the tender will plough straight through any following waves and not ride over them. Probably longer is better than shorter. (I know of 200ft towlines in similar situations)

chewy · 15 July 2010, 07:31

Quote:

Originally Posted by RIBRyda

In terms of the cable I would always tend to ensure that any cable you use doesn't have too much stretch in it,

What rope do you use?
I would have thought a nylon tow rope would have been ok as it takes some of the shock out of the tow and puts less stress on the tow points?

9D280 · 15 July 2010, 08:45

Quote:

Originally Posted by cabo35kk

The only way to davit a boat of this size (500lbs+) effectively is to put a hoist system on the transom and swimstep that would severely impair fishability - can't do that!

I maybe didn't expalin my thougt too clearly..... sit the rib at 90 Degrees to the Cabox transom. Nearest toob sits on the swim step, then support the outbord side with davits - they will only be taking half the weight, as the other half will be taken by the swim step. So if your Ribette weighs in at 500Lbs, the davits will only be looking at around 250lbs. If you use portable fuel tanks, they can be removed or put at the step side to further reduce the davit loading. Thus can use removable davits.

RIBRyda · 15 July 2010, 20:24

As usual, two ways of looking at it; bearing in mind we're talking slightly bigger boats here, steel cable - I'm assured that in a good blow, the middle of the night, raining cats and dogs, 50 miles offshore, the reassurance that the tender is still there is worth far more than a few (relatively) minor jolts on the towline!

IMHO. As always!

chewy · 16 July 2010, 07:25

Quote:

Originally Posted by RIBRyda

As usual, two ways of looking at it; bearing in mind we're talking slightly bigger boats here, steel cable - I'm assured that in a good blow, the middle of the night, raining cats and dogs, 50 miles offshore, the reassurance that the tender is still there is worth far more than a few (relatively) minor jolts on the towline!

IMHO. As always!

A fair point, I'd rather use something with some give in it though just to make sure the tender is still there and not just the D-ring you clipped it to.