RIB Dinghy on CD 22?

[MikeR]

Mike, What speed do you get with the 9.5' air floor and 6 HP (one and two people?).

Bob, I get about 16-17 mph WOT on the 6 hp Suzuki with just me on board, no gear, and using the Suzuki's internal fuel tank.

From there, weight starts affecting it pretty quickly. If I am running from a 3-gal external tank (full), have a cooler of beverages, BBQ grill, and lawn chair on board, top speed drops to about 14 mph. With 2 people aboard (200 lbs each of us), it will not get onto a fast plane, but will push water pretty good up to about 7 mph, but that is really straining the engine, so instead just run at displacement speeds with 2 people. However, I have seen others running the same boat/motor combination with 2 people and they do get up on plane - those people must be about 150 lbs each, or less.

Here's a link to a video I took during a dinghy cruise in Echo Bay last year, loafing around at about 3/4 throttle and about 10-12 mph (ideal cruise speed with one person).
http://www.c-brats.com/albums/album2585/Echo_Bay.mp4

And a few photos from the same trip:

 

[JOHN C]

Adding weight to the roof:

It is bizarre, but it can actually help. Adding weight to the roof increases the moment of inertia of the boat so the roll RATE decreases which makes for a more comfortable ride. The bad part is the obvious one that it decreases the "Oh Shit" angle - point where the boat tips over.

We went with a rib because I didn't think anything else would do well (other than a non-inflatable) with rocky and coral shores. We also needed a 9.9 kicker (to have enough power to do anything) so we got the smallest rib rated for that hp. It is stored upside down on the roof so no cradle is required.

We have a Rosborough, but it is only 2 ft. longer, but I think it is a lot heavier.

John

 

[JamesTXSD]

Adding weight to the roof:

It is bizarre, but it can actually help. Adding weight to the roof increases the moment of inertia of the boat so the roll RATE decreases which makes for a more comfortable ride. The bad part is the obvious one that it decreases the "Oh Shit" angle - point where the boat tips over.

We went with a rib because I didn't think anything else would do well (other than a non-inflatable) with rocky and coral shores. We also needed a 9.9 kicker (to have enough power to do anything) so we got the smallest rib rated for that hp. It is stored upside down on the roof so no cradle is required.

We have a Rosborough, but it is only 2 ft. longer, but I think it is a lot heavier.

John

That is a lot of weight to heft up there - how are you getting the RIB to the cabin top? Photos?

 

[DavidM]

Just thought I would relate what we plan to do about a dinghy once we buy a C-Dory 22 or 25 later this year:

We have a 25 year old Chech made 8-1/2' Hypalon roll up dinghy that we used many years ago on our first cruising sailboat. It has been through about 5 moves back and forth cross country over the years but is still quite serviceble.

We plan to keep it in the cockpit rolled up (and probably under some kind of sun cover) and then blow it up and toss it overboard when we need to use it- it only weighs about 70 lbs. We went through this drill on our first and maybe second sailboat and it worked ok. It probably only takes 5 minutes to blow it up with a DC pump and launch it.

Our dinghy use will only be in the protected waters of Floridia's Charlotte Harbor and Pine Island Sound inlets and bays so the roll up should do fine. What to do about a motor?

We have an equally old but quite serviceable Evinrude 3.5 hp two stroke. I could just keep it in the cockpit and lug it onto the dinghy after launching. It weighs about 50 lbs. Or I could store it on an O/B bracket on the transom opposite of the swim step which would make it easier to load. Is there room to do this?

I would love to have a Torqueedo Li electric O/B but the cost is daunting. Another thought is to use a trolling motor and hook up the house battery to power it. But that is probably more weight than the Evinrude to move.

Any other thoughts?

Having followed this thread I would be concerned about the difficulty of getting a heavy RIB up on the cabin roof, plus the added weight up on top. I used to hoist an RIB using the spinnaker halyard and pole up on the bow of our sailboat, but that is not an option with a C-Dory.

David

 

[ssobol]

The advantages to the trolling motor set up is that the weight is in multiple parts so you don't have to lift the whole propulsion system at once. You can also place the trolling motor battery more in the center of the boat rather than all the weight at the stern for better performance. A trolling motor is less expensive to buy and maintain and is easier to store on a small boat like a 22.

Disadvantages are probably lower top speed and needing a method of recharging the battery. Battery charging time could be long.

I have an inflatable dinghy. So far we haven't used it very much at all and just inflate it when needed. A foot pump will inflate it in about 10 minutes. I pump it up enough so it will float across the back of the cockpit then throw it in and inflate it fully from the swim step. When we do use it, rowing it works out fine and the exercise is good for me.

 

[thataway]

There are many "solutions" to the dinghy issue, and for many, the C Dory will go close enough to the shore (bow or stern) that a dinghy is never necessary. For us, with a dog, it becomes an essential because we prefer to anchor out. Just a minute ago, Marie asked me if we were taking our 3.5 hp (Merc 2 stroke) to Hontoon--and the answer was no, but probably on the Cumberland/Tennessee River trips. We use the 3.5 as a "kicker" on the 22. We do carry it on a bracket (raises and lowers) on the Stb. side (Port side is the swim step). On my Cat, I just put a bracket on the swim step, which has wing nuts (and lock washers) to hold it in place).

I predicate this with as we have aged, and had weight lifting limits of 20#, we have had to adapt to the dinghy situation in different ways. Also rowing or paddling is no longer an option due to back problems.

Most of the time we use a Torqeedo Travel 1003. We charge it when we charge our refrigerator batteries. We do have a small fresh water trolling motor, we have used on a few occasions. The problem with the small trolling motors is the size of the battery, the cables, etc...Of course it can be charged when running the main engine or off the boat's charger. A U1 AGM garden tractor battery is only 35 amp hours--about half of the group 24 which weighs about 2x. We used a U1 battery on our 12.5' RIB with both 15 and 25 hp outboards, for starting and running GPS/sounder, and lights. We did try it for short distances for the trolling motor, and it will give about half an hour--depending on speed etc...

I would think that the roll period vs the roll amount (angle) is still an issue on the narrower beam 22, than a C Dory 25 or Rossie 246. We store our 9.5' inflatable floor dinghy rolled up on the roof, until we are ready to inflate it. (either in the cockpit or on a dock.) We put the Torqeedo in the inflatable when it is blown up and on the top of the C Dory 22. We have also put the 3.5 gas motor there. One problem with the gas motor is getting the lower leg up high enough that it is not throwing spray from the wake of the 22, when the boat is heavily loaded.

Mike--thanks for the info on the 6 hp. I have always thought that a good 8 hp 2 stroke weight in the 60# area would be a good solution, but now we are close to finding antiques....Unless we could import a new one....(Yamaha 8 2 strokes are 60#)

 

[DavidM]

Yes, the way you describe is how we will handle the roll up inflatable. I am probably getting ahead of myself as we haven't bought a C-Dory yet. We close on our Punta Gorda, Fl condo in two weeks and need to get comfortable with that first.

The condo does have a dock with a power pedestal, so we will keep it there so the batteries will always be charged. My usage profile is to head down Charlotte Harbor and anchor out at Boca Grande, Cayo Costa, Useppa Island, etc for a day or so. In all cases the dinghy ride is less than 1/2 mile to the shore sometimes only a couple hundred yards.

I was thinking about upgrading the house battery to a larger Group 31 and I would use that for the trolling motor. That battery is pretty heavy- almost 70 lbs, but it is a lot easier to load up than an O/B. The trolling motor could clamp on to a bracket on the transom when not in use.

So I will probably start out with the Evinrude, see how that works and go from there.


David

 

[thataway]

David, I would not want a flooded lead acid battery in a dinghy, unless it was in a battery box...and strapped down. I have always used AGM batteries in the dinghies--even the RIB.

The group 31 upgrade is very useful. All 3 of our batteries are AGM Group 31 from Sam's club--and seem to be holding up very well. (but we run both a refer and freezer on longer trips).

 

[JOHN C]

https://mightywench.blogspot.com/2016/09/

I figure the dinghy and the motor both weigh about the same and are heavier than anything I would want to mess with by hand.

It generally takes about a half hour to launch, mount the motor, and load.

John

 

[thataway]

We managed to get the dinghy up on the roof by "hand" when we had the lighter dinghies--30# like the 7 and 8 foot slatted floor. But as we aged, we found that the Garheur Davit was the perfect solution--no power needed, and only takes a few minutes. See the photos in the "Thataway" Album about the dinghy davit and spreader bar. The Garheur davit, is fairly light, easy to put in several places on the boat if you wish, and easy to take down. Getting the lower post 12 to 15" longer will help to get the boat a little higher; we do fine with the standard 36" arm, angled up.