Raising Boom for Bimini

Simon Sexton · Jan 21, 2019

@76Oday20 ,

Good evening! Seeing as my mother took part in purchasing our Catalina 25, she has always wanted to put a bimini over the cockpit to keep us shaded from the relentless Texas sun. However, I, being a speed person, want to keep as much sail area as possible. I'm afraid that if we were to install a bimini, we would have to raise the boom and have the main cut a bit shorter, causing a possible decrease in performance. If performance doesn't matter too much to you, then I'd say go for it! You may have to get your main cut in order to ensure it still fits the rig properly. I hope this helps!

Joe · Jan 21, 2019

Simon, restating or re phrasing someone's question does not count as an answer.

nightowle · Jan 21, 2019

Here's a possibility that I thought about for my last boat, an O'Day 27. I got the bimini 2nd hand, in new condition, but then sold the boat before doing the install. My method would have been to cut the bimini bars a bit shorter to lower the overall height. The back stay on the boat would not allow me to fold the bimini backwards if I wanted to, but regardless, in order to keep the boom at close to the same height I decided I'd only use the bimini opened when at the dock, at anchor or raft ups. I found stainless attachments (at Overton's online) that would be placed on the coamings and articulated to allow the bimini to fold and slide forward. Sliding forward was important because then the folded forward bimini would clear the open companion way cover. I planned to use the topping lift to raise the boom enough to enable the bimini to fully open when it was slid back about six inches or so from it's forward and down position. It was a compromise, because it could therefore only be used when not under sail. But, I felt it was going to be a good happy medium. Hope this can help you plan similarly if you want.

Meriachee · Jan 21, 2019

You might consider, if the attachment of the boom would allow, getting another main, and cutting it so that the boom could be raised, use the shorter sail and the bimini, but leaving yourself the option of dropping the boom to the original position and having the full sail for the days where you could put it to use. If you bought a used sail, you could possibly get it done for a very reasonable price.

Gene Neill · Jan 22, 2019

We are planning to do exactly this on our Albin Vega. We will be sailing her full time in the Caribbean, so shade is of paramount importance, along with the ability to stand up in the cockpit. It will be about like sailing with 1/4 of a reef in at all times. It's a compromise we are more than willing to make.
Like you, we will be getting new sails anyway, so no additional cost involved there. Just need to decide how to reattach the boom. I'm thinking perhaps a sliding gooseneck like our C22 has.

daviddp · Jan 22, 2019

I owned an O'day 23 with a pop top My boys both grew over a winter and topped out at 6'3"and 6'5" @ 13 and 15 years old. I had a much needed new main built in the spring of that year shortend by 4" which was enough to provided some needed headroom in the cockpit at anchor and underway. We used the boat to cruise all over Lake Ontario for 3 more years before trading up. I never regreted the loss of preformance vs headroom even during 50 mile lake crossings. I think the new main made up in performance for the "baggy" old main. It was loose footed with extra material hanging below mid boom. Going slower allowed us more time to sail and less time in urgent care.

Simon Sexton · Jan 22, 2019

Joe said:
does not count as an answer.

I'll be sure to keep that in mind next time, sir. Thank you!

Sandy Stone · Jan 22, 2019

There is one other possibility, if you have an extra reef line available. Have your sailmaker put a reef cringle far enough up the leech of your main so that when the reef is in, the boom is lifted up enough to clear the bimini. Depending on how close the bimini comes to the mast, this may not work out for you, but it is a simple fix.

Will Gilmore · Jan 22, 2019

I would like to see pictures of your boat. Looking at images online of the O'Day 20, it looks like plenty of headroom under the boom.

-Will (Dragonfly)

31seahorse · Jan 22, 2019

Hello 76Oday20, Oday boats have long been favorites of ours. We owned several over the decades, but as they say, "That is a whole 'nother ball of wax."

We are having a mainsail made for our Celebrity daysailor and have discussed sail size with the sailmaker. He asked us whether the boom was a "head banger" or not due to the cut of the old mainsail I sent him. In our case the angle of luff to foot was 90 degrees, whereas the original specification for that boat is 86 degrees. The original angle would raise the aft part of the boom without changing the position of the gooseneck. We chose to let the sailmaker cut the new mainsail to the original angle and hope the change in boom height will be useful to us.

My point is this.....perhaps resizing the main by adjusting the luff/foot angle might provide you the extra height that you desire over the cockpit. Shortening the mainsail's luff to raise the boom brings into play several things: (1) could the boom disconnect from the mast depending on the way it is connected. Our gooseneck slides into a wide part of the mast sail track and pulls down. (2) Raising the boom will raise the forces that the mainsail exerts on the boat and on the mast. (3) If the boom is secured to the mast at the gooseneck then that securing ...either rivets, screws, or chewing gum....will need to be reattached a bit higher.

31seahorse · Jan 22, 2019

76Oday20 said:
My boom has a fitting that slides into the track on the mast so I am hoping that it can just slide up higher. I am feeling better about doing this …. Gene!

That is the situation I tried to describe. First, I was trying to argue AGAINST raising the boom. Not because I am an authority on the forces at work on a sailboat, but because I had asked about the same type of change for our new sail, and the sailmaker had a concern about raising the boom. He felt that the higher the boom met the mast, the higher the force would be applied to the mast and that would not be the original mast was designed. Second, when you tighten the downhaul you will be pulling the boom down toward that opening. If the halyard slips or if the sail is not completely raised the fitting you describe might exit the mast. Nothing good would happen after that! Third, the sail being made will match the original specs for the boat.

Heading for Florida early tomorrow morning. Seahorse out.

Meriachee · Jan 22, 2019

76Oday20 said:
I am curious when you refer to a loose foot on the main what exactly does that mean?

A loose foot is essentially a sail that doesn’t have a bolt rope which would normally go into a boom.