Transom & Stringer replacement

[PAR]

Resin is the strength of the job. A "higher" quality fabric will not offer a substantial difference (unless you get into exotics or uni directionals), certainly not enough to compensate for a weaker resin.

The amount of resin will be relatively low. Since you'll want good stuff on the other elements of your boat (stringers, sole, etc.) skimping on resin isn't wise economy.

Piecing in the transom can be done, though it's not something I'd do, unless the transom was so big it required multiple sheets.

The grain needs to run athwartship, preferably staggered with subsequent layers to help spread loads. Each joint will be a weak point, especially if it's a butt joint.

Cutting the top of the transom off isn't going to add much more work for you and has the benefit of permitting the new core to be dropped in from above.



This is the way I usually arrange the plywood sheets in a transom, especially if it's to carry a lot of HP. 3 layers of 1/2" plywood, staggered as shown, of course cut to shape. Yes, it does leave a lot of odd shaped waste, but it's the strongest orientation you can employ. Conversely you could use two layers of 3/4" plywood, each canted at about an 11 to 12 degree angle, though this isn't quite as strong.

I bond the plywood together outside the boat, where I have a lot more control on pressure and goo application. Then the core, as an assembly goes in the transom. I can remove the temporary fasteners this way and the quality of the laminations is more secure.

[blaze_125]

Originally Posted by PAR

Cutting the top of the transom off isn't going to add much more work for you and has the benefit of permitting the new core to be dropped in from above.

lol, you answered the exact question I was going to ask. You mentioned it earlier in another post but I wanted to make sure we were on the same line.



When you say remove the top, you're talking about the portion between the rear layer of fiberglass, and in my case, the splash well? I was thinking about that today and figured that's what you were talking about. It would make the job alot simpler than what I had thought previously by making multiple cuts and multiple butt joints. That peice will defenetly come off.

You make a good point on the resin. I did not know resin was that important so now that I do, I'll take your advice into consideration. What's an extra 50$ after all... Espescially if it makes the whole thing last longer... 50$ over 10 years is 5$ a year... oh well... 5 less coffees a year

I'm not quite sure my transom was originally 1.5" thick. When I removed it, it measured 1.5" but that's 1.5" soaked. I know wood expands when it gets too wet. I'm thinking the transom may have been 1" from the manufacturer. I'll check if I can squeeze 1.5" in there though. Maybe the wood did not expand as much as I think it did.

Off the top of your head... you think 1 gallon of resin would be enough to complete the transom and stringers?
What about my idea of using the glass tape for the stringers? I figures the width of the roll would most likely be a somewhat perfect wrap around the stringers and I would only need to cut lengthwise.

[PAR]

Your transom is 1.5" before the glass went on, trust me. It will measure more then that finished up. How much resin is dependent on how much fabric you use, how much filling you'll need to do, how neat you are, etc. I don't know how tall your stringers are, but rolls of tape ('glass) can be overlapped if the stringer is tall. The key is the amount of new fabric on the hull shell. Be generous here with several inches of tabbing into the hull shell.

[blaze_125]

I'd be using:
6oz West System cloth for the transom
West System 4" tape for the stringers
Bondo resin?

Hmm... yeah... I did the math this morning and revised my numbers and supplies lol

Screw the glass tape.
A 4"X10' 6oz roll sells for 13$ around here
I got 4 stringers @ 8' each, so basically 1 roll per stringer

A 60"X4.5' 6oz sells for the same price.
So I could cut 10 lengths of 6"X4.5', use 2 lengths per stringer, I have 2 lengths left in the end. For the price of 1 glass tape roll

West System already has its reputation, who else makes great quality resin?

[PAR]

You're going to need more cloth then that. You need as much laminate as was there originally.

www.boatbuildercentral.com

Try finding supplies mail order.

[blaze_125]

Latest updates from today.
Stringers and foam... it's all out. or almost. I have kept the fiberglass where the "cross memebers" were located so I can mark them before I completely remove them. And I have laminated the transom.

[blaze_125]

Todays update...
I laminated the stringers and decided the "cross member", the parts that go across the stringers, were going to be 2X4 so I can have plenty of "meat" to screw in the floor panel.

[blaze_125]

When I glass the stringers in, do I put something between the wood and the hull, or do I lay the stringers right against the hull?

Unlike other boats I have seen on here, the original stringers were not completely fiberglassed. The plywood was symply layed down and fiberglass patches were scattered along the stringers. I'll probably do the same. I'll put on a 2 coats of resin on my stringers and hold them in place the same way the manufacturer did it in the first place.

[blaze_125]

If I'm able to stick to my timelime I should be glassing the transom and stringers this weekend. I have another question concerning the stringers installation. I'm afraid things are going to move and not be straight if I do everything at the same time. By doing everything at the same time I mean: lay down the resin, place the stringers over the resin, lay the cloth over the stringer and soak the cloth with resin.

So what's the way to do it? All at once? Or the way I just thought of...

The attached gif gives you a general idea of the hull shape and the stringer location. From the top of the boat... the hull goes down at an angle, goes flat for the side stringer, goes down at an angle, then flat again for the center stringer. The blue portion of the gif represents resin. So here my idea...

Lay down resin where the stringers are going to be located.
Lay down the stringers in the resin
Let everything dry and harden
Once it's dry and hard, cover it all with cloth and resin.

Also, originaly the boat did not appear to have any type of bracing between the transom and stringers. My understanding is there should be braces that link it all together for force transfer when the boat accelerates. Is that right? So my stringers will run all the way to the transom, and I'll join everything using triangular shaped plywood brackets. How's that?

Edit:
There is just so much to learn :s
So yeah, I just read a thread where people were talking about drilling drain holes in the stringers? Once the floor is back on, I'll be filling the underside with expandable foam. Do I still need to make holes? If I start drilling holes all over my stringers, won't I end up in the same situation I'm in right now? That is ripping everything appart to start fresh?

[PAR]

Your stringer and sole failed because moisture that got in there didn't have a way out. I always provide a drain, foam or not.

The cross braces (bridging), between the stringers can be a single piece, just butt them up to the stringers and glue in place. Think egg crate and leave the fancy triangles for cabinet makers.

I wouldn't try to do them all at once with your skill level. The goo is slippery and you'll end up wearing as much as applying.

Do one side at a time, which will offer a place to walk without stepping in goo.

The stringers and braces should have "limber" or "weep" holes to permit water to drain aft. Typically these will be in the corners on the lowest side of the compartmentalized stringer/bridging assembly. Dry fit everything first, including the cutouts for the weeps. You can't have enough weeps so if in doubt, drill another one. A 3/4" tall notch will work.

Once the dry run is placed, mark where everything goes with a "Sharpie" so you'll be able to see it come goo time. Now remove all the pieces and set them aside.

All the pieces need to be COMPLETELY coated with epoxy, at least two coats, preferably three, especially the end grain. They should be coated, just prior to installation so the last coat is just barely tacky or just past this stage of the cure. Do only those pieces you be install with the first day's efforts.

Wet out the hull with unthickened epoxy in the areas where only the pieces you're about to install live. Next mix up a thickened batch of epoxy, say a 50/50 mixture of silica and milled fibers. If you need to error on one side or the other, use more milled fibers then silica, it creates a good bond.

Place a healthy bead of thickened goo along the line for the first piece, then place the pre-gooed up piece on and into the thickened epoxy. Smear the oozed out goo into a fillet along the lower edge of the stringer or brace. This makes a transition for the fabric, from stringer to hull. If you need more thickened goo, mix some up and make a continuous fillet on both sides of the installed piece.

Now butt a brace piece up against it to keep it standing upright, again using thickened goo as the glue and forming a fillet along the adjoining edges and the hull.

You ain't done yet, get over it, now it's time for the fabric. Apply more unthickened epoxy to the parts just installed, then lay your pre-cut pieces of fabric over them. Push it down into the wet goo. Use you gloved finger and make it contact the fillets. A chip brush, roller squeegee or whatever works good for completing the wetout process. When you've done it right, the fabric will goes transparent, except over the thickened goo areas. If applying more layers of fabric, do so now, the same way.

I don't piece meal the tabbing to the hull, but prefer to make continuous tabs. You're stringers failed with broken tabbing last time, you can be the judge of how you should approach this time.

[blaze_125]

Originally Posted by PAR

You're stringers failed with broken tabbing last time, you can be the judge of how you should approach this time.

lol very good point.
I'll stop by the marine shop tomorrow and buy the needed supplies.

[blaze_125]

Originally Posted by PAR

Next mix up a thickened batch of epoxy, say a 50/50 mixture of silica and milled fibers.

So basically, I mix up the resin with hardener as per the manufacturer specs, and then I add silica and milled fiber? 1 part resin for 1 part silica/milled fiber(which would be half part silica/half part milled fiber)?

http://www.thechandleryonline.com/
That's where I'll buy my supplies. They are local so my project cost won't go sky high with shipping charges and cross border fees. According to your post, I get a decent idea of the supplies I need.


Silica

Micro fibers

Resin

Hardener

6oz Cloth

And eh... are you saying I shouldn't bother bracing the transom to the stringers? I just glass the transom plywood against the back of the boat and call it a day?

Now drainage.
I just cutout a small portion at the back of the stringer so water can get at the back of the boat and drain when I take the plug out. Meaning I'd remove the white portion in this picture.

[PAR]

Log onto www.westsystem.com and down load their "user's guide" it will cover how to mix, adding fillers, fabric wetout, etc.

It will take several layers of 6 ounce fabric to make your tabbing. It has to be at least as thick a laminate was it was before.

[blaze_125]

All the supplies are purchased.

[PAR]

The "user's guide" will tell you how to work with the supplies you purchased . . .