Mast angle

[Paddyt]

Hi everyone,

I acquired a ‘66 DS1 last month and have been fixing her up to get ready to sail. One of the things I had to do was make a new mast stub as the PO has cut the original so it was just flush with the deck when the mast jack was all the way up. Anyway, thanks to this forum I knew where to go to get the parts I needed. What a great resource this forum is.

So I attached the new tabernacle onto the new mast stub and slid it into the deck and onto the mast jack. What I see is the mast is at an angle and does not sit flush on the jack. Is this normal? The picture shows how the mast is angle back to get through the hole in the deck.

Lastly, I have a question about searching on the forum. Understandably the search omits words that are very common. How do I get the common word to be included in the search? Adding a + before the word does not work. ie searching “mast angle” ignores the word ‘mast’.

Thanks

[GreenLake]

Welcome to the forum.

For search tips, please check the "How to use this forum" part of this forum.

The angle for the mast (called mast rake) is given by the placement of the mast partners (=deck opening) and the mast step.

Your mast is supposed to be raked back somewhat. You can check for correct mast rake by tying a tape measure to the main halyard and using it to measure the distance from mast head to transom.

The expected number is something like 25' and couple of inches. (Locate a North Sails tuning guide for a more accurate number).

(The measurement assumes that the top of the mast track is at 22' 6" above the deck.)

Assuming that nobody messed with the location of the mast step, it should be in the correct position, and then the angle should be the correct one. I have a mast-jack like that, but don't see this effect. However, my mast jack can "wobble" a little bit, presumably that's how it makes the adjustment, so there's no wedge shaped gap between mast foot and the circular nut.

[Paddyt]

Thanks for the reply.

What you say makes sense. As I apply downward pressure on the mast, the jack will rock to meet the rake of the mast.

One more question about this setup; there is a slot under the mast step on either side of the keel. It looks like it lines up with the hole in the jack. Am I missing a pin that keeps the jack in place?

[GreenLake]

Can't get to my boat immediately, but it makes sense for the mast step to be fixed in the fore/aft position.

Your mast jack looks brand new, shiny copper colored and all.

The fore/aft position of the mast step controls the mast rake (angle). If your mast step is free to move, then you need to measure your mast rake (using the North Sails tuning guide for the DS). After you have the correct rake, you need to fix the step so it can't move out of position. Could be that a simple bolt would be enough.

Would love to confirm from my boat, but not able to, immediately.

[Paddyt]

It’s all coming together now, sometimes it takes a while to sink into my brain. Thanks for your help. I’ll put together a bolt and washer setup to hold it in place.

The jack had been painted over in some spots so I used the wire wheel on my bench grinder to take it off then decided to do the whole thing so it can acquire a nice even patina. The threaded part looks brass and the rest looks like it is made of bronze.

[GreenLake]

Make sure to lube it well. The threads are under some pressure when you raise it.

Was just able to check mine, and I do have the bolt, but in a single hole, not a slot.

Looks like the slot was some previous owner's attempt to make the mast rake adjustable. The mast rake affects your boat's balance and you do want to set it to the correct angle.

The North Sails Daysailer Tuning Guide tells you that the distance between the top of the mast and the top of the transom at the very back of the boat should be between 24'11" and 25'1". You measure it with a tape measure pulled aloft by the main halyard.

The result should be that sailing in 8-10 knots of breeze, going upwind, there's not a very strong force on the rudder, so the boat is balanced. If you need to pull hard on the tiller in those conditions, your boat would be imbalanced with too much "weather helm", which is like sailing with the parking brake on.

So, raise the mast, adjust the mast rake until you get the target numbers (read tuning guide for details of how to measure). Then, fix the mast step, go sailing and see whether your boat is balanced. If too much weather helm, you can let the mast come forward a bit, if lee-helm (you need to push the tiller upwind) you can let the mast come back a bit.

Once you have a setup that's correct, mark it, and secure permanently.

[RobH912]

I was looking for some info / guidance on correcting weather helm and this post, particularly this quote seemed like a good starting point for my questions / starting a dialogue.

The North Sails Daysailer Tuning Guide tells you that the distance between the top of the mast and the top of the transom at the very back of the boat should be between 24'11" and 25'1". You measure it with a tape measure pulled aloft by the main halyard.

The result should be that sailing in 8-10 knots of breeze, going upwind, there's not a very strong force on the rudder, so the boat is balanced. If you need to pull hard on the tiller in those conditions, your boat would be imbalanced with too much "weather helm", which is like sailing with the parking brake on.

So, raise the mast, adjust the mast rake until you get the target numbers (read tuning guide for details of how to measure). Then, fix the mast step, go sailing and see whether your boat is balanced. If too much weather helm, you can let the mast come forward a bit, if lee-helm (you need to push the tiller upwind) you can let the mast come back a bit.

Have followed the NS DS Tuning Guide these past two years and have gotten my mast rake (to between the 24'11" and 25'.1" target numbers) and shroud / stay tension measurements to recommended.

Recently had one of the Club's sailing instructors sailing with me as crew in 8-12 knots with gusts and asked her to take the tiller for awhile as I wanted to see how some of the changes I made for jib and some other controls actually worked. She had the tiller for about 30 seconds and said "OMG you have SO MUCH weather helm that I don't want to sail this boat today, would you please take the helm back?"

Last year was the first year I sailed this boat, and with this year have now sailed my DS maybe 9 times in total, certainly have felt the weather helm, but I guess not having ever sailed a "balanced" helm DS never thought of it as a problem.

My mast is keel stepped into a track (see picture) and the front of the mast does come out and touches the front edge of the mast partner part of the deck where it exits the cuddy.

mast step.jpeg (30.63 KiB) Viewed 15285 times

I've been re-reading up on Center of Effort, Center of Lateral Resistance, rig tuning, and sail adjustments to reduce weather helm etc. and I think that I have a rigging problem, rather than a sail adjustment issue. Yesterday sailing in somewhat lighter winds than previous week, I had to move my traveller far to leeward to noticeably reduce the weather helm, but then felt very underpowered and slow. Talk to some others that raced (and finished significantly ahead of me... more ahead than usual ) and they didn't touch their travelers yesterday. One person suggested that I move the mast butt back a notch, which would lean the mast forward / have less rake as a suggestion.

Would tightening the front stay more also help move CE forward? Forget what tension I have the stay at now, but I do have a Loos tool so I could check.

Any thoughts would be appreciated.

Thanks!

[GreenLake]

Rob, in some ways, I'm supremely unqualified to answer your questions because my DS has been sweetly balanced, and nothing I've done over the years has changed that .

However, the NS tuning guide measures only the position of the mast top.

That position is influenced by both the location of the mast foot as well as by the balance of shroud and forestay tension. The shrouds, since the spreaders are swept back, would pull the hounds back - and forestay tension should be able to counteract that to some degree.

I suggest the following experiment: measure the mast top with rig slack, with rig as you normally set up, and a third time with higher forestay tension. Note any changes. Then do the same with mast step moved aft. Also sight up along the mast to observe bend. (Note those results).

That should give you a good feel for which adjustments position your mast where (and which result in prebend).

From your other post about the centerboard, I would advise you to not worry about getting the balance correct until you have sorted out your centerboard position. As it stands, I don't think you know what the actual position of the CB is when your handle is down. While a loose pin should allow the CB to be pushed aft, which would produce lee-helm, from the point of view of getting the balance right, you want to be sure that you understand where your CLP is (and that requires having a positive relation between CB position and handle).

I still think you should do the measurements, as they would be useful no matter how the CB fix turns out. But once you have the CB fixed, you can directly observe the weather helm in various conditions. And then you can tweak the mast rake and compare.

Another thing about the numbers from the tuning guide: they depend on having a standard mast length. If your mast is taller or shorter for any reason, then that would violate the assumption about the distance from the transom.

[RobH912]

GL - Thanks for your thoughts on mast angle and weather helm.

Like your experiment idea, a good approach to capture measurement data for the different scenarios, then see what the results are when I can get the boat in the water.

I suggest the following experiment: measure the mast top with rig slack, with rig as you normally set up, and a third time with higher forestay tension. Note any changes. Then do the same with mast step moved aft. Also sight up along the mast to observe bend. (Note those results).

That should give you a good feel for which adjustments position your mast where (and which result in prebend).

You bring up "prebend" in the mast and I have read that having a tapered mast, properly tuned, allows for creating prebend in the mast and has some positive impact on sail shape... not sure what that positive impact on sail shape really means, but by having more prebend in the mast am I also moving the CE aft? Seems like anything I do should be moving CE forward.

Interesting thought about standard mast length, tuning guide measurements. My boat is somewhat a "frankenboat" in that the previous owner rescued the hull, then found a vert old, used Proctor gold mast for the boat. Last fall when a fellow DS sailor was helping us all unstepping the masts from the various DS he noted that my proctor mast was a lot heavier than the previous 4 silver proctor masts he had just unstepped... now makes me wonder if I have a standard mast length. If the mast is higher, the CE would be higher, and then more weather helm?

Understand your comments on the centerboard, centerboard position as they impact balance, fixing that first, etc. Makes sense... can't sail the boat until fixed. Still very bummed out that CB needs to be fixed right here in the middle of July. Currently also have some back issues that I am getting treatment for so I am not careening the boat, wrestling with a CB, etc. in the near term, so have not moved forward with anything regarding D&R and going to get parts. There is a Club owned loaner DS 1 that I can use this Sunday, and it will be interesting to see how she sails, balanced helm(?), etc. as a comparison to my boat.

Thanks!

[GreenLake]

Having another boat to compare is always good.

Hypothetically, if your mast is longer that standard, the tuning guide would result in more rake.

Check out this diagram to help you understand how much raising the CE affects heeling the boat: viewtopic.php?p=36850#p36850

However, you can compensate to a degree by hiking out harder. For boat balance, the only compensation is the tiller...

Prebend is its own lore. Tom will be happy to explain.

[tomodda]

Prebend is its own lore. Tom will be happy to explain.

Ugh, prebend. After yesterday's sail, I'm happy if I manage not to drown myself, let alone worry about prebend. But, in a nutshell, mast RAKE affects CE. Mast PREBEND affects power/speed/pointing ability. In automobile terms, think of rake like tire weights to balance your steering and prebend like the gearing ratio on your transmission. Apples and oranges. Learn to steer and "shift gears" before you worry about gearing ratios, though!

Speaking of which, imagine that you fry your brains out rigging your DS on the 100F+ degree tarmac at your local boat ramp, then you launch and sail away enjoying the (relatively) cool breeze. When you reach the other side of your lake, you miss stays 50 feet off a rock-lined lee shore. After surviving the panic-jibe, you go back across the lake, miss stays again and notice you've only made 50 feet to Windward, if that. How many more jibe-arounds till you realize that you've left your board UP?!? Doh! Anyway, this just to say take care of the big, obvious things FIRST, the rest will come in time. Fix your CB mounting first. Then sit further forward, get a longer tiller extension if you have to. Measure your mast, maybe it really is taller than normal, lower your boom to "Band 1" from the measurement bylaws. Lastly, try raking your mast a bit. Besides, a bit of weather helm is good, you know that, right? Maybe 5 degrees max... keeps the boat on "best behavior."

In meantime, I'll be in Maine in 10 days, can't wait! Of course, I'll have to come up with a new excuse besides mild heat-stroke for my many nautical mistakes. Lobster poisoning?

[GreenLake]

Nice perspective.

Left my CB up and wondered why I could turn up from a downwind mark (not a race, just using a buoy to have a destination). That was earlier in the week. A few seasons back, left the CB up and actually drifted into a motorboat that I was sure to pass upwind. . .

Today things went like a charm; pretty much Goldilocks temps and wind on the water. Lots of boats on the lake to make things interesting.

[tomodda]

Funny thing is that you never realize the board is up when you're IN the boat, it's painfully obvious when you're watching from OUTSIDE the boat. Case in point, Maine again, a few years back, I was happily watching a Daysailer cast off from a Camden marina (surrounded by million dollar yachts) when I noticed them going dead sideways, straight into a mooring field of more million dollar yachts. I hailed them as loudly as I could, "Hey Daysailer! Put your board down!". A look of surprise then hurried fumbling with the CB handle. Did I get any gratitude, a knowing wave of the hand between like-minded DaysailOrs? Of course not! The skipper shot me a look of pure venom, plus I got the finger from the crew. I think they didn't appreciate being "shown up" in front of the entire harbor...

Bottom line, whenever you feel the boat "acting funny," the first thing to do is look at the CB handle. Yet another lesson relearned this season!

[RobH912]

Tom - thanks for the thoughts on pre-bend vs. rake, understand your comments on rake vs pre-bend. Trying to reduce weather helm so will continue to focus on rake, mast location, and weather helm.

GL - I spent a couple of hours yesterday tuning, moving the mast butt aft one slot (about 1 inch), used a Loos tool, measuring tape, etc. capturing measurements for the "experiment" along the way.

Image 7-15-21 at 10.57 AM.jpeg (36.23 KiB) Viewed 15211 times

So not sure at all what the take away is... by moving the mast butt aft 1", I've got .75" more rake in mast? I had thought that moving the base aft, the top of mast would move forward (pivoting on the mast partner hole) and I'd have less rake... maybe not. Do you see anything with this data?

I'm not going to be able to get on the water until tomorrow to see if there is any difference in weather helm.

AFTER I did this work someone mentioned to me that there is also a mast butt to transom along the floor measurement. Re-read North tuning guide referenced a couple of posts above and they do say that a recommended starting point for mast butt to transom measurement is 11’.5” By me moving the mast butt one slot aft, I am now measure at 10’ 10.5”. Thinking that CE would move forward if mast butt were forward. So instead of one slot aft maybe it should have been one slot forward ? Still would not be at recommended placement. Looking up the mast from inside the cuddy out seems like the only way the mast moved forward will clear the deck is if there is a lot more rake to the mast, going out on an angle.

Anyone know what there mast butt to transom measurement is? I was going to measure some other DS later today.

I'm going to sail with current mast butt aft back one first before making any other changes.

Thanks for any thoughts / comments.

[GreenLake]

Rob,

if I understand your numbers correctly, your col C and E leave the mast tip in the same location, but the mast bottom is 1" aft and the tension in the shrouds is 50% higher. The conclusion is that you are bending your mast.

If you had no shrouds, moving the mast step aft and leaving the partners (deck opening) fixed, your mast should angle forward, increasing the distance between tip and transom.

Now you apply tension with the shrouds and that pulls the hounds backwards, bending the mast a bit. Too bad you didn't sight up along the mast while doing these to observe the bend.

The 180 pounds of tension sound like they are in the ballpark, if I remember correctly from my long ago attempts to verify that my replacement shrouds were sized correctly. I remember shooting for 200, but decided to back off a bit as we sail mostly in lighter winds. The 120 (if in pounds) would seem too loose.

Your column F figures (with the tension in the shroud the same as when "starting") do show and increase in mast tip to transom distance, but like you I'm surprised by how small that is: the distance from mast step to deck is so much smaller than the distance from deck to mast tip, that you would expect a change about 4 times larger. If you are adding a bit of forestay tension into the mix, that should mean some of the shroud tension is offset by the forestay tension, which should allow the mast to go further forward.

I'm afraid that these results puzzle me just as much as they puzzle you. I would suspect measurement error in the Loos gauge number, before anything else. There are other ways to measure shroud tension that are based on % elongation.

However, going on the water and observing things there sounds like a good plan!

It occurred to me that we have not discussed the two remaining elements that influence boat balance and the appearance of weather helm. One is the jib. Just confirming that you are not sailing with an undersized jib, or have it rigged in some way to make it way less effective.

The other would be the rudder. If that, for some reason, is not as effective as it should be, then you'll need larger tiller deflection than otherwise. The extreme case is when the rudder has kicked up. You can still steer, but it feels like strong weather helm. So, I'm assuming that your rudder is standard and fully down.