I've looked but haven't seen anything like this discussed...This will be the third time I will be putting my P18 back together from total disassembly, and I have a problem: The boat just doesn't seem to go back together "square". I don't think it ever was, as I noticed a real problem pointing on one tack versus the other almost from the first sail. The owners manual has you keeping the hulls in the cradles they were shipped in for assembly. Anybody got a set of those sitting around? This time I plan to put it together indoors on a large cement slab, so at least I can use a tape measure to ensure the hulls are at the same height front to back, but how do I make sure they are both canted the correct amount? Also, after each previous assembly, the corners of the cross-beams didn't measure the same (like from one catty-corner of the tramp to the other) so I guess one hull was farther forward than the other.
I think this is mainly a problem for those of us with "banana boat" hulls. I think the NACRAs sit flat on the ground generally, although I don't know that for sure.
Any ideas or thoughts would be welcome.
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Posted: Dec 19, 2012 - 09:49 PM
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Posted: Dec 20, 2012 - 09:45 AM
I would frame up an alignment rack that held everything plumb, level and square. you could then adjust the attachment points on the hulls and crossbars. I grant you, this is no easy task. You will need the factory specs on the boat. The framing will have to be right on. The slab is a good start. I would frame up a cross braced rectangle out of at least 2x6. Make it of a size a little larger than the foot print of the boat. Get it dead on square. Anchor it to the slab. Make sure it's level and plumb. Add some hull carpeted hull cradles with a stop across the transoms so they are in the same plane. Get the factory specs on how the hulls cant in relation to level ground and adjust the cradles to that along with the specified beam. Spec out where the cross bars go and set cradles on the frame for those. Adjust the attachment points on the boat only. Don't compromise the jig.
Like I said, no easy task. This would take me many trips to the building supply, any number of retries, a lot of beer,and the invention of new middle names for the savior. If all else failed the wood would make a great bonfire.
Good luck, let us know how it goes. GH
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'82 Super Cat 15
Hull #315
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Posted: Dec 20, 2012 - 04:04 PM
Wow this all sounds way more complex than it needs to be. I have dissembled 3 P16s and put various parts of 2 of them back together into a single boat but I have never taken apart my P18. I did this in the back yard. I did need help from one of boys in holding hulls while I got bolts started and threaded some. I used silicone around the ones that went through the hull on the front beam but once I hot it all started it was a matter of tightening it all up. I did use my oldest's long arms and fingers to reach in the port and get a wrench on the nut inside the hull. (I didn't tell him about the wasps nest I had just cleaned out of it.
)
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Dustin Finlinson • Magna, UT
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Posted: Dec 20, 2012 - 04:38 PM
are the hulls original or has one been replaced? has the boat been crashed that you can tell? there are only 8 bolts holding the boat together and there are no adjustmens...strange indeed...
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bill harris
hattiesburg, mississippi
prindle 16- "BLUE RIBBON"
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Posted: Dec 20, 2012 - 09:08 PM
Yes, complex indeed. I think the points about the possible mismatch or damage are valid. It sounds like just bolting her up hasn't worked out so far. I can't imagine any Prindle shipping cradles still laying around, so something like them would need to be fabricated. If anyone has dimensions or specs they could post I bet PB27 would appreciate it. Let us know how it goes. GH
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'82 Super Cat 15
Hull #315
Virginia
Previously owned: '70 H14, '79 H16, '68 Sailmaster 26, '85 H14T
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Posted: Dec 20, 2012 - 09:23 PM
mayby get all the bolts finger tight first then measure corner to corner and start tightening them up like a tire, a little at a time, alternating corners. my p16 had a newer starboard hull by a few years and the lip profile was a little different...thicker on the newer hull. i'm replacing all the bolts on mine this year when i paint...think i'll measure just out of curiosity.
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bill harris
hattiesburg, mississippi
prindle 16- "BLUE RIBBON"
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Posted: Dec 21, 2012 - 06:51 AM
All great thoughts guys...thanks for the help!
I'm pretty sure both hulls are original. In fact I may have been the first person to separate the hulls since first assembly. I would say half of the bolts were bent and half were loose, allowing sand to get between the CBs and the hulls, where it looked like it sanded a few spots on the joint area. This lead to my first bad idea, which I did for both assemblys: I applied silicone all over the joint areas prior to assembly, and both times the stuff "set" before I was happy with the alignment. The other part of my problem may stem from the fact that I put the boat together each time on the trailer. One of the trailer crossbeams was bent, and although I replaced it before the second assembly, I don't think it's exactly square even now.
Soooo here's my new plan:
1.No silicone! (I may add some after, like caulk)
2.On the flat slab as discussed
3.Slow and steady tightening of the bolts (ala Coastrat) with constant tape-measure checks.
4.At some point along the hulls, I will make sure via a large home-made protractor that the "cant" is the same on both sides
I hope to have my repairs done and finish assembly by Jan. 1
Thanks again for all the ideas...like Quarath says it should be simple right!
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Repairable P18
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Posted: Dec 21, 2012 - 08:20 AM
Be sure to liberally apply Tef-Gel to all the bolts and anywhere 2 metals are bolted
the stuff is amazing, and very long lasting... -
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Posted: Dec 21, 2012 - 09:46 AM
Nuthin' wrong with that. It's a father's perogative.
Manny was sailing with his girl friend off the coast and they were watching a few gulls land in the water around them. He happened to look behind them and saw a gull eaten whole by a shark not 30 feet from their transom.
He neglected to mention this to his girlfriend (who I think was trapped out) until they were off the water.
Sometimes silence is golden.
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Posted: Dec 21, 2012 - 03:56 PM
Yes but did he calmly mention she might want to come in off the wire or just her hang out as bait. I personally probably would have crapped myself then called it a day.
Edited by Quarath on Dec 21, 2012 - 03:58 PM.
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Dustin Finlinson • Magna, UT
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Posted: Dec 21, 2012 - 04:16 PM
I would go with all new bolts. You might have to shim the connection points if they've worn.
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'82 Super Cat 15
Hull #315
Virginia
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Posted: Dec 22, 2012 - 02:14 PM
I think they were both trapped out and were headed straight to the harbor anyway, so he figured they would get there fastest if they stayed out.
Edited by klozhald on Dec 22, 2012 - 01:15 PM.
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Posted: Dec 26, 2012 - 07:25 AM
I looked this stuff up and found nothing but good, although I've never used anything like it I think it's a good idea to pick some up. I'm gonna try Academy, but if they don't have it I guess West Marine?
Sharks don't bother me...they don't like the old tough meat you know
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Posted: Dec 26, 2012 - 08:46 AM
http://www.jamestowndistributors.com/userportal/show_product.do?pid=546&engine=adwords!6456&keyword=tef_gel
or call mike at Ellies sailing in clearwater, perhaps he can ship it to you -
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Posted: Mar 23, 2013 - 08:12 AM
Here's an update on the assembly/alignment problems: I was right! During our first assembly attempt this weekend, we tightened the bolts slowly and when everything was good and snug we went around with a tape measure from the slab to deck lip front and back, and one bow was 3/4" higher than the other! At the sterns, the other side was 3/4" up from the high bow hull. (the cant of each hull seemed identical though)
So one wife sat on the high hull, one wife sat on the high stern, and we tightened the bolts slowly again....and got the exact same measurements as before! So we loosened the bolts again, adjusted the hulls again so the high bow was down and the high stern was down, and began tightening while measuring as we went. The more we snugged the bolts down, the more it reverted to the first measurement. When the bolts were again at final torque, the hulls were off the &%*%$ same amount again! We also had about 1 inch total difference bolt to bolt diagonally, but I'm not sure how accurately they are drilled from the factory. We tried measuring the hull plug holes to each other, and they were so far off that they were surely put in with a hole-saw by hand. Does anyone know if the bolt holes were hand drilled during first assembly?
What to do? Being machinists, our first thought was "shim it", but the next thought was "where?" I think the front beam should be considered off limits since it has the weight of the mast and all the rigging on it, but whose to say that putting a shim under the rear beam wouldn't simply result in an angled crossbeam? In the end, we ended up shimming the front/underside of the high stern side beam with a 3/16 thick piece of hard rubber. That got the bows to about 1/2" off with the sterns off just 1/4" or so. This represents less than 0.3% of the total boat length, but it still seems like a lot.
So how far off do you guys think is "too much"? Anybody have any idea of what tolerance the factory allows? I'm planning on leaving it like this and sailing it to see how things go, but if it still seems to track differently on opposite tacks, I guess I'll plan on building some kind of cradles, and then re-glass the mounting points with some kind of release agent on the beams.
Any and all thoughts are welcome and appreciated
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Posted: Mar 23, 2013 - 10:06 AM
Pirateboy, I'm no expert on how exacting hull alignment really needs to be, but it seems like 3/4 of an inch over 18' of hull isn't that big of a deal on an older boat. A solid mount between your cross bars and the hulls should be of greater importance than an absolutely identical entry to the water. It is a multihull after all, designed to sail with one hull bearing the majority of the dynamic force under sail based on your point of sail. If it really bothers you aesthetically (Which i totally understand being a bit OCD myself,) have you checked to make sure that your cross bars are both perfectly straight? A small amount of bend in the fore or aft cross bar could be causing the variance you're seeing. Also, try rigging the boat to see if the standing rigging could help with leveling things out.
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Jeremy Hales
1974 SOLCAT 18
Salem, OR
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Posted: Mar 23, 2013 - 10:16 AM
Congratulations?
Here's my thought. Assemble the boat, sail it, and forget you ever measured the hull alignment. Put it out of your mind, never think of it again. Enjoy the boat.
If you are sailing, and you get the feeling the boat does better on one tack, don't attribute that to miss-aligned hulls. Ask someone close by to slap you the next time you mention your (30 year old?) fiberglass catamaran not being perfect.
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Damon Linkous
1992 Hobie 18
Memphis, TN
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Posted: Mar 23, 2013 - 11:59 AM
Throw out the measuring tape when it comes to the hulls you are way over thinking it. You are only out one half of one percent. One inch vs 216 inches.
If the boat sails different on different tacks it is likely in the rig or the rudders. I bet most boats are out more than that. JMHO, Ricardo.
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Lake Perry KS
H-18
N-5.5 UNI +spin
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Posted: Mar 23, 2013 - 03:20 PM
Pirateboy, you're looking in the wrong area. As Ricardo stated, the issues are in the rigging and foils. I had a similar problem that after months of the best experts trying to fix it, it was resolved by buying a new mast extrusion. A 30 year old aluminum will fatigue. In my case the mast was more bendy on one tack than the other and it was soft. Still, I don't think that is your problem. You should look at the standing rigging and foils, that is most likely where your issues are.
The beams should not have any spacers in them, especially hard rubber. You want a stiff platform and this will cause it to rack and flex (not good). If you want to learn more about bedding the beams you can search it, although I don't think it is that important for you on that platform.
Focus on the rigging and foils. Stays should be identical in length.
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Philip
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Posted: Mar 23, 2013 - 05:49 PM
My Nacra 5.7 was two different boats on different tacks. After trying everything you have, I looked closely at the beams. Turned out the front beam had a "ripple", right where the beam met the inside of the hull. A spare beam fixed that.
The Nacra 5.0 also handled differently, but it was square. We were tightening the diamond wires by feel. Once a Loos gauge was used, it quickly showed that tension was not the same on both sides. The diamonds are one of the most important rigging tunes. Evening them out made the boat handle nearly symmetrical. The rest was in the rudders.
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