Cracks in gelcoat at the transom

[MCL]

Im slowly restoring a 20ft glastron sierra 199.Im studying to become a ship engineer so I only get to do a little now and then,more in the summer.Im almost finished with the interior and a pretty much brand new engine.

I dont have any pictures of the cracks so I try to explain this the best I can.The Plywood is Thicker in the bilge part of the boat.Im not sure if there even is any plywood on the sides.This is the best picture I have to explain it:

The Plywood in the transom is dry at the holes i drilled to test.The bottom of the transom is a bit "swollen,but im not sure if the plywood is saturated or if they used extra cloth there.The "swollen part extends about 1 inch from the bottom of the transom.I now for sure than the plywood is completely dry where the housing is attached and a bit lower.

My problem is I have a few cracks on the gelcoat on both sides where the thick part ends.And the cracks are far up the transom on the sides,not at the bottom at all.And I know for 100% the transom is completely dry there.The cracks are above water level.

Now my dilemma is what could cause these cracks as the transom is solid.A failure in design?The drive getting hit and the flexing of the transom causing these cracks at the edge of the thick plywood?

The gelcoat on this boat seems very brittle,it has several cracks in the gelcoat,mostly caused by idiotic owners.This is a slow project and I plan on redoing the complete transom,stringers and floor in the far future.But as for now Im planning on reparing all the gelcoat cracks this spring and use it in the summer to get some inspiration to continue with this project.

Whats your take on this dilemma of mine.I dont want to do anything half assed and pay for it later.But its frustrating to have a boat and not get to use it at all.

Thanks in advance
Matias

 

[MCL]

Re: Cracks in gelcoat at the transom

I would like to add that the cracks are vertical maybe 1/3 to 1/2 inch long,And there are 5 of them all together on both sides.Up on the transom exactly at the side edge of the thick plywood.

 

[SawDust{RM}]

Re: Cracks in gelcoat at the transom

Are they just spider cracks around the drain to transom hole ?

 

[ondarvr]

Re: Cracks in gelcoat at the transom

If, as you say "The wood is dry" then at least you don't need to re-do that part....but....what it does mean is the transom is under built.

Its not uncommon to have stress cracks at the edge of a stiff core like plywood if the design or workmanship isn't done correctly. You have a large area with zero flex (cored section) abutting an area that can flex comparatively easily (rest of none cored transom), this concentrates the forces right on the areas that have cracked.

To fix it and not have it come back means you need support the rest of the transom in a better fashion than it is right now...add glass...add a core...stiffeners...whatever may work best in this specific case. If you repair the cracks on the outside without rectifying the issue that caused them they will return in a very short period of time.

It is possible that these cracks were the result of one good hit to the lower unit, but that can happen again at any time, and you don?t know how hard (or soft) that hit was.

 

[Yacht Dr.]

Re: Cracks in gelcoat at the transom

I agree...

Too much energy and not enough dispersment ..

Corners are under built IMO..

Inspect your glass lams on the inside and outside of the corners ( specific mind to the inside tabbings of your trans ).

Try to get some pics up .

YD.

 

[MCL]

Re: Cracks in gelcoat at the transom

Sawdust.They arent spidercracks,just simple small cracks pretty much in line.

Im actually very happy that you agree with me on the design issue.As that way I can get a few seasons out of it before I tear it apart.I just want to get my studies finished before I start redoing the transom,floor and stringers as its a large project.Boats at this age have more or less saturated foam and rot,and I want to bring this baby back to her glory days.

Now that I really think about it I doubt there is any plywood except for the large thick one at the drive.The only thing that supports it are the stringers,which could explain why the cracks are high up on the transom and none at the bottom.Some webpage stated that this boat is only rated for the 135hp merc,although I have a hard time to believe that for a 20f cuddy cabin.The boats had a 175hp merc,but the block was cracked.I replaced it with a new longblock,vortec heads,performer manifold,edelbrock carb and aluminum manifolds with runners.I reckon it make 230-240hp at the crank so the transom will get even more stress now.

I never half do anything.So the stringers and transom will be redone and strenghten to withstand even larger engines.I have a few ideas that will make it very solid.

As for pictures of the cracks,sorry.I have the boat at my parents house,and thats a 7h trip.I might get some pictures in a few weeks when I go on a visit.Here is a picture of the boat when I bought it,I think its one of the nicest looking boats at that size&age.

Thanks for the help and advice,much appreciated.

 

[oops!]

Re: Cracks in gelcoat at the transom

very nice boat......why are you going to rebuild the stringers?...are they rot?

there is a basic rule with boats.......if it aint broke dont fix it.......AND replace what was there....the second rule can be bent a little....lol

 

[MCL]

Re: Cracks in gelcoat at the transom

very nice boat......why are you going to rebuild the stringers?...are they rot?

there is a basic rule with boats.......if it aint broke dont fix it.......AND replace what was there....the second rule can be bent a little....lol

Im realist.Its not a high end boat,some of the glassing looks suspect from the factory and the boat has had its share of bad owners.A boat this age are bound to have some rot and waterlogged foam.Boats cost here alot more than in the states,so its worth to do a full overhaul and have a good boat for decades.

Other than that I like to have projects to work on.

 

[proshadetree]

Re: Cracks in gelcoat at the transom

She may not be high end but dang she looks good. This ride would get thumbs up at my lake.