Likely displacement weight folkboat

[Laminar Flow]

To approximately calculate the displacement of a boat (in metric):
LWL x BWL x depth of hull sans keel x a factor of 0.30-0.34 for a vessel of this type and era (Marconi)

I checked this on my own boat and it was surprisingly close.

 

[GeoffNZ]

Wow great discussion and lots of ways of coming up with a weight but then it sounds like going above 5 KW wont gain anything other than a bit more weight and a little more expense. She apparently had a Volvo 8 hp but came to me without any power unit,
Had to pull all the stainless tanks (twin diesel) aft and twin water tanks midships to repairs ribs/frames. Also removed the liberally diesel soaked ply that used to surround the engine so she is now pretty empty aft and no longer reeks like a diesel spill.

So its strap an outboard to the transom, a small replacement diesel unit, or go with an electric unit.
I am considering a setup like offered in Thunderstruck.ev, 5Kw sailboat kit - Motoenergy 1718, a Curtis or Servon controller and a bank of 4 AGM 12 volt batteries 100 AH plus + bits and pieces to hook it all up. Run as a 48 Volt system. Charge from shore power and solar panel.
Seems pretty much plug and play and within my skillset to install. Should we wish to venture further afield a small back up generator would be an option.

Each route having its pros and cons.

 

[Tranona]

Each route having its pros and cons.

Indeed. Not familiar with that particular electric setup - but that battery capacity will give you little more than enough range for on and off mooring! With a small light boat such as yours adding decent capacity to enable some motoring while away cruising will add weight, take up space and only make useful recharging problematic. Even in your more sunny climes , solar is limited by the area you can fit. A generator backup just does not make sense on a small boat and means carrying petrol.

If you just want to sail and use a motor when you can't and for getting in and out of berths then an outboard is first choice. If you want a reliable source of power for motoring fit a Yanmar 1 GM or for a bit more money and sophistication Beta/Nanni 10. These are not smelly, smoky, leaky etc and sit there obediently waiting to be called upon. 50l of fuel will give you over 100 hours of motoring.

 

[doug748]

Each route having its pros and cons.

It does.

I think the weight issue has been covered but Nordic Folkboats were down in the 4000 lb area. I agree with the others, your boat may be 6000 lbs and, if I had to guess, I would say nearer 6500 with some cruising gear.

However I still would go for the smaller power unit, it's function is to work for 3 minutes to get into a berth, you have to avoid the notion that you can motor into headwinds for a couple of hours. Folkboats are so handy you hardly need an engine at all, particularly if you have a swinging mooring, are perhaps involved in local sailing/racing and have a measure of patience when the wind is dodgy.

I had a plastic version that probably displaced about the mid range of those figures, the best engine I had was a 6hp Evinrude, if I had that boat again I would go down to 4hp, Just for the ease of use.

.

 

[jamie N]

STAKKR, when last lifted out weighed +/-3000kgs, which surprised me as I'd always gone along with the line that they're 2,000kgs; why was mine a 'chubster'?
She's from the 60's, she'd been in the water a while and so on, so 3,000kgs is a good mean weight I'd say for the real world.
8hp engines are enough, but only just and will still labour into a good wind/sea, or other places that aren't the North of Scotland. Up here a 5kW electric wouldn't crack it I reckon, although I realise the Pardy's sailed without an engine, I'd not like to be crossing the Pentland Firth without an engine that can run for a decent period of time.
As an outboard option, I have a Honda 2.3hp that has fulfilled the role many times before I got the inboard sorted, but that required planning, and I always felt safe enough with it as it'd give me a chance, provided that I'd planned for losing the wind near the Skerries for example, but an 8hp, or more inboard does cover so much more ground, and does make life easier. I'm lucky also in that I keep my Honda on the back of the boat as it's SO useful around a marina with its directional thrust. Folkboats are super going forwards, but utter rubbish astern!