Dory Floatation

[Fritz Koschmann]

I have recently completed a Bolger Stretched Light Dory. It is 19'6" ,okoume ply, and has no provision for sail or outboard power. Only recently I realized that there is no built-in floatation. This seems unusual and I would think that floatation would be a USCG requirement. Perhaps a couple of round bouys tied fore and aft would be the best. Any suggestions or clarifications?

[paladin]

Take the weight of the unit, figure about 55 pounds per cubic feet for flotation, and add it in whatever manner you choose. Small fenders work. If the boat is wood it will float except for the heavier materials in use. You shouldn't need much, just enough to keep peoples afloat.

[Thorne]

No, there is no required flotation for this type of boat unless it is made for resale -- and the design can be built outside of the USofA so the USCG need not be involved.

Do some research on flotation and recovering swamped boats, as that will determine what you put in the boat. If you row with others or know of rowers at a marina or yacht club, go ask 'em -- nothing like direct experience in local waters!

Some folks want to be able to bail out a swamped boat, climb back aboard and go on their merry way. For this option you'll have to carry a lot of flotation, have the oars and locks lashed to the boat, probably carry a rope ladder/boarding device, and be physically able to climb over the side from the water (much harder than you would think).

You may even find that you want to add decking with flotation at the bow, stern, and side-decks -- you see this modification done on light pulling boats that are used offshore sometimes, as the decks can keep the boat a lot dryer as well as provide true recovery from swamping.

Here's a photo of Art Parker's Herreshoff Rowboat, modified for use in Puget Sound with decking -


Others just want the boat to stay upright in tumbling seas or swells -- aka "not sink or turn turtle". The fenders or flotation bags will work for this option.

It all depends on the type of boating you'll be doing, your tolerance for the additional weight and bulk of flotation and/or decking, etc. If you don't row far offshore, and the water is really cold, you may not want to faff around with flotation -- by the time you got the boat bailed out and climbed back aboard you'd be hypothermic. It never ceases to amaze me just how much water a boat can hold!

Much better to swim to shore and get someone to tow the boat in for recovery in those conditions...

[boatbear]

Fritz, I have a compartment at each end of my dory, and they are filled with empty soft drink (soda) bottles. That's a couple of cubic feet of trapped air at each end. I've only ever swamped the boat once, and the boat didn't sink. (My ex-wife and my girlfriend were among the crew and helped bail with their champagne flutes. It was mid summer and a good time was had by all).

A local friend sailed his 14' dory under a few years ago. He didn't have any flotation installed and was using about 40Kg of cast iron blocks for ballast. Fortunately his wife (a very strong swimmer) was aboard and was able to hold the boat up while he swam down to throw out the ballast. It is good to consider what can go wrong when boating. Pragmatic pessimism works for me.

I'll add to Thorne's excellent advice above, that to bail out a boat you will need a bucket, securely lashed to the boat. It is good to have a flattish bailing device as well. I use a cut-down 5 litre oil container.

[adampet]

I have the 15'6 version and don't carry flotation. I gave it the swamp test in warm fresh water and came to the conclusion I wasn't going to be able to bail it enough to get back in. It will float by itself, assuming the anchor isn't too heavy. It needs to get to shore and dumped out. This is one of the reasons I don't go alone in the winter, carry a complete change of clothes in a dry bag, and don't carry extra weight in the boat.
That said I've been out in conditions that I probably shouldn't have. Wind against the tide creates some really fun standing waves in places around here. I also don't often brave the surf of the inlets. It's possible with the right conditions. Going out usually isn't the problem.....

So, try a planned capsize and see what happens. Your idea about round bouys may just be the ticket.

Adam

[ahp]

A simple thing to do is to cut flotation blocks to fit under each seat. Secure to the underside of the seat and not touching either the sides or the bottom.

[TerryLL]

Fritz,
I see you are in Gustavus. Don't know how long you've been there, but you absolutely positively do not want to swamp this boat in those waters, unless you're wearing a survival suit. By the time you get it bailed you'll be severely hypothermic, if you're lucky. I lived 25 years in Sitka and knew way too many who did not survive a quick dunking.

[Fritz Koschmann]

Thanks for all the suggestions. At this point I think it will work very well to attach a couple of plastic floats (fenders) for and aft. maybe sometime in the future add decks fore and aft but I hate to add the weight.

Terry,
I grew up in Sitka, late 50's- early 60's. I spent most of the summers rowing little boats in front of Sheldon Jackson, where my father worked, and the area that is now Cresent Harbor. I know how cold the water is, I spent 20 minutes or so in the water a couple years ago after my dinghy overturned. Luckily I had a float coat on or I would be dead. I do remember swimming (purposely) quite a bit when I was a kid in Sitka though, maybe my tolerance was greater then.

[Thorne]

That Bolger Light Dory isn't the most stable boat around, so I can see why you are concerned about recovering from a capsize. You may have to either stay in sheltered areas near the shore, or consider a more seaworthy but slower craft...

[Peter Eikenberry]

Look here for flotation standards http://newboatbuilders.com/pages/flot1.html The boat itself probably doesn't need any flotation. Since it has no motor it doesn't need flotation to support the motor. It may need flotation to support the persons capacity.

here's the formula for calculating flotation for persons weight. There are two. One for persons weight over 550 lbs and one for under 550 lbs.

If you need this in metric I can give it too you.

Fp = flotation for persons in cubic feet
Wp = persons weight in pounds
Wdw = dead weight. Since you don't have an engine deadweight = zero

Flotation for persons Weight (Fp): over 550 lb persons capacity
F p = (0.5 X 550) + 0.125(Wp-550) + .25(Wdw) / 60.4
= 275 + ______ + _____ /60.4 =________

For boats with less than 550 lb persons capacity
Fp = (0.5 X Wp) + .25 (Wdw) /60.4 = Fp = _____ + _____ / 60.4 =________

You may be able to actually subtract some from that for boats that are wood. Here is the formula for flotation to support the boat. For a wood boat it should be negative which means it is buoyant. -0.81 is the buoyancy factor for plywood.

Boat weight (Wb) = ( ____ X K -0.81 ) =_______

Flotation for Boat Weight (Fb) = (Wb ) / 60.4 =
(cubic feet of 2 lb density closed cell foam)
=Fb /60.4 =________


By the way Flotation doesn't have to be foam. It can be airchambers on a non powered boat with no penalty for air chambers. It can be balsa or whatever. You just need to use a different factor instead of 60.4. For airchambers it's 62.4
If you ave questions send me a private message

[Daniel Noyes]

Fritz,
I see you are in Gustavus. Don't know how long you've been there, but you absolutely positively do not want to swamp this boat in those waters, unless you're wearing a survival suit. By the time you get it bailed you'll be severely hypothermic, if you're lucky. I lived 25 years in Sitka and knew way too many who did not survive a quick dunking.

yeah what terry said, dont flip to begin with.
We do rollover drills each year at the Rings Island Rowing club and we use our gull. you can get some water out by sloshing the boat fore and aft, the water will sluice out over the raked transom, The boat sits too low to bail successfully in choppy, wavey water, flotation down low near the floor will help the most.
I would suggest making up some floor boards out of 2" thick blue foam insulation and a layer of door skin ply epoxied or guled on either side, screw these down with cleats between to alow air circulation between the bottom and the foam. And your problems arent over even if you get back in and the boat bailed, then you have to get back to shelter and get warm, the dry bag with heavy warm clothing is a great idea.
Dan
http://dansdories.googlepages.com

[Fritz Koschmann]

Daniel,

You suggest floatation down low. My understanding has been that floatation placed too low can cause a boat to want to turn turtle when swamped. It would be relatively simple to enclose the space on my dory just forward of the forward frame and aft of the aft frame and even with the tops of the frames. This would place floatation against the floor as low as you could get it which caused me to rethink the idea because of the problem I mentioned above. Is my assumption wrong?

[Bob Cleek]

That's sure a pretty Herreshoff pulling boat, Thorne, but what does he do with THREE oars?

[Ben Fuller]

Daniel,

You suggest floatation down low. My understanding has been that floatation placed too low can cause a boat to want to turn turtle when swamped. It would be relatively simple to enclose the space on my dory just forward of the forward frame and aft of the aft frame and even with the tops of the frames. This would place floatation against the floor as low as you could get it which caused me to rethink the idea because of the problem I mentioned above. Is my assumption wrong?

Turtle problems are primarily sailboat problems. Your issue is basically keeping the boat afloat enough to support you swamped and then if you can keep it up enough to be able to bail it. If you can get some floatation in permanently down low easily that would be good. A couple of fenders or float bags at under the thwarts or at gunwale level could help provide stability. Testing is good. You are in cold water; borrow a dry suit or a survival suit if you don't have one.

[boylesboats]

Do you have a permanent thwarts?
Glue in some 2" blue foam sheet under them...

[Fritz Koschmann]

Here is a photo, not my boat, but the same design. There are three moveable seats that can be placed along the two "stringers" so as to balance various loads of passengers and cargo. It has four rowing stations.

[Yeadon]

Put a riser along the interior of the boat in the stern and in the bow. Get some fat fenders. Tie them in. You're set.

[JimD]

Some folks want to be able to bail out a swamped boat, climb back aboard and go on their merry way...

Others prefer to live on the edge and would rather run the risk of clinging to a capsized or swamped boat in frigid water until they succumb to hypothermia. Its nice to have options. All my small boats have enough built in flotation to allow bailing and reentry. This apparently makes boating less exhilarating.

[wtarzia]

Wouldn't floatation on one side of the boat allow it to spill much of the water when the boat is tipped on the floatation side? --Wade

[boylesboats]

Wouldn't floatation on one side of the boat allow it to spill much of the water when the boat is tipped on the floatation side? --Wade

Kind of odd thought... but it may work...

[Thorne]

We need to get back to the basics here:

1. He is either within swimming distance of shore -- or not.

2. He is either boating in temps that allow floating alongside the boat for 10 minutes (or however long it takes) and bailing it our -- or not.

If the answer to #1 is "yes he is" and #2 is "not", then he needs to be prepared to swim to shore, and have the boat towed to land by another boat to be emptied out.

If the answers to #1 and #2 are "not"....then he needs to build a lot of flotation into the boat, which will increase the weight on a very light boat.

As suggested above, partial decking will reduce the internal volume that can hold water plus add flotation. Foam attached to the floorboards will float the boat level for the bailing-out process.

Here is another very light pulling boat -- one as per plan, the other decked for rough conditions -

[boylesboats]

Poor guy... (still confused about floatation)...
Good points above, Thorne... thumbs up...

[JimD]

1. He is either within swimming distance of shore -- or not.

2. He is either boating in temps that allow floating alongside the boat for 10 minutes (or however long it takes) and bailing it our -- or not.

1) If he swims there is no guarantee he will ever see his boat again. If the boat has plenty of flotation he can bail and reenter it in less time than it takes to swim anyway.

2) Provided one is properly dressed, one can survive in even the coldest water for the ten or so minutes it takes to bail and reenter provided the boat has enough floation to allow for bailing.

Seems like a no brainer to me.

[Thorne]

Jim -- his dory is made from wood, and will be visible in most conditions whether it has flotation or not.

I agree that more flotation = quicker bailing -- up to a point.

Don't know the last time you tried to bail out a 19.5' boat while clinging to the side, but it can easily take more than 10 minutes! While it is possible to swamp a boat in calm water, chances are much higher that it will be swamped in windy conditions -- making bailing take even longer.

Depending on how you board the boat, it often then takes on more water that you'll probably have to bail out.

The last two times I encountered this problem was not with my boat, and bailing just didn't make sense - the shore wasn't far away. We towed the boats ashore, pulled them up a bit and tipped most of the water out. Anything else would have taken at least twice the time, even when bailing with a 5-gal bucket -- which we tried first.

I'm not really looking at theory here, but at an open boat of a fast but not stable design, being rowed in very cold waters. In my opinion (and that's all it is) he should stick close to shore or other larger boats and use them for rescue -- not trying to row in a full cold-water survival suit so he can bail it out himself.

And if he wants to boat far offshore, my opinion is that he either needs to partially deck the dory or get another boat for that purpose.

[wtarzia]

Kind of odd thought... but it may work...

I mentioned it because I noticed that my skinny outrigger canoe with 3 feet of each end sealed in would float at 90 degrees, held up by buoyant mast and spars, and when righted took on only enough water to take me 5 minutes to bail out of the 19 inch deep center cockpit. Granted we are talking a different boat, but side flotation on a wide monohull might have the same effect. Sealed in sport-sail-boats do the same thing, more or less (flotation under side decks) so why not for a row boat? Cockpit space would lost, but what it is being used for now, compared with having a sea-survivable row boat? With some weight sacrifice, the side floatation could in the form of airtanks with screw-in access hatches to store some gear dry. --Wade

[JimD]

Enough floation to allow you to bail much of the water while you're in the boat would be my preference.

[S B]

From my point of view, you are approaching the problem from the wrong point of view. Unless you have complete confidence in the boat you have built, do not get in it. Something has put doubts in your mind, a close call or stories of other peoples' troubles? There is nothing wrong with preparing for the worst, it happens, but it should be to counter unforseen, not the inevitable.

[Tom Hunter]

Fritz,

Looking at your initial question and the answers it appears there is no requirement for floatation to be built in.

I'm familiar with the type, and I don't think you will swamp or roll unless you get caught in really bad conditions. I'm sure this will cause a lot of comment, but I think the best strategy is to avoid those conditions.

It's a good boat, if she gets overwhelmed by conditions you are in really big trouble. It's theoretically possible that some bozo will swamp you with a wake, but I'm doubtful.

There may be conditions local to you that make this bad advice. But if that is true then you should get a different boat.

[TerryLL]

I need to say a few words here about cold water survival. The water is so cold in Southeast Alaska that many deaths occur not from hypothermia but from cardiac arrest due to thermic shock. Gustavus is located at the mouth of Glacier Bay and has some of the coldest waters in Southeast Alaska.

At these temperatures, if you do survive the initial shack, numbness in the extremities happens within a minute or two. In ten minutes your hands will be useless clubs. Swimming to shore is usually not an option beyond 25 yards. If you do manage to get your boat bailed and climb back in, you won't be able to grip the oars. And in the boat in your wet clothes, exposed to the wind, your body quickly spirals down into shutdown mode, allowing blood to flow only to the inner core, arms and legs go numb.

So, my initial advice still stands. Every effort should be made to stay out of the water. A dump from a boat like this more than a few yards from shore will likely be fatal.

[JimD]

TerryLL, yes, I agree for the most part. You would want to be wearing a very expensive dry suit/survival suit such as some of the kayak gear available. These outfits are pretty good at preventing cold shock.



Note in the photo the paddler is wearing gloves. The warmest gloves available might keep the hands from freezing long enough to get back in the boat. The guy on his back would loose use of his hands in moments, most likely. I did make reference in an earlier post about dressing for the occassion. This is what I had in mind.

[Ian McColgin]

The very bow and stern of this boat is not useful for accomodation anyway, so I'd be inclined to put in a bulkhead and deck and then foam inside that. Leave a hatch hole in the bulkhead so you can air it out and not stress the wood on very hot days.

You want the floatation that high because you need to be able to at least sit in the boat while pumping - nothing like a good 1-1/2" diaphram modified for foot operation - or even rowing with her swamped - as I have done in a Light Gull for a test. These boat's shapes are such that you might not have enough floatation to keep the gunnels well clear if you're sitting upright in the swamped boat as your out-of-water weight is driving the boat down, but it'll be close enough.

If the floatation is low it will cause the boat to be most unstable when swamped. If nice and high, even with free water problems she'll stay upright. I used to deliberatly swamp Leeward to row safely home in big Oregon surf.

G'luck

[TerryLL]

TerryLL, yes, I agree for the most part. You would want to be wearing a very expensive dry suit/survival suit such as some of the kayak gear available. These outfits are pretty good at preventing cold shock.

A decent Mustang suit or float coat will buy you some time, that's for sure, and these are worn by prudent boaters in SE Alaska. Dressing for the conditions is always important. However, the Coast Guard regularly recovers dead bodies inside survival suits. Having a boat that keeps you out of the water in the first place is the highest priority in these waters.

[Thorne]

Another issue is trying to row in a float suit -- this is a performance pulling boat that he's rowing for fun, remember. That means getting pretty warm and sweaty when the weather is nice but the water is still cold...

[JimD]

...Having a boat that keeps you out of the water in the first place is the highest priority in these waters.

I agree 100% but the forumite has already built a boat with little guarantee of doing that.

[JimD]

Another issue is trying to row in a float suit -- this is a performance pulling boat that he's rowing for fun, remember. That means getting pretty warm and sweaty when the weather is nice but the water is still cold...

The sporty ones that kayakers use are intended for human powered boaters, but yeah, they can't be much fun to wear while rowing and paddling. That's one reason I'm a fair weather paddler only.

[Ben Fuller]

Best rig that I ever saw was bathtub floation in a fast 21 foot double ended chine boat called Banana Split designed and built by a friend of mine Steve Barnes. The interior bulkheads were structural allowing the skin to be lighter. Cleats for seats for fixed seat triple rowing and enough space for double slides. Outriggers on the side decks so we could pull long oars even though she was only 4 foot or so across the deck. Won a few Blackburns. We put a self bailer in it and tested the rig by rowing it dry with the bailer. It was faster for one person to bucket while the others rowed. We intended this boat for open water rowing in the worst conditions that one was likely to find in anything approaching sane Maine 4 season rowing.

The caveat or extreme in all this is Harpo and Samuelson's boat the Richard K. Fox. From the description she was fully decked in the ends and had floatation under the thwarts.

The good news in rowing craft is that unless you are in a huge blow with seas that can swamp they stay upright pretty nicely. There is no rig heeling and having no keel they slide pretty well. You weight is low and in desparate circumstances like dory fishermen sometimes found sitting on the bottom would allow you to survive almost anything. The place that people mostly fall in is getting in and out of skinny boats on icy docks.

[Daniel Noyes]

Ben makes a great point about going in the water wen getting in and out of the boat, I would also add shifting position in the boat while on the water. This is especially true of the G. Gull, but the streach is a significantly larger and heavier boat so is far less skittish under foot.
The streach gull is a very capable boat, we have had one at the rowing club here in Newburyport for years, The 15' gull and the streach are very seaworthy with a banks dory heritage and the reduced windage that alows them to row against the wind better than a typical banker. Should be a very safe boat when handled properly.
Dan
http://dansdories.googlepages.com

[Bob Triggs]

One basic rule of survival at sea, from the Coast Guard point of view anyway, is to NEVER LEAVE YOUR BOAT IF IT IS STILL FLOATING AND YOU CAN HANG ONTO IT. Of course there are circumstances where one may be better off swimming briefly. But the waters mentioned here are far too dangerous to contemplate swimming to shore. And one should be planning for the worst, not hedging their bets. I saw a good removable flotation system in a camping sail oar boat recently, it was inflatible beach rollers lashed to the underside of the seat thwarts, arranged athwartships. Pleanty of floatation and stowed out of the way. (He carries a repair kit for them too). I believe he said the beach rollers came from Italy and are available in a range of sizes. Very durable.

[Peter Eikenberry]

This boat does not need A LOT of flotation. It only needas a couple of cubic feet to suppor the persons. if you run through the formulas I gave you you will see that you probably do not need any flotation for the boat itself, only for the people and gear. A couple of cubic feet of foam will only add 4 lbs to the total weight of the boat, and if you put it under seat or in enclosed compartments it will not take up any passenger space. Even if you squeezed four people into this boat that would require about 4 cubic feet which would add 8 lbs to the boat. However if you use sealed air chambers the weight added is 0. Airbags would add a few pounds but would take little space until inflated.

Trigg is right. The basic rule is always stay with the boat. Far too many times the boat survives just fine but the people die because they left the safety of the boat. How well you can swim has no bearing at all. Water saps heat away 25 times as fast as air. A survival suit is great but are you going to wear one in this boat? A wet suit maybe. Besides it is a heck of a lot easier for a rescuer to see a boat than it is to see a person in the water from a helicopter 500 feet up.

See http://newboatbuilders.com/pages/flot1.html