Beefed up swing keel for Catalina 22

Discussion in 'Boat Design' started by Michail, Feb 3, 2015.

  1. Michail
    Joined: Aug 2011
    Posts: 61
    Likes: 1, Points: 0, Legacy Rep: 15
    Location: Chile

    Michail Junior Member

    I need some advice for improving stability for a Catalina 22.

    I am doing coastal sailing on the Pacific in Chile, where the waves can and do get pretty high (4-6 meters are quite frequent), plus if you have strong wind, it can get pretty fast out of hand... So:

    I have a swing keel. I have strengthened the keel box by putting 3 triangular wood inserts to spread the load onto the left side of the hull, epoxied it, and increased the thickness of the hull where the load acts by about 8-10 mm. (in an area of about 30 x 30 cm).

    The standard keel weighs 250 kg. and hangs on a bronze pin in hangers, and these are attached with 4 5/16 bolts. I have replaced the bolts with new ones and the bronze pin is in perfect condition.

    I plan to put lead to the tip of the swing keel, but I am not sure how much exta weight one can add. I have two issues to deal with: the increased weight of the keel and the increased torque on the keel box.

    The increased weight will be transmitted directly to the bolts, and as there is often slamming going on, I believe that the shock loads on the bolts may be considerable. Any advise as to how much weight one can add without changing the bolts (that would involve consdierable reingeneering)? I was thinking about adding at least 40 kg (15 %), but if feasable would go as high as 70 - 80 kg (30 %).

    The second issue is the torque on the keel box. An addition of 40 kg. would generate at least 50 % in the extra torque, and 80 kg. would double the load. I have strengthened one side (left side of the keel box), but I am not sure whether I should do the same to the other side (this would involve cutting out decorative covers and putting several nasty pieces across the passage on the right side of keel box... The livebility of the boat would be drastically reduced...

    So I need some opinions as to the safe weight which can be added in this way and whether it is worth it installing reinforcements on the right-hand side of the keel box...
     
  2. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 494, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Which version of the Catalina 22 do you have? Adding a significant amount of additional ballast to the swing keel will affect more then just the case. The pivot, the ballast bolts, the case laminate, the rigging loads and their related pieces (chainplates, tangs, etc.), as well as the mast and boom sections might also require some upgrades.
     
  3. Michail
    Joined: Aug 2011
    Posts: 61
    Likes: 1, Points: 0, Legacy Rep: 15
    Location: Chile

    Michail Junior Member

    It is a standard 74 Catalina... But in very good shape, it seems that it was not sailed a lot before I bought it last year.

    Actually, I plan to change mast to a thicker one, the chainplates are reinforced already (in original, there were simple washers, now I have put 10 x 15 cm. backing plates), I have upgraded the wires to 4 mm. The weak point is the mast and the spreader attachments which must be changed.
     
  4. tom28571
    Joined: Dec 2001
    Posts: 2,474
    Likes: 117, Points: 63, Legacy Rep: 1728
    Location: Oriental, NC

    tom28571 Senior Member

    I had a 1973 Catalina 22 and had similar problem with the keel slamming side to side in heavy water. I dropped the keel and built up the thickness of the part that remains in the trunk when extended. I don't remember exactly how much it was thickened as this was 35 years ago, but I think it was a bit over 1/8" to each side. This solved the wobbling issue which was also a bother when sleeping with the keel raised in shallow water.

    I'm sure the designer, Frank Butler, sized the mounting hardware to suit the expected loads of the factory keel and might be wary of increasing it too much. Your proposed increase to the bottom of the keel sound like it is probably beyond the safe limits. If you are intent on doing this, I would consider a rebuild of all the hardware to make it stronger. The lifting cable and winch (clutch) might also need an upgrade. The Catalina 25 probably has a stronger winch and mounting pin hardware that should work for you if it can be found in Chile.

    Another issue with the C22 of that era is the cast aluminum spreader brackets. Mine broke and were replaced with newer stainless ones. I think that the mast, when properly supported, is strong enough for the modest sail area. Many C22s also had spinnakers and I don't remember a mast failure, but that is only memory.

    I sometimes wished that the boat had more ballast but realize that seamanship is really more important. All the rigging is based on the whole package and more ballast might stress that more than is good for it. I know of one bow fitting that was pulled up by too much backstay tension. My boat was raced and cruised extensively and finally appreciated for what it was. It provided as much or more enjoyment for both activities as any other boat we have owned.
     
  5. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 494, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    The mast section of the Catalina 22 was beefed up in the late 70's. There were also rigging and other "model run changes at this time. The wing keel didn't show up until the late 80's. I suspect the hoist clutch is able to tolerate much more weight than the stock board, though some adjustment to the hoist might be necessary (simply turn a nut). All the original hardware should have been replaced by now, if not, it shouldn't be trusted, as all of it was pretty cheap. Leaking lanyards are a common complaint, though mostly from MKII's from my data base. Another issues was the lanyard would fall out of the sheave groove or the sheave would break and the lanyard would try to cut the boat in half.

    Basically they suffer from the usual disappointments, spreader bases, mast step fitting, stem head and bow eye bolt, backing plates and 'glass reinforcements around highly loaded areas, keel locking bolt, cockpit scupper thru hulls, etc.
     
  6. Michail
    Joined: Aug 2011
    Posts: 61
    Likes: 1, Points: 0, Legacy Rep: 15
    Location: Chile

    Michail Junior Member

    Well, I have worked through many of the issues, replaced mast step, had to reepoxy bow eye bolt with a new backing plate support, reinforced the keel locking bolt area with about 10 mm. epoxy (it was leaking up to 8 l/an hour because the metal plate where the bolt goes in separated from the keel box). I replaced the keel cable, but the sheeve seemed OK. I installed a 40 mm. scupper. I reduced cockpit volume by installing a board over the rear part of the cockpit and stuffing there three gasoline cans of 45 and 2 x 25 liters under it (recently made a trip through the fiords to Laguna San Rafael, it was 600 nautical mile round trip, often without wind and against currents, had 180 liters of gas on board)...

    And when I took down the keel to change the bolts and check the pin,I epoxied about 3 mm. on each side so that there is virtually no lateral movement of the keel.


    The mast seems to be the earlier type, with 2 mm. thickness. I am thinking of replacing it and also replacing the spreaders... I am actually a conservative sailor, have made a second row for reefing and purchased a 3 m2 storm jib (30%) and came to love it, because that is the only way you can sail single-handed in a 25 knot wind, and I do not hesitate to reduce sail area at the slightest potential trouble.

    The issue of the mast must be dealt separately, but what I am more worried is to get caught in high waves. The boat has probably about 100 degrees AVS, which is not nearly safe. I need the higher stability not to run faster, but to run safer...

    Therefore, the question is, how much extra weight one may consider to add safely to the tip of the swing keel in terms of hull/bolts/etc, not rigging?
     
  7. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 494, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    It's not a simple question, in terms of how much more weight the bolts/hull can tolerate. Yes, the rig must be addressed, if you add much weight so far from the CG. Lets make some assumptions. Your bolts will tolerate about 2,500 pounds (1,136 kg) before breaking, so guessing a reasonable 3:1 safety margin they're 833 pounds (379 kg) of holding power as designed (1/3rd of yield). Lets increase the load to 1,000 pounds (455 kg), which reduces your safety margin to 2.5:1 and is typically below what an engineer or NA would recommend, except on special purpose craft (racers). The question you need to ask yourself is how much of a reduction you can live with, in regard to bolt yield to safety margin, without the designers loading data in front of you. Simply put, you're just going to make a guess, which is a difficult thing to live with in a big blow, farther from shore than you can swim back to. I don't know what role Frank Butler now plays, but he was still very active in the company, not that many years ago. Maybe a quick phone call or email would be the wisest course. In other words, it's not likely anyone is willing to second guess his scantlings or loading calculations, so unless you're willing to do or hire this work done, anything else is just wishful thinking.
     
  8. Michail
    Joined: Aug 2011
    Posts: 61
    Likes: 1, Points: 0, Legacy Rep: 15
    Location: Chile

    Michail Junior Member

    Thank you Par for frank answer.

    There is one detail: the keel weights 250 kg, so if I add 60 kg., the total weight is still only 310 kg.

    Would you be worried about the torque on the keel box? When I started sailing, I noted that the top of the keel box wobbled by about 10 mm. (+-5 mm) when running with the wind and waves pushing to one side and then the other. I reinforced the keel box on the left side using triangular wooden props which were epoxied, and the wobble is now imperceptible, probably less than 2 mm. However, adding about 60 kg. would increase the torque load on the top of the keel box by about 60-70 % (this I have calculated, estimating the changes in fulcrum). Would you feel OK with it? And the qustion is whether it is worth it to distribute the loads on the right side of the keel box with more props, but that would involve blocking the passage.


    As a rather crazy idea it ocurred to me to install two small keels (steel plates about 10 mm thick x 50 cm deep x 60 cm long with torpedo-like bulbs and a long base (a strip maybe 10 cm wide by 80 cm long). This would be much less efficient in terms of weight necessary (I estimate that 2 kg. of lead there would be equivalent roughly to 1 kg. of lead on the tip of the swing keel). And the boat can surely take 150 kg. without any problems. The plates can be bolted, the only issue would be to stregthenen significantly the points of attachments (hull thickness), but it seems to be relatively easy.

    I suspect that the sailing characteristics would be affected, but I am not sure by how much. The balance of the boat is probably not such a problem, as they can be put slightly aft of the main keel, preserving lateral point of attack, but the total resistence defintively would increase.

    Any opinions about this idea?
     
  9. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 494, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    The problem with this sort of thing isn't the weight, but the leverage. Your boat should have 363 kg (800 pounds) of ballast. Yeah this isn't much weight, but at the end of a lever, it's a bunch. If this weight is at the end of a 3' lever, like that on a swing keel or board, it exerts 1,089 kg (2,396 pounds) of leverage across the fulcrum (pivot pin, board/swing keel root, case sides, etc.). Yeah, a wee bit more then anticipated and also why getting specifics, without doing the math will be a difficult thing to get in a simple discussion.

    The case will move a bit, which is normal with 'glass boats. If it didn't move, things would break. Adding 60 kg (132 pounds) and assuming the same relative center and load points, using the dimensions above, you've added 180 kg (396 pounds) of additional leverage over the various bits and pieces in the assembly. Given you have a fair bit of movement (before reinforcing) in the case, I'd be damn worried about adding another 15% (or so) of additional torque to the case, pin, etc. If you do add this weight, use laminate to reinforce the case, not lumber. Yes, this means cutting or removing the liner, but you need the reinforcement on the case, not the liner. You can cut access, grind and reinforce the case, then glue the liner piece back in with little damage. Error on the side of way too much additional fabric if you do reinforce the case. The logic is to new laminate will also flex in use, but will be stiffer and strong enough to not break out under load.

    Additional appendages, ballasted or not isn't a good idea. You'll gain something, but mostly just drag. I do think you can "get away with" putting this amount of weight on the swing keel, but it will generally cause more strain on things. The safety margin on this boat will likely tolerate this additional load, but if you see some tabbing or reinforcements tearing out, don't be surprised (which is why I recommend additional fabric). This extra leverage on the rig, will be the first place you'll note things are being over loaded, especially with the first generation mast, which was known to break.
     
  10. Michail
    Joined: Aug 2011
    Posts: 61
    Likes: 1, Points: 0, Legacy Rep: 15
    Location: Chile

    Michail Junior Member

    Thank you PAR for the time to answer in such a detailed way.

    In fact, I had some tabbing torn out (in two instances) by the slamming with the standard keel, but I redid them with much thicker epoxy/cloth and it worked very well so far. Every time I get some problem I try to repair it making at leat twice as strong as it was before...

    I uploaded the photo of the modified keel box, the original Catalina design had only one plywood reinforcement (the left-most on the photo). I added two more plus a piece of wood which I covered with epoxy/cloth and it spreads also on bulkhead (right side of the photo)

    I think that I would proceed with "caution" and will limit the weight to about 35-40 kg for the keel tip.

    However, to get desired effect (I am trying to get an AVS of about 110) I need more ballast...

    Now, the next idea which came to my mind is to add balast inside the hull. The problem is obviously that Catalina 22 is relatively flat-bottomed, so that the weight can not be brought very deep (it is around 35 cm at the deepest from the waterline). Still, I estimated that 4 kg. in the bilge are equivalent to 1 kg. at the tip of the keel…
    The idea then would be to put about 100 kg. inside the bilge.

    I was thinking about simply placing steel bits and scrap inside the bilge area (one excellent area is in front of the keel box, it has a volume of about 8 liters, the other spot is between the reinforcements which appear in the photo), and then simply poor in poyester resin (not all at once, obviously, due to heat). I worry about one issue - since polyester sooner or later will separate, would it not produce hard spots which will break apart the hull and the liner (polyester is about 10 times cheaper in Chile than epoxy, so as filler it is out of question)? Also, I would never be able to get it out, for instance if a have to repair a leak. Also the flow of bilge water will be blocked...

    The other option would be simply to poor concrete (fine sand with cement with lots of steel, this filler being much denser than polyester (about 2.5 versus 1.0))?

    Is it worth it?

    I do not care how the boat will look like, but am a little bit worried whether this is a sound idea...
     

    Attached Files:

  11. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 494, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    The best you can hope for with concrete, even if the aggregate is replaced with iron punchings is about 150 pounds a cubic foot, which simply isn't much. Steel is much denser, but it'll rust in no time, so maybe epoxy encapsulation of each piece of steel, before it's installed. It'll still rust, but it'll take a lot longer.

    Your idea of adding 88 pounds to the end of the keel, will have better than 200 pounds of additional leverage, over the pivot and localized portions of the cases. Yeah, stuff will likely be tested to breaking strength, without significant reinforcement.

    I'm not sure how you're calculating your AVS, but a first gen Catalina 22 is in the 118 degree range. Simply put, even with your "down sized" ballasting ideas, you're still adding 25% more ballast, to the leverage on the structure.
     
  12. Michail
    Joined: Aug 2011
    Posts: 61
    Likes: 1, Points: 0, Legacy Rep: 15
    Location: Chile

    Michail Junior Member

    I never calculated the AVS, but I could find only anectodal data stating that the boat remained "neutral" with mast in water and if people cling to shrouds, it would not rise, and in two posts (from a different forum) a figure between 95 and 100 degrees was mentioned. So my assumption was that AVS would be around 100 degrees.
    Actually, if this is true (AVS 118), this seems like great news!

    I liked Catalina because it is rather narrow, especially the earlier version, but I always thought that the ballast ratio of 25 % (for the swing keel, which is only 250 kg, with empty boat weight of 1000 kg) was too little. The wing keel, by the way, has a weight of 360 kg / 1100 kg, which gives a ratio of 30%).
    But if the AVS is really 118 that is completely different story.

    By the way, I saw that the capsize value is close to 2,06 which is also quite excellent value.

    My problem is not so much that I can not control her in "bad" weather solo (25 + knots/4-5 meters is definitively not a problem, but certainly not on autopilot!), but I would like to have the option to go down at night to rest and not to worry that some freak wave will end the adventure (with AVS of 100 degrees one must be really crazy to let her steer on her own in such weather).

    ... So far I was able to do only coastal cruising (the most I did was a 300 n. miles run from Valparaiso to La Serena and beyond) sleeping in bays, but the sailing was in totally unprotected exposed waters.

    Now I have the crazy idea to go to Cape Horn. In January I sailed the fiords to Laguna San Rafael from Puerto Montt (310 nmile round trip/15 days) and I also was told it was crazy idea… but it was actually relatively easy. Cape Horn from Puerto Montt is about 1200 nm one way (I am thinking of a way to send the boat back then), and there are always windows of good weather (you have two days of 30+ 40+ .. ??+ knots, and then two days of 5 .. 10 … 15 knots). With good weather forecast and a lot of respect for the Ocean it is doable, there are only three open water passages…

    Also, I spent about 12.000 USD on equipping/repairing her (I know it sounds crazy for the US). Among safety features I have a smaller and raised hatch (50 x 50 cm.), obviously eliminated pop-top, and sealed off-all ventilation vents, and one lazarette hatch (the other one is always locked with a carabine hook when at sea), life lines near midship which do not allow you to fall overboard (the harness line is only 70 cm. so if you trip, you still remain on board), two reef points, storm jib (30%), system of lowering the jib without going to bow, replacement rudder (not just tiller), autopilot, chartplotter with ecosounder, second GPS, positive flotation, life raft, two electrical bilge pumps, outboard with charger, solar panel, large drains, reduced cockpit (with gas tanks filling in the volume), LED lighting (inside and navigational), good anchors (15 pounds with 10 m. chain/60 m. rode), and the list goes on…

    Sorry for the off-topic. But the idea was to show that the AVS issue is not an academic one in this case.

    Well, unfortunately today I already bought some 120 kg. lead. In the light of what you said, I would then reduce slightly more the keel tip weight to about maybe 30 kg. and
    install the rest of the lead inside the hull, as I said was thinking to poor in polyester resin to set it in place...
     

    Attached Files:

  13. tom28571
    Joined: Dec 2001
    Posts: 2,474
    Likes: 117, Points: 63, Legacy Rep: 1728
    Location: Oriental, NC

    tom28571 Senior Member

    Michail,

    You are going about this is a reasonable manner and your adventures should turn out fine if you take the precautions you have outlined. My main concern along with Paul, is the lateral stress on the hull from increases ballast. You talked about modifications to the trunk area as well a making the keel lock more substantial and both are needed. I suggested using the Catalina pivot mounting hardware since it is designed for more load than you would be subjecting your boat to.

    You have my admiration because I have never ventured into the conditions that you may be encountering along that coast. I might not have thought of a Catalina 22 as being a candidate boat for that task but we sail the boat we have and not the boat we might wish we had. I have several friends who have circumnavigated and two who did in singlehanded. One of them sailed a San Juan 30, which is not a boat many would have recommended for globe circling. He took the same path as you by beefing up those areas that might have the highest probability of failure. The boat did fine and is still sailing.
     

  14. Michail
    Joined: Aug 2011
    Posts: 61
    Likes: 1, Points: 0, Legacy Rep: 15
    Location: Chile

    Michail Junior Member

    Well, I started working on the right-hand side of the keel trunk today, it will look ugly, but I think it will be as strong as a tank after I am done...

    I started with the idea that I needed a trailerable sailboat. In the central area of Chile, most marinas are extremely expensive, you must become member of a club to get a place, and the entrance cost is between 8.000 and 30.000 USD, in addition to the monthly fee of about 200 USD. In that sense Catalina 22 is ideal because it does not involve any commitment to such investment.

    I have found two good places, namely Puerto Montt, where there is a marina for about 300 USD/month no strings (=entrance fee) attached, and also in Valparaiso there is another place, but the latter accepts boat up to about 3000 kg.

    I am actually considering buying something (in the range 32-36 feet) in Central America and bringing it here, but probably not this year.

    The point I am trying to make is that Catalina 22 was selected not because of its superb ocean-going qualities, but because the trailerability and launching from slip was the first priority. Also the bare boat can be bought for about 8.000 USD, which is "cheap" here.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.