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Go Back   SailNet Community > On Board > Gear & Maintenance > Very Large Hull Indentation
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Thread: Very Large Hull Indentation Reply to Thread
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Topic Review (Newest First)
06-09-2013 06:06 PM
AllThumbs
Re: Very Large Hull Indentation

Go sailing. It will pop out slowly over the sailing season. When you say "soft" what you mean is "flexes" this is common of large flat areas (similar to a car hood!). It's no problem at all.
06-08-2013 01:19 PM
pauloman
Re: Very Large Hull Indentation

sometimes this sort of damage goes away when the boat is back in the water for a while. You need to adjust your trailer so that the weight ins along the 'keel' line and not on the hull itself. This will also make it easier to get the boat on and off the trailer.
06-08-2013 06:58 AM
KeelHaulin
Re: Very Large Hull Indentation

Fiberglass does not yield and stay permanently deformed like steel. It stretches and distorts; but if the strain is relieved it usually pulls back into shape by itself. It takes time to create the dent; it also takes time for the dent to pop back out. Don't expect it to happen as soon as you lift the boat off of the pads. Once it is in the water for a few weeks (or months) it -should- return to it's original shape. Go sailing; don't worry about the pad distortion.
06-08-2013 12:33 AM
poopdeckpappy
Re: Very Large Hull Indentation

The concern is his description of the soft spot being simular to a car hood, that doesn't sound like something that will mend itself.

But then, I be no expert either
06-07-2013 11:17 PM
RobGallagher
Re: Very Large Hull Indentation

If it was me I would have those pads modified over the summer so they are adjustable.

When the boat comes out of the cradle those indentations may just go back.

I've seen bigger boats with cored hulls having similar indents that disappeared when lifted. Upon inspection with a straight edge I could find nothing.

Then again, I'm no expert.
06-07-2013 11:04 PM
SloopJonB
Re: Very Large Hull Indentation

I've seen that sort of distortion on small, light boats numerous times. I've also had it happen to one of my own boats. It will almost certainly pop out when the localized stress is relieved.

Since the inside of the affected areas is clear, once the hull has regained its shape, I would put some localized reinforcement in those areas. Some triangular or 1/2 round foam shapes glassed over with 17 Oz. biax, even some cardboard tubes glassed over - anything to give a shape to the glass so it will act as a stringer.
06-07-2013 04:26 PM
dabnis
Re: Very Large Hull Indentation

It may depend on where you sail. If your conditions are not very rough it might be OK?
However, if you sail in conditions like San Francisco Bay that could be hazardous to your health. The interior pics really show the distortion. Where you only have partial contact with the bulkhead, that could create additional stress points on the hull. No way to know how fast it might fail. Might be worth the cost to have a surveyor look at it. Then, ask yourself how much your life is worth? Especially if you sail in cold water.

Paul T
06-07-2013 04:18 PM
macwester26
Re: Very Large Hull Indentation

Quote:
Originally Posted by superhornet59 View Post
Hi all, I've uploaded some images of the indentations, and I believe they speak for themselves.

I didn't know non-cored fiberglass could become delaminated (I thought either the fibers or resin would snap/fracture first) but that wouldn't be so bad because then I could just perform a resin injection + vacuum repair, which I have the equipment for. I've also considered adding some reinforcing fiberglass (possibly with a core in between) to stiffen the area, but I worry about creating high stress areas around the perimeter.

In the interior you can see there is a fiberglass covered plywood sole, but there used to be another plywood 'floor' overtop of that which rotted. You can see the perimeter of it where I cut the tabbing flush with the hull. I don't believe it was structural, but a part of me is still not particularly comfortable with launching and sailing the boat without a new floor. I don't want to install a new floor, only to find that the hull deforms again after launch and messes everything up, or that I have to tear it off to perform a hull repair I could do now.


I've done some tapping with various objects to try and 'hear' delamination (would expect a dull, hollow sound) but I haven't noticed anything. Mind you this is while it is still sitting on the support, the rudder-lift was just a quick test to see if the glass would bounce back (it didn't). Maybe if pressure was taken off, the layers would indeed 'inflate'. In any case, I don't know what failed here. There is no core, therefore there is no rot. I'm essentially dismissing the possibility of water-related damage. There are no cracks, fractures, tears, etc... however it is soft. What on earth can create such symptoms (or lack thereof)...?


Edit: looking at those interior photos I really have to think to myself.. why in the world did they NOT tab that entire rear bulkhead to the hull, geeeez!
I don,t see a big problem here. the affected areas may in time return to shape.
However i would for sure be making much larger pads to the shape of the hull so as to add more support for next year.
Making a grp pad of the hull is quite easy to do and then fit the pads to the top of the support.

The way to make the new pads would be like this.

Apply several coats of wax polish to the hull in a large area around the new support area.
after polishing off each coat apply a coat of pva.release agent allow to dry fully.

Then start laminating layer after layer approx 16 to 20 layers should be enough.
because of the area to be moulded and the fact that the more resin you use on each coat gravity will for sure either slide it down to the keel or just drop off. use the min resin to glass ratio..

std polyester resin can be used for this along with chopped strand matting...
when cured ( next day ) peel of the new moulding and trim .
then fit to the top of the support post.
The larger the moulding the more support it will offer.
06-07-2013 03:14 PM
jameswilson29
Re: Very Large Hull Indentation

Quote:
Originally Posted by superhornet59 View Post
I'm considering putting the boat in the water, pressing the dents out, then tabbing that bulkhead into place (after it has been persuaded back into it's original position of course) but then I worry about creating a local hard spot if the hull remains soft.

Don't get me wrong, it's clear that the boat isn't going to sink as it is, but I want to make sure this problem is permanently contained, if not completely fixed.
Read Don Casey's material on adding new fiberglass and tabbing the bulkhead. I believe you are supposed to put a layer of high density foam between the bulkhead and the hull to cushion and prevent a hard spot there. Just make sure you extend your laminates/strips far enough out to spread the load of the attachment to the hull.

Why don't you add some large layers of laminate to the soft areas first?

If you really want to stiffen that area, you could add stringers, using half cardboard rolls as a mold, and extending the laminate wrap no less than several inches on either side of the cardboard.
06-07-2013 12:16 PM
guitarguy56
Re: Very Large Hull Indentation

Superhornet.... curious about the boat year... according to Sailboat Data the US-25 last year of building this length boat is 1982... I have a 1982 built hull... are you sure you have a 1984?

US 25 sailboat specifications and details on sailboatdata.com
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