View Full Version : Hull Strake Core ?

10-18-2011, 08:58 PM
I am finally starting to tear-out the engine bed stringer area in my benchseat 18 project.
Only the aft two feet of the stringers appear to be rotten; along with the lower half of the transom plywood core
which I will replace at this time also.
The right hand (starboard) stringer & aft stringer support gusset has pulled away from the inside of the hull near the front motor mount's aluminum bracket . I suspect the now missing old H-M engine's rotational torque did this in the old hull's former life ?

On the outside of the hull I see that there are several large & deep cracks on the inner lifting strake just below the area where the inner stringer cracked , and seperated, from the inside of the hull. The outside cracks are full of rust & dirt.

My two questions ?
Is this right side stringer/hull seperation at the motor mount area a common problem with the early 70s 18 hulls ?
How can I now beef-up this stringer area to prevent future stringer seperation ?
I suspect I will be adding a bit more horsepower than the original Holman -Moody Ford once had.

Did Donzi use any wood core material when laying-up the actual hull's lifting strakes ?
Is there any core material actually hidden in the hull's bottom lifting strakes themselves that can rot & must also be replaced ?
Are the stringers themselves the only wood cores in this hull area ?

10-18-2011, 09:57 PM
Brad, you need to read the first 15 or so pages of the TR thread. This is very common and my thread explains why and what to do.
Read it a couple of times and then ask any questions you have.
The hulls were laid up in two stages. The gel, mat and a couple of courses of glass makde up the outer stage, then the strakes were filled w/an almost non-hardening putty that was smeared over a larger area than just the strakes before a couple of courses of roving was laid in. The joint in the area of the putty didn't bond well so the inner and outer stages move in relation to each other.
I don't want to even get started on the stringers and how they were added.
Read the thread.

10-18-2011, 10:17 PM
Brad, I don't know if it's common but it did happen to mine. Not while I've owned it, many years before I got it. By chance, a couple of years ago I met a former owner and he told me what happened and what they did to fix it. It looks like as they built them and set the stringers in, they didn't bevel the bottoms for a full seat on the hull. This left a hole under there that as they layed up the glass would get voids and gaps from the heavier courses not following the bends. In tension(port), this held up fine. In compression(starboard) it seemed to crush, flex and tear the glass. It was fixed by filling the bottom gap in solid before reglassing the stringers. They only did the starb. side, I did the port two years ago just so they were the same, not because it was failing. I've run pretty big power for years and have no stringer issues. Those dam gussets are another story, Of the eight mating surfaces on four pieces, I repair up to three spots per year. Either my glass work stinks or the boat flexes alot more than you'd think.

10-18-2011, 10:20 PM
Yes, they do flex, it helps to lay in a few courses of 1708 in the bottom.
It really makes it a lot stiffer.

10-19-2011, 12:17 PM
Thank's Guys ~

Two feet of the starboard stringer, and it's gussets, in the engine bay are actually torn completely loose from the hull's inner bottom.
I will get some digital photos of this damaged stringer area to post here when this darn rain stops.

Outside the hull on the inner starboard lifting strake there are several large & deep "stress cracks".
At least one crack looks as if it had actually been leaking bilge water for some time as there are rust stains in this crack.

You have to remember that this project hull sat outside uncovered in the weeds on a very poor trailer ,with very little hull support, at the boatyard basically abandoned by it's owner for 25+ years.
It had a ton of water sitting in it's aft bilge which I suspect had frozen many times over two and a half decades.
This surely added to the cracks , and aft stringer & transom core rot situation.
I am a bit shocked that the stringers only appear rotted in the engine bay area.
Foreward of the engine bay they appear to be very solid~~~At least to the time tested ball peen hammer test.

We shall soon see ?

I just re-read your early Testa Rosa posts on this subject.
From your photo posts~
My 18 hull appears far worse in this starboard stringer area.

The bilge pump's bottom hull mounting pad is very punky & soft also.

10-19-2011, 02:52 PM
Brad, just rip out the pump pad, along w/the transverse frame in front of the engine, and even the stringers for the aft 6'-7'.
Then strart over.
This part of the job is very easy to do.

Then lay severfal courses of 1708 in the bottom from chine to chine.
Next, build your stringers and install.

After that, you'll have to flip the hull and work on those strakes. I think I have some pictures that cover that operation pretty well. But flip it after the inside is finished.

10-26-2011, 11:12 AM
A local builder out here has been using PL construction glue for many years with great success, he makes the hull then lays down a bead of PL along the lines. he set the stringers down into the PL and has jigs to hold them in place, he like George uses a tongue depressor to form the fillet. The next day he removes the jigs and lays his glass. Which ever way you decide to go remember one important thing, isolate your stringer wood from your transom wood.

Quite a few of use have done extensive hull work, most all transoms go bad from the bottom up. IMO from poor drain plug installation, the water migrates from the transom wood into the stringers and then seeps forward. My structural work was done by the head glass guy from Hustler, my rot was very similar to yours. Bottom 1/3 of the transom black and rotting and about 4 feet of the stringers were wet with only about 8-10 inches rotting aft. He kept cutting the stringers advancing forward until dry dust came out of the cuts, ended up about 6 feet he capped off the old stringer ends with glass. He then made up doubled replacement stringers which overlapped screwed with glass and resin between to the originals, I ended up with doubled stringers fro the fuel tank aft. He also added two additional bulk heads and four new gussets, he said it would handle a very powerful big block with no sweat. Doubt I will break any of it with my mouse motor!