JEM Watercraft

Hello there, İ have probably a typical beginners question on floatation. İ am planning to build a 5m canoe this winter for use on the Dardanel straights. Nice place but a bit busy. İf İ build closed compartments in the bow & stern of the canoe and fill them both with expanding builders foam will İ be steering a fair course or foul. İ am in Turkey so most of the nice technical bits & pieces are not available here. İts a mater of DiY with a vengance or use the local basic stuff and hope for the best. İ asked my local hardware guy for marine epoxy and he looked at me like İ had asked for the keys of the harem.
All suggestions welcome...... About floatation that is.

foam inside the ends works fine. If you can help it, makes sure it's closed-cell foam so it doesn't soak up water. Sealed plastic water bottles or jugs do the trick as well (inside a bulkhead chamber).

Be careful when using expanding foam - I've heard that some types can exert considerable force and if the vent/fill holes get clogged with foam while the stuff in the middle is still expanding then you could end up with a split or bulging hull. I think the counter for this is to apply relatively thin layers but others here may have better/contrary advice.

Personally I would not use foam fill as I think it would be difficult to dry out if water did enter somehow eg seepage or damage. I always worry about the effect of this moisture sitting in the compartment for a long time and in the case of a damaged hull it could make repair more difficult. A hollow compartment with a sealed hatch can accomodate air filled bottles or bags (wine cask bladders are good) and when not in use the hatch is left off so it dries out completely. Again, others may disagree with this - it's just a personal preference.

Hope it all works out whichever way you go.

Derek,

My Son was stationed in Turkey; loved the area and glad to get home again.

I would avoid the myth of an airtight chamber. Doesn't exist in wooden boats. If you do somehow achieve one, differences in air pressure will work to destroy it. It's a lot like trying to fight gravity; it's always waiting to cheat you out of victory.

Closing in the stem ends of your boat with bulkheads and sealed hatches could accomplish the flotation you seek. If the hatch does actually seal itself airtight, I'd drill a very small hole in the top of the bulkhead to allow air pressure to equalize, but water wouldn't flow. Maybe a spoonful or two if submerged for a long time, but not anything that would endanger a boat.

Then, you could carry gear inside the ends, leave them empty, or add jugs and beach balls.

Valid and often over looked question Derek, personally I would advise the use of Juice or plastic milk containers Jugs as the lads on this site like to call them (over in the UK jugs are something quite different!). The use of these containers allows you to trim the craft by filling some with water, this also keeping the light refreshments cool. Expanding foam has its merits in some applications and have seen it used in a plastic bag to form the shape. If you want to seal your compartments use pool noodles, these provide excellent buoyancy.

Happy new year to all

If you have the area sealed , some Styrofoam popcorn ( the stuff they use in packages ) work's really great. It does not expand , hold water or do any of the crazy stuff.
For neat freaks , put them in a Zip Lock bag just for extra safety.

Chuck.
PS. Personally for my use I just seal off the ends with a air tight chamber. One of the pleasures of living at sea level and not running up and down mountains. I have done that with some of my boats and so far none of them have exploaded on me due to the change in altitude.

Air pressure changes with temperature too, Chuck, as well as with changes in elevation. And whether or not you know it, your chambers are leaking air both in and out. Moisture, however, only goes in.

Kayak Jack wrote:Air pressure changes with temperature too, Chuck, as well as with changes in elevation. And whether or not you know it, your chambers are leaking air both in and out. Moisture, however, only goes in.

They are really sealed , good fillets along the seams and glassed , if they leak air I would be surprised. I'm sure of one thing , they don't leak air like I do at the higher altitudes..... BURpppppppppp.

Besides I feel they are safe down here , I think our highest elevation above sea level in in the Pan Handle and it is something like 135 feet. I know for sure in the Glades it is 3 feet since they have a marker showing it. ( Most of the/our highway overpasses and large bridges are higher then either of them ).

Chuck.