Hi Graeme,

It feels good for me to hear that you are confident about what I am trying to do, as I don't have any experience myself to reasonably assess this. I actually have quite a bit ahead of me, as the boat also needs to be restored.

My next steps will be the following:

1.)I will buy an aluminium mast tube. Most likely yet the one described in my first post wich have a100mm diameter with 5mm wallthickness and wich weighs 32 kg . I feel better using this tube instead of the 90mm variant because I have calculated that it will withstand offshore conditions. This gives more safety reserve but of course unfortunately also more top weight.

2.) The conversion of Ingeborgs sail plan for the conditions on my boat and the start of sail construction with the help of the instructions from the „The Cambered Panel Junk Rig“

3.) As soon as the outside temperatures allow it, I will also glue the mast step into the hull and the partner reinforcements under the foredeck together with the other necessary epoxy work.

When I get that far, I will document my progress here.

Best regards

Sven

PS: Please excuse me for misrepresenting the SJR mast position in my post.

Hi Graeme and Arne

Thank you very much for your tips, all the information and especially your drawings ! I am really overwhelmed to get so quickly the necessary criticism and answers.

Graeme:

Your comment on the mast position of the SJR is interesting. I have dealt with the SJR a bit superficially before, but I was more interested in The special features of the split sail itself. Knowing that with the SJR the mast position can be the same as with the Bermuda Rig was actually new to me. Cross-reading some of some JR conversion threads, I could sometimes glean that it might be better for some boat owners if they could keep the old Bermuda-mastposition. However, on my Alacrity, the SJR-mastposition would be less favorable than the position I was originally aiming for. This is due to the really very small and narrow interior of the cabin. Without a mast or mast support at this point, the interior is more habitable for me. The further the mast moves forward, the more freedom of movement I gain.

Arne:

Your sailplan looks really great ! Of course, I will not be using my "draft" that is a adaptation and provisional, but the plan that is your suggestion. Thank you very much for that. Also for the notes about the yard angle and the effect of my faulty CE on the weather rudder.

How fortunate that I can actually use the well documented sailplan of the Ingeborg!

This allows me to start building soon instead of spending time on calculations and with the planning. Of course, this also means that I will get on the water with my boat faster.

Ps: I am really glad that I decided to post my request here !

Sven

Sven,
it is tempting to make use of existing sailplans to save time and trouble. However, in this case I found a couple of arguments against it.

• ·         Your drawn CE sits 2.59m aft of the bow, while the CE I found of the Bermuda rig sits only 2.27m from it. I believe your sail in that position would result in more weather helm than you would like.
• ·         The 60° yard angle I used on the Ming Ming was to let me push the sail forward and get a good helm balance without needing that jib.
• ·         I aim for seven panels if the AR of the sail stays between 1.90 and 2.20. Reducing the number of panels is in my view false economy.

Now I found that a standard Johanna sail (Johanna 70, these days) with an AR of 1.90 and batten length B=3.40m would produce your required 17sqm. This happens to be the same planform as I use on my own Ingeborg  -  just a coincidence. The fore-aft position of its CE is in the same place as in the Bermuda rig. The combination of about 15-16% mast balance and 70° yard, results in a halyard angle (halyard to vertical) of just 12°. This ensures easy setting of the sail, and freedom to move the sail a bit forward or aft to get steering balance just right.

To produce a ready-to-use sailplan for your boat, I therefore suggest that you download Ingeborg’s sailplan and print out sheet 1 to 4. Then you downscale all the dimensions, using the scalefactor SF = 3.40m/4.90m =0.69388.
On sheet 4, showing the batten pockets, you may draw in your mast position, and possibly adjust the batten pockets a little.

Good luck!
Arne

PS:
The needed running lines can be found in Junk Rig for Beginners.

(For full size drawing, go to Arne’s sketches section 7, photo15)

I am sure Arne will be able to give good advice here, and I believe the mast position you have chosen (through the forward hatch) will quite possibly suit one of Arne's Johanna variants, and satisfy your needs, so what I am suggesting here is probably just for academic interest. 

I am basing this on the bermudan sail plan for the Alacrity 19, according to "SaiboatData.com".  A VERY rough eye-ball calculation of the centre of area of the designed bermudan rig is shown in the first part of the diagram.  (I don't have CAD software so don't take this as 100% accurate).

Just for fun, let us consider a Split Junk Rig.

I am more and more confident now of the rule of thumb given by Slieve McGalliard - that is: the centre of area (CE) for a split junk rig (SJR) should coincide with the centre of area of a correctly placed bermudan rig. This allows us to impose a split junk rig onto the drawing without having to go back to first principles and calculate the geometric centre of the underwater hull (CLR). Because the SJR requires the sail to have a mast balance of 33% it is now possible to derive the correct mast position for the this particular rig. As you can see from the second part of the diagram, this derivation places the mast between the cabin and the fore hatch, just a few inches forward of the original mast position. (The sail shown here is the Amiina Mk2 designed by Slieve).

If this is a more convenient position for your mast, then you might want to consider a low yard-angle high mast-balance rig such as the SJR.

(My personal opinion is that this rig might suit your boat quite well - it's pretty well-proven now, and the mast position looks to me to require no changes to the standard interior layout and would allow you to retain the forward hatch. You might like to scroll down through the "Boat of the Month" archive here, until you come to Feb 2022, and have a look at Amiina.)

I have no doubt a Johanna rig will suit your boat very well too. The McGalliard rule of thumb may not apply exactly to Arne's suite of Johanna rigs - I am not sure - but the high yard-angle/lower mast-balance of these rigs will need the mast position further forward than the Amiina Mk2 sail we see here. For modern conventional junk rigs, the lower the mast-balance, the higher the yard angle, and the further forward the mast needs to be placed. This makes me feel confident that one of Arne's sail plans will most likely suit your proposed mast position through the fore hatch area.

PS: The split junk rig is an extreme high mast-balance rig, and places the mast as far aft as a junk rig mast could possibly be placed on a single mast configuration. This gives you one end of the spectrum of possible mast positions. My guess is that somewhere around the centre of the fore hatch is probably the extreme other end of the spectrum of possible junk rig mast positions for your boat. A suitable junk sail type  can be drawn which will be in harmony with any chosen mast position between these two points.

PPS: "mast-balance" is a term coined by Arne which conveniently describes the ratio: (area of sail profile ahead of the mast centre line) divided by (total area of sail profile)

Edit: that SJR sail I imposed onto the Alacrity 19 sail plan drawing might want to be scaled down in size just a little, it looks like slightly too much sail area, on second glance. That is easily done and won't really affect this discussion on mast position.

You most certainly can make your own sail and I would recommend you do so. 

Amiina racing with her Mk 1 Split Junk Rig

The above sail was professionally made and although it was strongly built and is obviously pushing the boat along very well - as you can see from the photo it is not a particularly good example of a well cut modern cambered junk sail. 

The Mk 2 (below) was home made.

hello to all of you

In may 2022 i bought an alacrity 19 sailboat, which is a 50 years old bilgekeeler with a bermuda rig. The boat is 5,70 meter long, the beam is 2,11meter, it weights 680 kg and it has a ballast share of 32 %. Actually, it was my plan to have a Junksail made by a sailmaker for my boat in the fall of 2022. Unfortunately, I had to give up my plan for the time being due to various problems.

In the meantime, however, the thought of equipping my boat with a junksail did not let me go. I dealt with the extensive literature available on the JRA website and some forum entries on the subject of junk rig conversion. At some point, the DIY instructions from Arne Kverneland ( The Cambered Panel Junk Rig ) came into my hands. I realized that with these instructions it should be possible for me to sew a cambered junksail and build a mast myself instead of having to buy everything. I soon realized that DIY is the fastest way for me to finally get my boat on the water with a junk rig.

So I started to calculate with the instructions where I would have to place the mast, what diameter and quality it should have etc.. In the meantime I managed to calculate the CLR and the lead of the Alacrity 19 and to create a preliminary sail plan.

The planned sail has an area of 17 square meters. It is noticeable that the CE in my plan is almost exactly above the CLR. I think that the mast should actually be further forward. Unfortunately, this is almost no longer possible.

However, I am a little afraid to have made a mistake with this first step. Therefore, I would like to ask the experienced forum members to take a look at my sailplan and report back to me whether everything is so far in order. I also have the following specific question:

I am able to buy two types of 8 meter aluminum flagpoles (AW 6082 T6) with different diameters that I could use as masts. I have calculated the breaking load of a 90mm diameter and a 100mm diameter flagpole with the help of the instructions from The Cambered Panel Junk Rig. For coastal-cruising the 90 mm diameter mast, 4mm wallthickness and a weight of 24 kg should actually be sufficiently strong enough. The 100mm diameter mast with 5mm wallthickness wich weighs 32 kg would even meet offshore conditions. I tend to the 90 mm mast because of the smaller weight. But i thought it would be better to ask profesional junk sailers to which diameter of the mast would you advise me to choose ? Actually i only want to sail in the near of the coast of the baltic sea with an adequate safety reserve.

I would be very happy if some one could give me feedback to my projekt. It would really help me a lot to finally be able to start with the conversion.

Sven