Andrew wrote: ...I've done some preliminary work on the CLR and CE which is well out of my comfort zone.

You really don’t need to do that. If your boat handles satisfactorily with the existing rig, then find or make a reasonably accurate drawing of the existing Bermudan sailplan and determine its CE. Then superimpose a scale drawing of your chosen junk sail so that its CE coincides (on the same vertical line) with your existing Bermudan CE. (The CE of the junk sail will normally be on a vertical line which passes through the midpoint of the boom, near enough).

Now that the two sail plans coincide in terms of CE you can expect the handling (lee helm/weather helm) of the junk rig to be about the same as the bermudan rig. Experience has shown this to be the case with cambered junk rigs.

Now, this will show you where the mast has to go, depending on the type of junk sail you have chosen.

You will have discovered that different junk sail planforms have different amounts of “balance” – the percentage of sail area ahead of the mast. 

This is where you can experiment, on paper, until you find a planform which puts the mast where you want it to go. As David pointed out, the extremes are the Weaverbird wingsail type with ultra low balance, which puts the mast as far forward as you could go, - the SJR with its ultra high balance, which puts the mast about as far aft as it can go - and a range of “normal” HM and Johanna-type junk sails which can be found which will put that mast anywhere between these two extremes.

Summary: determine the existing CE. Find a junk sail planform, scale to the same sail area and fit it to the existing CE.  Choose the type of junk planform which matches both the existing CE, and the desired mast position.  

I hope this (not to scale, and slightly exaggerated) drawing explains how junk rigs of different balance give you a range of possible mast positions, with the CE matching the original  bermudan CE. 

This is not rocket science, it is merely geometry.

… use the existing mast and halyards to put the new mast in position, then de-rig the old mast and use the new mast to unstep it.  That has been done before, successfully, and it is a very good idea.

Hi Andrew, I agree the being able to use the forward hatch is a great feature on the Sabre 27 and in designing my installation I retained that feature. It did mean positioning the mast in the deck area immediately in front of the doghouse as had been done before on the boat fitted out by Sunbird Marine. However, this position is a bit too forward according to the PJR book and caused me problems as described later.

The sailplane used on the boat from Sunbird Marine (Sunbird 80's rig as illustrated in PJR) appears from photos to have an AR of 2 of greater with the sail is sheeted to a traveller on the bridge deck by the companionway as per usual arrangement for the BR rigged Sabres. In conversations with  Robin Blain he explained that the boat initially  suffered from extreme lee helm which was corrected by raking the mast aft 3 degrees. I also raked my mast aft by the same amount to meet the PJR recommended CE position of the sail relative to CLR of the hull. However, as mentioned in my earlier posting my original flat cut HM sail AR1.5 batten length 5.5m generated to much weather helm when off the wind which was corrected by recutting the sail, AR 2, all battens & Boom 4.2m. The mainsheet blocks are attached to a bridle across the transom. The CE of the recut sail coincides with that of the BR sloop.

I had considerable freedom in the fitting out of my boat because I was starting from a bare hull & deck moulding which had been stored in a barn for 20+ years by the original owner and  was in 'as new condition' according to the pre-purchase survey. No work had been done by the original owner mainly due to business commitments.

To distribute the weight towards the centre of the boat  I positioned the water tanks (2x 62liters)  over the bilge keels, as opposed to fitting a 120litre flexible tank forward as per the conventional Sabre arrangement. I thought this might compensate for the compromise with the mast position and associated weight more forward than ideal.

Further, I was able to move the heads compartment aft to starboard besides the companionway taking advantage of the offset companionway.  This arrangement enabled me to create two full-length single bunks forward with an infill panel to convert to a large double berth which is our usual set up. I also repositioned the anchor locker bulkhead further aft immediately in front of the mast to strengthen that area. The anchor locker  drains overboard.

I do have an ongoing issue with the forward position of the mast which with my current anchoring set up which makes my boat too bow heavy and negatively affected the motion of the boat upwind in anything but smooth water.  I am currently using an all-chain rode which together with an anchor totally 100kg+. Last year, to reduce weight up forward, I tried a rope/chain rode but just didn't feel secure overnight and the amount of scope required was problematic if there were other yachts at the anchorage. I'm now planning to move the chain locker aft and directly above where the head compartment is located for the conventional Sabre 27 layout.

You commented that you're  on a tight budget, so was I, which accounts for my taking 15 years to complete the fit-out! I hope your project can be completed sooner. I've uploaded a photo to give a better impression of the layout.

Best wishes, Frank

Anonymous wrote:

Hi Andrew, I read with interest your intention to fit a Junk rig to a Sabre 27. I fitted out, from a bare hull, a Junk rigged Marcon Sabre 27, twin keel. To my knowledge my vessel was the second Sabre 27 with a junk rig. 

It would make more sense to provide a scale drawing of your current sail plan.

You should aim to geometrically match the proposed junk rig to the original Bermudan sail plan (that is, the geometric centres or CEs of the two sail plans should match), if you want approximately the same helm characteristics from a cambered panel junk sail.

I don’t know whether or not this drawing is true to scale, or whether it represents your version of the Sabre 27, but at face value and doing some rough calculations: to match that sailplan a SJR (33% balance) should have its mast at least 30" - 33” forward of the above mast position.

Having said that, I don’t necessarily trust the Sailboatdata drawing, having seen an example which was considerably in error. If your drawing would show the current mast position, and the planform of your current rig, the calculation for mast position of any junk rig is fairly simple.

(The hands-on experience of Frank is valuable in this regard too, taking into account the bilge keels, his flat-cut sail and the tendency of the boat to acquire weather helm when heeling).

I don't include myself in the expert category at all, and I don't have the means for accurate drawing, but my guess is 22" is likely to be marginal to say the least, even for SJR, if the above drawing can be believed. 

Maybe you could consider what is a fairly commonplace conversion: take the mast down through the forward hatch, offset a little, and lose one of the forward berths. That would open up a range of JR options. There are plenty of documented examples of thru-hatch arrangements, for example Jes's Mwera conversion (JRA Magazine #100 March 2026).

This begs the question: "enough for what?" 

We know:

1. that SJR has a mast position quite well aft, so probably enough for that.
   
2. that a wingsail similar to mine has the least balance, so probably not enough for that.
3. that in between those extremes, one of Arne's sailplans can probably made to work.
4. that a higher AR generally results in a mast position further aft.

You've demonstrated that you can make a drawing, so now it's time for you take ownership of, and responsibility for, the design process, and rustle up some initial design sketches with that knowledge in mind, and with some idea of what kind of rig you would like, to suit your style of sailing - relaxed family cruising, as I understand it. If you can  make and show us these sketches, we'll have something to comment on.