One of this year’s off season projects is to raise the boom on my Hunter 31 in preparation for fitting a bimini this summer. Raising the boom will provide some much needed headroom. After looking at it last fall, it appears that there is enough play to raise the boom about 14” on the mast and still keep the mainsail luff taunt. Moving the gooseneck seems straightforward enough but I’m not sure how to reattach it to the mast. Is it best to rivet it or drill and tap holes to screw it on? Do I need to use aluminum rivets/screws to prevent galvanic corrosion on the aluminum mast? What’s the best way to refill the old rivet holes? I will also need to cut into the edge of the sail track with something in order to provide an entry point for the sail slides. My plan was to use a Dremil cutting disk to remove the edge and sand it smooth with a Dremil sanding drum . Does anyone have a better idea? If you’ve done this before, I’d really appreciate any pointers you may have.
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don't use aluminum rivets
Alum. isn't strong enough. Use SS with an anti-corrosion protector. I think Loc-Tite makes it.
Alum. isn't strong enough. Use SS with an anti-corrosion protector. I think Loc-Tite makes it.
Paul....
I asked the same question some time back....see link below and some of your questions might be answered. I have not yet tackled this project, but will before spring. I'll be watching the thread too. Good luck...Gary
I asked the same question some time back....see link below and some of your questions might be answered. I have not yet tackled this project, but will before spring. I'll be watching the thread too. Good luck...Gary
Angle
Have you given any thought to just raising the end of the boom? The only thing you would have to do is have your sail re-cut. In theory you would only loose half the sail area compared to moving the boom up parallel.
Have you given any thought to just raising the end of the boom? The only thing you would have to do is have your sail re-cut. In theory you would only loose half the sail area compared to moving the boom up parallel.
Think about resale.
I suggest that when you do these type of projects you think about the potential resale of the boat. I own a H'31 (original owner) and if I were looking for a replacment for some reason and I found your modified setup and a stock setup, a modified rig would probably eliminate your boat from my consideration. If your main is 14" short, you have something seriously wrong with your main or someone just through on a sail to make a sale. I think that having THIS mainsail modified so the boom end could clear the bimini makes a lot of sense because there is already something wrong with the sail (so no loss, no gain). The 31 is not the fastest boat on the block in light air, if you do remove 14" you should be able to keep up with a slow 22' boat. When you take about carving up a $10k mast to make it easier to install a bimini I really question some reasoning. This is just my opinion, but it gives you something to think about.
I suggest that when you do these type of projects you think about the potential resale of the boat. I own a H'31 (original owner) and if I were looking for a replacment for some reason and I found your modified setup and a stock setup, a modified rig would probably eliminate your boat from my consideration. If your main is 14" short, you have something seriously wrong with your main or someone just through on a sail to make a sale. I think that having THIS mainsail modified so the boom end could clear the bimini makes a lot of sense because there is already something wrong with the sail (so no loss, no gain). The 31 is not the fastest boat on the block in light air, if you do remove 14" you should be able to keep up with a slow 22' boat. When you take about carving up a $10k mast to make it easier to install a bimini I really question some reasoning. This is just my opinion, but it gives you something to think about.
Look at...
... a 3 piece setup dodger. fly and bimini and leave the boom alone. There are a couple of H31's in my harbor setup like that. The fly section has glass so you can keep an eye on your trim. Next year when I replace my old dodger thats the way I'm going.
... a 3 piece setup dodger. fly and bimini and leave the boom alone. There are a couple of H31's in my harbor setup like that. The fly section has glass so you can keep an eye on your trim. Next year when I replace my old dodger thats the way I'm going.
We Did it and Loved it
We moved the boom up 15" on a Legend 37 and loved it. Gave us plenty of stand up head room under a bimini. The boom would hit me in the side of the head when standing flat footed in the cockpit before the raise. We had the mainsail recut removing 15-20 square feet at the bottom. We didn't notice any speed loss or tenderness. We later had a new main built for the dimentions regaining a little of the loss at the foot. Used Stainless pop rivets. You're right about having to make a new opening in the sail track. We did as you mentioned by grinding a new opening and drilled and tapped to move the gate. I had a lot of people telling me that I should recut the sail and sail with the boom at an angle and build a goofey bimini to match. I was happy with the boat after the change and I believe that the new owner is also. Bill
We moved the boom up 15" on a Legend 37 and loved it. Gave us plenty of stand up head room under a bimini. The boom would hit me in the side of the head when standing flat footed in the cockpit before the raise. We had the mainsail recut removing 15-20 square feet at the bottom. We didn't notice any speed loss or tenderness. We later had a new main built for the dimentions regaining a little of the loss at the foot. Used Stainless pop rivets. You're right about having to make a new opening in the sail track. We did as you mentioned by grinding a new opening and drilled and tapped to move the gate. I had a lot of people telling me that I should recut the sail and sail with the boom at an angle and build a goofey bimini to match. I was happy with the boat after the change and I believe that the new owner is also. Bill
A few comments
Thank you for the comments and ideas so far. Please keep them coming. In reference to Patrick's reply: If the image in my head is correct, the setup you are describing would have a bimini which does not extend far enough forward to interfere with the boom end. The forward edge of the bimini would be connected to a sloping fly which would be low enough to fully clear the boom when under sail. Correct? That does seem workable, though I would only be able to afford the Bimini this year. In reference to the reply by Steve Dion: As far as I can tell, both the sail and the mast are original. The sail has the H31 logo on it and the mast is the Isomat model that Hunter says was OEM on the 1884-85 H31. When looking at the link supplied by Gary and others who answered it, the 14" of free space at the top of the mast when the sail is raised does not seem to be out of order at all. I can't believe the luff of the main sail could have shrunk this much over time (more likely that it would stretch). The angle of the boom while under sail is definately downhill by a significant amount and the sail tack must be somewhat larger than 90 degrees to allow this to happen. I am no expert to be sure, but judging by everything I have seen and read, I have to conclude that it was designed this way.
Thank you for the comments and ideas so far. Please keep them coming. In reference to Patrick's reply: If the image in my head is correct, the setup you are describing would have a bimini which does not extend far enough forward to interfere with the boom end. The forward edge of the bimini would be connected to a sloping fly which would be low enough to fully clear the boom when under sail. Correct? That does seem workable, though I would only be able to afford the Bimini this year. In reference to the reply by Steve Dion: As far as I can tell, both the sail and the mast are original. The sail has the H31 logo on it and the mast is the Isomat model that Hunter says was OEM on the 1884-85 H31. When looking at the link supplied by Gary and others who answered it, the 14" of free space at the top of the mast when the sail is raised does not seem to be out of order at all. I can't believe the luff of the main sail could have shrunk this much over time (more likely that it would stretch). The angle of the boom while under sail is definately downhill by a significant amount and the sail tack must be somewhat larger than 90 degrees to allow this to happen. I am no expert to be sure, but judging by everything I have seen and read, I have to conclude that it was designed this way.
Great Idea
I raise the boom on my H31 inches only, install an ample bimini top with 6' 4" under it, and continued to use the orignal mainsail. If you do this you will find that the end of the boom will probably sag down enough to scrape the leading edge of the boom when you sheet in the mainsheet, and there I had a different problem. I needed to replace the original mainsail, which I did, and which was cut to original specifications, and it works very well; no more scraping the leading edge of the bimini top. Finally I installed a boom kicker and removed the top lift. Now I have ample head room under the bimini, no more scrapes of its leading edge, do not have to worry about the boom falling down on the bimini top when I lower or reef the mainsail, and the boat can use, if necessary, a regular mainsail, rpovide that is in good condition, which it now has. I hope this helps. regards Ed
I raise the boom on my H31 inches only, install an ample bimini top with 6' 4" under it, and continued to use the orignal mainsail. If you do this you will find that the end of the boom will probably sag down enough to scrape the leading edge of the boom when you sheet in the mainsheet, and there I had a different problem. I needed to replace the original mainsail, which I did, and which was cut to original specifications, and it works very well; no more scraping the leading edge of the bimini top. Finally I installed a boom kicker and removed the top lift. Now I have ample head room under the bimini, no more scrapes of its leading edge, do not have to worry about the boom falling down on the bimini top when I lower or reef the mainsail, and the boat can use, if necessary, a regular mainsail, rpovide that is in good condition, which it now has. I hope this helps. regards Ed
So......
if I read Ed's post correctly, he aserts that the aged mainsail stretches over time, and consequently, the aft end of the boom is contacting the leading edge of the bimini. Paul, I agree with your conclusion, it was designed this way. I still think the most logical remedy is to raise the gooseneck as far as possible. On mine, I just hope by doing this coupled with dropping the bimini to about 6' to 6'2", the boom will clear the bimini. I wouldn't stress over modification of the sail plan, as one could easily change back to the original setup, and I doubt that an additional 4 small holes in the mast would compromise the mast strenght. I'm not an expert either, but this is what common sense is telling me.
if I read Ed's post correctly, he aserts that the aged mainsail stretches over time, and consequently, the aft end of the boom is contacting the leading edge of the bimini. Paul, I agree with your conclusion, it was designed this way. I still think the most logical remedy is to raise the gooseneck as far as possible. On mine, I just hope by doing this coupled with dropping the bimini to about 6' to 6'2", the boom will clear the bimini. I wouldn't stress over modification of the sail plan, as one could easily change back to the original setup, and I doubt that an additional 4 small holes in the mast would compromise the mast strenght. I'm not an expert either, but this is what common sense is telling me.
Here is the type of Dodger/Bimini we have
We have a Dodger/Bimini combo like this one. The boom is stock height. This one is from Boat Tailors in Sturtevant, WI.
We have a Dodger/Bimini combo like this one. The boom is stock height. This one is from Boat Tailors in Sturtevant, WI.
Main Sail Modification vs Boom
I believe Alan has a good point as do others questioning raising the boom (or goose neck) 15", which is an awfull lot of change. I have the next smaller Hubter, the 28.5 and had the same concerns over moving the boom up to install a bimini with decent head room. Since I already had a flattening reef in my mainsail, I tied it in to measure the adjusted height of the outer end of the boom in that position and found it perfect to provide a bimini clearance of about 6'-1". Since I needed and wanted a new loose footed Main anyway, I had it cut 8"to 10" higher at the outhaul end, and the sail maker compensated by adding a little more leech curve and cutting the mainsail foot and hoist to the maximum designed lengths. The bimini is wonderful, the boat sails great with the new main and the mast, and the boom and goose neck are still 'original'. I'd suggest you not make the bimini any higher than you actually need it and mount the Bimini frames out on the forward edge of the stern pulpit for maximum width over the cockpit and best clearance to your winches.
I believe Alan has a good point as do others questioning raising the boom (or goose neck) 15", which is an awfull lot of change. I have the next smaller Hubter, the 28.5 and had the same concerns over moving the boom up to install a bimini with decent head room. Since I already had a flattening reef in my mainsail, I tied it in to measure the adjusted height of the outer end of the boom in that position and found it perfect to provide a bimini clearance of about 6'-1". Since I needed and wanted a new loose footed Main anyway, I had it cut 8"to 10" higher at the outhaul end, and the sail maker compensated by adding a little more leech curve and cutting the mainsail foot and hoist to the maximum designed lengths. The bimini is wonderful, the boat sails great with the new main and the mast, and the boom and goose neck are still 'original'. I'd suggest you not make the bimini any higher than you actually need it and mount the Bimini frames out on the forward edge of the stern pulpit for maximum width over the cockpit and best clearance to your winches.
Minor Correction
Hi, I realized too late that I had omitted to provide the fact that I had raised the boom six (6") only, and this gave me all the room that I spoke of in my previous email. I understand the concern about increasing the righting moment; however, six inches will not increase it dramatically. I do like that the bimini that has two heights, but I will much prefer to have about 6' 4" all the way into the companionway. Thanks Ed
Hi, I realized too late that I had omitted to provide the fact that I had raised the boom six (6") only, and this gave me all the room that I spoke of in my previous email. I understand the concern about increasing the righting moment; however, six inches will not increase it dramatically. I do like that the bimini that has two heights, but I will much prefer to have about 6' 4" all the way into the companionway. Thanks Ed
More on righting moments
I did a little research on this and determined that the notion of changing the righting moment of the boat by raising the boom is correct, but the change is an indirect one and its significance is questionable. I'll try to explain. The righting moment is determined by (among other parameters) the length of the moment arm formed between the boats center of gravity and its center of boyancy. Both centers are imaginarly points located within the hull of the boat and only come into play when the boat is heeling. With no heel the points fall into a straight vertical line and there is no righting moment. The centers change with the amount of heel, and the amount of heel will change with the boom height (all else being equal). However, the amount of change is not all that significant. Assuming we move the boom up one foot on a 47 foot mast (as we are discussing here) the overall difference in terms of rotational torque (heel) is about +2%. This means that if under a given set of circumstances the boat will heel 20 degrees before the boom modification, it will heel at 20.4 degrees after the modification. The change this makes in the location of the center of gravity/boyancy (and hence to the righting moment) is pretty much insignificant. Beyond that, if anyone here can actually feel the difference between 20 and 20.4 degrees of heel, my hat is off to you. Also, I want to point out that the 14" I wrote about in my original post is the space that is available for raising the boom, not necessarily the amount I actually plan to raise it. If raising it only 6" provides enough headroom (as in Ed's case), then there is no reason to raise it any higher. I am much more worried that I'll have problems with removal of the annodiized finish when cutting a new sail slide entry or having problems drilling out the old rivets on the gooseneck than I am about some imperceptably minor change to the boats sailing characteristics. Once again, thanks to all for their input.
I did a little research on this and determined that the notion of changing the righting moment of the boat by raising the boom is correct, but the change is an indirect one and its significance is questionable. I'll try to explain. The righting moment is determined by (among other parameters) the length of the moment arm formed between the boats center of gravity and its center of boyancy. Both centers are imaginarly points located within the hull of the boat and only come into play when the boat is heeling. With no heel the points fall into a straight vertical line and there is no righting moment. The centers change with the amount of heel, and the amount of heel will change with the boom height (all else being equal). However, the amount of change is not all that significant. Assuming we move the boom up one foot on a 47 foot mast (as we are discussing here) the overall difference in terms of rotational torque (heel) is about +2%. This means that if under a given set of circumstances the boat will heel 20 degrees before the boom modification, it will heel at 20.4 degrees after the modification. The change this makes in the location of the center of gravity/boyancy (and hence to the righting moment) is pretty much insignificant. Beyond that, if anyone here can actually feel the difference between 20 and 20.4 degrees of heel, my hat is off to you. Also, I want to point out that the 14" I wrote about in my original post is the space that is available for raising the boom, not necessarily the amount I actually plan to raise it. If raising it only 6" provides enough headroom (as in Ed's case), then there is no reason to raise it any higher. I am much more worried that I'll have problems with removal of the annodiized finish when cutting a new sail slide entry or having problems drilling out the old rivets on the gooseneck than I am about some imperceptably minor change to the boats sailing characteristics. Once again, thanks to all for their input.
Raising the Gooseneck
Hi, We raised the gooseneck about six inches and it still leaves about four inches to the top of the mast cutout for inserting the mainsail slides. In fact, the new mainsail that I got is full batten, somewhat more difficult to handle, but easy to insert. relocating the location of the mast goose neck plate (or whatever it is called
is easy and will not cause any weakening of the mast at all. I'll be a t the boat this weekend and see if I can take a few pictures for you. Regards Ed
Hi, We raised the gooseneck about six inches and it still leaves about four inches to the top of the mast cutout for inserting the mainsail slides. In fact, the new mainsail that I got is full batten, somewhat more difficult to handle, but easy to insert. relocating the location of the mast goose neck plate (or whatever it is called
is easy and will not cause any weakening of the mast at all. I'll be a t the boat this weekend and see if I can take a few pictures for you. Regards EdGood info....
My previously owned Oday 25 was designed with a gooseneck slide system allowing it to move up and down about 18". Great for a downhaul/cunningham to tighten the mainsail luff to make room for a bimini or whatever reason. Paul....please post results. Thanks
My previously owned Oday 25 was designed with a gooseneck slide system allowing it to move up and down about 18". Great for a downhaul/cunningham to tighten the mainsail luff to make room for a bimini or whatever reason. Paul....please post results. Thanks
Modify the Sail
I had a similar problem, and I agree with Don's comment, I would not modify any of the mast hardware. I had a sailmaker look at my boat. He recut my sail, reducing the leech by 18 inches and made the sail loosefooted. This raised the boom 18 inches. The overall sail area was minimally decrease and the boom now cleared the newly installed bimini. I liked this so much that the next year I had a new mainsail made with this new measurement. A $50 modification of your main my save you hundreds.
I had a similar problem, and I agree with Don's comment, I would not modify any of the mast hardware. I had a sailmaker look at my boat. He recut my sail, reducing the leech by 18 inches and made the sail loosefooted. This raised the boom 18 inches. The overall sail area was minimally decrease and the boom now cleared the newly installed bimini. I liked this so much that the next year I had a new mainsail made with this new measurement. A $50 modification of your main my save you hundreds.
Thanks Tracey, I always wondered....
how I'd like a loose footed main, and now's my chance to find out. Are there any disadvantages to the new cut? $50 sounds very reasonable....I was afraid it would be much more. Given this info, I think I'll go with this remedy rather moving the gooseneck. Thanks much
how I'd like a loose footed main, and now's my chance to find out. Are there any disadvantages to the new cut? $50 sounds very reasonable....I was afraid it would be much more. Given this info, I think I'll go with this remedy rather moving the gooseneck. Thanks much
Hate to sound ignorant but...
What exactly is a "Loose Footed" main? What are it's advantages? I will check out the possibility of getting the sail recut, but my guess is, it will be much more expensive than $50 in my area. I also don't see how its going to save me hundreds with the recut. Please explain. I also want to point out that any modification that moves the boom upward by recutting the main sail changes the righting moment and or/ heel angle just as if the gooseneck had been moved. Either operation moves the "center of force" of the sail upward and hence, changes these parameters. I also believe the changes are negligable regardless of the method used to raise the boom.
What exactly is a "Loose Footed" main? What are it's advantages? I will check out the possibility of getting the sail recut, but my guess is, it will be much more expensive than $50 in my area. I also don't see how its going to save me hundreds with the recut. Please explain. I also want to point out that any modification that moves the boom upward by recutting the main sail changes the righting moment and or/ heel angle just as if the gooseneck had been moved. Either operation moves the "center of force" of the sail upward and hence, changes these parameters. I also believe the changes are negligable regardless of the method used to raise the boom.
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