raft

[woodsitter]

Hi Bushcrafters,

Here comes another question.

I want to build a raft.
Fine, just cut down some tree’s, tie’m together and get some champagne for the christening ceremony.
Al ‘manuals’ I found in books and on the net just say to tie up an bunch of logs. The extra secret ingredient is to build it in the water as rafts are very heavy. That’s not enough.

Nope, I want one that can sail :shock: .

I build small rafts as a kid, from all types of wood, planks, boards and drums, with the main idea to push each other of the raft, once afloat. (that of course worked fine ).
A few years ago I made a ‘real’ one. On holiday in France my (now ex-) girlfriend got fed up with my hiking and we spend the last week with her parents who where sited on some family campsite next to a lake. I got bored to death of course but after three days I found a big pile of redundant telephone poles. :notworthy I made myself a very nice but heavy raft and had a good time crafting and paddling after all, without bee botherd by my inlaws.

Now I also know how to sail, but the problem is that a raft is just drifting. You can push it around with a long pole of even a paddle, but sailing is very different. You need a keel to counter sideways drifting and for a keel to have any effect you also need a certain speed. Therefore the whole raft and especially the keel need to be more ore less streamlined.
That would require to build a boat of course, but we are bushcrafting, so the limitations are: basic tools, basic (woodland) materials and relatively easy and quick to build. As sail I could use the footprint of my tent, and (para)cord for building and rigging, the rest needs to be found or made on site.

Now my idea was to build a medium sized raft, capable of carrying two people + their gear. At least the gear should stay dry so we need to make a platform. To sail we need a mast and the damn keel and of course a rudder to paddle and steer. My main problem is how to make a sleek but ridged keel and how to erect a mast and sail (a sail capable of cross wind sailing) without needing 200 meter rope for rigging. (A simple square sail would not be good enough.) The whole raft has to be vastly more ridged than my previous constructions, but unfortunately trees are usually round and any rope is somewhat flexible. To make things even more complicated, it would be nice to make a keel that can be lifted, so make landing and traversing shallows possible. This hower is the first thing I'm ready to sacrefice.

These are my problems, any suggestions? Am I asking too much?

 

[Stew]

Am I asking too much?

Probably, but that doesn't mean it's not possible.

Personally, I think it's going to be a lot of work for what you will get out of it - good for a try though! Personally I would just stick with a normal raft, but maybe that's just me.

Good luck!!

 

[woodsitter]

Actually, the idea got stuck in my head since some time ago friends of mine went on a hiking trip in Sweden. Lovely country, lots of wood and lots of lakes. After a few days one of them strained his ankle quite bad. The weather was fine, they had food for an other week so there was no real emergency. No need to call a helicopter. They decided to sit it out and after a few days the foot fit the shoe again and slowly (2 days) the managed to get to a road and hitched back to their car.
I thought about this and what I would do in their place. I thought about the option to build a raft and transport the injured hiker by water. The lake they where camping by was connected to a series of other lakes, that lead to a village just 20 km away. The building keeps you busy while waiting, its better for the ankle and much less painful.
(But that’s all a bit off topic)

(the 'rescue' would justify cutting down two dozen healthy tree's )

 

[maddave]

The keel will always be limited to what local materials are available. A big thin slab of slate set into slots on 2 uprights would be ideal, but where are you going to find slate? the thing is, it has to be hydrodynamic to work efficiently and the only thing in nature that's hydrodynamic are fish !! I think raft design is simple because all the materials you have to hand are simple. otherwise suvivors would be building yachts to sail away on. Remember Keep It Simple

 

[george]

Hi woodsitter

Have a look at this link here http://www.inquiry.net/outdoor/summer/boats/man_friday/index.htm

A really interesting site (if a little twee and old fashioned) Worth an explore anyway.

George

 

[woodsitter]

Thanks George I did.
Now I really go into my head. The ‘raft’ on that site is more like a catamaran than a raft. With is good, as the drift is much less and so is the drag. But in his happy picture three people sit high and dry on a two log raft. That is by far not consistent with my experience (apart from throwing each other in the water of course ).
I did some research and weight of pinewood is 580 kg per meter. If we behave nicely and only take dead wood it still contains 15-20% water. That makes about 700 kg or 70% of the weight of water. So the buoyancy is 30%. Great, that’s the load we can add.
We take a log of lets say 6 meters and 30 cm in diameter. That’s 240 kg and it can carry 70 kg. (240kg for one log, so that’s why you have to build it in the water!)
But if two sailors and their two rucksacks make a 200 kg cargo we need three logs alone for that. We also need to ad about 50 - 80 kg for the superstructure and a reasonable margin of safety (20 %?) and we have to take in account that the logs will take on water.
Hmm, that makes six logs. A raft of about 6 x 2 meters is o.k., but 1,5 metric tons is a bit difficult to handle. We still have a raft and not a catamaran so we still need that keel (and we definitely need the sail!).

So far…my research!

 

[Andy]

maybe make something from animal skins. i sore a programme (I think it was what the Romans did for us) where the romans hand build a bridge that foated on a load of goart skins. if you want to get more foat for the mass of raft

the way i would go at this though would be to make a raft using a tarp stretched over a frame. you could then lash on a keel of ruder on both sides which you could take of for shallow waterand maybe build an upright log that you could rig a sail to

 

[Roving Rich]

A few pointers that may help.
There is that Archimedes (i think) principle of displacing more weight of water than your mass. Hence steel ships float. So your logs will also be having this effect.
Have you come across Thames Barges atall ? These are keel less for sailing up the Thames, but also sail across the Europe. They do this by having keels on the side of them, that pivot down into the water and stop em slewing sideways in a cross wind. They look a bit like the fins on the side of a fish. I guess they would be far easier to attach on the outside of the raft than the middle. Construction wise I'd suggest planking the wood as best you can, with an axe and wooden wedges or a Fro if you include under the Bushcraft heading.
The other thing that comes to mind is that "Kon Tiki" lot who built more of a boat than a raft out of reeds and sailed it across the atlantic if memory serves me right. They also have the reed boats ob lake Titicaca in Peru.
Sail wise reeds or split bamboo have both been used. woven together.
Hope this helps, happy rafting
Rich :-D

 

[gurushaun]

Aren't the side mounted *keels * calle Lee Boards?

Cheers

Shaun

 

[Roving Rich]

Probably. That must be why you are the Guru oh wise one :notworthy
Rich

 

[woodsitter]

I don’t know what they are called English, but they are very widely used in traditional flat bottom boats in Holland. I am from Holland so I feel quite stupid that I did not come up with it myself. Thanks for that.
About the animal skin’s it would make a substitute for empty canisters of barrels. But with skin’s you can also make a kayak like the inuit. Maybe not so crafty but still much leaner and faster than a raft. But I am already burdening my conscience by cutting down healthy tree’s let alone kill dozens of animals to satisfy my yachting needs.

I am still a bit puzzled about that picture of the two log catamaran raft of George’s site.
Here the mast was attached by drilling a hole in a board. I have no board and I have no big drill with me, but a hole right thru the centre of a big log would make a strong enough connection to leave out al rigging. That would save a lot of rope or paracord, and allow for much more freedom to handle the sail. Major benefit! But how do I drill a 5-8 cm hole in a 30-40 cm log without a drill? We need a very tight fit, so cutting two notches between two logs will not do. Did anyone ever try this with a wiresaw?

If we extend the mast thru the log, we have a ridged pole under water. That might help to figure something out for the keel. Anything flat and ridged might help. I also thought about some webbing of some natural fiber. I made floor covering once from split bamboo, I think it is strong enough. (Very large tropical bamboo would solve al my problems, very light, very strong, water tight, etc).

The two log raft catamaran is still in my head. If I tie up three logs as a triangular bundle I can make the two catamaran hulls and still have the lift of six logs. That way I also have the two hulls, making for much less draft in the sailing direction and much more resistance in the sideways drift! Probably we don’t need a keel anymore of a much smaller one at least. It does limit the usable space on the raft but we have to make a platform to stay dry anyway.

Well I think were getting somewhere.
Any ideas on the drilling part?
I could bring a hand drill but that’s a bit heavy. A powerdrill of course is out of the question, as there is no power (I could ask the guy’s from www.extremeironing.com how they solve it ) Drilling with a drill is a bit cheating in bushcraft anyway.

 

[Roving Rich]

You can drill in Bushcraft. I have never tried it but the principle is the same as the bow-drill fire method, just keep adding an abrasive such as sand. It looks like hard work, and must wear spindles out in no time.
Probably easier to get a hot coal and burn a hole through.
The north American Indians used to build canoes out of birch bark. But i can't figure how ! Surely its gotta be lots of little pieces and needs a frame.
If you are trying to keep deck space free you may be able to fly your tent as a kite, and pull the raft along behind it. Works for canoes and surfboards
Cheers
Rich

 

[martin]

Rich
Theres a book called "Native American Crafts & Skills"
ISBN 1-58574-070-5
Its got the plans for a Birch Bark Canoe

 

[sargey]

i suppose you could use a bashaboat for short crossings

perhaps with a big enough basha, lee boards and a stayed mast you could sail one.

cheers, and.

 

[Tony]

Basha boats are cool. Me and my mate got a big tarp and with some young men from a youth group we made one 12' by 6' and put 8 people on it and it didn't move an inch, solid as a rock :-D took a long time to build though!

 

[Gary]

Sargey that bullboat pic was it taken in Scotland - lake looks familiar?!

 

[Wayne]

Hi

The basha boat loks like fun.

Any advice for having a go.


Also have you thought of making a Coracle.

 

[Tony]

Ray Mears book bushcraft has some good pictures on it

 

[PC2K]

sargey didn't the other crew of the other basha boat got wet ?....

 

[woodsitter]

Nice pic.

A basha boat is very light (compared to a raft). I is filled with a lot of air, like a real boat. Because it’s so light I think a sail is less necessary to go somewhere 9or to avoid drifting some place you don’t want to go). By construction it is much more like a crude canoe than a raft, though by needed skill and the availability of tools and material it is much more like a raft of course. The big downside is the need for a very big sheet of waterproof fabric. The tarp is doing fine so to see. When it is used for a longer trip you could dismantle the boat at night to sleep and continue the next morning.
How long did it take to build it? How big is the tarp? Finding and cutting some scrubs and branches must be fairly easy, compare to felling half a dozen trees and building a 1.5 ton raft! But it is stronger and more durable. What do you do with your basha boat when it rains? You already used your tarp and you cant get the water out without turning the whole thing around. As a boat, it is sinkable, a raft is not.
I guess if you just have to cross a river a raft is not worth the effort.

Did by chance anyone come up with a way to drill wrist size holes in man size logs?