95' 245 Explorer stress cracks in hull

[chris222ccp]

Hi There,

Looking for some feedback.  I purchased this boat 2 years ago.  Not much use.  An older couple owned it since new.  It spent most of it's life hanging on a drydock.  I bought a bunk trailer and towed it home.  20 hours!  Long drive.  It spends most of it's time on my bunk trailer.  i just noticed today, some small hairline cracks on the hull right along where it sits on the bunk.  I know it's hard to get the boat centered on the trailer and I have been meaning to slide the bunks inward to get them off the lip on the front part of the hull.  Not quite sure what that rib or lip is called.  I will post some pics.  Should I be worried?  I do alot of hauling of the boat on the trailer.

Thanks!

Chris



http://s113.photobucket.com/albums/n233 ... rt%20pics/

[seabob4]

The trailer bunks need to be centered underneath the stringers.  Get into the bilge via the hatch to starboard and the small door just inboard of the transom door, get a rough measurement from the keel to the inboard stringers.  Then see where this measurement ends up on your trailer...

[slvrlng]

The "rib" is called a lifting strake. The flat area helps lift the hull when running to keep it on plane.
The bunks either need to be moved out or in. I am betting out, this will also make it easier to load at the ramp. Was this trailer custom made for this hull? Do what Bob said and report back as to what you find and we can try to help more.

[wingtime]

I agree the bunks should not be under the strakes.  The weight on the strakes is causing a torsion type load that is trying to make them twist them out...  this explains the stress cracks on the outside of the strakes.  Move the bunks ou under the stringers in the hull and have the top of them cut to the same angle as the deadrise of the hull.  Also I can't tell by the pics but make sure the bunks extend all the way under the transom to ensure proper support there.

[chris222ccp]

Thanks guys.  You know your stuff.  I should have asked this two years ago when I bought it.  I am hoping I didn't do any permanant damage to the hull.  Are the stress cracks in the gel ok?  Should I have them looked at?  I will ad some high def pics today with my friends 1080p camera.

[chris222ccp]

Hi Guys,

I just added a photo of the boat on the trailer.  It's the only one I have.  It's a good camera so you can zoom and still see pretty clear.  The bunks go just about all the way back.

[chris222ccp]

Hi Guys,

I can't stop obsessing about the stress cracks in my last post.  Should I have them repaired/looked at?  Never had this problem before with any boats.


http://i113.photobucket.com/albums/n233 ... G_1563.jpg

I know winter is coming and I don't want to make the situation worse by freezing weather...

Thanks again!

Chris


http://s113.photobucket.com/albums/n233 ... rt%20pics/

[flounderpounder225]

I will show these to my neighbor who assists me with boat "engineering" issues, he owned a boat building business and marine repair for many years, and is extremely knowledgeable on structural fiberglass problems.

[chris222ccp]

thanks...I appreciate that.

[seabob4]

Those cracks are very odd, given their location.  That area is what we call an "unsupported panel", a large flat area with no stringer or bulkhead traversing it to give it strength.

There is also a possibility that there is either some de-lam going on (225) or debonding (245/250).  I saw similar cracks on hullsides at Proline when the stringer grid plexus bond broke loose from the hull, allowing the hull sides to flex more than intended...

I know, Plexus is supposed to have a death grip, but the material was old (past it's shelf life) and they new it...

[fitz73222]

I agree it is in a strange place but maybe not critical. Are you sure it wasn't there before you put it on the trailer? See if it will sand out with some 1000 or 1200 grit wet sanding, compound and wax. Mark the ends of the spider web and see if it grows when using it. I always thought that delaminating stringers showed up as a chine crack because of the buckling effect of the hull without adequate "backbone". Seabob knows alot more about this than I do; I'm just saying not to lose sleep over this until you see a change in the condition; like having a freckle for 20 years that changes shape and color, then worry about it. I've had spider webbing on my 73 22-2 transom for years, the twins move back and forth in heavy chop and yet the cracks remain the same; so I don't worry about it. I just keep an eye on it!

[seabob4]

Fitz,
What I have seen in stringer de-lam is that now one has a very large unsupported panel, on the hull bottom, that sees probably the most stress as any part on the boat.  Even though the deflection the de-lam allows is minute, the force exerted is enough to cause gel cracking, the weakest part of the structure in any boat.  Keep in mind F= ma.  A very large force, with a considerable mass, would minimize the acceleration needed to do the damage...

[flounderpounder225]

Fitz,
What I have seen in stringer de-lam is that now one has a very large unsupported panel, on the hull bottom, that sees probably the most stress as any part on the boat.  Even though the deflection the de-lam allows is minute, the force exerted is enough to cause gel cracking, the weakest part of the structure in any boat.  Keep in mind F= ma.  A very large force, with a considerable mass, would minimize the acceleration needed to do the damage...

Neighbor Kenneth came over and looked at the pics, hard to really know what is going on, other than the area/s are getting stressed, and agrees with Bob 100% about the unsupported panel, but why it is unsupported, don't know.  He has seen many boats with fatigue stress cracks in the gelcoat on the hull, really, just as Fitz said, the best thing to do is watch them.  If they are what you consider superficial, like those that commonly appear along the boat cap from stress, it's really nothing to worry about.  However, if you can get a fingernail into one of the cracks, then that is a different story.  You won't be able to sand anything out really, I suppose if you went below the gel and re-gelcoated, they would go away for a while but if the substrate is being stressed they will re-appear.  Fixing the reason why the panel is being stressed (no support) and then grinding the hull down, and relaminating and gelcoating the area is the only true fix.  I think Fitz has the best idea, mark the cracks, I would take a small drill bit, and very very gently put a small pock mark in the gelcoat at the end of the cracks, and come back after running the boat each time and see if they are walking.

As far as reassurance.... I don't think your going to get a lot, unless someone does some exploratory investigation on the inside of the hull.  Sorry

[gran398]

Have been following discussion. And wondering why.

SB's Plexus old shelf-life theory holds the most credence.

Stringer bonds let loose on both sides...same portions of the hull...more than happenstance.

 Easily...hairline cracks could occur where they shouldn't.

[chris222ccp]

Thanks for having your neighbor check.  I am 99% sure they are from the bunks of the trailer.  I have them too far out.   They are about 3" too far to the outside of the stringers.  I measured yesterday.(just learned where to place bunks)  I do alot of highway trailering in New England.  Pot holes EVERYWHERE.  So I am guessing these are highway "impacts".  I have no where to strap the back of the boat down on the trailer.  I will move the bunks in directly under the stringers.  Mark the cracks and keep and eye on them.  I can't get a finger nail in them, but if you look at the right angle you can see they are bumpy.  Not smooth like glass anymore in that area.  Thanks again.