Pearson 33 with pressure dents from jack stands

[sailingdog]

It depends on how far depressed the area. If the pads are overtightened... it might just be a temporary pressure dent from the overtightened pad. It also might be due to the boat's weight not resting primarily on the keel. I can't tell from the photo, how well the keel is blocked.

The hulls on fiberglass boats can oilcan, given pads that are misadjusted, since the forces are much higher than what the hull will ever see in normal in-water usage.

[T34C]

It is a big heavy boat. If it is on a cradle that was not built for the boat or if stands are place poorly so that they don't line up with internal structure the hull can flex. If there is no cracking/crazing in the area and no thru hulls that could get damaged, it is very likly a non-issue.

The yard poorly placed one of the stands on my boat a couple years ago. The port quarter flexed pretty significantly. I had the stand relocated, dent stayed. After boat was relaunched and weather warmed up, it was gone. I know my hull in that area is around 1 - 1 1/2 inches thick with solid glass.

[Sailormann]

Don't walk away from this boat - RUN. The hull is a bit soft and whoever organised the blocking was less than expert.

As far as the "pops back into shape" goes...

It is possible that this will occur, however the hull has been permanently damaged and is probably not seaworthy any longer. The fibres in the fibreglass roving have a crystalline strucure. When they are bent or crushed, the damage is permanent. They are the fibres that hold the hull together, and if enough of them get damaged, the resins will fall away from the fibres as shear force is applied.

Fibreglass is an inelastic substance. The boat's hull should be stiff and strong, not flexible at all.

[camaraderie]

Dimples are perfectly normal on many moderately built production boats of the 70's and 80's. It is nothing but cosmetic most often and is not something to be concerned about unless a survey shows actual damage. I've owned two boas with dimples from day 1 and never had a moments issue with hull integrity on either one.
Certainly have your surveyor take a hard look if you want the boat...but don't abandon an otherwise good boat over ths issue.

[sailaway21]

Originally Posted by Sailormann

Don't walk away from this boat - RUN. The hull is a bit soft and whoever organised the blocking was less than expert.

As far as the "pops back into shape" goes...

It is possible that this will occur, however the hull has been permanently damaged and is probably not seaworthy any longer. The fibres in the fibreglass roving have a crystalline strucure. When they are bent or crushed, the damage is permanent. They are the fibres that hold the hull together, and if enough of them get damaged, the resins will fall away from the fibres as shear force is applied.

Fibreglass is an inelastic substance. The boat's hull should be stiff and strong, not flexible at all.

That will come as news to the manufacturers of fishing poles and radio antennas. (g)

While repeated point stressing may well result in the damage to the fiberglas structure you cite I believe there is ample evidence of fiberglas' resiliency in both the automotive industry and the boat building industry. I've witnessed the type of disconcerting flexing being discussed and also seen it pop back with no evidence externally or internally on the boat of any significant damage.

[Sailormann]

While repeated point stressing may well result in the damage to the fiberglas structure you cite I believe there is ample evidence of fiberglas' resiliency in both the automotive industry and the boat building industry. I've witnessed the type of disconcerting flexing being discussed and also seen it pop back with no evidence externally or internally on the boat of any significant damage.

There have been many replies similar to yours. I am not speaking of fishing poles or automobiles. The resin used in those applications differs compositionally from that favoured for boats. Boats are designed to be stiff.

That said - the damage does not occur so much to the resin. The thing that is irreparably damaged is the glass fibre in the roving, and unless you open it up and look at it with a microscope, you are not going to notice it. It is not likely to show to the naked eye until the damage has become quite severe.

There is "resiliency" in the fibreglass, and it can return to it's original contours, as that is the shape that is inherent hence requires the least amount of energy to maintain.

The fibres are not elastic however, and once bent or crushed, they are forever changed. It is possible that their structural integrity will allow them to avoid being bent or crushed in the case of light impact, however, in the case of prolonged loading - particularly if you hear that brittle crunching kind of sound when the boat hits the jackstands and one of the stands is too high - the damage is permanent.

[rdbeales]

The Pearson is in a different spot in the yard now on stands. No idea how old the pictures are. I am going to definitely ask about moving the stand though and see what happens. Thanks Everyone!

[T34C]

I'm going to go out on a limb and guess that as long as you don't hit any icebergs, you'll be fine.

[KeelHaulin]

Originally Posted by Sailormann

The resin used in those applications differs compositionally from that favoured for boats. Boats are designed to be stiff.

That said - the damage does not occur so much to the resin. The thing that is irreparably damaged is the glass fibre in the roving, and unless you open it up and look at it with a microscope, you are not going to notice it. It is not likely to show to the naked eye until the damage has become quite severe.

There is "resiliency" in the fibreglass, and it can return to it's original contours, as that is the shape that is inherent hence requires the least amount of energy to maintain.

The fibres are not elastic however, and once bent or crushed, they are forever changed. It is possible that their structural integrity will allow them to avoid being bent or crushed in the case of light impact, however, in the case of prolonged loading - particularly if you hear that brittle crunching kind of sound when the boat hits the jackstands and one of the stands is too high - the damage is permanent.

I think there is too much "guessing" going on in this post. Fishing poles are designed to be flexible; but it's the orientation of the fibers and taper of the pole that allows it to flex repeatedly without failing. Boat hulls are similar in the sense that they do need to flex in order to dissipate the point load(s) and thereby reduce the stress at those locations. If it were totally inflexible it would be more similar to solid glass (shatter prone) than reinforced plastic; which is what FRP is.

ALL fiberglass hulls will have quite a bit of flex; regardless of construction. Have you ever heard of a "hard spot"? That's usually due to a bulkhead or other internal glassed-in stringer that is "too stiff" and prevents the hull from flexing. On either side of the hard spot the hull will weaken because it is forced to bend at a sharper angle and at a higher local stress. The result is weakening due to fibers getting broken; and then the "matrix" (resin) not being able to transmit the load which then results in cracks.

A dish in the hull due to a tight jackstand can usually be corrected by loosening the stand. You can't expect to put a boat on stands (long-term) without some localized flex due to the stands putting point loads on the hull. The dishing of the hull should not be permanent; the fiberglass may have "stretched" a bit but it should recoil once the pressure is removed. I can't say for sure; if you are interested in the boat a surveyor should check the hull for structural integrity to be absolutely sure.

To say that something made primarily of "plastic" (the very definition of plastic is something that is not a permanently shaped solid); and glass fiber (which does stretch/flex) should not flex or deform is simply incorrect. It depends on the type of deformation and overall stress applied to the FRP; as to whether it has seen a load stress that has caused failure of the fibers.

[SimonV]

It is below the water line whose going to notice if it does not cone all the way out. Its getting on 40 yrs old, it will out last most of us. If you like it get it surveyed. Very pretty real boat.