Thank you very much for the encouraging words Arne!

Your opinion is very important to me....

I wish you a soon recovery

Mauro

I think I got it!

Looking between the sketches of Arne I’ve find one, showing Pilmer with a junk sail of 21.4 sqm. 

In his drawing, Arne moves the mast position forward to the original one and uses a sailplane with 70° yard. The boom is 3.76m, the mast has the same hight of the original one (8.3m).

As I wrote before, I’d like to get a new mast for my KF 20+. Nevertheless, I’d like to left untouched the mast position and be able to increase the sail area in the future. 

I grabbed a sailplan with 60° yard and AR 2.18 and I overlaid it on Arne's drawing using the same boom length and position. With my surprise, the mast position shown in the 60 yard sail drawing, largely overlaps with the original mast position of the KF20+! 

I must admit that I used power point for doing this…yes, I am a digital neanderthal…

Anyway, scaling the boom from 5077cm to 3760 would mean to have a linear scale factor of 0,74.

The area scale factor is accordingly 0.5848. The desired sail area of the new sail will be 24.791 which means a SA/Disp of 20.65. The new mast should have a length of approximately 9.5m. 

This is the measure I was looking for in order to commission the new mast!!!

Moreover the new sail could improve light wind performance and reduce weather helm.

Every comment to my first sail plan, is very welcome and appreciated!!

Attached are the sketch of Arne and mine (with the overlaid sail).

Mauro

I‘ll post their answer Graeme….

Hi Mark,

thank you for the reply! With a fixed hinge, folding the mast is a quite straightforward procedure…. I have rigged running mast lift and topping lifts, lowering the sail bundle on the deck takes a couple of seconds and when folding the mast I don’t have to disengage anything….the boat cover is already made for this mast! 

Maxspar is a professional company making spars for super yachts, I will ask them about combining alloy and carbon, thanks for the advice!

Hi all,

After 3 years of intensive use, it is time for Shui Jen to get a new mast. 

Her hinged one is a very smart piece, made of two parts connected by a hinge and with an alloy tube sliding on the hinge. Folding and unfolding are easy procedures that I can manage alone making the boat ready for crane and trailer in about 45 min. The hinged mast transforms this pocket cruiser into a trailer sailler which is an intiguing feature that expands the range of our costal sailing. Last but not least, the folded mast enables an easy inspection of the top gears and works as a support for the boat cover.

Unfortunately the mast is 50+ years old, is quite heavy and has a lot of sign of intensive use. My aging iliosacral joint and multiple reports about old alloy spars snapping suddenly make me think about replacing it.

I’m thinking about an hybrid one: 1) the lower alloy part will be reinforced with an internal carbon tube making it double and stronger; 2) the upper part will be replaced with a new carbone spare; 3) the hinge will remain the same one; 4) the sliding tube will be also replaced with one of carbon fibre. The idea is to make the mast lighter to fold and unfold but stronger. I’ve already found a company that would make the job.

I am also thinking to incorporate the mast top in one piece and to make the upper part of the mast a bit longer in order to reduce tension at the halyard blocks and give me the opportunity to increase the sail area in the future. This is the second point: Shui Jen appears to me a bit undercanvassed (actual SA/D 16.8) and with a bit too much weatherhelm.

Shui Jen is a KF 20+JR and like Pilmer (the last boat of Blondie Hasler) is a JR production boat. Her mast has been probably set a bit too far aft and her original mast from needlespar is thin. Nevertheless, I’d prefer to work on mast materials and sail balance rather than starting a major surgery project by changing mast position and its diameter.

In a former post on this thread Arne wrote: “Maybe that tactics could be used on your boat as well? Now I checked. If we start with one of my master sails, the one at AR=2.20 and remove the lowest panel, and then scale it down until B=3.65m, the AR will drop to 1.94 and the sail area to 20.1sqm. It will look like a close cousin of Frøken Sørensen’s sail, only with six panels. Then, later you may find that you can fit a taller mast and set a seventh panel. This will bring the sail area up in 23.4sqm and the SA/disp. to 19.4, which is not bad. Moreover, the sail’s fairly high AR will give a tall leading edge for better upwind performance“.

Would be such a sail with a lower yard angle a good solution for me? How much higher should be the new mast to get her? Any suggestion about dimensions of the top gear support? 

Dimension of the mast: 8,3 meters,  7 m above the deck; 10 cm diameter at the base and 6 cm at the top, 3mm thickness.

Actual dimrension of the boat: LOA 6.58; displacement 1315 kg; 

Actual dimension of the sail (same of Frøken Sørensen): 20.2 sqm, 70 deg. yard, batten length 365 cm.

Sailing ground: the Adriatic sea, light winds and sudden squalls.

Thank you for the inputs,

Mauro