Water spray from dinghy

I had trouble with our Cutwater 30 and the RIB on Weaver Davits. Above about 12 knots, a lot of water was hitting the lower port side of the tubes, enough to knock the strut off the the transom and make me afraid for the life of this little boat (the RIB). I trimmed the bow down, trimmed the port up a little, all to no avail. I finally slowed her down and am afraid that towing her might be a better option. No outboard.

The Cutwater is new to us, and this was our maiden voyage with the RIB. To Roche Harbot at 6 knots, back limited to 10-12.

Any suggestions?
 
Bel Canto: Try the extra straps I discussed in my earlier post above. I had the exact same problem as you describe and these straps solved it. They need to be attached to the rigid hull and pulled tight enough to lift the dinghy several inches higher and pin it to the stays and Davies. The should be very little movement.
 
I'm not sure why it would lift the RIB. I always run with what I would call spring lines to stabilize the dinghy. Bow eye and stern eye. It just keeps it from rocking side to side.
 
I agree it is not obvious that it would lift the RIB but it does if the rail connection of the spring lines are higher than the RIB connections and you attach to the Rigid part of the RIB and tighten it enough. Ivan Guzman from Ranger Tugs told me to make them very tight. I had to reconfigure my spring lines to do this.

The RIB tubes are somewhat soft even if you overinflate them a bit. The weaver yokes mount on this soft tube. The softness of the tube and the yoke design allows the angle of the yoke relative to the RIB and Tug to vary considerably. The weight of the RIB causes the yoke to press into the soft tube at a low angle resulting in the RIB sitting just low enough for the stern extension of the tube to hit the water at higher speeds. This causes the RIB to bounce and swing side to side. Each time the RIB swings back to port it compresses the tube more and hits the water again even more violently. While we never had a stay (strut) become detached we were concerned it might and the RIB hit the RIB motor on the swim rail and dinged it up a bit.

We also had spring lines attached previously when this occurred but they were not tight enough or in the correct position. They were not attached to the rigid part of the hull and were not attached low enough on the RIB. By moving the springs to the inside bow eye and lower stern eye and up to the tug rail I was able to get the lift described. This upward and forward force changes the pressure point on the weaver yokes such that they sit at a different angle relative to the RIB and tug and thus lifting the RIB almost two inches. For our boat this was just enough to keep the RIB from hitting the water at all speeds.

Since your boat is different this may not be enough. It sounds like you are already connecting the spring lines to the correct location on the RIB if you are on the inside bow eye and the lower (when tipped up) stern eye. If you pull and lift the RIB tight enough to the stern rail you should notice the RIB lift significantly as the yokes change their position. You may have to actually lift the RIB yourself while tighening the spring lines to get this effect. The spring lines have to be really really tight.
Also the spring lines should not cross each other. I was doing this before and it allows the RIB to rotate around the cross point causing less stability. Mine are connected to the rail at the vertical rail mounts which are about 18" apart.

You may also want to check that your RIB is centered on the swim step. Ours sits about 2 inches to port. Not sure why, but since I was successful getting the RIB not to hit the water I plan on leaving it where it is. If yours is off center as well you could move the Davits to starboard a bit. The bow of the RIB has more clearance due to curve so it can sit further starboard without a problem.
 
The davits are a little off of center, but the boat sits symmetrically on the stern. I needed to make sure it didn't stick out as we are already a "wide load" and didn't want to paint outside these lines. My springs are on the swim step cleats (cute little things). I will try to spring her to the rail (not while on the highway), which, as you said, should lift her a little.
 
Great. I'll post some pictures when I get back to the boat. Let me know how it works for you.
 
We have towed many little boats many miles. However, only at sailboat speeds. Our 14 foot RIB with a 50 HP Honda (about 1000 lbs) slowed us down a half knot. The fun of the RIB made up for it.

A lot of people tow their boats with too short a line. I prefer a stretchy yachtbraid, as you can tie proper knots. Many recommend polypropylene. Attach a couple of floats to yachtbraid to keep it from fouling a prop. When going slow, anywhere, but especially when coming to a dock or mooring, either tie off very short or side tie. Don't store anything in the dingy, I would include oars and thwarts. I prefer to remove the outboard also. Place a light on the dinghy if you plan to operate at night and make it the responsibility for one crew member to look back every so often. Remember, at 20 knots, three minutes is a mile. Also be wary of wives that want their husbands to ride in the dinghy to make sure it won't get lost. I learned that lesson the hard way.

Weaver davits, like everything boating, are a compromise. Some good, some bad, some funny.
 
OK, I posted some photos in my photo gallery (and linked to them below) to show how to solve the dinghy stability/ water spray problem.

A few key comments:
The springs need to be substantial.
The springs need to connect to the Rigid part of the RIB.
The other end of the springs need to connect directly to the tug or tug rail. The swim rail is not strong enough.
The tug end of the springs need to be higher than the RIB end.
The springs need to be really really tight such that they lift the RIB significantly.
You need to lift the RIB as you tighten the springs. Just pulling on the springs till they are tight is not sufficient.
When correctly done the RIB should have very little ability to rock back and forth and should be sitting significantly higher above the swim step and should not hit the water at any speed.

Starboard spring.

Port spring

Weaver yoke angle without spring

Weaver yoke angle with spring

Dinghy swimstep gap without spring

Dinghy/swimstep gap with spring
 
What would happen if I reversed the dinghy mount on the tube? It looks as if it would also raise the dinghy. I will take a look at it next time I go to storage.
 
Interesting idea to reverse the yokes. It wouldn't be hard to try. It may make it difficult to dock however. It may also bring the dinghy so close to the swim rail that there is interference. Worth a try.
 
The other issue I am concerned about are the Weaver struts. If I lift the boat too high, they won't be long enough. Perhaps I won't need them with the ratchet straps. It's frustrating being 100s of miles from the water. It's all theory until I get out there, then , it's too late.
 
You should have no problem with the strut length. They have plenty of length adjustment and you can also just lean the dinghy a bit more towards the stern of the boat.

You absolutely still need to use the struts even with the straps. The straps need something to pin against to lock the dinghy tightly in place.
 
I recently talked to one of the factory guys about this, and he said be careful not to trim the bow down too far or the trim tabs will create a large wave behind the step, leading to more spray.
 
I had the same problem with my R27. When we bought the R-29 CB we went to a Highfield dinghy with the heavy weaver standoffs on the 4" weaver brackets. The heavy standoffs are mounted to the aluminum tub/body of the dinghy, not the tubes, so even if the tube were to deflate the dinghy stays up and high and dry. We have had no deflation issues with the Highfield and the 17" tubes give us a dry safe ride and lots of capacity. Got the dinghy at Ballard Inflatables. Ed is unusual, but knows his business.
 
I did place the Weaver yokes upside down. I asked a number of my neighbors to look at it to tell me why it was a bad idea, and had no negative comments. The dingy did seem to lift a couple of inches, and if anything, is easier to get back on the davits. I think it helped.
 
What size dinghy do you have? My C30 has a 270 and my brackets have zero step up, made special, so it sits 4" lower than yours. No issues with splash from the wake. I believe the Cutwater suggested dinghy is a 310. I do enjoy not having as much side overhang for docking and the brackets are much more flush with my yokes for attaching.

Kip
 
Ok so I have a new dinghy. I need to stick on new weaver yokes. Any advice for placement to raise the height of the dinghy to avoid these problems? What do you mean by upside down?
 
Cutwater28GG":2b5t21ui said:
Ok so I have a new dinghy. I need to stick on new weaver yokes. Any advice for placement to raise the height of the dinghy to avoid these problems? What do you mean by upside down?
Click to expand...

The yokes are the metal brackets that are installed in the pads that are glued on the inflatable's tube. What was talked about in this post is to install the yokes 180 degrees to the manufactures instructions. Instead of sliding them down in the pads, slide them up in the pads.

If you have a 8'6" RIB Use the suggestion that ( Red Raven ) Curt gave me. If you have the stern of the RIB on the port side. Offset the Rib so that only 2" is past the port side of the boats hull. I took a long straight edge, laid it against the hull and used that has my reverence point. The end of the RIB tube is 2" past this point. The Transom is 8'1" wide (26'Cutwater) same has 28'. This makes the bow section of the Rib hang over 3" starboard side. The bow section of the RIB is curved up so it is higher. It took me a afternoon to measure and put a plan together. Proper placement of glue on pads to the Rib. Installation of the brackets on the swim platform. I am happy with the results. I did get a some get some water splashing hitting the bow section of the RIB at WOT. but not bad. I have a 8'10" RIB so the bow section as a 7" over hang starboard side. I took Curt's advise on fixing that by using ratchet strap attached to a lifting eye at bow section of Rib and attached to cockpit stern rail. I snug it up and this lifts the bow approx 2"
Brian Brown
26 Cutwater 26
PORT-A-GEE

 
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