Level Flotation

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Some of you may know that I'm extending my 22-Classic by four feet at the transom. As I come down the home stretch toward actually building my hull extension, the subject of buoyancy has floated to the top of my thought process. Many experienced boaters and C-Dory owners have stated in this forum their confidence in the stability and safety of the hull, and I don't doubt them for a second (I've read nearly all of the threads). There are some of us, however, who might rather opt for a bulletproof solution to staying on top when things go really, really bad.

My objectives are: stay alive, keep boat on surface, keep engines and batteries and radio dry. Most recommendations for level flotation only have the expectation that decks would be awash. That's fine for keeping the boat visible, but I'd really like to be able to motor back to port, drain the cockpit and reflect on my luck.

Toward that end I've explored installing all foam, part foam - part buoyancy bags, and all buoyancy bags. Certainly all foam is the most bullet-proof requiring no human or mechanical intervention with the stuff hits the fan, but my initial rough calcs are indicating upwards of 20 cu. ft. of foam to maintain level flotation with 10-inches below the sheer line; so much for all that extra storage I had planned... The combination system would allow for some more storage but development and installation of a small buoyancy bag system is nearly the effort and almost the money of a whole-boat system. So, at this point I'm leaning toward a buoyancy bag system that is mostly externally-mounted with two smaller bags under the lazarette to support the heavy end: engines, batteries, etc. By mounting externally, I'll gain more stability as well. The only storage impact is that of the high-pressure air tank.

I want the bags to operate without human intervention since we might be pretty busy with other things should the bags be needed. I'd hoped to find a hydrostatic valve that functions in a manner similar to the automatic inflators CF Hammar makes, but for bigger volumes of air; it appears that they're not available to us mortals. Next best hands-off solution seems to be a solid-state bilge pump switch operating a solenoid valve similar to those used for propane tanks. These switches have an 8-second delay and it seems mounting them in the space under the splash well with a baffle is likely to avoid accidental inflation.

Once I figure the bag volumes and pressure I can solve for the tank size and pressure (PV=PV). It's looking like it wouldn't take a particularly large tank and if filled with diver-style dry air shouldn't have problems with icing up upon inflation.

This issue has been a proverbial needle in the haystack to research. I've got all the info USCG provides to calculate the buoyancy of my boat and made a nice spreadsheet. I've only found one company (FloatLogic) in the U.S. that made auto-inflated buoyancy bag systems and they don't appear to be currently operating. Here's a picture of their system inflated to get some idea of what it looks like:
FloatLogicPic.jpg

There are several companies in the U.K. that appear to provide similar systems.

It appears that a pair of Hypalon tubes with a protective shell cover installed flat over the middle hull "lapstrake" would be the best deployment location to achieve the flotation height I want. I'd let it curve upward and extend almost as far as the front of the cabin. Although it would let the V-berth hang lower, I could make way better with the engines.

Anyway, I've gone on waaaayy too long here, but those who've made it this far are probably as interested as I am in the subject. And, you may have some idea of where I might look for more information to help me tweak the design and avoid unforeseen pitfalls.
 
Did you calculate the volume and number of gallons?
How many bilge pumps are being installed? Maybe one high capacity pump higher than the others and connected to its own battery would be an option
 
Tom-

That automatic inflating air bag system seems pretty complicated and seems to violate the both KISS Principle and Murphy's Law! :lol:

I can't really help you on the technical details, but my experience in small sailboats would lead me toward favoring a sealed double bottom over the entire inside of the hull with the top of it above the waterline and a really big pair of scuppers exiting water out the rear of the boat though the transom. I'd consider adding a permanent flotation collar around the boat al-la the RIB (Rigid Inflatable Boat) style or approach. Make the whole thing permanent so nothing has to happen to change the boat into the unsinkable/self-rescuing mode. :wink

But that's just my 2¢, worth just about that much, too! :lol:

Joe. :teeth :thup
 
Brent,

Gallons are upwards of 3,000. My old setup was a Rule 750 for incidental water and Rule 2000 for problems; the 2000 solid-state switch was mounted an inch above the 750. Current plan is for two 3700s to replace the 2000, keeping the 750. The big guys collectively will draw about 31A, so I should have about four hours of full-blast continuous operation should I need it. In theory I should be able to pump the boat dry about 30-45 minutes after a hull breach is staunched – hopefully within four hours… With the collar, I should be able to motor away even if the bilge pumps can’t get all the water pumped out due to battery capacity.

Joe,

I really wanted the flotation solution to be hands-off and not dependent on any mechanical/electrical intervention. I spent quite a bit of time considering the placement of foam vs. loss of interior space. The least intrusive placement would float the boat, but likely upside down even with billets forming a collar under the gunwales; the most intrusive and effective would essentially be a foam collar about one-foot square running around the inside at a height of 18-inches or so. The inflatable collar option provides a roomy boat and much more insurance against rolling; a handy thing if the seas get rougher than I should be out in.

The actual operation of the float bag system isn’t terribly complicated; wet switch flips valve, bags inflate, sigh of relief. For me, it’s the calculations that are complex – particularly when it comes to placement. I’m confident that my own work will keep the boat afloat, I’d just like it to be quite level so as not to further complicate making whatever repairs may be necessary.

As for the RIB collar, it’s susceptible to puncture and might likely result in a C-Dorky. The auto-inflatable collar would only be deployed when appearances are way down on my list of priorities. I think that a thin fiberglass protective shell gelcoated to match the hull would have a minor impact on the appearance and operation of the boat and keep the bags safe. The other set of parameters is devising a way to test system components in a regular basis.
 
Tom,

Helicopters that operate from land, but work over water are often equipped with inflatable bags (pontoons) that can be deployed on command. (Some may have auto-inflate features like PFD suspender's, but I'm not sure.)

Look at some helicopter pictures (sorry, I don't have any...). You will see the landing skids, and on some you will see a small diameter linear bag-like gizmo attached on the topside of the skid. That's the inflatable emergency float/pontoon.

A couple sites you might want to review:
http://www.apicalindustries.com/floats.htm
http://www.aireindustrialproducts.com/p ... /?group=28
http://www.rescuefloats.com/rfhome.asp

Best,
Casey
 
Casey,

I've seen videos of those helicopter bags and their operation is along the lines of what I'm thinking. They're using them for emergency ditch operations and special rescues. The only Web site that published a price for their product listed it for about $103,000. Even if I win the big lottery, I won't be doing that. Nearly all of my searches for auto-inflating flotation bags resulted in helicopter applications.

Brent,

I was looking at Armstrong brackets a number of years ago, but decided against it. At that time I still had the convex transom sported on the "true Classics"; modifying the transom to accommodate the bracket would have resulted in a rather kludgey, less than workman-like result. I thought of Beer-Thirty's nicely-done custom bracket as well, but then I found the transom rotten and liked the idea of four more feet in the cockpit and ended up with the current design. I expect to have around 12 cu.ft. (720 lbs. @ 60 lb. per cu. ft.) of buoyancy in the lazarette storage which will go a long way to float those engines. I still may need inflatable bags below the lazarette/splashwell (where most folks have their gas tanks) to ensure that the engines stay up and out of the water.
 
Thanks Tom

There are some of us, however, who might rather opt for a bulletproof solution to staying on top when things go really, really bad

Can you define this statement?

What is your scupper setup?

I am more concerned about running aground and hitting submerged objects near the surface. In case of a hole in the hull, I have foam balls and sponges, 2 or more bildge pumps and inflatable dinghy.
 
I am going to be the devil's advocate. If you are boarded by a wave which fills the boat with water, you will have so much collateral damage by the water, the pressure of the wave, and submersion of the engine/engines, that you will not be able to motor back to port. I have rescured several Boston Whalers which had swamped--and the reality was that the engine didn't work, the boat was so heavy filled with water, that any progress under power would not be practical.

If I was going to make the boat as bullet proof as possible, I would follow something along the line of what Jim is suggesting, and make the boat self bailing. This is one of the objections of the C Dory 22. Some of the other C Dories are self bailng (for example the Tom Cat). My smaller cat is self bailing. That means that the floor is higher than the waterline, and will foat to an extent that any water which intrudes will go out thru the scuppers.

As for hitting a dead head or rock--again, there will be massive damage to the boat, and it will not be mobile.

In reality the chance of either of these events happening to a C Dory are very slim. I belive that you are already building the stern so that the most likely point of water intrusion (the splash well) is eliminated).

You are correct in that even the best closed cell foam will take on some water--and boat with sealed in foam become waterlogged (such as the Whalers).

Although the bag floatation system may work--there are many problems with making the design so that you can run the boat with any water aboard...without filling the entire boat with floatation. Once the boat has water aboard, it is susceptable to more water intrustion, and the performance will be very sluggish--limited to slow hull speeds. The reality is that under a distress situation you would be far better off deploying an EPRIB and having a life raft, if you think that there is a risk of the boat sinking (again very unlikely). The EPIRB will assure that professional help is on the way with a minimal time delay.
 
Brent,

Define that statement... ...well, a massive wave or hole in the hull would qualify in my mind. I've been considering this temporary hull patch for holes http://www.turtlepac.com/products/collisionbandage.html.

Bob

Thanks for your sage, if devilish advice... I appreciate you lending your experience to this issue. In regard to your first paragraph, I understand that if the engines are running as a large wave hits, water will be sucked into the carbs and you're dead in the water. If one were to stop the engines prior to taking such a hit and the engines only took a quick dunk are they still susceptible to not running? Or, is turning off the engines in this case kinda like jumping up in dropping elevator just before it hits?

You're certainly right, I won't be running anywhere with a cockpit full of water. The bilge pumps will have to handle that. The flotation bags would simply keep me from heading to the bottom, allowing the bilge pumps time to do their job. I'd expect less than 10 seconds from the time a wave hits until the bags are fully deployed.

You're also correct that I'm planning on a splashwell setup similar to the Venture Series which won't allow the cockpit to drain the way the stock C-Dorys will. I decided on the higher freeboard because I've read that taking water over the splashwell is the more common occurrence.

P.S. I hope you're healing up and feeling well after your recent medical adventure.
 
Tom,

Where and when are you going to be boating that presents an excessive danger of a boarding wave? Only two C-Dorys have been known to have been capsized/filled with water. Unless you are planning on boating in winter storms this should not be an issue.

Instead of creating an auto flotation system that you could not test short of filling your boat with water, why not buy an auto inflate system for an inflatable dingy or carry an emergency life raft and eprib.

USCG level floatation requirements in under 20 ft boats have to be tested by placing the boat in a pool with the max number of occupants in the boat and then filling the boat with water. The boat has to remain level and not capsize.

Unless the flotation system has been tested in adverse conditions, I would not rely on it. I would rather have a liferaft or survival suit and inflatable dingy.

As for hitting a log hard enough to bust the hull, there are a bunch of C-Dorys operating in the PNW in 'log land' and we have not heard of any such disaster yet. In an area of extensive debris, reducing speed and keeping a sharp lookout is normal operating procedure. And for sure, do not drive the boat into the sun if the sun glare is blinding the operator such that the logs are hidden.
 
Larry,

Thank you, my friend, for your considered comments. I certainly don't plan on heading out with the threat of bad weather.

A friend used to buy boats for USCG and help sink them at the Baltimore facility. As I learned the hows and whys of USCG requirement for flotation for smaller boats I couldn't understand why the requirements stopped at 20-feet.

In regard to system testing, I was planning on testing the basic function of the system; not whether it would float the boat. For that I was planning to rely on proper calculations for buoyancy requirements and balance.

My interest in this is also because I'm not that experienced a boater. All my USPS classes are helpful, but I've not spent that much time in the boat to learn what might constitute a dangerous situation. And, I kinda like my wife and am willing to take extra precautions to ensure her safety as well as others on the boat.

Anyway, I'm not done with the idea as yet, but the comments from you and other experienced mariners do give me some pause to reflect. Oh, and my middle name is Overkill.
 
tomherrick":2zhnmb41 said:
My interest in this is also because I'm not that experienced a boater. All my USPS classes are helpful, but I've not spent that much time in the boat to learn what might constitute a dangerous situation. And, I kinda like my wife and am willing to take extra precautions to ensure her safety as well as others on the boat. ...Oh, and my middle name is Overkill.
Click to expand...
Redundancy is your friend for propulsion (twins or a kicker), navigation devices, radios, heat sources (if it's cold!), and so on - I suggest you would be better off with a redundant hull.

Rather than "overkilling" your boat by taking it from being able to survive 99.99% of situations to 99.995% (guessing at those numers, but I think you'll get my point), I suggest you explore backup / redundant options as others have suggested. Carry an inflated dinghy or liferaft (or both!), tow a backup boat, or always buddy-boat with someone else - any of those approaches will be much less expensive and will have a greater impact on your ultimate survival rate.
 
Tomherrick - remember your fuel tanks( even full) provide much flotation. You could even rig up a canvas to go across the front of the well to keep water from sliding up and over into the cockpit. If you broach and take a wave from the side into the cockpit, then you have probably already lost power and can't maintain steerage anyway or have not employed a sea anchor.

A mooring cover over the cockpit ( the kind that slants from the roof downward and snaps over the front of the well and over the gunwales) will keep a lot of water from getting into the cockpit. Of course you have no rear vision with that setup. Yes, that setup can be rigged on the water. I have one and occasionally have used it -primarily to keep water out when caught in cloud bursts.

Larry H mentions only several C-Dorys capsizing. I know nothing about those stories, but I would wager they lost power, couldn't anchor, and got rolled in the surf. Maybe I'm mistaken. Someone with knowledge of the stories, please post.

With proper steering and some control with the engine, I can't imagine you getting into the kind of problem you are anticipating. If the water is that tough, unless you have lost power, someone erred in judgment or ran into incredibly back luck.

I've watched the Coast Guard self righting boats practice in twenty five foot surf on the Oregon coast and get rolled, but they deliberately put themselves into harms way. But these are water tight craft, yet in spite of that, some of the operators get killed. The sea can be a cruel master.

Adding another four feet to your cockpit should really add the space. Good luck in your project.
John
 
Here is a link to a thread about the 25 that got in trouble in the Cook Inlet.

http://www.c-brats.com/viewtopic.php?t=2258&highlight=swamp+capsize+bilge+pump

And here is the story on the other one.

PostPosted: Mon Apr 12, 2004 7:27 pm Post subject: Reply with quote
To all- I called up the previous owners. Here is the story of the wreck.
In 1998 they were out in the Ocean somewhere off Oregon. A sudden storm whipped up with great furry and vengeance. Feeling the need for shelter they headed in. They ran out of fuel just short of thier objective with driving wind and pounding waves the boat was forced into shallow water and rolled with them in it!!!! They both survived but lost two little dogs to the sea. Both her and her husband were air lifted to a Hospital for care. The next day the boat was recovered. They took the insurance money and purchased a second C-Dory!!! She just loves these boats. I bet they will never run out of fuel again.
I recall reading a forum about fuel and if one should take extra. I think this would be a good illistration of how a little extra fuel can save your hide.
Click to expand...

That quote was from here:

http://www.c-brats.com/viewtopic.php?p=6209&sid=c4d826c71c0f63258e92f38db872bbba
 
Yellowstone":3leghi0k said:
Tomherrick - A mooring cover over the cockpit ( the kind that slants from the roof downward and snaps over the front of the well and over the gunwales) will keep a lot of water from getting into the cockpit. Of course you have no rear vision with that setup. Yes, that setup can be rigged on the water.
John
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Tomherrick, not only a mooring cover as John mentioned above, but the camperback that many of us have for our vessels can be effective in keeping water out of the cockpit and those usually have "windows" for visibility. Years ago, I got caught out in seas that I should not have been in with my former 16' C-Dory and with green water over the top, the enclosed camperback kept most the water out of the cockpit (One wave that hit us slightly abeam did manage to dump several gallons of water into the cockpit when the snaps on the side of the camperback popped open. It was a rough ride but we made it to safe refuge. (That was the time my daughter (who was then about 10 year old) said, "I don't know dad, but I think this is the Perfect Storm". (We had recently seen the movie).
 
To answer a couple of questions. The smaller boats are mandated to have foam floatation because they are less likely to be self bailing and to have a life raft aboard. Unfortunately the foam floatation does not work all of that well in many boats--in some it does. I had a boat which filled with rain water, and the sea water was going freely over the splash well and holes, yet, the engine would run and the boat was level; bilge pumps got the water out fairly quickly. I have seen others which sank to the gunnels, or floated bow up. Most of the deaths in these size boats is due to drowning or hypothermia. You can avoid both of these with fairly simple and in-expensive gear purchase.

If the engine has been soaked with water, it may nor may not run. If it is running and ingests water, that is the end. But that is so unlikely. The boat I mentioned above was a Ray Hunt design, and very seaworth even though it was small--I often took it out into rough weather, with seas up to 8 to 10 feet. The only time I serious water aboard (other than spray or slaps of waves) was when I was attempting to rescue a dinghy in heavy weather and backed own--foolish thing to do.

My father's boat was a sailboat very similar in freeboard to a C Dory 25--but with a self bailing cockpit--completely sealed, except for an outboard well. The cabin wash sill was about 2' above the cocpit floor. It was not unusual to take half a cockpit full of water as we beat up into "Hurricane Gulch" San Pedro, the boat was heeled and a tuna clipper came by at 8 knots throwing a 3 to 4 foot wave. That wave would slop back out, and drain out through the scuppers--sure we got a bit wet--and cursed those fishermen, but we were always safe. The boat did fine, and the water went out.

Both of the C Dory which were lost, were invovled in very unusual situations--one was caught into surf, the other had the stern snagged by the anchor line (similar to the 25 foot boat sunk and where the foot ball players were killed several years ago).

If you are really in heavy weather, buddy boats may not be able to help you--they may also be in survival mode--don't count on that--take care of yourself.

As for dealing with holes in the hull: Get a set of tapered wooden plugs for any thru hulls (better yet, don't have any thru hulls, of if you do, be sure that they are bronze, double clamped and closed unless in use. Carry a water proofed canvas triangle about 3 feet on a side, with 10 feet of rope on each corner. This will handle any serious hole you might get in the boat. A more "permant" repair could be affected with some plywood (1/4" is thick enough"), along with several cans of the foam sealant "Great Stuff". I have seen some badly damaged by hurricanes which were floated and salvaged with these types of devices. This is all which we carried (bigger patches) on boats we used to cross oceans, and were in seas far greater than any C Dory would have survived without rolling or pitch polling.

Spend time getting to know how your boat handles. With the higher freeboard aft you have eliminated 80% or more of the possible sources of boarding water.
 
tomherrick":1yn6lzpg said:
My interest in this is also because I'm not that experienced a boater. All my USPS classes are helpful, but I've not spent that much time in the boat to learn what might constitute a dangerous situation. And, I kinda like my wife and am willing to take extra precautions to ensure her safety as well as others on the boat.
Click to expand...

I'll make the note that if there were a demand for a sytem like this, it would be offered.

I find that sometimes the inexperienced boater tries to overcomplicate things. Many envision boats slipping down to the bottom as happening almost daily.

The reality is that boats very rarely sink, and a large percentage of those are at the dock due to poor maintenance.

Be prudent, of course, but get out and enjoy the boat.
 
Matt,

Certainly I don't expect frequent sinking and death. But, it does happen and I'd not like it to be me. Inexperienced is what I am when it comes to practical boating - no question. Perhaps I take that old Boy Scout motto too seriously...
 
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