Considering buying a boat with aftermarket mast

[PaulDaniel]

I’m considering buying a Catalina 270 that has an aftermarket mast. The previous owner was told this was done as an upgrade but I think that it is more likely that the old mast failed and was replaced with a similar specced mast. The new mast looks larger/thicker. I think the new mast will have more weight aloft and thus reduce sail performance. I don’t race, just cruise, but I still want my boat to perform as well as possible.

Has anyone replaced their stock mast with a thicker mast and found it to noticeably reduce sail performance? Or have you found that the difference was barely noticeable or not noticeable at all?

Thanks.

 

[jssailem]

Has anyone replaced their stock mast with a thicker mast and found it to noticeably reduce sail performance? Or have you found that the difference was barely noticeable or not noticeable at all?

Based on this statement, "I don’t race, just cruise." In my opinion, " the difference is not noticeable at all."

In order to explore the mast's actual impact on the boat, you would need to define the terms "thicker mast" and "similar-specced mast."

The mast may improve sailing performance. It may allow you to carry more sail. The stiffer mast may help maintain the best sail shape as the breeze increases.

 

[PaulDaniel]

I’ve been trying to get the height from the current owner but I don’t have that information yet. All I can tell is that it is visibly larger in girth than the stock mast (judging from photos).

“Thicker mast” = wider in diameter and circumference.

“Similar specced mast” = what I mean in this case is a mast that is roughly the same height and weight, but differing in exact measurements.

I don’t think it’s very likely to improve sail performance.

The implications of extra weight aloft would be most relevant when sailing into the wind, especially close hauling. Weight aloft is more relevant at greater heel angles. The shape of the mast under power will mostly be determined by the shroud placement and shroud tightness, but the rigidity of the mast does factor into bending between the shroud tangs.

- The keel ballast on the 270 is about 2,000 lbs.
- I’m not sure how much the mast weighs but let’s assume that the stock mast weighs 120 lbs and that an overbuilt aftermarket mast weighs 150 lbs (+30 lbs or +25%).
- At the dock, when COB is over COG, the extra weight aloft won’t have an effect.
- As you begin to heel over more, the extra weight aloft will subtract from the righting moment of the keel.
- Let’s assume at 90 degrees of heel that the keel has a 5 ft lever arm and the mast has a 20 ft lever arm. This means that for every extra 1 lbs of weight on the mast, it is like subtracting 4 lbs from the keel. (I know this is an extreme simplification).
- At reasonable heel angles (30 degrees while close hauling), the mast will not be x4 the lever arm…. Perhaps x2 (righting moment is not linear). So 1 lbs extra weight on the mast might be similar to a 2lb reduction in keel ballast. +30 lbs on the mast might be similar to -60 lbs on the keel while close hauling. 60 lbs is 3% of 2,000.
- extra weight aloft affects how much power you can take while sailing into the wind. In this case, we are talking about a small difference.
- extra weight aloft also affects capsize risk, but I’m not sure if I will ever sail this boat in the ocean.

 

[dlochner]

I’ve been trying to get the height from the current owner but I don’t have that information yet. All I can tell is that it is visibly larger in girth than the stock mast (judging from photos).

“Thicker mast” = wider in diameter and circumference.

“Similar specced mast” = what I mean in this case is a mast that is roughly the same height and weight, but differing in exact measurements.

I don’t think it’s very likely to improve sail performance.

The implications of extra weight aloft would be most relevant when sailing into the wind, especially close hauling. Weight aloft is more relevant at greater heel angles. The shape of the mast under power will mostly be determined by the shroud placement and shroud tightness, but the rigidity of the mast does factor into bending between the shroud tangs.

- The keel ballast on the 270 is about 2,000 lbs.
- I’m not sure how much the mast weighs but let’s assume that the stock mast weighs 120 lbs and that an overbuilt aftermarket mast weighs 150 lbs (+30 lbs or +25%).
- At the dock, when COB is over COG, the extra weight aloft won’t have an effect.
- As you begin to heel over more, the extra weight aloft will subtract from the righting moment of the keel.
- Let’s assume at 90 degrees of heel that the keel has a 5 ft lever arm and the mast has a 20 ft lever arm. This means that for every extra 1 lbs of weight on the mast, it is like subtracting 4 lbs from the keel. (I know this is an extreme simplification).
- At reasonable heel angles (30 degrees while close hauling), the mast will not be x4 the lever arm…. Perhaps x2 (righting moment is not linear). So 1 lbs extra weight on the mast might be similar to a 2lb reduction in keel ballast. +30 lbs on the mast might be similar to -60 lbs on the keel while close hauling. 60 lbs is 3% of 2,000.
- extra weight aloft affects how much power you can take while sailing into the wind. In this case, we are talking about a small difference.
- extra weight aloft also affects capsize risk, but I’m not sure if I will ever sail this boat in the ocean.

The effect won't be that great because the extra weight is distributed over the length of the mast. Assuming 1# per foot of mast, the first pound will have negligible effects, to counter act move the beer outboard. Each additional foot will have a greater impact, the result will be a curve, not a straight line. The calculations will fall into the realm of calculus, which my understanding of has not improved since I barely passed my first calculus course over a half century ago.

A closer approximation might be had by using half the weight of the mast in your calculations which will significantly reduce the amount of keel weight needed to offset the increased mast weight. So that might mean 30 pounds of keel weight.

There are other factors in affecting heeling and boat speed that the extra mast weight will make little to no difference in real life performance. In a light weight boat, crew position will make a huge difference. A 200# crew member is 10% of the ballast, put the crew on the rail. An old main sail will increase heeling, an over trimmed main will induce heeling. All in all boat speed will only be affected by fractions of a knot.

Weight aloft is more of an issue when it is concentrated at the top of the mast. Heavy coax cables, lights, antennas, shackles, wind instruments, halyards all add weight. Offset some of the mast weight by removing any of those things or replacing with lighter weight versions.

 

[shemandr]

A mast is just a mast, of course, except if it's ... tapered or has a wider foot print, or a thicker extrusion, or has swept back spreaders, or an adjustable backstay ... There's a fair amount of engineering that goes into the mast.
The test is best summed up by how has it worked so far. If you test sail it does the boat seem more tender than you expected? Is the mast in column when you are sailing upwind in 12 pts true? How long has the mast been in service? Was there an insurance claim and was the boat totaled? Either could impact your insurance and re-sale value.
Willlbeeeerrrr!

 

[jssailem]

Wow. That is a lot of technical supposition. Nothing I question in that the things you are saying are structural considerations. The issue is there are no engineering details to support the proposed conditions.

Since this is a discussion seeking detailed analysis it would need detailed information on the hardware, mast manufacturing and materials.

Or you could go sailing and using a tilt meter test the system performance to get a subjective observation of the heel angle, lee slippage of the hull at 10/15/20 degrees of heel

 

[PaulDaniel]

The effect won't be that great because the extra weight is distributed over the length of the mast. Assuming 1# per foot of mast, the first pound will have negligible effects, to counter act move the beer outboard. Each additional foot will have a greater impact, the result will be a curve, not a straight line. The calculations will fall into the realm of calculus, which my understanding of has not improved since I barely passed my first calculus course over a half century ago.

A closer approximation might be had by using half the weight of the mast in your calculations which will significantly reduce the amount of keel weight needed to offset the increased mast weight. So that might mean 30 pounds of keel weight.

Your point was already taken into account in my calculation. The mast on a catalina 270 is about 32 ft. If the boat is heeling 90 degrees, then the tip of the mast might be somewhere between 32-38 feet from the center of gravity. The mass on the bottom half of the mast is on a shorter arm, and the mass on the top half of the mast is on a longer arm. The way that you would calculate this is by calculating the lever arm as halfway up the mast, which might be about 16-22 ft from the center of gravity. I said 20 ft in my first calculation.

I agree that in this case for cruising the extra weight of the mast will not be meaningful.

 

[PaulDaniel]

Thank you all for the responses! I really appreciate the input from everyone. I feel like I've answered my own question. I'm confident enough in my back of the napkin calculations to have an order of magnitude appreciation of the implications of a modest increase in mast weight.

 

[Captain Larry-DH]

extra weight aloft also affects capsize risk, but I’m not sure if I will ever sail this boat in the ocean.

I think you’re wrong to discount this. Wave size is not the only issue. Righting moment is a very important part of sailboat stability, not just when sailing to windward, but also on beam reach it will affect heel and downwind it will affect roll. Even if you only ever sail her on lakes and bays; all it takes is a summer squall or a blustery day to encounter knockdown conditions - maybe even when reefed.
My advice is to find out the height and weight of the OEM mast and measure/weigh this one, so you know just what you’re getting.

 

[David in Sandusky]

First, I think your calculations are in the ball park, and my conclusion from them is Negligible - ignore the difference. I am trying to lose 60 pounds. I am down 9 now. If I sit on the toerail at my target weight, that is the same as losing 60 pounds on the keel. No real impact. I do have a degree in aeronautical engineering, and could do the calcs on loss of sail efficiency with a 1% reduction in heel, but the result would be the same. Negligible, and a list of 10 other actions that would improve sail efficiency more.

With respect to capsize risk, there is no increase in capsize risk. Extensive testing shows that taking a breaking wave as tall as your beam directly in the side of the boat will always capsize it. Lesser waves will not. If you are coastal cruising with ports within 6-8 hours, breaking waves of a capsize height take longer to build up than it would take to get to a safe port. If I add the excellent forecasting of wind and wave heights from NOAA, you will only sail on the ocean or Great Lakes where such waves are possible when there is zero chance of encountering them! (Who would leave port if the forecast is gale winds, and waves over 8 feet?)

If you like the boat, it is a great prospect for cruising. If you don't like it because of the mast or anything else, keep looking.

 

[Barnacle Bill]

I haven't read all the posts, so sorry if I repeat something, but one post did catch my eye when they said that a heavier, thicker mast can carry more sail. Partially it has something do to with righting moment [look it up]. I disagree as tests have shown that carbon rigs [lighter] on the same boat design with an aluminum rig [heavier], can carry more sail area into increasing wind velocities. The same, more negligible, would apply with heavier aluminum rigs. Also, some designs have increased wall thickness on fractional rigs that carry various sizes of spinnakers, especially hoisted from the normal fractional rig position and also from the top of the mast, to eliminate mast failure. So, for cruising, I don't think that an after market mast will make much difference as long as it is consistent with original designed sail plan, etc. There are many boats with masts from manufacturers that no longer exist and so an alternative manufacture is required to employ for mast replacement [LeFiell is one example]. Most cruising designs have telephone pole type masts that have so much safety measures built in the structure [unlike an America's Cup Boat], that absolute performance is a not a concern on most production boats.
To keep weight aloft on an America's Cup boat, they will use one halyard to raise the mainsail and then send someone up to the masthead to clip in the head of the main and the same halyard will be used for the spinnaker, for example. You can imagine how heave the halyard for a boat with a 150' or whatever mast height is. So, one halyard is lighter than two. Performance cruisers, like J/Boats, for example, are the exception to the rule when it comes to production boats that sail fast regardless of the size or design.
That's my two cents.