[CraigD]

Originally Posted by Cedars

The foam is a good idea. A friend of my brother travels all over the world spraying one type of that stuff on oil rigs so some types hold up under salt water for sure. I know they work with it underwater too cuz he had to take diving courses. I would also suggest filling any pvc tubing with that stuff for its extra buoyancy, then a hole in a tube wouldnt fill with water.

I’m curious about the spray on oil rig foam – got a link to something about it? Is it intended for floatation, or protection against bumps, corrosion, etc?

I’m decades out-of-date concerning foam, but I think it still holds that the design purpose of it is to keep you boat from sinking if it’s holed, capsized, sits too long without pumping, or otherwise unexpectedly filled with water, NOT as an alternative to having a watertight hull.

The last foam I installed came in blocks, which I cut to fit and stuck in various unneeded spaces –in the bow where a traditional chain locker would go, under v-berths and cabin cabinets and benches, and under the cockpit seats, and under the stern overhang. It was purposefully not fully fiberglassed to the hull, to allow it to dry if it ever got wetted, or even replaced (with some cutting and re-fiberglassing) if it got wet for too long time, or with something nasty like diesel.

It’s better to put foam at or above design waterline rather than low down, to assure that the swamped boat floats keel down , rather than keel up .

Even a large boat doesn’t need a lot of floatation – 1 cubic meter per ton displacement + 20% or so more for comfort. Filling a hull completely with foam is, in conventional building, just a waste of storage space and money, and worse, may make it hard to get at ordinary leakage and rain to pump it out, or make it puddle someplace you don’t know about. Hearing water sloshing about in a hull, but not being able to find it, is not happiness-making, and if you have a lot of it, can make a boat unstable.

The foam in my experience isn’t completely watertight, and slowly takes in water, loosing buoyancy. It’s the same stuff that’s bolted, strapped, or just stuck into boxes on the undersides of swimming raft’s and floating docks, which settle lower in the water as they age. After 5 years of so, the foam gets so ratty you can gouge out chunks of it with your fingers, and can get some interesting smells – not a big deal under a floating dock, but not something I’d want in boat cabin.

In short, the conventional wisdom is to use foam as backup, not primary floatation. It’s not an absolute rule – there are plenty of boats, especially open “board” boats and small catamarans built exactly like a surfboard, with solid, shaped foam cores covered in fiberglass (or, in one I saw once, a 2-piece injection molded plastic skin) but here the foam is just being used as a stay-in-place form for the fiberglass, not with the intention of touching water. My guess is you could cover a foam core in almost anything waterproof, such as inner tube rubber stitched and rubber cemented with no worse effect than it not being very slick on the bottom. Letting your foam stay wet, though seems to me to be inviting trouble.

Originally Posted by freeztar

The flotation foam we have researched is 10 gallons for ~$100 iirc.

The stuff expands a lot when dispensed, though, right? So a gallon gives way more than 0.0038 cubic meters volume of foam.

How much, I wonder? I imagine that’s documented somewhere prominent on the stuff’s packaging, or wherever you buy it.

[Turtle]

Originally Posted by freeztar

...
So between canvas and vinyl tent material, I guess it comes down to cost, durability, and weight. Does the marine paint just protect the canvas from degradation? Is there something cheaper?

Nothing is cheap about boat fittings. I don't know what paint the old man used on the canvas, but as I was using the canoe in saltwater decades later, I planned to redope it with an ablative marine paint. As luck had it, the canoe burned in the repair shop on a Friday the 13th.

If the boat will spend much time in saltwater, then special (and expensive) paint is needed. Here's a source for many different types of paints for the many surfaces found on/in boats. >> Marine Boat Paint - Bottom paint, topside paint, biocide paint

... These antifouling marine paints contain high levels of copper and can help to prevent or reduce fouling from biological organisms, slime, algae, and is a preferred in harsh marine environments where an ablative is desirable to prevent organic buildup and damage. ...

[Cedars]

Originally Posted by CraigD

I’m curious about the spray on oil rig foam – got a link to something about it? Is it intended for floatation, or protection against bumps, corrosion, etc?

I would have to ask my brother for the details. From memory it has to do with corrosion. I remember my brother saying they were diving down and applying the stuff underwater and thinking "wow, they have come along way since filling the car up with foam".

As far as a website, I doubt it but will ask.

[redshift200]

Craig D,

You bring up many good points, and that's what I want...to think well about this thing before I build it so that it we have as few probs as possible (and hopefully survive sailing it).

I have already thought of the microbial thing. I definitely don't want water in the hull at all. When you spoke of a surfboard you hit the nail on the head. I have envisioned this boat as a big surfboard, and one of my main reasons for basing the boat on this is that I would like the boat to be very light, like a surfboard. I have seen flotation foam washed up on the beach, and I have noticed that it does become quite crumbly.

It is on my list to research bailing in a boat. I have seen some boats termed as self-bailing, and, I assume, that boats have to be bailed because spray comes up over the hull. My idea is to create a ridgid frame (compared to a surfboard), but a frame that can flex without breaking, which is why I thought of pvc over wood (and the fact that pvc can't rot and can trap air), and this frame will be filled with foam and then completely sealed in supported, abrasian resistant rubber (or whatever), and my idea to keep spray out of the hull is to enclose the hull, like a kayak, but the hull would be covered living space, more like a houseboat. Part of my strategy for keeping the hull from being holed is to keep the vessel really light, meaning that with less weight there would be less force exerted in the event of an impact, although I know the surfboards do get holed and broken. However, I went oystering yesterday and I actually go cut up pretty badly doing it, which makes me think that if the boat got slammed up against and oyster reef that it would be difficult to keep hull integrity. I would like to come up with some system that would allow me to take the boat into some diverse and extreme situations, for instance, I would like the boat to be able to sail open ocean, navigate salt marshes, and sail on rivers too.

On idea that I have is make the hull out or some extremely tear resistant material like ballistic cordura. Is it possible to resin coat cordura, or would erethane coated cordura be waterproof enough and stand up being wet all the time? I am thinking about resin coated cordura with a vinyl inner-liner. My question is, 'how do other boat cope with being slammed up against an oyster reef?' Do people just use navigational charts to avoid the 'skinny' water? But, my thing is for this to be a coastal survival/exploration vessel, and this is why I really want to build it myself, because I really want the boat to be very difficult to hole, capsize, or break up. I want to explore the world, so is it even possible to have navigational charts for the whole world? Which, brings up another question, 'how can I get cheap or free, and really good, navigational info?' I saw that NOAA gives out electronic charts, but I assume that this is just for the US, and I am not sure exactly what program I would use to view NOAA raw data.

About capsizing...I will get a drawing up this evening...,but my theory about capsizing is two-fold: one, is to use outriggers (creating a modified trimaran), and two, to put flotational foam on the roof of the cab so if a wave turns the boat on its side, then when the roof hits the water the bouyancy will stop the boat from turning over and the keel weight (batteries) will right the boat when whatever force is acting on the boat (like a wave or wind) ceases. As far a the flotation foam in the hull, I want the foam to be below the waterline so if the hull integrity is lost, the boat won't sink partially, but will continue to function as normal until I can dry-dock it and fix the hull breach. For instance, if we were to have a hull-breach in very cold water, the boat might not sink, but we would be exposed to freezing cold water which would cause hypothermia, which is why I want the hull itself to be bouyant even in the event of a hull breach.

I have actually thought of the fact that if I get water in the hull that it might be difficult to get the water out. Therefore, I am going to have to create some sort of drainage system, just in case there is a hull breach, so that will require some thought. I have thought of a system that will make it easy for me to dry dock the boat, like a lift and a wench, where I could just pull it up on a beach, check the hull for tears, and drain any water that may have accumulated before it damages the foam or the reinforcement (like chicken wire).

I have thought of the chicken wire corroding, and I am very concerned about it. I intend to ruberize everything metal, but I do have to check on the performance of that rubberizing product (what I am looking at is called tool grip). I would like to replace the metal chicken wire with something that can't corrode, maybe like a nylon net or something, but I would have to find something that would be very strong. The purpose of the chicken wire is to hold the boat together even if the pvc frame is broken, and I believe that the chicken wire would perform well if I can seal it from corrosion, but I am interested in something that would perform as well and couldn't corrode at all.

About the floatation foam (thanks for the input Cedars)...I don't know yet about blowing it. Is that for home insulation? The foam that I have been researching is a 2-part liquid mix that expands in minutes when mixed. I am somewhat concerned about the force that it may exert when it expands, but I assume that it will expand in the direction of least resistance, and while I am constructing the hull I will make sure that it isn't trapped, and would therefore break the hull when expanding. But, I do know that it's used extensively with fiberglass boats, so there must be a way to handle it.

I do understand that the foam will add weight to the boat without doing much unless the hull is breached. I definitely don't want to use more than necessary, for this reason.

Question? I know that pvc does have some cold weather performance problems. Does anyone know if the frame of the boat would become too brittle, if for instance I were to sail in the arctic? And, this also brings up an interesting correlary about the floatation foam, which is that it is a great thermal insulator. I am hoping that the foam on the roof will stop the boat from capsizing and protect the cabin from the heat of the sun as well.

Thanks again,
T-Diddle

[redshift200]

To see a boat somewhat like I am proposing go to sunboat (dot.com), and check out the Loon.

[DFINITLYDISTRUBD]

Hi Redshift200

Have you considered a cat or a tri-maran type hull of large dia. PVC?

How fast do you want to go?

From my experience here on Lake Erie... a 26lb thrust trolling motor will push a 14' glass fibre canoe with two persons, a cooler, a lab, and fishing tackle at about 7MPH, and it will do it for several hours on a single typical 12v marine batery
(dad and I averaged about three hours to a charge in 1'> swells).

[redshift200]

Definitely Disturbed,
This is good info. I am considering using a trolling motor. I really don't want much speed. 5 mph would be plenty. My problem that I am trying to get around is that I would like to be able to use pedal power to push the boat and/or charge batteries. It seems that this may be a tall order. The reason that I want to have pedal power turn a prop directly is that I don't want to get far away from land and have my electrical system fail, i.e. by exposure to water. I could just set up a pedal power generator to charge batteries, which would be much simpler, and I would carry oars as a backup. I want to be able to charge batteries using pedal power, wind, and solar cells, so the electrical system will be somewhat sophisticated and I would imagine this would make it more vulnerable to failure. Perhaps someone can tell me what the risks are and what I can do to keep the power system safe.

[redshift200]

Craig D,
I am think about what you said about fiberglass. I may want to use it, but it will need to be strong. Do you know how much it would cost and how much labor (approx) that it would take to build a 18' hull of a simple fishing boat? I am thinking that I could probably just carry supplies with me to fix the boat if damaged.

Thanks,
Todd

[freeztar]

Originally Posted by redshift200

I would like to be able to use pedal power to push the boat and/or charge batteries. It seems that this may be a tall order.

I want to be able to charge batteries using pedal power, wind, and solar cells, so the electrical system will be somewhat sophisticated and I would imagine this would make it more vulnerable to failure. Perhaps someone can tell me what the risks are and what I can do to keep the power system safe.

Having three different systems for charging provides good backup/redundancy, but also carries the risk of complete failure in the event of water damage/shorting. Furthermore, PV cells and wind turbines (even if homemade) are not exactly cheap.

I'd like to see the mechanical design you envision. How do the pedals connect to the gearbox? How is the gearbox (or transmission) made most efficient? How does the electrical system interface with the gearbox?

BTW, I'm using the phrase "gearbox" to mean the "main hub" that serves the purpose of a transmission and a connection source that could house all the terminal connections, as well as axles, within a sealed "box".

[DFINITLYDISTRUBD]

Originally Posted by redshift200

Definitely Disturbed,
This is good info. I am considering using a trolling motor. I really don't want much speed. 5 mph would be plenty. My problem that I am trying to get around is that I would like to be able to use pedal power to push the boat and/or charge batteries. It seems that this may be a tall order. The reason that I want to have pedal power turn a prop directly is that I don't want to get far away from land and have my electrical system fail, i.e. by exposure to water. I could just set up a pedal power generator to charge batteries, which would be much simpler, and I would carry oars as a backup. I want to be able to charge batteries using pedal power, wind, and solar cells, so the electrical system will be somewhat sophisticated and I would imagine this would make it more vulnerable to failure. Perhaps someone can tell me what the risks are and what I can do to keep the power system safe.

Use fully tinned marine spec wire, seperate your charging systems with charging diods, and mechanical switches (battery cut off switches from your local auto parts store would fit the bill perfectly), also use appropriately rated fuses to protect each circuit. You should have no gremlins...

Now as for pedal charging...
I hope you're reeeeeeeally fit! Even with more modern battery technology your looking at pedaling for at least an hour for a full recharge from 25% charge. (Optima brags over their fast recharge time and it's over 90 min.)