Boom Reinforcing Sleeve installation

Discussion in 'Laser Talk' started by bjmoose, May 21, 2007.

  1. bjmoose

    bjmoose Member

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    So I'm installing a reinforcing sleeve into a boom, and I've got a couple new questions.

    Based on previous threads, I already learned to check the rules in Rule 18 for a diagram, and rule 18a, which tells me that the reinforcing sleeve is placed so that the outboard end of the reinforcing sleeve is at most 48" from the inboard end of the boom. This surprised me because it meant that the reinforcing sleeve is NOT placed right at the (inboard) end of the boom, but reinforces the area between the vang attachment point and mainsheet attachment point, while extending a bit beyond both of those.

    SO, here are my questions.

    1. Did I get that right about the position?

    2. The reinforcing sleeve is somewhat smaller in diameter than I'd expect; it's not a snug fit by any stretch. Any suggestions on how to place it within the boom? My thought is to try and have it resting against the bottom of the boom, so that the rivets that attach the mainsheet block go through boom and reinforcing sleeve with a minimum of space, and then once it's fixed in position by those rivets, drill and rivet the vang attachment strap into place.

    3. I'm pretty handy with rivets, but while I've got all the hardware off the boom, are there any fittings that folks would recommend I go immediately to a "through bolting" technique on rather than riveting? Through bolting anything that isn't right at the end of the boom, where you've got good access in order to place internal nuts, looks like quite a pain.
     
  2. brockman

    brockman New Member

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    Great questions. I am curious about the answer to this as well.
     
  3. bjmoose

    bjmoose Member

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    OK, I reversed my lower section and turned an old broken upper section into a new boom this weekend. Here are the lessons I learned.

    1. You want to have joined the class already, so that you have the class rule book and diagrams open in front of you while you work.

    2. A metric tape measure would be helpful, or be very comfortable switching back and forth between mm and inches. Double check everything before cutting or drilling.

    3. When cutting a mast uppper section down to a boom, a hacksaw works, but you'll want to use a miter box to get a nice square cut. Even WITH a miter box, one of my cuts wasn't as square as I would have liked.

    4. The rule book measurements are made with the mast/boom end caps ON. But you're measuring with them OFF, from the raw end of the tube. Measure the thickness of the end caps themselves and take this into account. (Hint: the mast base is thicker than the other end caps.)

    5. You're going to want to have new end caps in your hands before you start the job. I was able to save one end cap, but mostly removing them was a destructive operation.

    6. West marine does have some stainless rivets in their general hardware section. That's good because the "general purpose" rivets you can order from APS/vanguard aren't always the right ones for the job. I found they were too short to keep the outhaul clam-cleat.

    7. You can't just buy the rivet tool you need at the local hardware store, and local rental shops do NOT rent pneumatic rivet pullers. If I were to do it again, I'd order the following rivet puller well ahead of time:

    http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=41291

    (Harbor Freight has great prices, but they don't specialize in "fast" shipping.)

    This riveter is probably going to be good for one set of spars, more or less, as it is a cheap knock off of a commercial grade tool costing closer to $200 bucks. I bought a different riveter from Harbor Freight once and it gave out after I pulled a bunch of 316 grade stainless 3/16" rivets on my J/24. Which brings me to my next point.

    8. The 18-8 grade stainless rivets supplied by vanguard are not very strong. It's not a wonder they work loose over time. I used them for most of the jobs, but I reattached the vang attachment point on the lower mast using 316 grade stainless 3/16" rivets. 316 grade stainless rivets are MUCH stronger (and are even harder to pull!)

    If I did it again, I'd probably use the 316 grade rivets for

    Vang attachment point on mast
    Vang attachment point on boom
    center mainsheet attachment point on boom.

    You can buy 316 grade stainless rivets from McMaster-Carr http://www.mcmaster.com/

    9. For the boom reinforcing sleeve: As mentioned above, the rules call for it to be placed so that it NOT at the end of the boom. I built a little wooden jig out of a piece of 1x2 lumber with two nails in it to hold it in the correct position lengthwise, and I clamped that to the end of the boom with a C clamp. Then I made a little hook out of coathanger that went through one of the two mainsheet block holes, and I had an assistant hold the sleeve tightly as close as possible to the bottom of the boom while I placed the first rivet.

    Once those rivets were in place, I just went ahead and riveted the vang attachment point; so it ended up a little off of center to one side, and I'm pretty sure I don't care.

    10. Just go ahead and figure on "through bolting" the end mainsheet attachment point. You need two 10-24x 1/2" stainless with fender washers and aircraft (nylon locking insert) nuts. You need needle-nose pliers and a tiny 4" crescent wrench. I found it easiest to have the boom right side up, tape the screws into position, then put the washer and nut on from the inside with my fingers, then remove the tape and tighten the screws. Do one that's further in first ;-)

    11. When reattaching the outhaul attachment point you either need to drill smaller holes than you did for everything else, and use self tapping screws, or you need to use longer rivets than the "general hardware" rivets. ONE longer aluminum rivet comes with the new end cap; but you'll need an additional 3/16" x 1/2" rivet for the inside.

    12. Having a drill press and an asssistant to hold the end of the boom is very helpful in getting the holes placed correctly. For the gooseneck fitting on the mast, which has six holes, If I were doing it again I'd only measure, mark, and drill only the center TWO holes initially, rivet those in place, then drill through the remaining holes using the the fitting itself as a jig to ensure perfect alignment. As it was, I had to redrill a couple holes on that fitting once I started riveting it because a couple of my holes were off by a sixteenth of an inch or so, and the rivet wouldn't fit.

    Big job. I didn't keep close careful tabs on the time, but building the boom took somewhere between 8 and 12 hours. The mast lower section has a lot fewere fittings; so it was less than 4 hours. Haven't reversed the upper section yet. ;-)

    Search keywords: laser reverse spar replacement rivet puller riveter boom reinforcing sleeve
     
  4. Georg W.F.

    Georg W.F. Member

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    Through bolting is stronger, easier, and cheaper (since you do not need the tools).

    G
     
  5. bjmoose

    bjmoose Member

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    Cool. I can understand that for the mainsheet attachment at the end of the boom; the access is easy. But how exactly do you through-bolt, for instance, the outhaul cleat? Getting a nut (or turning/holding a screw) halfway down the inside of a nine+ foot long boom is a mystery to me.
     
  6. Ross B

    Ross B Guest

    drill it through to the other side
     
  7. bjmoose

    bjmoose Member

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    Drill it through to the other side.

    In that case, I'm not sure i'd agree with "stronger" since there are now twice as many holes in the spar itself. Especially for something like the gooseneck attachment point, where there are already 6 holes in the lower mast at the attachment point.

    Riveting, once you've got ahold of the right size riveter, isn't very difficult. The one I posted a link to is only 10 bucks (plus shipping) And 316 stainless rivets are hella strong.

    I suppose it's the nature of the beast, but it's funny that there's WAY more activity on this thread NOW that i've FINISHED the work and wrote about what I did, than when I was asking questions BEFORE I started the work.;)
     
  8. Garry

    Garry New Member

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    While 316 SS is recognised as marine grade it is a long way from aluminium on the galvanic scale which means a higher potential for galvanic corrosion, I believe this is why Vangard uses the grade that they do as is is as close as you can get with SS.

    If you are going to use 316 make sure you use an isolation /sealing compound such as 5200
     
  9. bjmoose

    bjmoose Member

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    That kind of isolation is a good idea both kinds of SS rivets and I should have mentioned that in the original post.

    In the past I've used something called "tef gel" or "tek gel" for this purpose. Ordinary silicon sealant is also a good choice.
     
  10. astevenson

    astevenson New Member

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    I recently upgraded most of the boom fittings and through-bolted the mainsheet, boomvang and outhaul fixtures.

    I through-bolted, instead of riveting, by tying a small thread around the bolt and then pushing it into boom. It took a bit of time, but eventually I was able to get it out the hole I needed. It helped to do it at an angle so the bolt slid down the interior of the boom and having a second person was helpful. For the record I was dubious that this technique was possible, but it was easier than I thought it would be.

    After the bolt was through, I secured the fitting and silicon nut to the outside. The last step was to cut off the portion of the bolt I didn't need and file away any sharp edges.

    I riveted parts that weren't under much load - the end caps, mainsheet bridal thing and outhaul cleat (which isn't used on the new outhaul system). I found that standard rivet guns (west marine, lowes and home depot) couldn't pull a stainless rivet - I bought three and returned three broken ones! I ended up with a craftsman professional from sears (~$30), which worked great. BTW, you NEED stainless.

    Hope that helps someone.

    A.
     
  11. 49208

    49208 Tentmaker

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    Not needed and will just weaken the boom.


    Use the thread method mentioned above to thru bolt the fittings that place the fasteners under a tension load

    (the cleat on the boom does not put the fasteners under tension, so rivets, even alum are fine for that)
     
  12. Ross B

    Ross B Guest

    My old boom was through bolted on everything through to the other side by a North American Champion, Kim Zetterberg, and survived several time up to 40 knots, it is more than strong enough
     
  13. Georg W.F.

    Georg W.F. Member

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    I second that!
    The method described above is exactly how I did it. It is not difficult at all. It will take a bit of time, but once you get going, it is very very easy.

    G
     
  14. bjmoose

    bjmoose Member

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    How do you keep the bolt from turning while you tighten the nut, since you can't apply a screwdriver or wrench from the inside?

    Extra long screw, held with vice-grips from the outside, then cut off once the nut is tight?
     
  15. 49208

    49208 Tentmaker

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    Exactly. Bolt length of 1" works just fine.
     
  16. 49208

    49208 Tentmaker

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    Read the following:
    http://www.laserforum.org/showpost.php?p=14301&postcount=3

    Ask any spar builder, drilling needless holes is never recommended.

    Also, when you thru bolt completely thru the tube as you suggest, you run the risk of collapsing the tube by overtensioning the bolt.
     
  17. Ross B

    Ross B Guest

    I've read it before, and I am telling you there's noting wrong with it, granted its a 15 year old boom, so the metal may be a bit stronger, dunno, but I would do it again


    don't go bashin till you've tried it yourself, it makes you sound like your uninterested in new/old ideas
     
  18. Georg W.F.

    Georg W.F. Member

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    Ross,

    It seems that we are not the ones uninterested in new ideas, but rather that you are not interested in a better way of throughbolting.

    Georg
     
  19. stick

    stick Member

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    ross, you didn't do any of the work. you bought it that way. if that's what you use, great. when you get your next boom, how would you do it? you don't seem to do alot of repair work on your boats, based on your posts.
     
  20. Ross B

    Ross B Guest

    I do my spars my self, but I take my boat to a guy, I want it to be done flawlessly, but I do fix my surfboard myself, I do ok with with fiberglass

    And I would through bolt my boom, but rivets work well enough, just gotta try not and screw em up when you take em out

    I know my way around tools and boat work, don't worry
     

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