Hemp rope waterproofing - need advice

[Puchal]

Hi everyone!
I have just finished whipping the ends and braiding loops on two hemp hawsers for my canoe.
I'm not really sure, if braiding went well, since those were my first two loops I ever braided (till now I have just tied the loops regular way). Now my goal now is to make both hawsers waterproof.
I noticed, that as long as it is summer wet hemp rope dries quickly, but during colder weather it keeps water well, and starts to rot if not dried.
The first thought I got was to oil, or wax the ropes. Trouble is that only instrucables I found over the net suggested usage of "tung oil"
Well.. is there any easier way to preserve the hemp ropes? I do have a can of Swedish oil for the wooden floor, will it be good?

 

[ged]

...I have just finished whipping the ends and braiding loops on two hemp hawsers for my canoe ... during colder weather it keeps water well, and starts to rot if not dried. ...

Centuries ago the old sailors (we used to call them "tars") used to use tar. Now you know why we used to call them tars. You need something which will not be very liquid at room temperature, otherwise it will rub off onto everything and everyone with which it makes contact. Almost anything that will kill living things will work to some extent, but if you keep a hemp rope wet for very long periods it will eventually be destroyed almost no mater how you have treated it. Man-made fibres like polypropylene and nylon are much better in this respect, they are stronger, they absorb less water and they are easier to dry. They will be damaged by long exposure to sunlight. If you get ropes which are black they are much more resistant to damage by sunlight.

 

[Puchal]

Got it Ged. I'll try to produce some tar from birch bark. This I hope will do...
I do want to use the hemp rope, because my canoe is really traditional, and my goal is to keep it like that Sure, the sisal, cotton, and of course synthetic ropes would be better and more robust, but would they keep the spirit :-D
Thanks!

 

[Eric_Methven]

If you want to keep it traditional, try using Hempex. It is a polypropyline rope that looks, and feels like hemp. It is what they use on the old tall ships for the rigging. These guys wouldn't get maritime insurance any more if they just used natural hemp, so Hempex was invented to - keep the spirit, and satisfy the safety aspects from an insurance point of view.

 

[forestwalker]

Got it Ged. I'll try to produce some tar from birch bark. This I hope will do...
I do want to use the hemp rope, because my canoe is really traditional, and my goal is to keep it like that Sure, the sisal, cotton, and of course synthetic ropes would be better and more robust, but would they keep the spirit :-D
Thanks!

Using birch bark tar for this application is the equivalent of using ermine skins as TP. Plain -- but real -- tar dilluted with turpentine is probably the way to go. I think there is a recipie in Ashely, else I think Brion Toss has it in his Riggers Apprentice book. IIRC the instruction is to make your "slush", and on a warm and sunny day apply liberally to the ropes. Too much and they become stiffer but more water resistant, too little and you just add some smell. Thei idea is to impregnate the rope, not cover it.

 

[jojo]

It would of course be easier to use the rope Eric suggests. No rot, not need to waterproof and it looks pretty much right. If I remember correctly it's a polyester and it does stiffen with age (just llike me...) I don't see why you couldn't "weatherproof" rather than waterproof, rope, use boiled linseed oil (which isn't boiled!) or Tung oil. Standing rigging in the old days would have been heavily tarred, I am not sure if they used anything to weatherproof running rigging, but probably would not have used hemp. as Manilla has a longer life span outside.

The oil need to get through into the rope, not just on the surface. I'd probably go for the tung oil myself, as it's thinner. It won't do any harm anyway. You got the rope now, Hemp does not have a long life span outside, maybe a couple of years, 3 at most. so you might as well try to oil it.

By Swedish, do you mean Danish Oil? It might be a good idea to try it on a spare piece of rope first though, I got a suspicion it might stiffen it quite a bit.

It's possible to make "oil cloth" by soaking the fabric with linseed oil, so it's got to do the same for rope!

 

[John Fenna]

The traditional "tar" for rigging was IIRC "Stockholme Tar" - "distilled" from Swedish pine roots (Uncle Ray watched this being done in one of his progs).
This "Tar" is still available in some farmers suppliers as it is also used in animal husbandry to treat such things as small cuts (such as from a gelding knife....)
I

 

[forestwalker]

Brion Toss (The Complete Riggers Apprentice) suggests this for standing rigging:

6 parts Stockholm tar [i.e. real pine tar, not chemically processed stuff]
3 parts boiled linseed oil
1 part Japan drier
1 part spar varnish

For your application I would either buy my rope tarred, or just use a three part mixture of tar, linseed oil and turpentine (1:1:1). The latter is called "Roslagsmahogny" in Sweden, and was used for wooden boats, etc. Gives wood a nice color, and protects against rot. The name is derived from a region of the Stockholm archipelago (Roslagen) and mahogany, since it gave even cheap woods a "mahogany" like look.

 

[Toddy]

It's Stockholm tar we use in the boatbuilding workshops. I love the smell, Stockholm tar and linseed oil

On the old leather boats the lanolin that was used on the hides transferred itself to the hemp ropes and it kept them in good order too.

cheers,
Toddy

 

[Martti]

Well.. is there any easier way to preserve the hemp ropes?

An old Finnish (or Baltic-Finnish) way to preserve hemp and nettle gill nets was to boil them in container filled with water and alder bark. After a while the net is taken out from the container and ash is spread over the net to help the reddish colour to fix. Alder resists rotting underwater very well, so the treatment probably transfers this ability to the nets. Also the otherwise white nets would not catch fish as good as the reddish ones.

 

[Puchal]

Chaps!
Thank you all for help. I need to treat my ropes before the extended weekend in Poland begins - 23rd June is Corpus Christi, so half of the nation takes 24th as day off. I will be canoeing with my family, and would like to have ropes waterproofed by then.
Therefore option with tar must wait for the atum, when I will have more time to produce some birch tar. I suppose, August in Poland will be busy with hurricanes again, and we will have forests full of fallen trees. Unfortunately before the end of the spring most of those will be cleaned up by forest rangers...
BTW: State Forestry in Poland earned 0,5 miliard (US bilion) € on wood trade, mostly due to the heavy hurcanes we have had for past few years. On the other hand forestation in our country is also growing, so green guys must be doing good job

Jojo: you are right. This is Danish oild, from backers I guess. Proved to be excellent for wood, but I also used it several times for the leather. No problems found. Gives nice deep dark color, and leaves no smell.

So I will treat the ropes with linseed oil (no chance to get tung oil as far as I'm concerned), and will let you know, how it worked.
Cheers
Puchal

 

[mrcharly]

Linseed oil mixed with paraffin(kerosene) will work well.

After reading of it's use in Classic Boat magazine, I used it on a plywood dinghy that was stored outside all year. The wood survived snow, rain, ice without damage.

Like others said, it needs to soak right through. The linseed oil will oxidise to a dark colour after a while.

 

[JohnC]

Is it better (if making a rope from string) to treat the string first then twist the rope? I'd been having a go at making thin ropes from gardening hemp string and was thinking about the waterproofing aspects of it when I saw this thread...