Raft Design

Does anyone have a tried and tested fast raft design (or good ideas / advice) based on the following criteria please:

8 or 10 people (can be either depending on design)
Can be prop etc if driven by man power (tried one year with a bicycle to prop)
Must be made from 45 gallon drums
You must sit on the craft not in it (no canoes)
River course is 3 miles long and shallow in places and generally slow current

Last year we had 4 barrels in a line end to end each side and aluminium scaffold frame in between (forming a cat hull) We found this was restrictice as sometimes you need to row in the middle to aid steering. Would a single hull with out riggers be faster??

Help..... We need to win this!

Thanks

 

Go with ten paddlers. Two paddlers per drum plus bow and stern drums truncated and tilted upwards to give clean entry and exit. So total length is 7 drums.

Set say 2" pipe crosswise through the centre of each drum and run planks along each side over the pipe. The planks can have a seat cushion at each paddling station. The planks should end up about 4" above the water level.

You will need some form of stabiliser to stop it from rolling. If only drums allowed then you need two set about 6 ft out from the centre hull and set up to just touch the water when the boat is loaded. These outrigger drums can have slight bow up so they lift rather than plough. If you are allowed to use other buoyant material then something long and slender would be better than the outrigger drums.

And yes a single long hull will be better than two shorter hulls of the same beam as the long hull.

Should be able to do the 3 miles in 20 minutes with a half fit crew.

Rick W.

 

Thanks Rick.

Do you think 7 barrels will be enough?
Say 5 + 2 halves of barrels submerged = 6 x 200kg = 1200kg bouyancy.
10 paddlers at say 75kg each + raft say 50 kg = 800kg
meaning barrels will be 2/3 submerged?

Do you mean run the 2" pipe horizontally through each barrel (ie under where we sit) port to starboard? with the planks running bow to stern? I dont see how the planks will be 4" above water? Unless you have the plank on the top and you mean to run the barrells 2/3 submerged?

We are allowed outriggers, I will use some 100mm or 150mm dia drainage pipe extended about 5 foot out each side, bow up. These will have to extend further than the length of the hull and be connected on splayed bars to give room for rowing for the person front and back, unless you have another solution?

Many thanks.... hopefully we'll be on to a winner!!

 

You are right about the number of drums. Need to go one each plus two. So total of 12. You want the drums to sit higher than half submerged. Place the pipe through the drums above mid height so the bottom of the pipe is at midheight. You could make straddles if you did not want to damage the drums but the through pipe is simple and stronger.

You could extend a few of the pipes to support the outriggers.

You end up with something around 36ft long. Will go even faster. Length is strongly related to speed.

Continuous planks either side will give you the ability to pull the drums up end-to-end so they may not need any other method of securing. Small tabs welded or riveted between the rims at each butt point would make it more secure.

The planks need to be just above the waterline so the paddlers sit low. They will need stirrups on either side of the plank to react on. Say 1" water pipe bolted under the plank.

The main idea is to get a long slender hull with paddlers in a comfortable position. They will use a single bladed paddle and padlle on the outside of the plank.

Rick W

 

I understand you now, sorry I was being a bit dense. You sit on the planks either side of the barrells. This is a better solution that straddling the barrells?

I can see that would make a fast raft, just now got to make the thing split in to 3 pieces for transportation purposes!

Thanks for the info.

Tom