I need to get at the inside of my boom at the mast end. It appears to be attached to an aluminum casting by 4 'pop' rivets. Is there an easy way to remove the rivets other than drilling and punching? Is there any reason not to replace these rivets with machine screws if the casting is thick enough?
Thanks for your help.
I hope you are well...
While stainless-to-aluminum contact is unavoidable on our masts and booms, galvanic corrosion will result from it when salt water is present. In attaching aluminum to aluminum, aluminum rivets might actually outlast stainless screws, or rather the aluminum in contact with the stainless will corrode, while that in contact with aluminum rivets will not.
Despite some research, I have never been able to get a straight answer on if coarse-threads (such as a sheet-metal screw) or finer-threads (such as a machine screw) has longer life-expectancy, or a comparison of either screw to aluminum rivets, under these conditions. If anyone has direct knowledge of this comparison, I'd be glad to hear of it.
This corrosion can be reduced somewhat by removing salt water (rinse regularly with fresh), but I recommend applying Lano-coat paste to the threads and contact areas of the screws or bolts. This helps exclude water and lubricates the threads, but more importantly provides a partial insulating layer, reducing (but not eliminating) the areas where dissimilar metals are in electrical contact and thus corrosion-prone.
Cheap, and it can't hurt...
Note that the alloy of aluminum used for the endcap was probably picked for strength and casting properties, and is likely not an especially "machinable" alloy, and tapping the holes for screws might not be easy. I suggest using cutting oil intended for machining aluminum, and take small bites...a broken-off tap is a real pain to deal with.
I have disassembled my boom (closer to 7 rivets, mine is a '73). It was fairly straight forward to drill the rivets out. You might not be able to "punch out" all of the rivets as a couple of mine ended up in support flanges. I drilled close to the shank size. Try an 1/8" drill bit carefully! I plan to use screws when reassembling and up sizing screws to approx. 3/16 or slightly larger depending on what the hole needs for a tap size.
The casting on mine is approximately 1/4" wall thickness with support ribs to a center round support. The end tapers from approximately 1/2" thickness in the middle to 1/4" on the edges. It has a flat section to clear the track in the boom making the walls a D shape. There was some surface corrosion, but it all cleaned up.
Hope this helps.
3I6 SV Serenity
I suggest that the rivets be drilled out and replaced with 5/16 hex bolts (or similar). The end fittings on my '74 I36 are original LeFiell and had plenty of meat.
Based on my experience in the SHTP (Single Handed TransPac) (and from what I read about Cassiopeia in the Pac Cup last year) the gooseneck is a part of the I36 that will benefit from close attention. Among the changes I made before the race was a replacement of the rivets with ¼-20 screws - but the end fitting worked loose during the race so I first drilled thru and bolted with 3/8 all-thread, and then replaced the ¼ screws with 5/16 bolts. After the race I had the bronze toggle reworked to add metal and increase the pin size from 3/8 to 7/16 diameter. Also, the holes in the bronze toggle were elongating, thus the strap to the mast in the bandaged image (during the race). When the bronze piece was reworked, this was also corrected. The new gooseneck and boom fitting are tight.
Below are images of Frolic at the start of the SHTP and the gooseneck before and after a retrofit improvement. (Click for larger image.)
Great follow-up comments! Some feedback for consideration:
The load on the boom end can be both compression and extension, guaranteed. I watched mine push and pull when the main was back winded as Frolic surfed down waves, or in light air with a prevented main and big swell. The ¼-20's worked their threads and loosened. So far the 5/16-16's with the 3/8 thru-bolt have stopped the end fitting from moving. I was tempted to use 5200 to fix the end piece in place, but I thought I might need to be able to disassemble it again someday, so I didn't…
When using SS on Al, corrosion is a real problem. More than fifteen years ago I tried aircraft quality Al bolts on mast fittings but I was disappointed: the heads corroded away pretty quickly. So back to 316 SS. TefGel is reputed to be very good at slowing corrosion but it'$$. I've had good success with the much less expensive Lanocote greatly slowing the corrosion - I've easily removed mast fittings after years of exposure - but I had the opposite problem when I first replaced the boom end rivets with machine screws. That is, the screws worked loose while sailing! On the advice of Marty Spargur, I solved the backing-out problem using Rule Sealant (now called Sudbury Sealant, clear or black) on top of the fastener heads - you can see it in the goop in the pictures I sent yesterday. The sealant keeps the fastener in place and is easily removed when it's time for disassembly. And if you use clear sealant you can see what's going on. (For what it's worth, I tried silicone but it kept coming off. Perhaps if I'd prepped better…)
M. Daley's advice to tap slowly is spot on, I learned that the hard way. Cutting oil is best, but in a pinch, I've used Kroil as the lubricant without a problem. And it pays to use a new, high-quality tap, not the cheapies from the big boxes.
Steve Hodges [firstname.lastname@example.org]
I have a different type of boom on Willow. But, what I'm picturing for your type is that this fitting should most be experiencing mostly a compression load which is borne by the end casting itself. The rivets merely hold the boom/casting in place and are maybe subject to very minor shear loads (from boom twisting). If this is the case, I'd stick with aluminum rivets. Besides, that's what was working for how many years?
Regardless of salt water presence, galvanic corrosion WILL occur between stainless and aluminum. If you must use SS screws, I highly recommend Tef-Gel. I'm not an expert but, I would think that coarse thread, having less contact area, and more "meat", would be preferable.
Roy, et. al:
Another thought on the boom issue. I had rivets let go on a reefing cheek block on Sandpiper in 30 knot winds on SF Bay. It tore the main but luckily the line got caught on another fitting on the boom and it was not catastrophic. I then used small bolts to re-attach all my boom fittings. I learned a trick from the makers of Hidden-hitch. They use it for using existing holes in auto frames and by using wing bolts they bind up inside the frame for final tightening. Given the diameters of bolts you might use on the boom, my alternative method here might work for you.
Use a small extension spring that will match (or is slightly smaller than) the diameter and threads of the size bolt. Feed it from the fitting hole on the end of a small wire out the end of the boom. Thread the spring on the bolt. Use a longer bolt to allow you to hold the bolt on the outside of the hole and a slightly larger hole will make feeding a tad easier. You can also put a washer on it if you want extra bearing surface inside the boom. Pull it from the end of the boom through the fitting hole. I used a nylox nut and held the bolt with needle nosed pliers and then vice-grips to tighten it from the outside. I then cut the excess bolt(s) off flush with the top of the nylox and never again worried about a fitting carrying away or tearing out. Using lanolin on the bolts, washers, nut, etc. is still a good idea when using bolts.
Good luck with the repair.
John T. Sutton
I'm a new I36 Association member, located in Long Beach. I used your Association for assistance/experience prior to buying Svanen (ex-BACKDRAFT), our new 1982 I-36. Your membership was wonderful in giving me pointers and addressing some of my concerns re: reliability of Pathfinder engines. Plus, your maintenance pages were a comfort in preparing me for what I might expect, as well as what to look for in the survey. Well, I need the association's assistance again.
The gooseneck fitting on my Kenyon boom has broken where the horizontal bolt goes across. Rather than having a complete hole on the tang where the bolt goes through from the starboard to the port side, I now have a half-circle, C. I believe I need to replace the entire boom-end fitting.
Do any of the membership know of a used one or a process I might use to get a replacement without getting a new boom? I believe Kenyon no longer makes spars?
Any assistance would be greatly appreciated.
Ken Kropf - email: email@example.com work: (310) 771-6432
Date: 07/26/99 11:32:49 PM GMT
Sail magazine publishes an equipment guide that covers almost anything and gives manufacturers names and phone numbers. When my boom was stolen in Florida in a boat yard, I ended up getting a replacement from Metalmast in Putnam CT. Unless you find a used part, a good spar company should be able to help.
From: "Kropf, Ken" <firstname.lastname@example.org>
Date: 07/28/99 05:23:58 PM GMT
Subject: RE: Gooseneck
Dear Skipper Wall,
Appreciate your prompt reply. I have been able to locate:
63 Centerville Road
Warwick, RI 02886 USA
They bought out the old Kenyon stock and have other discontinued spar stock. Their web site is extensive and lists the Kenyon 3550 Boom section and replacement gooseneck and outhaul cast aluminum parts as well as all sheaves, tangs, pins, etc.
I spoke with them on Monday, however, they have not answered the phone yesterday or today. I'm assuming that they have the stock to backup their web site info. Don't know pricing.
On another issue (this note for Harry Farrell and other Pathfinder owners), I have discovered in response to my earlier request about Pathfinder diesels (installed in Islanders late 79 - 83) that
PO BOX 1284
Champlain. NY 12919-1284
Phone (514) 695-6676
FAX (514) 695-1080
has a very active support organization and parts/technical service program. In fact, they have a Pathfinder Service Club (application $95) one of which benefits is a complete service manual tailored to your specific engine serial number and transmission. Another benefit is an engine exchange program (old 1.5 liter engine traded in for newly rebuilt 1.6 liter) for $6000, including shipping.
Inge and John are the owners/stewards, and they are very fussy how their engines are being maintained in the field. They say they have about 1500 Pathfinders registered in their Service Club. Their mail drop is US, however, they are located in Canada - no tax, 10% parts discount to members.
Let's hope that this RIG-RITE lead works out for me. Otherwise, I may be looking for a new boom.