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PostPosted: Sun Feb 19, 2012 8:38 pm 
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Let's see if I can explain this correctly.

I just reassembled my boat after some major hull work(H18 1986). The dolphin striker that I used for this boat was excessively loose and so I am attempting on adjusting it correctly.

This is how it went.

After initially adjusting while the mast was not on the boat, I got all the measurements to measure 80 5/8ths. This was with the mast off,

This measurement was taken in three locations.
1) Right under the plugs, center line to center line
2) Right under the bow lips, center line to center line,
3) Bottom of the hulls 20" below the bow lip.

I put the mast up and all my measurements were still the same.

Then......I tentioned everything my rig as I normally would and raised the sails. At this point the front measurements decreased by 5/8ths and now measured only 80" at the bow while the back of the boat was still 80 5/8ths. :shock:

What am I missing here?

Obviously as soon as I tightened the rig up the bows pulled together through the bridle wires. Is this acceptable? It doesn't seem right that bows and sterns are off 5/8 when we try to manage the rudders to 1/8 toe in.

Where do I go from here? I can't make sense of tightening or loosening the the striker at this point. I don't think my rig is to tight but....????

If I was just sailing for fun this year I would just leave it but I am planning on racing this boat this year.

Thanks for your thoughts guys.

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H18 '89 "Knotty Passion"
H20 '96 "20/20 Vision"
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PostPosted: Sun Feb 19, 2012 9:06 pm 
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I read with interest this post from back in 2005 as follows;

I have an 81 and an 82 18 and here is what I was shown to do with dolphin striker tension.

An individual that raced Hobie 18 Worlds told me to just set up everything snug and then raise the mast. This allows the weight of the mast to force the front crossbar down. As a result, the hulls will then be canted outward which is undesirable. You will want to make sure that you have the hulls sitting on something flat and soft. I initially did this with the boat sitting in my driveway on some long strips of carpet under each hull. After raising the mast, we then measured from the top of the bows just under the lip from hull to hull. We then measured the distance between the hull bows approx. 12 to 18 inches lower. After collecting these measurements, we then measured from the center of the rear of the hulls just under the drain plugs at the rear.

Once you have these three measurements you can then determine the amount of cant in the hulls. The three measurements should be the same. As the mast pushes down on the front crossbar this will cause the hulls to cant outward. This will result in a larger distance on the lower front measurement than the top. As you tighten the striker, this will induce more upward bow in the front crossbar and result in less cant. Initially, I had to back the tightness of my striker off. Ironically, this is not going to be a huge adjustment. Once we had mine set, we dropped the mast and the striker actually became loose to the touch .

If you really want to get hardcore then try this also. Once you have everything set, take the boat out to the water and ensure that everything is seated correctly (crossbar bolts, crossbars, etc.). Bring the boat back up to shore and check everything again. If all the numbers are equal, then condsider yourself finished with the hulls. Now on to the rudders, but that is for a different post.

Hope all of this helps, and hopefully someone might add to this or even have a better way. In all reality, if you just want to sail, then all you really need to do is snug the striker down until all the play is gone. Then go play.

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PostPosted: Mon Feb 20, 2012 4:38 am 
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You're putting way too much thought into this. A sure way to psych yourself out before you even hit the race course is to measure and weigh your boat.

Within 5/8" true from stem to stern, I'd say you're as close as you're gonna get. These boats flex, bend, and wiggle around and you're going to drive yourself crazy tring to get everything dead nuts on. The only measurements that you want to make sure are good are the rudder toe in measurements. Otherwise, just make sure everything is good and tight and go out and sail it.

One blown start and your perfect hull alignment won't mean squat anyway.

sm


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PostPosted: Mon Feb 20, 2012 5:35 am 
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srm wrote:
You're putting way too much thought into this. A sure way to psych yourself out before you even hit the race course is to measure and weigh your boat.

Within 5/8" true from stem to stern, I'd say you're as close as you're gonna get. These boats flex, bend, and wiggle around and you're going to drive yourself crazy tring to get everything dead nuts on. The only measurements that you want to make sure are good are the rudder toe in measurements. Otherwise, just make sure everything is good and tight and go out and sail it.

One blown start and your perfect hull alignment won't mean squat anyway.

sm


All of that - and measuring the boat when it's static is kind of useless, since it will load up in a completely different manner on the water.

Think about this, too - optimum trim upwind is to have one hull just clear of the water - so aligning the hulls makes no significant difference. Going downwind, the forestay is unloaded, so the bows will spring back.

I guarantee that nobody that's won an 18 North American Championship has ever worried about hull alignment to this degree. They go out and sail.


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PostPosted: Mon Feb 20, 2012 8:02 am 
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By the way, if the tip of the bows are toed in 5/8" relative to the stern, that means your hulls are toed in a whopping 0.166°.

I would also not recommend ever sailing with the dolphin striker loose at all. It should be "snug" to "tight". Oherwise you will eventually crack the front crossbar at the mast step.

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PostPosted: Mon Feb 20, 2012 8:36 am 
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Thank guys for the comments. Everything stated makes perfectly good sense and I have seen you all make similar comments on many other posts. With that said, this is the first time I have assembled/reassembled an 18. Just looking for some assembly tips to do it right the first time.

I figured there would be guideline somewhere. I did read that older post out from 2005 but I couldn't get the same results. sounds like what I have now is good enough.

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H18 '85
H18 '89 "Knotty Passion"
H20 '96 "20/20 Vision"
Fleet 259 Central Coast California


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PostPosted: Mon Feb 20, 2012 9:08 am 
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Quote:
With that said, this is the first time I have assembled/reassembled an 18. Just looking for some assembly tips to do it right the first time.


Really not much to it. Make sure the dolphin stiker is good and tight. Re-install the crossbars, starting with the inside bolts. Leave all bolts loose until you get them all started. Then work your way around the boat tightening up the bolts. Hit all of the bolts at least twice. Then install the tramp. First get all the lacing threaded just snug, then do your final tensioning so its drum tight. Do the aft lacings first, then do the center lacing.

Then sail the boat once or twice. After it's settled, go back and tighten everything up again. You're done.

Leave the tape measure in your tool box.

Also, be sure you put anti-seize grease on the crossbar bolts, especially the four inside bolts.

sm


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PostPosted: Mon Feb 20, 2012 11:21 am 
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I have to agree in part with all above that has been said;........

Albeit some comments;

1 Loking at my Hobie here in the garden on this magnificent summer's day (+30 deg C), (with no tape measure), I think my hulls are perfectly vertical
2 However I have a crack on my front crossbar just behind the mast step.
3 I queried this crack on a past forum and the reply was ... TOO LOOSE

So how now to set. Sorry but I am stirring the pot a bit

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PostPosted: Mon Feb 20, 2012 1:13 pm 
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First off, if your front cross bar is cracked, then it needs to be replaced.

The mast step is the spot where they fail, specifically at the rivet holes. If you pull the mast step off your front crossbar, you will likely see the crack starting at the dolphin striker hole, going through the aft mast step rivet hole, and then continuing downward. I would not suggest sailing the boat with a cracked crossbar as the whole front crossbar could collapse. However, if you decide to sail with the damaged crossbar, then you should drill a very small hole (about 1/16" diameter) at the end of the crack. This should help prevent the crack from spreading.

The most important thing is to have a tight dolphin striker. With the front crossbar mounted on the boat, grab the bottom of the striker post and wiggle it forward and aft. If you can see the mast step moving on the front crossbar, then it's time to replace the rivets. Completely loosen the dolphin striker nuts, then drill out the existing mast step rivets and install new ones (stainless steel). It's tricky but possible to put washers behind the rivets inside the crossbar, doing so will help to keep the rivets tight.

Unfortunately Hobie doesn't provide torque specs for the crossbar bolts or dolphin striker rod, but just know that they should all be "tight." The striker bar should not rattle or clunk when you hit it. It should be solid. To tighten it, hold the inboard side of the striker rod with a pair of vice grips right where it exits the bottom of the crossbar. Use a deep socket on the outboard nut. I usually tighten it until all looseness and rattling stops and then go about one full turn tighter.

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PostPosted: Mon Feb 20, 2012 2:59 pm 
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Hi Guys,

What Matt Bounds and Mr SRM stated is VERY GOOD advice ....

... though when I re-assemble my H18 when I have taken the crossbars off, there is one thing I do/did that I don't see mentioned here. I measure the diagonial distances from portbow ==> starboard stern and starboard bow ==> port stern. This is to make sure the hulls/crossbars are perfectly square and are not a "parallelogram" .... usually I'm happy w/ +/- 1/4inch.

Assemble the hulls/crossbars using silicone caulking for bedding compound, tighten snug/firmly but don't crank-down on them, yet ... flip them over so the boat is upside down and raised off the ground ... you can use "sawhorses" or "milkcrates" .... measure from the gunwale at the bow along the "keel" and mark on bottom approx 18" ==> 24" .... IMPORTANT: the distance measured MUST BE EXACTLY the same on both hulls. Now measure the overall diagonial length from the mark on the keel at the bow to the centerline mark at the stern .... loosen the crossbar bolts as needed and square up the boat, and then re-shug the bolts ... note: you may need to use a "rachet strap" to "pull' the boat square and hold in position to allow time for the silicone caulking to cure that the crossbars should be "bedded" in .... also note that you can do this w/ the hulls upright, it's just alittle of a "PIA" to get a accurate measurement over the hump of the front crossbar ..... after allowing time for the silicone to cure (overnight), then crank-down on the crossbar hardware ... and check the dolphin striker tension ... firmer is ALWAYS better then loose as stated in the instructions above ...

Now if you think that you have "over-tensioned" the dolphin striker place the hulls on sawhorses ..... install and lowwer the daggerboards ... and then measure the distance between them at the top, or the keel-line and at the very bottom tip .... they should be reasonably close .... say with-in 1-2's" should be good .... (the bottom tip to tip measurement should the shortest as you want the front crossbar to be slightly "humped" up which resultes in the daggerboards being canted inwards .... vs outwards .... as mentioned above, OK?)

Remember ... it's "toe-in" or "toe-out" that is the big speed killer .... just being a little "canted" does not have as big effect ... just study/look at the new "curved" foils .....

And ... the BAD NEWS .... if you have a crack in the front crossbar at the mast step ... the front crossbar is DONE ... FINISHED ... KAPUT ..... the front crossbar is "heat treated" aluminum ..... and can not be welded .... unless you know how to "reheat treat" aluminum which is "problematic" to say the least ....

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PostPosted: Mon Feb 20, 2012 6:01 pm 
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Thank you Harry. This makes sense to me and will give me good direction. I will let you know how it goes after next weekend.

Richard, If you need another dolphin striker let me know. I have two sitting in the back yard. I am in CA

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H18 '85
H18 '89 "Knotty Passion"
H20 '96 "20/20 Vision"
Fleet 259 Central Coast California


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