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elias_sol82

Going from deck stepped to keel stepped mast

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My old 26' Centaur carries a mast & rigging very different from the initials, 33,4 ' length edge to edge - a cutted piece of another 38' boat and 7mm 19x1 rigging. Seems that previous owner overreacted while setting a new rigging. The 7mm wires charged to the 15% of breaking load had a bad impact to the deck :( ... Also the mast is short and fat that makes it very stiff. So there is an urgent need for replacing the mast. I found one that is 35' from a half tone as the seller says. I was thinking of placing through hull and attaching it where the inner mast support is attached (check the photo of the tube), not exactly to the keel. So there is no need cutting the new mast .

Will it work?


Oh, the interior shown in the pic isn't mine

post-121875-0-65284400-1451231627_thumb.jpg

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Simple answer: no. The reinforcing rod lands on the floor structure and only has a vertical component. A mast stepped there would have vertical, sideways, and fore and aft components. The new mast step would have to be engineered to accommodate these forces and might involve cutting into the bulkhead. This could weaken the bulkhead and lead to structural problems. Cutting a hole through the cabin top big enough for the new mast could also weaken the structure there and cause problems. Getting advice over the internet on structural issues is an iffy proposition. Pictures of YOUR boat might be more useful.

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Simple answer: no. The reinforcing rod lands on the floor structure and only has a vertical component. A mast stepped there would have vertical, sideways, and fore and aft components. The new mast step would have to be engineered to accommodate these forces and might involve cutting into the bulkhead. This could weaken the bulkhead and lead to structural problems. Cutting a hole through the cabin top big enough for the new mast could also weaken the structure there and cause problems. Getting advice over the internet on structural issues is an iffy proposition. Pictures of YOUR boat might be more useful.

Thanks a lot for your time and answer.

What exactly is the components? The rod ends about 20'' above the floor as i marked in the pic. Pictures of my boat will be available in a few days..

post-121875-0-44216600-1451239435_thumb.jpg

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Simple answer: no. The reinforcing rod lands on the floor structure and only has a vertical component. A mast stepped there would have vertical, sideways, and fore and aft components. The new mast step would have to be engineered to accommodate these forces and might involve cutting into the bulkhead. This could weaken the bulkhead and lead to structural problems. Cutting a hole through the cabin top big enough for the new mast could also weaken the structure there and cause problems. Getting advice over the internet on structural issues is an iffy proposition. Pictures of YOUR boat might be more useful.

Thanks a lot for your time and answer.

What exactly is the components? The rod ends about 20'' above the floor as i marked in the pic. Pictures of my boat will be available in a few days..

 

 

In this case component is just the direction of force.

So as it stands your deck mounting point for the mast takes all the sideways and forward and backward loads, the mast compression post simply takes the compression load from the mast so it doesn't crush the coachroof.

 

If you bring the mast down to keel stepped you will need to make a foot that can withstand the various loads that will be placed on it, fore / aft / sideways etc.

Also the mast 'partners' where it passes through the deck will need to be suitably reinforced.

 

And all this of course assumes that the new mast would still be in the same position as the old one, but if you're switching to for example a fractional rig then the mast would usually be further forward, and the cap shrouds would be swept back, not inline. If you're already having deck problems just from upsizing rigging then I doubt the structure would support the loads of a bigger mast.

 

Can you not simply do back to the original rigging diameter?

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Simple answer: no. The reinforcing rod lands on the floor structure and only has a vertical component. A mast stepped there would have vertical, sideways, and fore and aft components. The new mast step would have to be engineered to accommodate these forces and might involve cutting into the bulkhead. This could weaken the bulkhead and lead to structural problems. Cutting a hole through the cabin top big enough for the new mast could also weaken the structure there and cause problems. Getting advice over the internet on structural issues is an iffy proposition. Pictures of YOUR boat might be more useful.

Thanks a lot for your time and answer.

What exactly is the components? The rod ends about 20'' above the floor as i marked in the pic. Pictures of my boat will be available in a few days..

 

 

In this case component is just the direction of force.

So as it stands your deck mounting point for the mast takes all the sideways and forward and backward loads, the mast compression post simply takes the compression load from the mast so it doesn't crush the coachroof.

 

If you bring the mast down to keel stepped you will need to make a foot that can withstand the various loads that will be placed on it, fore / aft / sideways etc.

Also the mast 'partners' where it passes through the deck will need to be suitably reinforced.

 

And all this of course assumes that the new mast would still be in the same position as the old one, but if you're switching to for example a fractional rig then the mast would usually be further forward, and the cap shrouds would be swept back, not inline. If you're already having deck problems just from upsizing rigging then I doubt the structure would support the loads of a bigger mast.

 

Can you not simply do back to the original rigging diameter?

 

Yep this is the goal, back to the roots. But the mast I've found is 3,25 ft longer than the original and has almost the same diameter and is much lighter. So i was thinking instead of cutting it just getting it though hull and stepping it like the pole in the pic. But as you suggest and from the reading i ve done it is better not to mess with that change.

Oh, you mentioned that if the new one is fractional it should be placed forward , the present mast step offers choice of few inches placing forward, would be that enough? Or should i turn the fractional new mast to masthead?

Thanks !

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You also need to consider such things as the gooseneck attachment point, spreader spacing etc. Was the proposed mast keel stepped? Are the spreaders the same configuration (swept, unswept etc.)? an Extra 3 1/2' on a typically under rigged British boat would be an improvement, not a problem IMO.

 

Talking to a rigger who can see things in person would be good.

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Simple answer: no. The reinforcing rod lands on the floor structure and only has a vertical component. A mast stepped there would have vertical, sideways, and fore and aft components. The new mast step would have to be engineered to accommodate these forces and might involve cutting into the bulkhead. This could weaken the bulkhead and lead to structural problems. Cutting a hole through the cabin top big enough for the new mast could also weaken the structure there and cause problems. Getting advice over the internet on structural issues is an iffy proposition. Pictures of YOUR boat might be more useful.

Thanks a lot for your time and answer.

What exactly is the components? The rod ends about 20'' above the floor as i marked in the pic. Pictures of my boat will be available in a few days..

 

The point about advice over the internet shows its head: Your second picture (not the first) shows that the compression post does not go all the way down to the cabin sole/floors, but ends on top of the dinette seat (which, one assumes, has reinforcement to carry the load down to the floors of the boat. (Floors in this sense are the structure of the hull in the keel/bilge area - not the surface that you stand on - that is called the cabin sole.) This works because there is only the downward force to worry about with the deck-stepped mast. Installing a keel-stepped mast will likely require cutting away the seat for the mast step and also cutting away part of the seat so the mast can pass through. This will take up a lot more space than the compression post did, and might make moving around in the cabin more difficult. Cutting away the seat and the area around it could also weaken the structure of the boat - you might want to contact the builders for their advice on this. If you are having deck compression problems, the compression post and its load path may need to be redone in order to fix them and not have them happen again. Stepping the longer mast on deck and cutting it to the right size might be the simplest solution - though as has been pointed out, shrouds, spreader angles, halyards and where the gooseneck for the boom is fitted all have to be determined. It is not necessarily easy.

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You also need to consider such things as the gooseneck attachment point, spreader spacing etc. Was the proposed mast keel stepped? Are the spreaders the same configuration (swept, unswept etc.)? an Extra 3 1/2' on a typically under rigged British boat would be an improvement, not a problem IMO.

 

Talking to a rigger who can see things in person would be good.

 

 

 

 

Simple answer: no. The reinforcing rod lands on the floor structure and only has a vertical component. A mast stepped there would have vertical, sideways, and fore and aft components. The new mast step would have to be engineered to accommodate these forces and might involve cutting into the bulkhead. This could weaken the bulkhead and lead to structural problems. Cutting a hole through the cabin top big enough for the new mast could also weaken the structure there and cause problems. Getting advice over the internet on structural issues is an iffy proposition. Pictures of YOUR boat might be more useful.

Thanks a lot for your time and answer.

What exactly is the components? The rod ends about 20'' above the floor as i marked in the pic. Pictures of my boat will be available in a few days..

 

The point about advice over the internet shows its head: Your second picture (not the first) shows that the compression post does not go all the way down to the cabin sole/floors, but ends on top of the dinette seat (which, one assumes, has reinforcement to carry the load down to the floors of the boat. (Floors in this sense are the structure of the hull in the keel/bilge area - not the surface that you stand on - that is called the cabin sole.) This works because there is only the downward force to worry about with the deck-stepped mast. Installing a keel-stepped mast will likely require cutting away the seat for the mast step and also cutting away part of the seat so the mast can pass through. This will take up a lot more space than the compression post did, and might make moving around in the cabin more difficult. Cutting away the seat and the area around it could also weaken the structure of the boat - you might want to contact the builders for their advice on this. If you are having deck compression problems, the compression post and its load path may need to be redone in order to fix them and not have them happen again. Stepping the longer mast on deck and cutting it to the right size might be the simplest solution - though as has been pointed out, shrouds, spreader angles, halyards and where the gooseneck for the boom is fitted all have to be determined. It is not necessarily easy.

 

Thank you all for your advice.

Yes , advice on the internet is tricky but it can really give a way out . The ideal thing to do is to reach a rigger , buy a new mast and have it installed. Paying at least 3000 euros for it in Greece right now is a luxury. Also i prefer the DIY way cause it will upgrade my knowledge and skills. For example i decided years ago to change the engine by myself. Took me weeks but i now own the confidence of knowing A to Z my engine. Why not mast and rigging? So , I ll wait for more data from the proposed mast seller (pics and drawings). Keep the mast deck stepped and come back for your advice (if you don't mind). Hey, is there an amateur level entry boat design book you suggest? I have basic knowledge on fluid mechanics and mechanical engineering.

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You're boat is setup for deck stepped. Why would you want all that work to modify it is o keel stepped? You gain nothing, except another hole in the deck that will leak all the bloody time.

 

As others have said, spreader type and size is important. Ensuring the spreader tips fall in close to the same place above the deck as the current rig is pretty important. Both rigs need to be either swept back or inline.

A little extra mast height would probably not go astray on a centaur.

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You're boat is setup for deck stepped. Why would you want all that work to modify it is o keel stepped? You gain nothing, except another hole in the deck that will leak all the bloody time.

 

As others have said, spreader type and size is important. Ensuring the spreader tips fall in close to the same place above the deck as the current rig is pretty important. Both rigs need to be either swept back or inline.

A little extra mast height would probably not go astray on a centaur.

As i mentioned , for not cutting a proposed mast that I ll buy cheap. Spreader tip is an issue , when i have the mast dimensions and pics i ll see if it is suitable. Isnt 3-4 ft taller mast an issue? My main's P is 27.3 ft and mast length is 33 ft

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Yep this is the goal, back to the roots. But the mast I've found is 3,25 ft longer than the original and has almost the same diameter and is much lighter. So i was thinking instead of cutting it just getting it though hull and stepping it like the pole in the pic. But as you suggest and from the reading i ve done it is better not to mess with that change.

Oh, you mentioned that if the new one is fractional it should be placed forward , the present mast step offers choice of few inches placing forward, would be that enough? Or should i turn the fractional new mast to masthead?

Thanks !

 

 

Depending on the mast, its quite possible to cut that off the bottom of it and re-rivet the foot back on in the new position.

However as has been said, an extra 3 foot would likely be an improvement.

 

I doubt a few inches would be adequate, a fractional rig has a much bigger main with a consequently longer boom, so I imagine the mast would need to be a few feet further forward.

Also the cap shrouds, they will sweep back so as has been said spreader size is important. Remember on a fractional rig the backstay doesn't support the mast, its there for tuning purposes, so the cap shrouds also stop the mast falling forward and bear a higher load than they do on a masthead rig.

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You're boat is setup for deck stepped. Why would you want all that work to modify it is o keel stepped? You gain nothing, except another hole in the deck that will leak all the bloody time.

 

As others have said, spreader type and size is important. Ensuring the spreader tips fall in close to the same place above the deck as the current rig is pretty important. Both rigs need to be either swept back or inline.

A little extra mast height would probably not go astray on a centaur.

As i mentioned , for not cutting a proposed mast that I ll buy cheap. Spreader tip is an issue , when i have the mast dimensions and pics i ll see if it is suitable. Isnt 3-4 ft taller mast an issue? My main's P is 27.3 ft and mast length is 33 ft

 

 

Not an issue - if you use your existing main it will look like you're reefed but what the hell - when you need a new main you can get a taller one and the better performance it will bring.

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I find it hard to move the mast fore. So I ll modified if it is fractional to masthead. Any book of sailboat design suggestions?

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I find it hard to move the mast fore. So I ll modified if it is fractional to masthead. Any book of sailboat design suggestions?

Do not change the new mast to masthead.

Talk to a sailmaker and a rigger about the changes, once you have all your dimensions and details sorted out. You will be modifying your sail plan in some way to fit the new rig, and will have to buy bits and pieces anyway, so make friends with both early and get some advice.

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You're boat is setup for deck stepped. Why would you want all that work to modify it is o keel stepped? You gain nothing, except another hole in the deck that will leak all the bloody time.

As others have said, spreader type and size is important. Ensuring the spreader tips fall in close to the same place above the deck as the current rig is pretty important. Both rigs need to be either swept back or inline.

A little extra mast height would probably not go astray on a centaur.

 

As i mentioned , for not cutting a proposed mast that I ll buy cheap. Spreader tip is an issue , when i have the mast dimensions and pics i ll see if it is suitable. Isnt 3-4 ft taller mast an issue? My main's P is 27.3 ft and mast length is 33 ft

Not an issue - if you use your existing main it will look like you're reefed but what the hell - when you need a new main you can get a taller one and the better performance it will bring.

Increasing a rig and sail without fulling addressing the hull, chainplates, bulkheads, keel and rudder might be a serious underestimation. You might have to look at deck joints and study what is under your rub and toe rails that hide separations and often are keys to hull stiffness and integrity.

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This entire thread is full of lousy ideas and misinformation - rather the blind leading the blind. You've demonstrated that you have little idea about what's going on, you really need to just stop and get some professional help.

 

The length of the mast tube is only one relatively small indicator of its suitability. At least as important is the moment of inertia of the cross section of the extrusion. The moment of inertia must be matched to the righting moment of your boat or the mast will fail.

 

Then, you need to pay attention to spreader placement along the tube, standing rigging loads and attachments, mast head design regarding headstay, backstay & cap shroud attachment.

 

Next comes gooseneck height and attachment. Same for the vang. Then mainsail track and loading gate selection. Then inboard reef mechanisms.

 

After that, spinnaker pole attachment, whether ring or track + car + uphaul & downhaul.

 

Then there's halyard location, placement, exit orientation, material selection, sheave sizing, etc for each halyard (main, jib1, jib 2, staysail, spin1, spin 2).

 

Finally, there's attention to VHF antenna, masthead running lights, anchor light, steaming light, deck spot or spreader lights, wind instruments, etc.

 

In the big picture, the length of the fucking tube is like studying a flea on the tail of a dog. Stop obsessing about the flea and start looking into whether the damn dog has four legs and is breathing.

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It's a centaur 26 moon. They have a small stump for a mast, and twin bilge keels, so a 2.5 KT SB. Anything is likely to be an improvement on OEM, provided it fits the approximate dimensions, and a fair portion of the parts on you list will never appear on a centaur.

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You're boat is setup for deck stepped. Why would you want all that work to modify it is o keel stepped? You gain nothing, except another hole in the deck that will leak all the bloody time.

As others have said, spreader type and size is important. Ensuring the spreader tips fall in close to the same place above the deck as the current rig is pretty important. Both rigs need to be either swept back or inline.

A little extra mast height would probably not go astray on a centaur.

As i mentioned , for not cutting a proposed mast that I ll buy cheap. Spreader tip is an issue , when i have the mast dimensions and pics i ll see if it is suitable. Isnt 3-4 ft taller mast an issue? My main's P is 27.3 ft and mast length is 33 ft

Not an issue - if you use your existing main it will look like you're reefed but what the hell - when you need a new main you can get a taller one and the better performance it will bring.

Increasing a rig and sail without fulling addressing the hull, chainplates, bulkheads, keel and rudder might be a serious underestimation. You might have to look at deck joints and study what is under your rub and toe rails that hide separations and often are keys to hull stiffness and integrity.

 

 

Adding a couple or three feet to the spar on an English built (read under-rigged) boat does not require a complete engineering analysis. It's just not that big a deal - I had a similar size boat that had 3' added and it had exactly zero effect except for more speed in light wind.

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More evidence of the blind leading the blind. To say that replacing a mast with one of different length and section doesn't require engineering analysis is to say that you don't understand moment of inertia and righting moment. Sure, you might get lucky but then again, you might not.

 

And when you say that a fair portion of those considerations don't apply - really? Does the boat have no halyards, no standing rigging, no gooseneck, no mainsail track, no loading gate, no halyards? At best, it might not have mast wiring or provision for a spinnaker, but nearly every other element is an essential part of any Marconi rigged yacht of any size.

 

So sure, if you want to replace the existing mast with some oversized section and then replace the step, reorganize the deck, rebuild the chain plates and/or rigging screws, raise the cg a few inches and toss out the existing sail inventory and possibly the boom, too, what the fuck - go for it!

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You're boat is setup for deck stepped. Why would you want all that work to modify it is o keel stepped? You gain nothing, except another hole in the deck that will leak all the bloody time.

As others have said, spreader type and size is important. Ensuring the spreader tips fall in close to the same place above the deck as the current rig is pretty important. Both rigs need to be either swept back or inline.

A little extra mast height would probably not go astray on a centaur.

 

As i mentioned , for not cutting a proposed mast that I ll buy cheap. Spreader tip is an issue , when i have the mast dimensions and pics i ll see if it is suitable. Isnt 3-4 ft taller mast an issue? My main's P is 27.3 ft and mast length is 33 ft

Not an issue - if you use your existing main it will look like you're reefed but what the hell - when you need a new main you can get a taller one and the better performance it will bring.

Increasing a rig and sail without fulling addressing the hull, chainplates, bulkheads, keel and rudder might be a serious underestimation. You might have to look at deck joints and study what is under your rub and toe rails that hide separations and often are keys to hull stiffness and integrity.

Adding a couple or three feet to the spar on an English built (read under-rigged) boat does not require a complete engineering analysis. It's just not that big a deal - I had a similar size boat that had 3' added and it had exactly zero effect except for more speed in light wind.

Nice little boat - working coastal and gunk holing.

 

Did you add the 3 feet of mast to a bilge keeler? A draft of 2.5' has different properties than a deep keel. Moreover the boat is most likely 40 years old. Rigging upgrades are imperitives as is replacing chainplates. The deck needs inspection as well. The bulkheads and old built in furniture examined as they most likely have floated over the years removing hull integrity.

 

I am reading the book A Voyage For Madmen - 2 golden globers in 1968 had bilge keelers barely escaping lost a sea and leaving the race. I know things are different - essentially these small keels boats showed thier strength and weaknesses. We need to take note from what others have learned.

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Duster, apparently you haven't but If you had bothered to actually read the thread you would have discovered that he already has an oversized section and rigging - from a 38 footer no less - and wants to replace it with one sized more like the original.

 

It's a fucking old Centaur FFS, not some high strung, marginally rigged offshore racer. He's found a rig that's close and if ever there was a situation where close was good enough, that's it.

 

Additionally and again, if you actually bothered to read the fucking thread, there have been numerous comments pointing out the actually important things that you mentioned and steering him away from some ideas that actually would create problems.

 

Your engineering analysis alone would cost more than the boat is worth.

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Sloopy,

 

You see, that's just the thing - I did read the thread.

 

There's no mention of section considerations or righting moment - and while no real engineering is required, some math certainly is, whether you like it or not.

 

Similarly, there's no discussion of gooseneck or mast track or loading gate - all of which must be understood in order to understand whether the boom and/or mail sail can be reused.

 

There's no discussion of hole sizes in the chain plates, tangs or the mast head and no discussion about how the standing rigging is or is not connected to the spreader tips.

 

The whole thing reads more like someone setting up a christmas tree than a mast and the cost of that approach is far, far, far more than the cost of actually sitting down, making a list and checking it twice.

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Hey hey guys sorry it isn't twin keeled! It is something like Mediterranean version. I'm not willing to make it ultra fast. It can't be done easy. Just changing a bad mast and rigging in an affordable way. The new fractional mast may ask the step to move fore. I thing itwould be easier to turn the mast to masthead than turn the boat to fractional

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Hey hey guys sorry it isn't twin keeled! It is something like Mediterranean version. I'm not willing to make it ultra fast. It can't be done easy. Just changing a bad mast and rigging in an affordable way. The new fractional mast may ask the step to move fore. I thing itwould be easier to turn the mast to masthead than turn the boat to fractional GR894.pdf

GR894.pdf

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Also I m still looking for a used mast about 33 ft deck stepped and masthead type to buy. Maybe someone of you is sailing the Med with an aluminium tube in the side!

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Sloopy,

 

Similarly, there's no discussion of gooseneck or mast track or loading gate - all of which must be understood in order to understand whether the boom and/or mail sail can be reused.

 

There's no discussion of hole sizes in the chain plates, tangs or the mast head and no discussion about how the standing rigging is or is not connected to the spreader tips.

 

 

 

I guess my age is showing - I sort of took checking & confirming all that as a given when changing out a spar. Just putting a Headfoil on my boat back in the 70's required all my foresails to have new luff tapes for example.

 

Considering the experience level indicated in the OP you may well be right. I still disagree about worrying over the moment of the spar and such though - on a boat that size if it looks O/K - eyeball close to similar boats spars - it's going to be strong enough.

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Sloopy,

 

You see, that's just the thing - I did read the thread.

 

There's no mention of section considerations or righting moment - and while no real engineering is required, some math certainly is, whether you like it or not.

 

Similarly, there's no discussion of gooseneck or mast track or loading gate - all of which must be understood in order to understand whether the boom and/or mail sail can be reused.

 

There's no discussion of hole sizes in the chain plates, tangs or the mast head and no discussion about how the standing rigging is or is not connected to the spreader tips.

 

The whole thing reads more like someone setting up a christmas tree than a mast and the cost of that approach is far, far, far more than the cost of actually sitting down, making a list and checking it twice.

 

Slight over reaction don't you think?

The OP asked a simple original question, which was regarding converting to a keel stepped mast. And would it work, most of us then proceeded to tell him it probably wasn't the best idea and then listed some of the difficulties. Sure it wasn't a comprehensive list, we're listing potential problems, not engineering a solution for him.

 

Your first post you just listed a load of shit that's on a mast, most the stuff you mentioned is so obvious that it doesn't need mentioning by us. Determining halyard lengths and diameters just requires taking a few measurements, its not a fucking shuttle launch.

 

If the mast is from a half tonner then its going to designed around a greater righting moment than a centaur can provide, remember most those yachts are raced with full sail for as long as possible with an army camped out on the windward rail.

The limiting factor is most likely the modifications that would be required to the boat to fit it are likely outside the scope of that the OP can manage.

 

Back on topic, elias, you can't covert a fractional mast to masthead rig, If you want contact the manufacturer, but I'm 99% certain it won't be possible. Usually the section on a fractional starts tapering after the cap shrouds, the whole mast is designed around its original function (fractional), you would be substantially weakening it, its not as simple as moving the shroud attachment points.

The Centaur is a popular boat, but there must be loads of abandoned ones that are past restoring, its probably going to make more sense to get see if you can get a mast off one of those. If not then you'll have to look for something masthead and around the same size and section unless you're planning major surgery to your boat.

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I'm not sure you can say for certain that a half ton will have more RM than the Westerly For example the Farr 920 displaced only 4900 lb with 1900 lb ballast while a Centaur is some 6800 lb with 2800 lb ballast. Further, IOR made it very favourable to have a high VCG, which is why even though bulb keels have been around for almost forever (even a Cal 20 has one) you never saw one on an IOR boat.

 

One item that I believe that hasn't been brought up is the number of spreaders. The Centaur I suspect is single spreader while the half ton is likely double spreader (which may be why the OP noted it is much lighter than the current mast). So chain plate mods will be in order if that is the case.

 

Something is not adding up for me though. The OP says the new mast is a 35 ft long section set up for a fractional rig half ton, which sounds very short - even for a deck stepped Half Ton (a Farr HT would typically have a P close to 35 ft), 35 ft sounds more in line with a deck stepped MH rig.

 

So, if the replacement mast was a deck stepped fractional and you sink her down say 4-5 ft, the spreaders and in particularly the lower ones will be at a very odd height - maybe 6 ft above the deck?

 

And as MDGun said - in your case, don't even consider relocating the shroud attachments to convert it into a MH rig. Besides the reduction in sectional inertia above the cap shrouds you will also be increasing the panel length and the required sectional inertia is proportional to panel length squared.

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I'm not sure you can say for certain that a half ton will have more RM than the Westerly For example the Farr 920 displaced only 4900 lb with 1900 lb ballast while a Centaur is some 6800 lb with 2800 lb ballast. Further, IOR made it very favourable to have a high VCG, which is why even though bulb keels have been around for almost forever (even a Cal 20 has one) you never saw one on an IOR boat.

 

 

 

 

You make a good point.

The half tonners I'm used too seeing usually have a massive amount of crew stacked on the rail and flying the kite in absurd conditions. But as you and Moonduster have said that doesn't ensure suitability. It would depend on the boat it came from.

 

I think realistically the OP needs to be looking at a masthead rig from the same era, my Sadler 25 was built around the same time and just a quick glance around the mast rack at the club shows tons of stuff that would be probably be suitable, nearly everything from that era seems to be masthead rig and of a completely overbuilt section.

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Thanks again guys for the enlightement. I decided to abandon the fractional mast. Seeking now for a similar to the original mast. I ll come back with pictures of my weird present mast. if you check my above posts there is my orc cert with dimensions

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