The mast position in the drawing Matt posted was just a a guess. The one I show here is my 2nd attempt and is based on some rough calculations I made using the methods suggested in PJR. I should point out though the scale of the sail is slightly different to the scale of the boat. it was more to give myself an idea of how it would look. I have since scaled an image of the Tophat but I haven't printed it yet. Life getting in the way and all that.

Anonymous wrote:

Mast length for a Top Hat 25

Member Gary Pick drew up this (below) sail plan for a Toppie.

He was looking at a timber mast 220mm at the partners tapering to 100mm at the top, 9 metres long, which weighs in at 87kg (about 3.6% of the weight of a Toppie - Arne reckons 3% is ideal). Gary's already made it.

I thinking of going with the same, but I'm unsure about the length.

I've decided to go with a timber, keel-stepped mast right in front of the cabintop. That would give the mast 1.2m of bury, from the partners to the keel.

The sail, when it's made, will need to have a shorter lead to compensate - somewhat like Speedwell's (see pic), though not as far forward.

Graham Cox wrote of his experience with his JR Toppie Blue Moon: "The ideal place for a proper junk rig is just fwd of the cabin top, on the foredeck. Blue Moon has more lead in the sail design, 22-25%, to compensate, but it is not ideal. About 300-450mm further forward would be better. If you placed the mast right up against the fwd end of the cabin, on the foredeck, I think the position would be perfect for your (Gary Pick's) sail."

Graham also reckons 11m would be a good mast length Toppie.

Step 1 in my junk conversion, and the most difficult step for me, is getting the mast.

Time, space and skills mean I'm looking at having a mast made for me. I'm looking at a birdsmouth timber mast, 220mm at the partners tapering to 100mm at the top. Just like Gary Pick's. The only question is the length. I reckon i can manage fabricating partners and step, and bracing the underside of the foredeck, but a mast is beyond me.

So, how long should it be?

In my cruising grounds (Victoria, Australia) often as not the wind is 'fresh' - often too fresh. Given Toppie's reputation as initially tender, I think I'd rather err on the side of shorter, and keep weight aloft to a minimum.

Cheers,

Matt

 At the risk of showing my ignorance again.....    The drawing of Gary's sail plan looks far out of balance to my eye with the C of E far forward of the CLR.   That's a lot of keel back there.   I'd be interested in hearing the explanation for this.

                                                      H.W.

My mast is 8.3m above the cabin top fwd, so about 8.5m above the foredeck.  Spar length is 4m with a 6-panel sail giving 23 sq m.  It is more than enough when the wind is 12 knots or more.  But if I ever replaced the mast, I would make it 1m higher and add an additional panel to the foot of the sail, giving 27 sq m, which is close to the bermudian sail area.  Reefing is easy!  And  the weight of the rig is in the sail, not the mast, so the centre of gravity of the rig comes down as you reef.  The top of the tapered mast, without standing rigging, is both light and has minimal windage. You could get more than 23 sq m of sail area by going for a lower aspect sail, like Speedwell, but I am not sure if you will have enough drift for the sheet. (Though Speedwell, at 25ft also, apparently does.)  When my sail is furled, there is only about 300 mm between the lower sisterblocks on the sheetlets and the deck blocks.  Of course, if the mast is further forward, there will be more room aft, allowing slightly longer spars.

Here is a photo of Blue Moon taken recently motor-sailing down Moreton Bay in light airs.  Click on the photo for full sized image.  I have the tack of the sail pulled well aft here.