Mastlength and masthead for spinnaker

[Pius Bielowski]

Hiya!

We hope to have our TIKI 21 in the water soon.

One of the last steeps is the constrution of the mast. We have ordered an aluminum tube but it is only available in 6 meters. So we will have to make wooden inserts on both ends. Are there any hints on how to fixate the inserts?

Concerning the mast we will follow the plan but I am thinking about two modifications:

Increasing the mastlength to 7m. I know about the importance of keeping the center of effort as low as possible but I imagine it would improve comfort on the plattform to hoist the main 50cm higher in light winds. Are there any experiences with this idea? We will anyway use 6mm wire for shrouds and forestay, the sails remain unchanged.

Secoundly I would like to use a spinnaker or gennaker. This means there must be a second halyard which exits the mast above the forestay. I have seen mastheads with a mastcrane and a pulley ahead similar to the arrangement astern for the gaff. Unfortunately this means the halyard goes down ahead of the mast and cannot be hidden by the luffpocket. I dont like the idea. So I am thinking about copying the jibhalyard disk-arrangment.

Please tell my your thoughts about this. Approved solutions and pictures are welcome.

Ciao

Pius

[kim whitmyre]

Pius,

Think about using aluminum tube sleeves to add the proper length: much less maintenance!

On the left is the mast, lower middle is the sleeve (with unseen slot for compression cut into it), and mast extension on the right. The cuts on the sleeve eliminate point loading that a straight cut would cause. Fix the sleeve with monel rivets, or use stainless machine screws with plenty of anti-seize, ie, Tuf-Gel. I have the formula for sizing the sleeve somewhere: I'll post it. (the tubes are all the same size: the mast is on horses, so closer to the camera.)

Here is a shot of my masthead arrangement:

The jib halyard is internal, the main and peak (gaff) halyards run through blocks that hang off the aft crane, while the forestay uses the shackle, and the fore crane hole is for the light-air halyard block.

[kim whitmyre]

Let me add that I applied polyurethane adhesive from a caulking tube to the inside of the mast and mast extension right before assembly.

[Rogerio Martin]

About spi halyard, you can use like this: 

[Rogerio Martin]

about extend alluminium tube you also do like this:

And follow the plans measures for top and foot mast

[Rogerio Martin]

Hanneke say to me a long time ago, when I wanted build one tiki 21 mast with 7m, using 6m aluminium tube and wood top and foot:

Can you not buy a wood that is reasonably light weight so you can make a wooden mast? Timber weight should be approx. 30lbs/cuft - 500kg/cum. If the wood is a bit heavier than that you could make the wall thickness thinner. Using the 4" aluminium tube with two 0.75m long (0.25m into the tube) inserts will also get heavy, particularly if you use solid timber.

[Pius Bielowski]

Thank you folks for your inputs.

Kim your solutions look very sophisticated and nicly done. However I think the lowest part of the mast should be wood not to damage the center beam.  And in addition we are not so familiar with metalwork.

I think we will stay with the wood inserts. Since it is easier to us and we can use srews to fix cleats just as we like.

The plan in the moment is to use solid spruce with 30 cm into the tube. So 100cm on the lower end, gives 70cm extension, and 60cm at the top, another 30cm extension.  In my opinion this should not be too heavy (and we have the heavier part down) but I don't know by now what the actual weight will be.

Rogerio how have you fixated the insert on the tube? Is it glued or srewed? I assume the shrouds and forestay keep the mast together anyway...

Fair winds

Pius

[Rogerio Martin]

Pius, I show two diferent masts. The frist, with halyard yellow is my boat mast. All wood wharram original tiki 30. The second mast is Aotea mast. Aotea is a Wolf's  Tanenui. See all pics here :

http://wharrambuilders.ning.com/photo/photo/listForContributor?scre... 

Pius Bielowski said:

Thank you folks for your inputs.

Kim your solutions look very sophisticated and nicly done. However I think the lowest part of the mast should be wood not to damage the center beam.  And in addition we are not so familiar with metalwork.

I think we will stay with the wood inserts. Since it is easier to us and we can use srews to fix cleats just as we like.

The plan in the moment is to use solid spruce with 30 cm into the tube. So 100cm on the lower end, gives 70cm extension, and 60cm at the top, another 30cm extension.  In my opinion this should not be too heavy (and we have the heavier part down) but I don't know by now what the actual weight will be.

Rogerio how have you fixated the insert on the tube? Is it glued or srewed? I assume the shrouds and forestay keep the mast together anyway...

Fair winds

Pius

[Pius Bielowski]

Okay guys, here is my solution.

I used solid spruce inserts as said before. Getting the mast up was pretty easy so it is not too heavy in my opinion.

I copied the fixed disk of the jib halyard for the spinnaker/gennaker halyard. It looks as follows:

[kim whitmyre]

Just to finish what I posted before about the aluminum version. . .Here is the drawing with the calculations for sizing the sleeve:

I used the same wall thickness for the mast and sleeve.

[Ian Bamsey]

Pius,

I'm building a new mast for my TIKI 21 also. Do you go for 7m or not? I'd be really interested in any details on your final design details.

Thanks

Ian

[Pius Bielowski]

Hi Ian!

We have completed the mast. It is 7 meters. BUT the boat hasn't been watered, so I cannot provide any practical experience!

We had the 6 meter aluminiumtube, 3mm wall in our case. We added two inserts made from solid spruce. the lower part is 100 cm in total but 30 cm slide into the tube (this part must of course be reduced to allow for the wall thickness of the tube. I would recommend to take away 1 mm more than the wallcthickness. we made the insert just fitting and it took an hour with a sledgehammer the get the inserts in place ).

the upper part is 60 cm total with 30 cm into the tube. The masthead can be seen in the image above. the inserts were turned out of a 12cm square timber.

When steping the mast it didn't seem too heavy to me. the whole thing was easily done by two persons and could certainly also be achieved "singlehanded".  but I have no comparison with the original hollow or all aluminium masts.

I hope this helps a little.

[Pius Bielowski]