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Extending the mast


johnMi

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I'm looking at extending my mast by a metre and wondering whether a it would be expensive to manufacture a tapered piece that could be bolted to the top of the original extrusion. (so far, unable to get a piece of the extrusion.)

The original extrusion has an internal track which could be an issue, but surely I could find an extrusion that could be butchered to suit.

Any aluminium welders care to comment?

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Nothing is impossible....if you have enough money to throw at it of course :wink:

 

OK, first question, what are all the measurements and it would be even better if you could include a Photo of the extrusion.

Second question, is the want of extending due to wanting more sail? or some other idea??

Is the Mast Anodised or painted or plain. Anodizing creates a slight problem. See the note (a)

 

Butt welding the section can be done. It will always be a weak point. An internal sleeve would be needed to ensure a real strong join. (a)An internal sleeve and both sections riveted would also work OK, but you see the join is all. Probably best scenario if the mast is anodized.

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You will find that a lot of production boats have joined masts. (Look at Bavarias for an example). They are joined with an internal sleave and rivets. I would not weld anything. The days of welded on spreader shoes and similar seem to be over due to failures at the hardened weld line. The internal sleave should be tapered so that there is no "hard point".

If you use Stainless rivets then you need to use Durolac or a similar anti electrolysis goop.

 

....just my 2 bobs worth.

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Of course if you intended racing under Cat 1 or 2 and extended your mast by 1 metre you would have to get certification from Europe, the designer, the constructor and every else in the room at the time ...

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Wheels,

I need more sail area and the mast is I think anodised.

Because it is at the top of the mast, and because there is less load up there I was thinking of manufacturing something with lugs about 100 ml longfront and sides at the bottom that could be bolted/screwed/rivetted to the top of the existing mast.

It's a rotating mast thats about 200 ml by about 100ml. The spreaders will be bought up the mast, but will still be on the original extrusion.

Danaide,I know about Zen, but he had the right extrusion available.

Idler boat, I agree with welding to original mast but what about the welding on the extension, that should be ok though?

And Andrew, cat 1 and 2 not a problem, but what about cat3?

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If the rigging attachment points are above the join, then the join "see's" the same load as any other point along the rest of the mast. So if you have the chance of folding it anywhere, it will be at the weakest point. In saying that though, a join can be made strong enough to take the load. So it comes down to where the best place to make the join is. So a little thought here, can you actually make the extension at the opposite end and lift the mast up. My question here would be, is she Deck steeped or Keel. If she is Keel stepped, then the addition could be any section capable. This is also presuming the Track is all the way down the section to the Keel or at least Deck. This would mean you can leave the mast head and all attachment poins alone.

If Deck stepped, I would assume you would not have a metre above the deck to Goosneck fitting, so adding a metre there is probably not an option.

 

So what did you want to weld exactly??

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Wheels, the part I was talking about welding would be the manufacturing of the piece to be added. I thought of tapering it.

Also, the rigging attachment points will be below the connection, so the only loads will be the sail loads.

If I had an extrusion piece I would add it to the bottom, but because it would need to be made up, it seems best at the top.

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OK, so what size are we talking? I happen to have a bit over a metre of section with internal track. It maybe too big for your needs though. It is a big section.

 

The problem with anodizing is that it is not conductive and is an oxide, so will not weld. So that coating has to be ground back to ally again. It can be re anodised, but it requires some skill and I doubt many places would take it on. Plus any welding will always come up a different colour to the non welded, so you see the Weld.

 

In regards to the stays terminating at the same point and the extension being above those points, that is beyond my area of knowledge and you would need to ask a spar maker about that one.

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If you are welding up the mast as in a taper then it should be ok, but welding around the mast is not a good idea. A sleave to the goose neck will place a huge amount of stress to a very vunerable place. Most comercial joins seem to be about a meter above or below the first spreaders.

As an aside, a boat I know dismasted in light winds. It had a sleave section to the first spreaders to increase the moment, whilst using a lighter section for the rest of the mast. Crevice corrosion in one cap shroud allowed the stay to part and the load snapped the mast through the spreader shoe through hole. The joys of a swept back rig with only the minimum of stays and section. This boat was a very long way off shore........

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Oh is this a Multi Hull Farrier??? If so, different beasty altogether. Loads are all different to that of a Mono. I wouldn't attempt to raise the height above what was designed, although the designer will tell you more about that and what you can and can't do. Remember a Mono is designed to lean over. A Multi is not...well at least not as much as a Mono anyway.

I would be looking at putting my money and effort into better sail design and technology. You would most likely make more gain with sail design than extending the Mast to allow a bigger sail. It's one thing having bigger sails, but it's no good if you can not get the "power to the ground...errrr water". It maybe that you need to get a lower aspect ratio sail with more power lower down, or something like that. Once again, I have dog paddled off down to the deep end again.

Oh and weight. Talk to KM about lines and the tricks he has in reducing weight. That can make a huge difference in speed.

Of course, if you own a Farrier, all the above is probably just telling you how to suck eggs, so sorry for saying what you most likely already know.

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Wheels, Thanks for the offer of the section, but at the moment I cannot send any measurements as I ama bit laid up. I should be able to find something here in Auckland once I get back together.

Mr wolf, I have talked to Ian Farrier about increasing sail size etc and he is against it. However, that does not suit me, so I have to get advice elsewhere.

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One of the things we looked at on Creepy was the thought of the upgrade from a Dacron old roach profiled stretchy mainsail to a square topped mainsail on the same mast, built from Kevlar/carbon. We worked out that it would work quite well but the mast we had was way way way to soft to handle the jandle, and it just so happened that we stumbled upon a mast that was slightly taller. Now we are taller and bigger.

 

I think you are in the same situation John, but it might pay to get a multihull specialist sailmaker like Ken Fyfe or similar to look at the sails you have now and see if he thinks enough power can be attained within the frame you have (remember that boats are running squaretops as big as 2m now (Lucifer) and maybe that might solve the problem without needing a new mast.

 

As to extending the mast, i would severely advise against that, No way would you be able to get a join, unsupported by stays etc to be strong enough to take the flogging it will recieve, while being light enough to not counteract any good it is doing. If you want to go taller sadly a new mast section is the easiest way...

 

Just the thoughts of a rigger that has been in the same situation with a similar boat very recently!! BTW Our mast goes in tommorow and we think we have gone a tad on the large size!! only 100mm under max height for 8.5m's :-S

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Horse before the cart, John !

 

Get on the phone to Ian Farrier and ask him what you should do!

 

I take it you want to make your boat faster and not have the mast fall over the side?

 

Ian F doesn't like people modifying his designs which was partially the cause of his divorce from Corsair Marine.

 

John, you may be aware that the F24 is no longer produced, however it lives on in the form of the Sprint 750, with a cut down cabin and a bigger rig on what is effectively the standard F24 platform. This should get you any accreditation you need (if necessary). The facelifted Dash 750 uses the Sprint rig but has bigger floats.

 

factory specs:

 

F24 mk2 9.7m mast 33.8 sq metres main and jib

 

Corsair 750 Sprint 10.8m mast 39.8 sq metre main and jib

 

For comparison the new F22 (which is actually 23 feet loa)

 

9.4 metre mast 30.2 sq metre main and jib

 

R version 10.7 metre mast 36 sq metre main and jib.

 

Go for it.

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BTW Our mast goes in tommorow and we think we have gone a tad on the large size!! only 100mm under max height for 8.5m's :-S

 

 

And then it gets measured.....

I hope you cut the prod off where you were shown.

I will be at westhven XYZ at 10:30 tomorrow checking Lucifer should you want to bring Creepy along send me a txt or PM.

Last measuring day is the 13th

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thanks Marshy, (I've tried to contact you, can you give me a ring? 021 993 863)

So do you think I really need a completely new mast section?

 

GregW, that's exactly what I want to do, go to the Dash sail plan, the only thing that I may have to be careful of is the Dash has 6% more floatation in the amas.

 

I have just sent an email to Corsair, to see what they think.

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I have just sent an email to Corsair, to see what they think.

 

id be suprised if Corsair or Ian give you much help, or any designer for that matter, they dont want the liability of giving any wrong advice.

 

Are you running masthead gennakers? that would help a lot.

 

Its great to see such action at the small end of the multi fleet, lets hope the other F25 comes to Auckland too!

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thanks Marshy, (I've tried to contact you, can you give me a ring? 021 993 863)

 

GregW, that's exactly what I want to do, go to the Dash sail plan, the only thing that I may have to be careful of is the Dash has 6% more floatation in the amas.

 

.

 

Yes, but the current Sprint uses the same rig as the Dash, with the standard disp. F24 float. While you're talking to Corsair it might pay to check whether they increased the chainplate/rigging specs etc for the bigger rig. The standard farrier boats were always fairly well built and conservatively rigged, I think one of the reasons they were so popular in the US. In recent years the rigs have got proportionally bigger on the various R versions. Using the Sprint/Dash rig would effectively be equivalent to a (hypothetical) F24R.

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