Thread: Tom Cat

My trip to the Tasmanian Wooden Boat Festival was just great! Spent four days in Hobart without the better half so was able to concentrate to soak it all in without the usual distractions. If you have the chance, just do it. This was my third festival and I’m already hankering for 2019!

OK, back to the boat – the Mast Support is coming together…the plug was fabricated and fit. Must say it was a pretty average fit but considering its use I’m sure the extra epoxy used won’t make a hell of a difference. It’s all good training for the real thing! My methodology was to epoxy together two staves at a time to end up with four pieces to finally assemble around the plug.

It all went together really well and am on to the finishing stages. Planing is done - 8 sided, 16 sided and the take off the corners left. Now down to the glass paper – to that end I found a piece of pipe this morning that I will use to assist in this final rounding process by gluing the paper to the inside of a piece of half pipe. We'll see how that goes and once that has been completed I will cut a tenon in the small end to fit the Mast Step and fabricate a spar support for the top end. Stay tuned!

Glue up of the Core...........................Core 8 sided to fit

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Final glue up....................................Rounding commences

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Awaiting final sanding
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How do you cut the internal mitres - is it router table job?

I always thought bird's mouth masts were hollow and that the technique was to give strength and light weight. Given that there is a solid plug inside this can't be correct.

So now I wonder what the advantage is over a solid mast/spar made of flat laminations?

I am lucky enough to have a Triton table saw workbench and it comes with a 45deg fence on the opposite side of the normal 90deg one. See pics...

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As a far as the Mast is concerned it is hollow for 75% of its length. Strength is required at the bottom where reinforcement is required at the base, through the Deck opening and past where the Boom Jaws contacts the Mast so that is about a metre long. It also has a reinforcement piece in the top about 265mm long. That provides a hollow percentage of 75% overall. Note also that the piece in the pics above was not only an experiment with this construction but was made longer than required for the Trailer Support so that I could see the transposition from a taper to the actual Mast diameter for 300mm or so just to satisfy my curiosity. I will need to cut it off about that 300mm mark. This Mast piece will have a Support piece glued and bolted on at 90deg with cut-outs for the Spars to lie into. Haven't figured anything out for the rear at this stage so any thoughts will be appreciated!

One thing I have learnt is to cut the bottom tongue prior to rounding the Spar as this should assist in obtaining its position accuracy.

Hi Laurie! Can you tell me that you made a decision to make the breast hook larger? As I approach this I think it makes good sense to extend the size of the breast hook aft so that it joins the fwd face of the deck beam and is strengthened by the support of the beam; yes?

Your work on the mast is very interesting. I think your trailer support means you're going forward with a non-hinged mast. I'll be interested to see how this works out with lighter hollow construction and stepping arrangement/management.

Best to you,

Greg

Hi Greg, you got it! Yes, I went for the extra strength in a full coverage of the area between the Bow and the initial Deck Beam. The thickness on the centreline after the two 25mm (1") laminations ended up at 50mm (2") so I have 12mm (1/2") extra thickness there fwd and aft.

As far as the mast is concerned I never ended up finding a mast hinge that "filled the bill" so to speak so am going forward as originally designed. It's not large and hopefully the hollowness will keep it within my lift / weight ratios!
Cheers
Laurie

OK , big help as always. Your documentation is so good that I can see pretty readily how the problems interpreting the plans to the build have been solved. combing and deck support have always been an area of question but with your help and some thinking I'm pushing forward.

i am going to consult with some people here on the hinge idea with stays and will have to see how it all goes. It certainly isnt an easy proposition...

You'll be launching before too long Laurie! That will be a glorious day!

my best to you,

Greg

More help requested please? Back in post 260 you made a mast collar (and a nice one). Can you tell me the inside diameter (deck hole size )? If your graph paper is inch based it's a 5 1/8" hole which seems right.

Follow up question...

Does the mast hole in the deck taper? If so, to match the mast taper?

Thanks and more thanks Laurie!

Hello again Laurie. It looks like the plan view on sheet 2 of the plans depicts 2 circles, neither one of which is 3.5" in diameter. I'm thinking this indicates a tapered hole in the breast hook which would be consistent with the profile view shown on the same sheet.

The tapered hole then provides enough room for mast wedges to be used to secure the mast. Is this how you saw it?

We’re getting there…but first answers to Greg’s questions.

a) The graph paper is metric - Aussie you know! Still can’t understand why the US population can’t get its international act together. It’s like you’re on another planet! Anyway, enough! The diameter of the hole is 4-1/2” giving a 1/2” gap all round (is that better?). My original intention was to insert about 8 tapered pegs to shore her up – the intention was for this larger hole to provide some play for insertion considering it was coming in and out every time I go sailing. However, I found that a piece of rubberized floor mat may be a better option then the pegs. It is as hard as nails but has that little bit of give whilst inserting and doesn’t move a fraction once in position. It can also be replaced at will. After much consideration and reflection I perceive Bill was providing a tapered hole for a tapered mast to fit into without any gaps. Just insert and it’s all over – drag her out when done.

b) The hole I have created doesn’t taper but should. This was a mistake in not understanding this area. The mast is slightly tapered from the base to just above deck level ie. 24” before tapering again before reaching its maximum diameter of 3-1/2” for a hollow birdsmouth spar. In answer to your question the hole should match the mast taper.

c) The plan view on Sheet 2 appears to depict the smallest diameter of the mast at the top and the widest diameter of the spar overall. In other words a plan view with the mast in place. This outer circle you refer to could be either 3” or 3-1/2” depending upon the type of mast construction. Mine is 3-1/2” being consistent with the hollow spar plan on Sheet 9. It’s weird because you are the second person taking great heed of the data on Sheet 2 when Sheet 9 provides all the facts about the spars. The only data I see there is the positioning of the spar not its dimensions. Mind you I have not purchased the plans, I’m building out of the book plans.

Meanwhile, work continues with the Mast Supports – the Bow Support is complete except needs finishing and the piece of matting installed. The Stern Support is coming along and will sit inside the Coaming and fit into a slot in the center seat board. Also the mast cutouts in the top of the Supports need lining with some spar friendly material. It’s a toss-up between some leather or more of the matting.

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So... just the top of the Aft Mast Support to be added, the Tenon and the bottom Seat Plate installed and we're ready for finishing.

I have pretty much come the the conclusion that I will have to go with an unhinged mast. The cat boats I see that have shrouds also have a quickly widening beam up forward giving the wide base of support while allowing the boom to let way out on a run. Gardens design is quite a bit narrower in this regard.

I will go birdsmouth too and figure out easiest mast step; maybe a 6' (2 meter) ladder always at the ready; clip on halyards and lazy jacks; gaff n boom with pins on the retaining wires...???

Garden switches! The book steps the mast through the partners with narrow clearance while the plans show a substantial collar. I like your approach best using the hard rubber; one or two pieces snugged in and all's well. I have had dislodged mast wedges too many times to stay with that, good thinking!

Best to you,

Greg

Hi Greg, thanks for the comments - not sure I understand the 6' remark! All the rigging can be completed prior to install each time. Can't be that hard!

All fitting is now complete on the Supports and ready for finishing with the exception of the fixings required to marry the Rear Support to the Coaming piece. I attached a brass plate to the seat to ensure the bottom of the Support doesn’t wear a hole in it.

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Unfortunately my existing Mast Collar fitted to the Deck does not meet my needs in that it is made from a single piece of wood and considering some previous comments I have decided to create a new one with grain orientation in all opposite directions. I have added a 3mm piece of ply between the top and bottom opposing pieces. The idea is strengthen this area.

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Finishing has commenced to the stage where three coats of epoxy have gone on the two uprights and my new Mast Collar - all sanding complete.

Unfortunately I now have to wait for more undercoat to be delivered! Ah well, the update is better than nothing!

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Moving on with the painting of the Supports and now have 5 coats Primer, 2 coats Pre-Kote and two coats Brightside. Used old paint colour from a previous build and got into trouble with the better half as the cream doesn’t match the boat! My view of the world is the Supports don’t belong to the sailing configuration and it was free so don’t see the issue!

After fitting I realized that the Rear Support needs a wood tapered piece with a thin piece of foam inserted where it meets the Coaming so am in the middle of getting that ready - not finished yet, hence the tape.

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Also finally attached the deck mounted Mast Collar so now that needs finishing – undercoat and finish coat. All time consuming.

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I have also made a move on the Mast and begun the slicing up of the roof rafter I have (Oregon pine). Looks OK but definitely in need of a bit more wood – too many nail holes on one side so it appears I will only get 6 of the 8 staves required - disappointing, I thought I had it covered. Before I commit though I need to do more sawing to see what I finally get.

You could always go with a six sided birdsmouth, instead of 8, if you have enough.