Comment

Comment by Bob Simmons on May 10, 2011 at 6:28pm

Having built docks and floating platforms with various materials before, I advise against using barrels.  They are fine as long as they work,  but they are a nightmare when one or more springs a leak, and they will most definitely leak.  They will seriously destabilize your platform, finding the offending barrel will be a difficult task and replacing it can be even more difficult.  Use polystyrene instead.  It's light, can't leak and is extremely easy to work with and replace.  You can also make your own 'homemade' version of polystyrene in a pinch for temporary emergencies, or so I'm told.

 

Regardless of what material you use, stability will be an issue that you must address.  You can't simply nail together any U shaped platform and attach flotation underneath it.  If the 'arms' of the U are too narrow, they will sink whenever anyone walks to the end of them or whenever any other weight is on them.  The weight of the water that your flotation material displaces must be greater than the maximum weight you want that area of the platform to support.  For instance, if you want the 'arms' of the U to support 1,000 pounds, then the flotation material under that arm must be able to displace 1,000 pounds of water without sinking.  Actually a little bit more.  Don't forget that the weight of the platform itself must be included in the supported weight.

 

You also need to consider what happens to the platform when weight shifts from one side to the other.  Un-anchored floating platforms have been known to flip over when the weight on them is not distributed evenly.  That is one of the few advantages that barrels offer over polystyrene.  Their weight makes them more resistant to flipping.  It also makes them more resistant to towing.  However, if the lake is shallow enough to drop anchors from the corners of the platform, flipping should not be an issue.

 

You didn't mention the freeboard of your vessel.  Any platform you use will require maintenance, and your vessel freeboard can be a key player there because your platform could potentially be winched clear of the water from your vessel, especially if you used polystyrene for flotation because it's much lighter.  Having to take the platform elsewhere for maintenance would be time consuming and costly.  This might also be a better way to stow the platform while traveling, rather than towing it.  That's something you'd have to decide.

 

How you transfer people and material between the vessel and the platform is something else you'll have to figure out.

 

Given that you mention amphibious aircraft as opposed to those with straight floats, and mentioned the issues of embarkation and debarkation of patients, I would have to say that Sebastien is actually on the right track.  I don't mean that you need to alter your vessel itself, but that your platform should allow amphibious aircraft to taxi onto it rather than to simply dock with it.  That would serve several purposes.  First, a square (or non-U) platform would be inherently more stable while still allowing aircraft to dock along the side if desired.  But having an aft end that dipped into the water and allowed the aircraft to taxi onto the platform would allow a far more stable platform for embarkation and debarkation of patients.  It would also allow a far more stable overnight tiedown spot for aircraft.  Actually the entire aft end wouldn't dip.  You'd still need some 'arms' on each side of the dipping portion to provide some flotation because the dipping portion would have less flotation in it.  The size of the platform, dipping portion and arms would be determined by your aircraft choices and their float dimensions, with obvious margins for error and safety considerations when taking into account varying water and wind conditions.

Comment by Clay E Hollenback on May 6, 2011 at 8:29pm

LOL... I love it Sebastien.. Ya gotta think BIG!!!!!!!

Comment by Sebastien Heintz on May 5, 2011 at 11:17am

That would make an impressive base for your operations! 

 

Comment by Phillip Owens on May 5, 2011 at 11:12am

Jonathan,  One thing I am familiar with is the fact that most missionary camps have limited funds and therefore must be very innovative. So here is my suggestions.  The idea of using a pontoon type of dock is good as it can be made from used oil drums and fastened togther by various means, in this case perhaps strapped to planking on top that serves as a platform on which to move people and supplies. The "U" shape configuration would allow the 701 or 801 on floats to taxi into the center for loading and unloading and also allow for an attachment point for the center towing from the mother ship. I would suggest you make the dock wide enough so that movement of personnel and materiels can move freely without worrying about falling into the water and have a railing system to contain them. The idea that it could also be powered independently is also good and cold be incorporated into the design, using one or more of the barrels as a fuel supply for an outboard motor or motors depending upon the design. One motor could be mounted forward in the center just aft of the towing point and pull the dock along when required if conditions found it advantagous to move independently to move personnel of materiel from ship to shore via the dock where perhaps the ship could not go due to draft or other reasons. It may also make moving supplies to the ship more effective. From a hydrodynamic standpoint it would be advisable to keep the barrels as close together as possible perhaps even to the point of a fairing between the barrels. They could be welded together however it is my opinion that this would not provide the flexability needed during rougher waters, If the dock has some level of flexability it can move with the wave action to some degree yet not so much as to cause it to seperate at any point. I would suggest the dock extend at least 3/4 the length of an 801 as you will need sufficent bouyency to hold people and equipment.

The design will need to be based upon the expected maximum weight to be placed on the dock at any given moment, as a result you may find it necessary to make some comprimises. 

I hope this will be of some help let me know if I can add anything to thi suggestion.

By the way if you are interested I have placed my completed 801 on the For Sale market.

Comment by Clay E Hollenback on May 5, 2011 at 8:28am

Anchor the boat and use smaller pontoon boats to service the villages. You could buy the pontoons and build the boat decks in Ghana. Points to consider:

A 10 meter 2 pontoon boat with a 90 hp outboard, is capable of 20-30 + knots depends on loading) till the gas runs out. And it's easy to carry A LOT of gas. You could hit far more villages cheaper and faster with 2 or 3 pontoon boats than with a single larger vessle.

They have a very shallow draft so they can be beached easily for loading and unloading.

A simple floating "U" Shaped dock behind the "mother" ship could be use as a dock for both the shuttle boats and the amphib.

They can be easily towed when the Mother ship moves.

Hitting a village and finding you need to transport 25 people will be no trouble for a pontoon boat but not cost or time pratical for an amphib. As you mentioned keep it for more critical needs.

 

Pontoon specs.  http://www.osvw.com/index_2.html

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