Windage implications of dinghys, davits, and arches

[stormalong]

Sure, if you have an Oyster 62 or a large cat the weight hanging over the stern is insignificant. Until it gets pooped in a storm and suddenly it has a ton of water in it. Maybe it has a cover over it to prevent that and maybe the complacent captain didn't bother.

For boats under 40 feet it is totally impractical. That does not mean that it is not done. Even on my 44 footer I would not have davits.

I prefer a rollup dinghy and a 3.5 hp engine. Never tow it because eventually you will loose it or it will fill with water or flip. It lives on the cabin top when coastal cruising and gets rolled up and put in a locker for ocean passages. It is light enough to hoist with a halyard and the engine weighs 30 lbs with an internal tank - easy to carry in one hand.

I never understood the need for a planing hull dinghy with a big engine to get around locally. If you are in such a hurry why are you in a sailboat? The big engine gulps gas and requires an external fuel tank. It is expensive and attractive to thieves. My little Tohatsu is virtually theft proof.

[picklesandjesse]

The 32ft Davidson I recently bought has an arch with solar panels and it will be off asap. And we have a hard rowing dinghy that nests, will be on deck behind the mast. Maybe a larger boat can get away with it. Not a good look though and I failed to see any boats in the recent Sydney to Hobart race with arches and davits. How come ???

[mowerandy]

Got (lightweight ss tube) davits on my Adams 31 mono. Not totally impractical at all. In fact one of my favorite bits on board. Incredibly convenient in sheltered or semi-sheltered waters. Once had a hard dinghy pooped full, but the weak-links in the davit lines dropped it onto its bow rope before any damage was done. Was a crappy old dinghy I would gladly have sent to Davey Jones locker but I wanted the practice of retrieving a giant fibreglass sea anchor in heavy seas (?)...was reasonably easy in the end to haul one end out first (on the davits), then lift the stern back up. Lesson learned! We now have a roll-up 2.5m air-deck inflatable, and the dinghy is put away below or lashed on-deck in any kind of sea since a decent pooping would take out the entire cockpit and pedestal along with the helmsman.
I also have a fairly thief-proof 3.5 Toey. Lots a power for weight out of those little motors. Mine hasn't pumped water in about 15 years and the water jackets are all bursting off the powerhead with corrosion and salt. Goes like a jolly rocket though, on the original spark plug no less, and I never have to flush it - hahaha. That was the problem in the first place (going back out in a coupla days - no need to flush it - wrong). It can idle all day and manage short bursts of full stick without cooking, which is all a dinghy of mine needs, but it looks like a bag of crap! Starts first time tho.
I will say that a davit hung dinghy on a small boat can stop you heaving-to due to the windage astern, but I figure if you might need to heave-to then it shouldn't be there in the first place. If hard on the wind it might affect performance in a small boat, but I cant say I have noticed, and it is a snap to put away a roll-up anyway. Can lift it into the cockpit or foredeck easily, dump the air and roll it, or just trample it underfoot until opportunity to roll it up presents

[a64pilot]

I want a big, fast dinghy so we can anchor further out away from the tiki bar music and away from thieves if there are any, and to travel distances that are further than you can in a non planing dinghy.
Tomorrow we plan to snorkel a reef here, it has mooring balls, and a 21’ Boat size limit on the balls, Anchorage is a mile or two away, our dinghy is good for that.
Then we have two folding Dahon Mariner bikes, it takes a big dinghy to carry them and the two of us.
Sometimes we may carry another couple, that takes a big dinghy.
We like to get into town with a dry butt, often that takes a big, planning dinghy.
Yesterday we resupplied at Maxwell’s in Marsh Harbor, it took a big dinghy to carry all the supplies.

There is nothing at all wrong with a small dinghy, but I can tell you that often having the biggest dinghy you can carry, with the biggest motor it can take, is a nice thing to have.
This on a 38’ Boat.

[daletournier]

I like my davits and keep the dinghy on them while coastal. Passage making the dinghy is secured forward of the mast on deck. I know people that cross oceans with their dinghy on davits, this isn't for me, when things go bad it would just be one more thing I'd have to worry about.

I have the luxury of two outboards, 1x 3.3hp and the 15hp. Mostly use the little one, just so convenient. When in a good diving area I use the 15hp.

[Tillsbury]

I too hate davits. I’m currently building an 11ft Spindrift nesting sailing dinghy which will have a home on the foredeck, and waiting for a local dealer to find me either a Torqueedo 1103 or an epropulsion spirit. We have a small inflatable as a secondary dinghy, and an electric inflator so packing it away each time is no big deal.. I am going to enjoy ditching the outboard on the rail and the petrol can.

[daletournier]

I'm not sure what's to hate? Use them in an anchorage because they are just so convenient and don't use them when underway if you feel they are an issue. Best of both worlds.

[thinwater]

I hope it is obvious that it largely boils down to the boat. The cats and larger monos truly do NOT feel the presence of a dinghy on davits. The weight is minor in the case of larger monos, and should have been allowed for in the design, and it is definitely a part of the original design in the big cats. Heck, removing the dinghy and davits would through them off, in a sense. The dinghy rests nicely protected, tucked between the hulls.

(Look at the avitar. Can you see the davits from this angle? No. Then how could they be a big deal to windward?)

My cat had davits, they were very nice, and I couldn't tell if the dinghy was there or not. In 10 years a wave never touched the dinghy. My current boat is smaller and I use a kayak. You see, it is about horses for courses. It's also about recognizing what boat you have, what it is, and what it is not.

[Don C L]

Originally Posted by Jammer

I see so many larger cruising boats that are set up with arches and davits, sometimes a dinghy in the davits, and it seems to me that there must be so much windage that the upwind ability of the boat is severely compromised.

Like most things, it depends. It depends on the boat, (mostly the size of the boat,) and where you are cruising and what kind of wind/sea state you expect to see. Will hanging a large heavy object off the stern of a boat affect its performance? Of course. And that effect will increase dramatically according to wind speed. It is drag and anything that slows a boat down doesn't do its upwind ability any good. The drag or windage also contributes to the stern being pushed away from the wind, yielding more weather helm. On a larger boat, the effect is harder to notice, true. And then there is the exposure to larger waves too. But, I have seen folks around here putting up with those negatives in favor of the convenience of having the RIB ready to go. And if you are just hopping from anchorage to anchorage, in mild weather, or if you have larger boat, that's probably fine. But even where I am, where it's only 25 miles or so across a channel from islands to mainland, I wouldn't risk it, due the the weather that can develop here. But that's just me. In my younger years I also fancied towing the dinghy, until I tried it on a day that turned windier and rougher than I had expected. That was a mistake. Now I am inclined to secure, strap and streamline everything before leaving a nice calm anchorage heading out into less than calm conditions. Just because it is coastal doesn't mean you can't get into big trouble.

[danielamartindm]

Originally Posted by thinwater

I hope it is obvious that it largely boils down to the boat. The cats and larger monos truly do NOT feel the presence of a dinghy on davits. The weight is minor in the case of larger monos, and should have been allowed for in the design, and it is definitely a part of the original design in the big cats. Heck, removing the dinghy and davits would through them off, in a sense. The dinghy rests nicely protected, tucked between the hulls.

(Look at the avitar. Can you see the davits from this angle? No. Then how could they be a big deal to windward?)

My cat had davits, they were very nice, and I couldn't tell if the dinghy was there or not. In 10 years a wave never touched the dinghy. My current boat is smaller and I use a kayak. You see, it is about horses for courses. It's also about recognizing what boat you have, what it is, and what it is not.

True that. A few posters have talked about preferring weight forward rather than aft, which simply doesn't apply to cats, and adverse windage effects upon pointing. While pointing is a real consideration in performance cats, condomarans are not pointing machines, and the sailing techniques of those who own them have a way of being shaped by that reality. Unless they find themselves running in breaking seas, cat owners tend to worry more about slowing their vessels to avoid burying the bows than being pooped. The penchant for davits in cat designs reflects these realities imho.

[Dockhead]

Originally Posted by jrbogie

It sure as hell does slow the boat when sailing to weather.

Indeed it does.


I carried an Avon 340 and 25hp outboard, wheel steered, in davits on my boat for a number of years. The windage is considerable. And actually beneficial at anchor as the dinghy in davits shifts the center of pressure back enough to stabilize the boat at anchor.



My cruising pattern in those days required me to sail 1500 miles every year against the prevailing wind, so hard on the wind or tacking for 1500 miles, and the dingy in davits was a big hindrance.



Another disadvantage is all that weight so high above the CG, so much weight aft, which are bad for stability and polar moment of inertia.


Yet another disadvantage is being dependent on davits. Mine were troublesome, and if they broke you were up the creek, as there was no other way to carry the dinghy.


And finally, the structural issues, all that weight swinging around in a seaway, bolts working loose, stuff cracking, wear on the dinghy if you can't keep it from moving, etc. etc. etc.




So I finally decided not to carry a dinghy in davits on passage. I got rid of the big Avon and downsized to a folding Avon Lite 310 with smaller, portable, tiller steered engine. I downsized the davits from big electric ones to smaller manual ones. Now I fold up the dinghy and put it in its bag and strap it down on the foredeck on passage. It makes a noticeable positive difference in how the boat sails and moves.


Gunkholing around I lift the dink with motor on the davits. The much lighter combo is far easier to handle in this mode as well.


Downside is the smaller dink is slower, less capacious, and less seaworthy, but it's good enough for my use (which included heavy usage during a whole summer in the Arctic, ferrying climbers and gear to and from the shore).



And a delightful, totally unexpected bonus was that the process of deflating, folding and stowing the folding dink, which I expected to be a huge PITA, is extremely simple and quick, and is not much trouble even single handed. So easy that I don't actually use the davits all that much. The only awkward part of this process is getting the motor on and off (I don't have a motor davit). I'm considering acquiring a Torqeedo for short distance ferrying duty (90% of my dink usage), to eliminate that problem, keeping the petrol outboard for other kinds of usage.




Unfortunately Avon is gone and this particular RIB is no longer available. The F Rib, made in Russia, looks well designed, but I believe it's PVC? I'm not sure what I would buy today if I had to replace mine. But the idea of a folding RIB is terrific.

[nhschneider]

I joke that our boat was built around our davits, which were made by Cooney Marine http://www.cooneymarine.co.uk/pages/davits.html and installed by the yard that built our boat. These davits have been very reliable and convenient.

In our cruising experience, it has been common for us to launch and retrieve our dinghy multiple times in a single day. Since we choose to NEVER tow our dinghy, lifting it easily into its home on the davits makes exploring new places a 30-second effort.

Since our rig has an inner forestay, we have no choice but to stow our 3.1m RIB on our davits, even for blue water passages. We are aware that if the do-do hits the fan, we might have to sacrifice the dinghy and cut it loose but in our recently-completed circumnavigation, we never came close to any conditions that were even close. Furthermore, when Jimmy Cornell designed Aventura IV, he equipped it with davits and kept his RIB there during his third circumnavigation.

Finally, we have two outboards - a 5hp and a 15hp. In many of the places where we have anchored we felt that the 5hp would have been at best uncomfortable and at worst unsafe. On the other hand, we’ve gone for months at a time only using the 5hp.

Fair winds and calm seas.

[P3sailor]

Never been on a monohull with davits but have been on a cat with them and I will say they were convenient. Having observed many many mono's with davits installed by folks other than the manufacturer I have to wonder about the structural integrity of the installation. Many look flimsy, in my opinion, and makes one wonder how long they would last when sailing in heavy weather, particularly with following seas, not to mention the the effect they have on an autopilot or the person at the helm. That's a pretty good sized basket hanging off the stern and has to affect how the boat handles. JMHO!

[wingssail]

Originally Posted by billknny

Jammer,

I agree with your thoughts that dinghies on davits while sailing is just a BAD idea, for lots of reasons. So much so that when we installed our arch to hold our solar panels we skipped the nominal additional cost of the davits. The only reason to have a dinghy on davits is for connivance--there is nothing that is better about it. It worse for windage. It is WAY worse for weight distribution, it is less safe for the dinghy. Other than being easy, I can't think of a good reason to do it.

One of our objectives has always been "clean decks." One is just plain esthetics. We do not want to be the boat that pulls into the anchorage, and the first thought anyone has is "liveaboard cruiser" because of all the crap on deck. But I have also been in weather bad enough that tons of green water swept across the decks for days. It is not where my dinghy, or anything else, should be. I have had stanchions ripped out by the force of water hitting a fairly small solar panel. I can only imagine what happens with the kayaks and SUPs that people seem to hang on their rails these days.

To square the circle of having a dinghy with reasonable performance, but still could be put away safely we chose a 10.5 foot folding RIB. It has been our "get around" for three years of full time cruising, and if it exploded tomorrow, I'd go the same way again in a heart beat.

It folds into a package that is small enough that it can drop into our stern locker, for passages, or be tied down on the aft deck for day sails. It is out of the way both physically and visually. We have an electric inflator that makes it fast and easy enough to inflate that we don't hesitate to let the air out and fold it up when ever we move the boat.

If we need to hoist it out of the water while at anchor, we use a three point harness and a halyard, and bring it to the rail. Just as quick, easy and secure as davits.

So... while we might have signed on to the 15HP RIB lifestyle... we found a way to do it without compromise to our yacht's sailing ability and good looks.

EVERTHING he said, and more, and twice over.

It's weight aloft, which you don't need (loss of stability).

It's weight it the ends of the boat, adds to pitching (slow).

It's windage for anything wind ahead of beam (slow).

It's safety factor in heavy weather (which emphasizes all the above).

It COMPLICATES windvane installation.

It looks ugly.

YES, a big rib with a big motor is great. So is a car, but IF we like sailing we'll chose that which makes us a better sailboat. If we don't care about sailing, we'll hang all sorts of junk up there. This is all about your priorities. We are sailors.

We chose a inflatable with a inflatable floor and a 15hp motor, both of which stow below deck, and we hoist them quickly and easily with a spinnaker halyard (going below though a bow hatch). With the spin halyard led to a big primary winch we can fling the dingy up to deck level in about 60 seconds from arriving back at the boat. We can sail with the dingy and motor on the foredeck but rarely do.

With decks clean and no monstrous structure aft we are always prepared for rough weather, and with clean decks, it does not bother us much.

[Pilot2]

Originally Posted by billknny

Jammer,...
So... while we might have signed on to the 15HP RIB lifestyle... we found a way to do it without compromise to our yacht's sailing ability and good looks.

Which RIB and motor brand did you settle on?