More like a Briar Patch

I'm working on a 79 barefoot that went way beyond the time of needing a floor/stringer replacement. I do have a diamond wheel, however, I have the one from harbor freight which is configured a little different. Has anyone compared the two as to performance? Don't matter, I'm going to buy the Lowe's version anyway and give it a try. I was also wondering if anyone has done repair using adhesives? They are really setting some presidence with adhesives and thought I might do some experimenting on my project.

Needing a fix! Tell me you have that engine cradle built. I'm waiting to see what you come up with before I build mine. In the mean time I'll keep grinding. There is no way a guy could do all of the required grinding in less than 40 hours. I don't see the end in site on my project.

I got to tell ya if your comfortable with polyester, epoxy would be like a walk in the park. Its just all around more pleasant to work with. I was able to make the entire floor of my mustang in one piece but I didnt get anywhere near the thickness on either the top or bottom lamination that would be required to hold a screw. The Aluminum cradle will definitely help, I used aluminum backing plates for my engine mounts but will consider a cradle when the boat finally hits the water again with the last round of engine upgrades. My main issue with using the lamination for the strength was ending up with flat surfaces on the stringers for the floor to mount to, I was unwilling to sand the tops of the stringers to the extent it would have taken. I considered making a mold for the the stringers on my 83 so I could end up with a dimensional product on the outside and just pour foam in the middle before laminating to the hull similar to the new construction boats but couldnt justify the effort so I went with the coosa method. Coosa is very easy to work with, eliminates the wood, but is very expensive, and while lighter than wood was heavier than the foam core method. To each his own, be careful, and try not to die.

8122pbrainard wrote: When Joe did his boat with the Coosa board, he carefully researched the structural modulus. All Chris is saying and I'm agreeing with is be careful. A boat repairer is not the same as a boat manufacturer. Did you ask him about any failures?

Of course the 83 was my second CC floor and stringer job, my first one I used cross linked pvc foam for both the floor and stringers and didnt refoam. There was a serious change in lamination schedule however over the stock. There are definitely some tricks to it, but it can be done. Cant exactly screw down the seats or the motor mounts into the foam when your done. It did help that the hull on the 67 was very thick and the span between the sringers wasnt very far. The floor in the mustang is not as rock solid as the 83 but its plenty solid. Good luck, you should be fine. Be careful with the polyester though if it ends up brittle you dont have the wood to back you up, measure carefully.

Thats it?..... I leave for a couple more hours of boat work expecting to return to more hammering. You guys have lightened up too easily! I am kidding with you guys because, I truly appreciate your thoughts and points of view. It is thought prevoking for me. Expense is not an issue with me, it is preferences. Additionally, when I take on a task such as this I do not want to do it more than once.
I will be posting progress reports and pictures when the project moves forward.

B.J.,
Keep going! I love the ambition in a different direction and make sure you keep up with the pictures too.

I didn't mean to discourage but rather point out some major strength differences that need to be compensated for when following the same stringer design using a different material. The biggest thing you have going for you is the fact that these early hulls were never engineered - They were over built using "seat of the pants" safety factors learned from many years of boat building.

I mentioned epoxy because I really feel it is a better resin for boat building. Besides not being hygroscopic, it has higher strength, is better bonding and its flexural strength is higher than Polyester. IE. it's not as brittle and will bend more before shattering. The mixing ease with the exact ratio metering pumps can't be beat. The only bad thing is it's higher cost.

Bj,
I'm glad you're counting on the glass around the H-80 and you had better be laying LOTS of it around the stuff!! This is especially true because you're using polyester and not epoxy resin. I was curious and looked up the specs. It's not much better than a wet noodle but at least it won't rot!

Ultimate tensile strength - MPa
Fir - 130
H-80 - 2.20

Tensile modulus - GPa
Fir - 11
H-80 - .08

Shear modulus - GPa
Fir - 4.1
H-80 - .0309

You have lost lots of strength without the Doug fir. Did you ever even look at the specs? Hopefully you're not just "winging" this project. Is Gary Baker a engineer (hopefully structural/marine).

hasbeenskier wrote: Thanks, Comosites are not experimental at all. You may know the better boat builders don't use wood anymore but, composites. The boat will be over built and better than original. bj

The composite may not be considered experimental but when you follow the same stringer design, eliminate the structural strength of the wood and rely solely on the glass covering of the new "stringer" it certainly becomes experimental. The composite in todays boat construction doesn't follow the same shape as our old boat stringer system.

When Joe did his boat with the Coosa board, he carefully researched the structural modulus. All Chris is saying and I'm agreeing with is be careful. A boat repairer is not the same as a boat manufacturer. Did you ask him about any failures?

Good luck with your project. I can only add that sticking with a traditional wood core / epoxy resin construction would give you some legal protection in the future, as it is well tested. If you use an untested design & it fails, you could be liable for any resulting property damage or injuries. When you go to sell this boat, please disclose your construction to the prospective buyers.

Hasbeen - Interesting choice of materials for your stringers. Has anyone ever used this before? I assume the epoxy will not adhere directly to the PVC substrate - how will you tie all your glass layers together for torsional rigidity?

Also - what will your engine mount lag screw threads bite into?

It is a little difficult to discern but there are three of the four strips as previously described, Two on the left one on the right. This was added to beef up the hull.

Somthing the original boat did not have in 81 is an aluminum engine cradle that will be added this time around

I also get a bang out of going back to look at what it looked like before hand.

I have a photo of three of the four strips I will post. But as a better description, the strips are to strengthen/reinforce the bottom of the hull. They run from the transom forward 12', (overlapping of course.)

I had a good day today. I fabricated the new composite stringers to the 81 BFN. They are constructed of two layers of Divinycell H-80 5/8" (5 pound density), sandwiching two layers of 1.5 ounce glass mat in between.
   Over the last week I laid up four 12 ft. strips of 24 oz.roven woven 12" wide along the length of the hull. Next, I am going to reconstruct the transom/lifting ring assembly.
When i can set time aside to work on this project I get pumped up.
bj

How about wearing some long pants too.

john