Sea Ox Rebuild

[Dipper]

So I will block the trailer and try to stabilize the hull a little more. Do you think this will be enough to avoid flex and go ahead with all the demo or should I leave the forward portion of the stringers and deck intact until I get the tunnel and transom done? Fuzz, good point I asked the guy I got the tunnel from and he told me 1/4" and 3 layers of 1708. Thought that sounded light. I will take a measurement tomorrow to verify thickness. Thanks for the replies folks. This is my first rebuild of this magnitude so I really appreciate al the help.

[Fuzz]

Question, what is the plan for glassing the tunnel to hull joint on the bottom side?

You might think about only cutting the stringers part way, 3-4 foot, back for now. At least a foot more than the tunnel length. Then after the transom skin is all cleaned up and the hull bottom where the removed stringers were you could set the tunnel in place. Glass over the tunnel and out onto the hull with 3-6 layers of 1708 and some tabbing. Install the transom core and then the hull should be stiff enough to cut out the rest of stringers. You would then cut the hull out where the tunnel covers it. I have not done it this way but it might work well

[Dipper]

That's pretty much what I was thinking. Were you suggesting to wait to cut the hull until after the tunnel was glassed on top to reduce potential flex? That would probably help in getting it in there without the edges of the cut warping at all. Do you think 8 total layers here is enough (3 on top, 3 being the tunnel, 2 on bottom)? By the way I put a caliper on the tunnel and it is only a touch over 1/8" so 3 layers 1708 as you said.

[fallguy1000]

I thought I posted, but don't see it now?

The tunnel was moulded at a minimum to maintain it's shape as long as you don't flex it too much.

The tunnel needs at least 3 more layers of 1708 over it that can be used as tabbing.

This is a core boat, no?

The tunnel would be placed on the core and liner inside as that is the strength. Then you will make a ramp of thickened resin to the hull. Make sure you are not bonded to paint or gel as the bond strength is extremely poor. Same outside.

You also need to determine how to deal with the core. The core would be a bit of an issue outside.

The tunnel gets laid on its location and when ready, cut the hole. Bonding the tunnel to the transom is the harder part. The transom ought to be relieved for exterior tabbing. You need to tell us more about the transom construction. If it is coming out, etc. The transom must be completed rough before the tunnel.

Once the hole is cut, you'll maybe want to temporarily bond the tunnel to the hull with a few spots of hot glue.

Then trim the angle of the hull to precisely take the angle of the tunnel all around. Then you can remove the tunnel mould. If the core is low density; remove it at the tunnel edge.

I am sort of assuming the boat is solid frp for the balancd of my comments. Intentional confusion above.

After trimming the hull to make the tunnel angles, you can set the tunnel. The transom interface is important here, so you need to say what the transom construction is. If I missed it, please say again.

Set the tunnel on clean fiberglass in a bed of epoxy. I would set it under the transom; the other way messes up the tunnel flow bad. Build a ramp of thickened resin to the tunnel mold like 2" wide and a good sized fillet 5/8" radius minimum to the transom. You may need a fillet all around the tunnel to avoid air entraining your work.

After it cures a day, you can sand it the new glass and all shine off, vaccum and wash with acetone and add layers of glass. Do it in such a fashion that the glass overlaps pure fiberglass all around the same way. If you have to do some darts, that is fine, but try to not dart same extact way each layer. I would apply 3 layers minimum over the tunnel, epoxy only. The first layer would overlap the tunnel a minimum of 8". Then say 6.5". Then say 5". If you don't like the strength after 3 layers, add more. You can test it by putting your weight on it after a weekend cure. The G forces from a tunnel smacking a wave can be high. It should not flex under your weight and pushing on it hard. The person who made the mould did it perfect to allow for more layers in hull.

So, there is not really much reason to tab inside if you have lots of layers of glass. A minimum tabbing would be three layers, four is also good. If, for example, you lay three layers of glass over the tunnel, you could tab a with a piece of say 6" wide 1708 for a final. The transom side and front side will have been darted likely. You'd sand the darts, fill with thickened resin and lay a could final tapes over those bonds.

Then the hull is flipped. In a solid frp boat, you would grind the hull back say 4" to a fine taper at the tunnel. Grind a radius into the tunnek hull intersection. Then you'll lay a single layer of glass over the taper grind and down into the tunnel. Then fair.

A cored hull would be done differently.

[fallguy1000]

If you have a cored hull, the core is not strong enough to take G forces at the tunnel/hull i tersection as I described in the prior post. Everything is the same, but you need to deal with the weaker core externally. Let me know what all hull and transom materials are and I will detail the exterior bonding better.

In the prior post, the tabbing to the transom outside was not mentioned, but assumed. If you are building a new transom, let me know. You cannot leave the transom and tunnel intersection unbonded or it'll crack there. The glass you lay in the tunnel must overlap the transom, dart as needed. The radius you ground for the glass to wrap must be made square for best performance of the boat.

I have not done a tunnel, but have lots of glassing experience now in the fourth year of the Skoota build.

[fallguy1000]

Do not tab into the tunnel. You can only lay full layers of glass over inside the tunnel (exterior) or you'll have a fairing nightmare

[Dipper]

Thanks for the detailed reply. That really helps me think through each step.

The hull "skin" is a just shy of 1/2" thick fiberglass with gelcoat. I am replacing transom core, stringers and decking all with coosa. My build and construction is nearly identical to Pamlico's '79 although my tunnel is angled as opposed to his round design.

As far as I can tell at this point, the hull is in great shape and I believe it is all original but we'll see when I get into grinding. I am hoping to be able to keep the transom outer skin and glass in a new core.

So as far as laying up the bottom you are saying I should run a full length layer of glass down the tunnel and wrap onto the outside of the transom. What exactly do you mean when you say the radius I grind should be made square?

[fallguy1000]

You will insert the tunnel mould under the transom and epoxybond it. After it cures and inside work is done, on the outside you will grind a glass relief into the exterior skins of hull and transom. And, you must make all corners round for glasswork. So at the tunnel transom i terface you will have a radius. After wrapping the glass and it cures to the transom relief, the radius you made must be returned to square afaik.

Clear as mud?

[fallguy1000]

Here is a rough sketch.

An 1/8" deep relief will allow you to lay in the glass and dart and wrap it and you can lay a single piece over the edge/darting if you want.

Ideally, the tunnel mold would have been relieved, but okayif not.

[Dipper]

Ok yeah I got you now. What method would you recommend to reform the square edge? Should I use thickened epoxy and another layer of glass?