Hull Deflection on 76' Daysailer II

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Hull Deflection on 76' Daysailer II

Postby Zinger88 » Fri Sep 30, 2016 12:21 pm

I'm a new member to DaySailer.org and currently in the market for a Daysailer. I have the opportunity to acquire this 76' Daysailer II but would like thoughts on the hull deflection shown in the attached photos. Boat has been sitting on trailer for extended period of time. Is this something I should be overly concerned about? Will deflection resolve itself once pressure is taken off when boat gets in the water?

Thanks in advance for any advice you guys may have!

Jim
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Jim H
'76 Daysailer II, Sail #7920, Windsong
Burton, TX
~~ _/) ~
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Re: Hull Deflection on 76' Daysailer II

Postby ciscovt » Fri Sep 30, 2016 3:34 pm

My guess with my limited knowledge would be that it should spring back, off of the trailer. That being said I would strongly suggest that you replace the bunks on the trailer with wider and longer ones. I went with 8' 2x6 covered with the appropriate carpet. My DS III sits much nicer now.

Scott
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Re: Hull Deflection on 76' Daysailer II

Postby KingsTransom » Fri Sep 30, 2016 5:09 pm

If the rollers have given way, then more of the load is on the bunks. This is what happened with my boat, which showed a similar degree of deflection. The bunks are really there to maintain lateral stability, more than bear most of the load, this as described in the instruction manual. It may also be that the PO adjusted the bunks too high.

If there are obvious problems, like cracks or crazing radiating away from the bunk contact area, then pass, otherwise, I would not worry about it.

Usually the bunk contact edge is square (horizontal), while the hull is at about a 10° angle, which means the bunk makes only a line contact with the hull. You will probably want to replace the bunk carpet when the boat is in the water. You can then use a hand plane to make the contact edge of the bunk match the angle of the hull.
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Re: Hull Deflection on 76' Daysailer II

Postby Solarwinds » Fri Sep 30, 2016 5:10 pm

From your pictures, there doesn't seem to be any oil canning on the port side of the boat, but the forward side of
the depression on the starboard side looks almost like it's creased.
Maybe I can't really tell from the picture, but that, to me, is a little extreme.
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Re: Hull Deflection on 76' Daysailer II

Postby GreenLake » Fri Sep 30, 2016 5:42 pm

Solarwinds wrote:From your pictures, there doesn't seem to be any oil canning on the port side of the boat, but the forward side of
the depression on the starboard side looks almost like it's creased.
Maybe I can't really tell from the picture, but that, to me, is a little extreme.


Probably just an effect of the asymmetric distribution of light and shadow around the boat. If the photo showed a straightedge it might be possible to gauge the deflection, but not this way.
~ green ~ lake ~ ~
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Re: Hull Deflection on 76' Daysailer II

Postby hsubman » Fri Sep 30, 2016 6:22 pm

The boat seems to be a little off-centered on the trailer. The keel seems to be to the extreme right edge of the center rollers. That is placing the starboard bunk more towards the bottom of the hull while the port side bunk is up higher on the hull. this would make a great difference in weight distribution on the bunks. If possible, I would try lifting up on the stern and try to slide the boat a little left to center the keel on the rollers. Could make a difference. Just a thought.
Last edited by hsubman on Fri Sep 30, 2016 9:39 pm, edited 1 time in total.
John
'83 DSII, 12279, MARY RUTH
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Re: Hull Deflection on 76' Daysailer II

Postby klb67 » Fri Sep 30, 2016 7:48 pm

I got a new trailer for my 76 a year or two ago. I had the new bunks adjusted as high as they would go and the hull was still resting on the keel with an inch gap to the hull. The hull relaxed down to the bunks within 2 days. At a minimum, upgrade to 2x4s on the flat rather than the edge. I would think that if there are no major cracks in the gel coal, your hull will relax too.
1976 DSII - #8039
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Re: Hull Deflection on 76' Daysailer II

Postby Zinger88 » Fri Sep 30, 2016 9:49 pm

Thanks everyone for your thoughts and insight. The current owner sent me the photos and I'll have an opportunity to inspect the boat in person next week. I will certainly check for cracks around the deflection and will also attempt to center the boat on the rollers and then see if anything changes. Should I purchase the boat, first upgrade will definitely be new bunks.

Thanks again! This forum is an incredible site for a wealth of information. Looking forward to becoming a Daysailer owner hopefully soon!

Jim
Jim H
'76 Daysailer II, Sail #7920, Windsong
Burton, TX
~~ _/) ~
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Re: Hull Deflection on 76' Daysailer II

Postby jeadstx » Sat Oct 01, 2016 2:42 am

I've seen that boat about 6 months ago (racing out of that yacht club) and found no cracks in the hull. The boat was off center on the trailer as someone noted.

John
1976 Day Sailer II, #8075 - Completed the 2011, 2012, and 2013 Texas 200
1952 Beetle Boat Swan Catboat
Early Rhodes 19
1973 Mariner 2+2, #2607 - Completed 2014, 2015 and 2016 Texas 200
1969 Day Sailer I, #3229
Fleet 135; Canyon Lake, Texas
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Re: Hull Deflection on 76' Daysailer II

Postby K.C. Walker » Sat Oct 01, 2016 4:26 pm

When I bought my 1974 boat it looked to be in excellent condition. The gelcoat was shiny. Though, I did notice that there were some deflections of the bottom where the rollers (the trailer did not have bunks) supported the boat. I sailed the boat that summer and enjoyed it. Somehow, I had the nagging suspicion that the bottom was a little soft. I should have moved on to a different boat but I decided to stiffen up the hull. It is a Daysailer 1 so I had easy access to the inside. I spent way too much time on it but it came out really nice. The difference in the way the boat sailed was night and day.

So, I would suggest checking the stiffness of the hull by pounding on it with a closed fist. If it feels bouncy it's softened up considerably. If it feels rock hard, it's like it was when it was new. If you can push the bottom of the boat with your hand it's really soft and I would pass on that. On a Daysailer 2 it would be VERY difficult to repair. Most of the damage to the bottom of these boats happens while trailering. Going down a bouncy road without very good support for the boat flexes the bottom. Every time it flexes it breaks down the laminate a little bit.

With that said, if you are not concerned about performance, they're still a fun boat and incredible bang for the buck.
KC Walker, DS 1 #7002
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Re: Hull Deflection on 76' Daysailer II

Postby jsbowman6 » Sun Oct 02, 2016 11:45 am

Not certain how DSII's are built, but on bigger boats, the keel is where the strength is. If you look at them in boat yards they rest on the keels and are only supported on the sides to keep them from tipping over. I adjusted my trailer so the rollers are supporting most of the weight and the bunks just enough to keep the boat level. If I let the keel rollers down, I noted hull deflection on mine as well.
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Re: Hull Deflection on 76' Daysailer II

Postby GreenLake » Sun Oct 02, 2016 12:37 pm

Forward of the CB, there's a keelson which serves to distribute the loads from the mast. Together with the deeper V shape this makes the hull stronger on the centerline. Aft of the CB, there's only a very shallow V. It provides little additional strength. On a DSII (according to my understanding) the cockpit sole and seats from a single shape that is not resting on the bottom of the hull; in difference to the DS1 where the seats are connected and therefore act as stiffeners. (The panels between seats and CB/centerline can still flex though).
~ green ~ lake ~ ~
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Re: Hull Deflection on 76' Daysailer II

Postby jeadstx » Mon Oct 03, 2016 1:38 am

This what it looks like in inside the bilge of a DS II (picture from my 1976 DS II, starboard side looking aft). Picture was taken through the inspection port prior to stuffing with "pool noodles".

DS II Starboard Side - Looking Aft.jpg
DS II Starboard Side - Looking Aft.jpg (177.42 KiB) Viewed 10315 times


John
1976 Day Sailer II, #8075 - Completed the 2011, 2012, and 2013 Texas 200
1952 Beetle Boat Swan Catboat
Early Rhodes 19
1973 Mariner 2+2, #2607 - Completed 2014, 2015 and 2016 Texas 200
1969 Day Sailer I, #3229
Fleet 135; Canyon Lake, Texas
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Re: Hull Deflection on 76' Daysailer II

Postby GreenLake » Mon Oct 03, 2016 1:41 am

The stringer is intended to limit flexing, but only in one dimension. If you place a narrow bunk under it, there's nothing that would limit it from being pushed up. Nothing that is, other than the hull laminate.
~ green ~ lake ~ ~
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Re: Hull Deflection on 76' Daysailer II

Postby KingsTransom » Tue Oct 04, 2016 1:07 am

Wouldn't a wider bunk simply move the supported-unsupported edges farther apart compared to a narrow bunk? Wouldn't those points experience the same bending moment? Somewhere around here I should have a copy of Timoshenko's Theory of Plates (or similar), which should have the answer.
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