Master Marine 28' stringer question

[tech_support]

Its not uncommon for the factories to just run the roving over the plywood with no fillet or tabbing. You are correct to remove it so that your new stringers are bonded to the hull.

[doug42190]

A couple of thoughts as I go forward.
First, the roving question: Do I need to add anything to the hull to compensate for the stiffness or strength or whatever the roving contributed to the hull -- not the stringers, just the hull.
Second, as I look at the transom, it appears to be tabbed on the sides and bottom with roving -- but the ace that installed it did not use any fillets -- at least none that I can see.




A: Should I grind back the tabbing and put in fillets and retab with epoxy?
B: Should I grind off all of the roving on the entire transom -- then tab, fillet, and reglass with epoxy and 1708/1808, etc?


C: It looks like he "gooped up" the bolts for the bracket but I do not think he drilled, filled, and redrilled. Do I need to redo
this correctly (I know that even because I am asking this question, I should).
D: Should I change these little squares and circles he used for backing plates to possibly two large horizontal backing plates
say 3"X3"X1/4"X 6 feet or so aluminum angle?

In the center of this picture, you can see a spot that I did a quick sanding on with 120 grit -- cleaned nicely!



Doug

[MikeS]

Is that a flex crack in the side above the area you sanded clean?

[FitzFisher]

Doug,
Most of what you are asking are structural questions best answered by an engineer or someone with a great knowledge of such issues, but I will weigh in with my opinion on some of it.

the roving question: Do I need to add anything to the hull to compensate for the stiffness or strength or whatever the roving contributed to the hull

If you get all the roving out and do a good job reinstalling the stringers with the proper fillet, tape and overlay, you should add all the stiffness to the hull that you will need. You can always add an additional layer of 1708 or something in the final layer over the hull to add some additional thickness if you feel you need it.

he "gooped up" the bolts for the bracket but I do not think he drilled, filled, and redrilled. Do I need to redo

I think this is a question of what will you feel better about? If you want to do it, now is the time. The goop will be good for a while, but we all know, that the overdrill-fill-drill method will have you sleeping better at night. With that many holes, It would be a bit of work, but would be good insurance against having to go in there again in a couple of years.

Should I change these little squares and circles he used for backing plates to possibly two large horizontal backing plates
say 3"X3"X1/4"X 6 feet or so aluminum angle?

If they are just acting as washers, they are fine.. If you are looking for more structural strength, how about glassing in another beam (s) in line with all the bolts, to act as stiffeners. you could use dimensional lumber or plywood and it would add a lot of structural strength to the bracket setup. Then you could just use the washers as shown in your picture. it looks like most of the bolts are lined up across the transom and then down on either side.

As for the sole prep, you shouldn't need to get down to the 120 grit as long as you clean of all the old stuff. A good rough surface will give you a good strong bond with the epoxy, maybe even stronger. Hope this helps. Maybe Jacques or one of the other engineers on here will weigh in to help with the structural stuff. You might even try to contact someone from Master MArine to help with your questions.

Good luck. That is a great looking hull, and you should have a great boat when you are done.

[doug42190]

Is that a flex crack in the side above the area you sanded clean?

Hello Mike,
Thanks for reviewing and your comments. I am trying to figure out what you are seeing in that picture. The short answer is there were not any cracks in the hull anywhere that I am aware of. I see above the shovel, along the wall, what looks like a crack -- if that is what you are referring to, that is tabbing -- thick roving that goes as you see it -- about 5 or 6 inches high -- sticks out like a sore thumb. It gets shorter as it approaches the transom.

This is another shot at the other end of that same shovel -- is that what you are speaking about?


This is a picture of the exact same area about 1 hour before I shot the other one. There was a roving seam going with the beam that is somewhat visible, but that is only the line that was left under that seam -- no crack.


Again, thanks.

[doug42190]

Fitz,
Thanks for your insight and comments. I think you are correct (until I hear otherwise from an engineer type) about just removing the roving and installing the stringers correctly. The "goop" issue is one I do not think I will risk -- like a ticking time bomb -- I will always know that the transom is likely getting wet in the core because I did not go back and do it right -- doesn't make sense to ignore what we all know will lead to a problem.
The circles and squares -- they are washers -- holding 1,000 pounds to the transom -- I can see that what looks like 5200 is around the edge. I guess in my brain there are about as many square inches not being used as support (between and around the squares and circles) as there are being used -- one solid "bar" would add more support -- I guess I do not know if that is a real issue or "only a true statement" of logic but no action needs to be taken. The thought about the other support is interesting.
About the 120 grit sand -- it was what happened to be left on my orbital sander when I grabbed it -- just sanded for about a minute to clean it up for the picture -- too tired to get up and get some 80 -- which is exactly what I plan on using -- as soon as the UPS guy gets me my order of sandpaper (and other fun goodies).
From what I can gather, Master Marine is actually True World Marine -- Master Marine had to do with the designer -- not really clear on that. True World is still in business somewhere near Morehead City NC -- they make what looks like a great boat -- mostly using Yanmar diesels. I met them before they moved from New Jersey -- almost 100% Japanese work force -- a few spoke English but very proud of their product and friendly.
Thanks,
Doug

[Seadation]

Hello Doug,

That is a neat boat you are restoring. I would not have a clue where to get started on a project so big but your pictures help show this is a MASSIVE project. Having recently finished my little FS14 project I have a basic understanding of glassing, fillets, tabs, etc but your project is at a whole 'nother level! Thanks for posting and keeping us updated - it is interesting to follow your work.

Good work! Atta-boy!!

Fair Winds,

/david

[doug42190]

Thanks Seadation,
It is a big project -- the learning curve is massive. I really should have started with something much smaller -- but this is what I have to begin with. It just means stepping slowly, carefully, asking plenty of questions, and learning to have a crystal ball so I can see what the next peice of the puzzle is -- quite an exercise is mental gymnastics, to say nothing of the physical and $$$$ aspects! Thanks for looking, come back often, and I will try to look at your project if it is a thread -- still learning about forums.

Doug

[MikeS]

Doug; having done a few of these projects myself I can tell you that the first thing you should do is sit down at the computer and read every last word of Shine's Aquasport rebuild and the other rebuilds on this site. Then go out and buy yourself 2 tools, a 7 inch grinder and a 4-4 1/2 inch grinder, grinding pads, and lots of coarse grit discs (36-80 grit) to go with them. You have to get all the crud cleaned up before applying new glass and that's a BIG boat! I've had real good service out of Dewalt grinders, both sizes. The method of mounting the Armstrong bracket is standard, except they normally use all square or all round washers; maybe your guy just ran out of one and substituted whatever he could find! Make sure the bolts and washers are all marine grade stainless or you will quickly find something new to repair after launching the boat!

[doug42190]

Mike,
Thanks for your advice. I have three good 4.5" grinders, a 7" grinder, 3 oscillating grinder/saws, 1 Milwaukee sawzall, etc. etc. and I am waiting on a fresh shipment of cut off and grinding discs. I agree about reading -- I have read all of Shine's posts several times, Strick on Seacraft, Ringleader and Warthog on Mako -- in short, everything I can -- you are right about using that for background.
I had not considered the marine grade bolt issue -- stainless? How is marine grade marked? Aren't stainless bolts all the same?
Thanks, and please keep the comments coming -- I need the help.
Doug