Notice:
The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.
There seems to be quite a bit of discussion about the installation of biminis on this board, so I thought I'd start a thread about how we built and installed a bimini on our '84 Tall Rig.
The basic geometry of the tall rig makes it impractical to install a bimini that's somewhat user friendly. While it's possible to build a bimini for a tall rig, it would be quite low. Difficult to maneuver underneath (it wouldn't be possible to stand), and even more difficult to go forward under the bimini to move to the foredeck. So, are basic requirements were to A) be able to stand under the bimini; B) be able to easily go forward with the bimini up; and C) the bimini needed to be strong enough to stand up to our small kids swinging from it's various parts!
All of these requirements meant two things: it wouldn't be an easy/quick project and it wouldn't be cheap. After a couple of quotes from local canvas shops and sail lofts, I rapidly calculated that a custom made bimini wasn't much of an option; so that left only two options, build a bimini from scratch or modify an "off-the-shelf" model. We went with option "B" and spent a lot of time measuring, and went even so far as to build a PVC mock-up (cost about 5 bucks!) to ensure everything would fit before we ordered our bimini. If I had to do it all over again, I probably would opt for option "A" since only slightly more work would be required! I also now know why custom made biminis cost what they do...
Anyway, the size and strength requirements dictated the use of stainless tubing, reinforced in some areas with double tubing. And, since we were going to use stainless tubing, we pressed with stainless fittings as well. We've always had great luck with Sunbrella fabric, so now we knew that we needed a stainless frame with Sunbrella fabric. The only thing that remained to be determined was the size. Different manufacturers offer different "standard" sizes, but most offer something in the neighboorhood of 36/48/72" heights. But first we had to determine where to mount the bimini, so we could figure out how wide as well as how high it needed to be.
If you want the bimini to cover a portion of the cockpit, you'll have to mount it either on deck (roughly abeam the location of the "Catalina 25" logo), the genoa track, or the raised area abaft the cockpit seats. For clearance of lines, and ease of use, we chose to mount the bimini to the deck. There is probably some convinience to mounting the bimini to genoa cars, be we planned to use fixed support poles to support the aft end of the bimini; so the deck mounting was the most logical. This allows us the option of "dropping" the bimini aft against the support poles, or forward laying down on top of the coach roof. With our rig, it's possible to sail with the bimini up, stowed aft against the upright supports or lying down on top of the coachroof. I think it's necessary to be able to "lose" the bimini in a hurry if conditions warrant. With the combination of a deck mount and fixed aft supports, we can stow the bimini in less than 30 seconds, and can remove it completely in just about a minute with quick-release fittings on all of the deck mounts.
Measuring we found that a nominal width of 76" would do the trick for the mounting location we planned to use. "Stock" biminis usually have a width range, e.g., 74-78". The uprights can be splayed in or out slightly within this range. You need to measure enough to at least be in the ballpark, however, because the angle of the mounting still needs to be taken into account (i.e., the tubing must be within a couple of degrees of the angle of the deck mount, or the mounting will not fit or will bind if forced. Remember, with the aft mounted mainsheet, you've got to put the bimini far enough forward to allow unobstructed sheet movement even with the boom deployed as it would be in a full run. Typical "stock" biminis are normally 6 or 8 feet long. A six foot length will allow you to cover about half of the cockpit and all of the companion way, a nice compromise that allows unencumbered use of sail controls and helps keep the cabin cooler in the hot Florida sun.
After determining the mounting location you can determine the height of bimini required. Keep in mind that you can remove a few inches from "stock" bimini height by removing the lower fitting and carefully measuring and hacksawing the tube. To figure out the hight we required, I simply stood in the cockpit and continued to raise the boom until it cleared my cranium by a sufficient margin. Remember, that in order to sail with the bimini up, you'll need to determine the lowest point that your boom will "fly" (i.e., maximum downhaul pressure on the gooseneck with the sail at full hoist) and still leave a couple of inches of clearance. You could reduce this margin to only an inch or so, but we felt it prudent to allow for at least two inches of clearance between the lowest point of the boom and the top of the bimini. Don't forget to include any hardware you may have hanging off or mounted to the bottom of the boom. Once the boom is perpendicular to the mast, you can swing it over the position on the deck you intend to mount it and measure for desired height. It's an off the shelf world with stock biminis, so you may have to compromise your ideal height a bit, remembering that you can reduce the height of a stock bimini by about 5-6" if required.
To make an extremely long story much shorter, you'll need to get a 6 foot, by 76" wide by 72" high bimini if you want reasonable standing room (and easy access to the foredeck under the bimini), assuming you mount it to the deck at roughly the end of the coachroof. Obviously, the boom is going to be in the way with a stock sail...not quite as much with a standard rig as a tall, but some modification of the sail plan is in order. You could simply reef the sail, or perhaps add a flatening reef to the end of the sail, have your existing sail cut (that's what we did with one of our "cruising" sails), or have a sail custom made to fit the required luff/leach dimensions of your "raised" rig. You need to be careful when you raise the boom to avoid having it ride at a height that would put it in the kerf slot (that wide spot in the slot where you feed your sail slugs or bolt rope into the mast). Yup, this raises the center of pressure of the sailplan, and any time we race or conditions warrant, the bimini comes down and so does the boom.
The other thing you need to be careful of whenever you raise a boom is to ensure that adequate clearance exists with the backstay. You have to assume worst case scenario, i.e., a flying gibe where the boom flies up as it swings (violently) across the stern on its way to the other side. Overall, we ended up raising our boom approximately 20" above the normal position, and we found that in a flying gibe, it would just barely contact the backstay. On a good bad scale, this is very bad. So we removed 4" of boom and then confirmed that adequate clearance was availalble. We then went out and did a few relatively uncontrolled gibes so that we'd have confidence in the new rig geometry. We found with our sail shortened (at the head with a more rounded leach aloft), boom raised 20" and shortened 4", she sailed just fine for cruising (and even well enough for social racing).
We had a local loft reshape the top of the sail for less than 100 dollars. The leech does rub the backstay during tacks and gybes, but this has not proven to be any sort of problem although in very light conditions, the boom occasionally needs a shove across. Some highly eliptical sails are designed this way from the git go, so we figured that we weren't too far off the mark.
So we first assembled our "stock" bimini and made a few modifications to increase its overall strength and then mounted it on the boat to check the fit. We had to reduce the height a total of 4" (measure twice, cut once--stainless is expensive!). After properly locating and mounting the deck fittings (check to ensure that you have clearance below and are not drilling into an unaccessable location--the aft end of the coach top is not symetric port and starboard, so take a careful look at both sides) the bimini can be installed. We used the fore straps to level it and then fitted the aft braces, which we custom cut to length in assembly to ensure a good fit. The forestraps can be connected to the base of the life line stanchions. If you install aft supports like this, you'll need to use ANGLED deck mounts as the top of this area is angled slightly.
Total cost: Just under 700 bucks! This was for an "off-the-shelf" stainless bimini, and the extra tubing and fittings required to beef it up a bit and make a pair of aft support tubes. It's been a great modification and certainly worth the money in our hot climate, but now I understand why a quality custom made bimini costs over a thousand dollars.
I hope this generates some thought and discussion.
Mike: what a wonderful post!. Thanks for the advice and explanation.
The bottom line, it seems, is that there's no way to install a bimini except for munchkins without making some major changes to the mainsail. I love my C25, but I think the weirdest piece of its design is that the tall rig offers LESS cockpit clearance than the standard rig. It seems logical (to me at least) that a taller mast would be accompanied by a higher boom.
The idea of altering the mainsail and the boom for the sake of a bimini is harrowing. The $ 700 is also harrowing.
Mike, several years ago I had the same problem with my 1983 Tall Rig. I choose a different route. Not wishing to cut my mainsail I went to used sail store in Annapolis and purchased a "Ranger 26" sail which is about 18" shorter than the one that comes with the boat. It also has a longer foot. The net result is that I only lost about 6 sq ft. of sail area and was able to buy a standard bimini which is mounted on the genoa track. The used sail cost me just less than 2 boat units.
Concur with the alternate sail option and forgot to mention that--turns out for us it was more inexpensive to modify a sail we already had than by even a good used main; but it sure is a good option. We have a full-hoist, full-batten main that we use for racing (with the bimini removed from the boat).
Mark--would love to provide pictures, but I'm in the military and am currently stuck in southwest Asia for a bit. I'll be happy to do another post when I get back to the States, but that could be a couple of months.
Cheers,
Mike Vaccaro about a half a planet from the "Swoose" 84 TR/SK #4707
<img src="http://im1.shutterfly.com/procserv/47b2d904b3127cce9f7cd9e65e340000001410" border=0> My bimini is a vinyl, not sunbrella, bimini that I bought from BoatUS for $139.00. It was originally $180, but it was a discontinued, off-the-shelf model, that was reduced to sell. The dimensions, I believe were 6 feet long by 82 inches wide and I mounted it to a pair of old track slides using external eye mounts($6.00) that I purchased separately. Since it was an off the rack bimini, I had to alter the height by about 10 inches, but that was done simply with my trusting pipe cutter I use for copper plumbing work. Since it is mounted on slides it can be moved both forward and astern. In the picture, I have it mounted so it's just forward enough not to interfere with the mainsheet. When not in use, I fold it up, put the boot cover on it, and slide it all the way back so it is standing straight up against the backstay(I simply bungee the bimini to the split backstay after disconnecting the snapshackle on the mainsheet)and the height of the folded bimini is over six feet so it is very much out of the way. It wasn't that difficult of a job, inexpensive($145.00), and the cooling shade it provides on those hot, sunny days is wonderful. If you have any more questions just let me know.
Notice: The advice given on this site is based upon individual or quoted experience, yours may differ. The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.