183 replies to this topic

[Fishman38]

Scott regarding your comment about beveling the stem, is it because of the curves?  I have zero experience with the process but could it be done with a router? There may be no way to set up a proper guide to avoid gouging and so on.   

Jerry

[Miyot]

Fishman38, the metal lath screws I got at lowes are Phillips head. Your hex drives may be better, test them on some epoxy work and let us know. I use an impact driver to drive and remove them. I used them for keel glue up,etc. I have broken one Phillips bit so far in this build, but not one lath screw.

Hokeyhydro, I to use a lot of drywall screws, I'll have to try your heat the screw to remove it. Since using the metal lath screws and never breaking one, I just can't bring myself to use drywall screws for epoxy work ever again.

Scott, the pictures hide many little mistakes, and I assure you my build has got them. Thanks for the nice comments fellows.
Dave

[Fishman38]

Dave I'll be glad to test the screws but for two reasons twill be a few weeks before I can do it (1) will be away from home for the next 4 or 5 weeks and (2) won't have any epoxy to test with 'til I get home.  I will be ordering it for delivery shortly after I get home.

Jerry

[Miyot]

Installed forward deck stringers, also 2 lamination's installed on inside of transom. One more lamination to be installed on transom, which will notch over the inboard stringers. I think installing the transom lamination's is easier now rather than fitting after turnover. I used clamps and culls to install the lamination's rather than using screws for clamping. My culls are cut slightly convex so pressure should carry across the face, I also used an additional strip of oak with a block in the middle to be sure of good pressure in the center of the face. This worked well and no holes are drilled in the transom. I'll spoke shave these lamination's fare to the bottom for a perfect fit.

I'll be adding trim tabs later, so I'll ad another lamination on the inside bottom where the screws to the tabs will be. The deck stringers would actually pass through the chine batten at about station 5 if left as one piece from stern to stem. I was a little perplexed at what to do here. The pics show my solution of the forward deck stringers. I just glued the deck stringer to the upper section of the outboard bottom stringer. Keeping it flush to the top . This worked well. The deck stringers pass through the inboard stringers at their ends as well. Making this area very strong. Bottom planking in a few days. Here are some  IMG_5978.JPG   84.57K   55 downloads  IMG_5979.JPG   89.12K   64 downloads  IMG_5982.JPG   94.01K   61 downloads  IMG_5983.JPG   94.33K   52 downloads pics.

[Miyot]

Notched frame for side stringers at transom. Transom lamination's. Cut some notches.
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[russell]

I was wondering why all the extra verticle stiffners? When I built my Marissa I found the glue fillets and the " egg crate" design to be very stable, seems to me that once the hull is complete there would be little or no stress in these areas. Next question, why did you wait to cut the stringer notches untill now? I getting ready to start on the all new OB 24. Just waiting for the plan to arrive. I've been following your build since your start, looks really good, I'm looking forward to see how the planking goes on your boat, I've never done a cold mold boat so I am wanting to see how you do it.

[Miyot]

Russell, the vert stiffeners may be overkill. However the Ocracoke 20 CD has the same type of stiffener put in by that builder. NZ Lance also used a similar method on his 20. I liked the idea, and it was hard to get the epoxy into those joints. My boat will see some offshore service when the weather is favorable. I'm going for extra beef when I think it is worth it. Gluing ply to me is only gluing to the first outer ply. So my thought is to spread the load and keep her stiff. Working in a sea the boat is under a lot of stress. Twisting, bending, in every way imaginable. Longevity and strength are my thoughts. I added a notched frame on the transom as well for the stringers to notch into, again thinking about strength and longevity. I feel the extra day of work or so is worth it for the life of the boat.

I waited on my notches thinking some may need moved slightly and indeed up forward a slight angle to the notches is favorable where the stringers make the curve at the bow around stations 2 and 4. However, to the designers credit, this is probably not necessary. And after cutting several notches using the stringer to find the most appropriate angle I gave up the idea and I'm just cutting out the notches and modify them as I fit the stringer.

As to planking, I have not done a cold mold boat either. I have spent a lot of time fairing and will spend some more before it is over. Thinking the better I do here the less problems I'll have fairing the hull later. I can say that on this boat up forward, the bottom planks want to flatten out after they pass the inboard bottom stringers. There is no support for the mid sections of the planks just forward of the end of the inboard bottom stringer. However if you install the forward deck stringer as called for in the plans, they will support the planks. Helping keep the convexity in the forward sections. I mention this because it appears some builders of the Ocracoke 20 appear to have left them out. I could be wrong on this. However I myself considered leaving them out as I may not deck this area over. Leaving a little more storage room up forward. After seeing my plank batten want to flatten out forward of the inboard bottom stringers I opted to install them. Only a 2 or 3 hr job. And I think well worth it. Now you probably could install these planks and bow them to match, but it would not be easy. When I get there, I may deck this area if I think it will stiffen and or strengthen the forward section.

Now I have been reading up on this cold molding planking thing some. And I will probably not epoxy the seams on the first layer of planking, initially. These first seams probably won't match perfectly on the first inner layer, especially the forward side planking at the bow. The second overlapping planking layer (overlapping the inner seams) will pull them fair when screwing the outer layer of plank down to the inner layer. The epoxy layer in between the planks should squeeze through and fill the seams on the inner layer of planks. And if it doesn't you would have to spend some time forcing some in from underneath to fill the seam. Perhaps a better way would be to glue the seam, then add the outer plank before the inner seam has a chance to gel. If
anyone with some good experience knows better please chime in. Sorry to be long winded, I'm not very good explaining things.
Dave

[russell]

Thank you very much for the insight. I considering trying the Raptor staples and or brads for attaching the cold mold process instead of screws and washers. The staples and brads/nails are plastic and can remain in the boat and  be sanded. They are a little expensive but would be much faster. I have been reading about them on the Glen-L website. Does anybody out there know anything pro or con? Looking forward to your pictures of the process. My plans should be here this week. Can't wait to get started.

[Miyot]

Russell, I don't think the brads or staples will pull the planks together properly. Even screws are a poor clamp. Actually a screw driven through two layers of plywood will actually cause a gap between them. The threads pull the screw through the first plank and just before entering the next plank, actually push the planks apart slightly before penetrating the second ply. Now the only way to get no gap between them is to clamp them first. This is impossible on the larger planks and probably not practical on the smaller ones. I have been considering drilling a pilot hole just larger than the screw through the outside plank so the threads don't bite on the first layer. My common sense tells me this will produce a better clamping pressure. I just don't know if its worth it, however it would take very little extra time.

Now I know this slight gap does occur through past experience. I have used clamps and screws as clamps in this build. I use only enough clamping pressure to pull the parts together properly. The screws I've used have been for clamping and keeping alignment, running the screws first, then clamping. I notice little or no squeeze out in the screwed areas. Back the screw out and you get a nice squeeze out of epoxy. Re-drive the screw, and without some kind of clamping pressure or applying hard pressure to the head of the screw with your driver, the epoxy actually sucks back in. The screw causing a slight gap. Now running down the screw, backing it out and running it back in again usually clamps a little better, but not always.

Now maybe I'm being to persnickety, but I want a nice solid glue line with no bubbles in the layers. Brads or heavy staples may work on the edges, driven into the keel or stringers, after proper clamping. But I would not trust them. I'll bet the staples are great for holding glass on the boat while wetting out. And I may use your idea for that part of my build. Wondering if they would cause dimples in the glass, where each staple is, especially if using with mat. Questions to be answered. I hope someone will chime in that knows.
Dave

[Hirilonde]

 I have been considering drilling a pilot hole just larger than the screw through the outside plank so the threads don't bite on the first layer. My common sense tells me this will produce a better clamping pressure.

 

 

Your common sense is correct.  If you drill the pilot hole through both layers not only will they be drawn together, but drawn to what ever it is you are screwing into.

[Fishman38]

If you're glueing a layer of say 3mm ply to a layer of 3mm ply and screwing into a structural piece such as a stringer wouldn't you want your screws to be threadless for at least the first 6mm below the head (if you can find such screws)?  Then the pilot hole depth would be irrevelant.or maybe unnecessary.

JO

[Hirilonde]

That would be ideal Fishman38, but a clearance hole also relieves most spliting forces exherted by the screws.  And like you said, it may not be easy to find the exact specs for a screw you want.  And if you are using dry wall screws which will be removed probably not possible at all to find such a screw any where near as cheap.

[russell]

I contacted Raptor, they are sending a sample of brads and staples, I will do some testing even though it will be some time before I will actually get to that point of construction. Have you tried the screws for Krag jig? I used them on my Marissa build, tho pull together most all joints, I was able to remove them easily and reuse many times before rounding out some of the square drive holes.

[Scott Dunsworth]

Russell, I thought about using the Kreg pocket screws and jig to install bulkheads and other various things. They would hold things together, very precise and add some shear strength if left in. But my hull and bulkheads are quite a bit thicker than most builds on this forum. I haven't checked to see if their available in stainless yet. I started using the pocket screw set up a few years ago and it is amazingly strong and easy. But I haven't used any applications on any boats yet, but can see a lot of areas that they could be used. I almost never use my biscuit jointer anymore.

[Howard]

Has anyone tried duplex nails for this use? They are made to hold things together temporarily and for easy removal. I would certainly want to use a small piece of plywood under my hammer head or pry bar to avoid damaging the wood when removing.

 

Next issue is how to seal up the holes once the fastener is removed to avoid leaving a void for moisture to find its way into. Thickened or even neat epoxy does not leach very far into a small hole like this. Probably best to inject neat, then thickened epoxy into the hole, using a syringe and large bore needle pushed all the way to the bottom of the hole to fill it completely.

 

Yet another option is to use bronze or stainless ring shank nails and leave them in place. The danger in doing that is the metal is left in place and if you ever want to go back to make repairs, you have the imbedded metal to deal with.

 

 

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[Hirilonde]

If you are coating the whole boat in 3 coats of epoxy before painting I don't think it matters whether small holes are filled or bridged over.

[Miyot]

The objective is to clamp and hold the two layers of planks together until the epoxy cures. Nails of any kind just won't work. The traditional method is to use a screw, either with a washer or small block of wood, covered with tape or some other release to keep it from becoming permanently glued to the hull. After cure, you back out the screws and either fill the holes with epoxy or glue in a wood plug. The holes are small so there is a problem getting plugs small enough. Some use wooden golf tees, epoxy them in and then cut them off and sand. My thought is to just use epoxy and a fairing compound.

Check out NZ Lances Ocracoke 20 on page 2 of the B&B forum and you will see exactly how its done. Now you will be drilling literally hundreds of holes if you pre-drill the outside planking layer (probably what I will do). The inner layer is only screwed to the Transom, keel and stem and stringers. I will probably use silicon bronze screws for this and leave them in the boat. This has to be done at regular intervals so you don't hit them while attaching the outer layer of planking. It is really a simple procedure. You have to remember there will be literally hundreds of screws driven through the outer layer of planks and into the inner layer to draw the planks together. You can't afford to use a screw that breaks frequently because they are epoxied in. Thats why I looked for and found the metal lath screws (recommended on another site) . I have yet to break one, even in a fully cured layup.

Remember these planks are plywood, with the first bottom planks 4 feet by 8 feet. Screws are really the only option and they must act as clamps. None of us have a clamp that can reach to the middle, let alone hundreds of them. If you look at NZ Lances build, you will understand.

[Miyot]

If you are coating the whole boat in 3 coats of epoxy before painting I don't think it matters whether small holes are filled or bridged over.

That is correct. Some builders of cold molded boats have complained about print through and so use unfinished golf tees to plug the holes. That sounds to much for me. And builders should remember there will be holes on the inside of the hull to fill as well. The inner layer of planking is only 3/8 thick on the bottom and 1/4 on the sides. Not thick enough to screw into without the screw coming out the other side. After epoxying with 2 or 3 coats on the outside, the hull is glassed.

[Fishman38]

I have to say these discussions are priceless.  They would be worthwhile if all participants were boatbuilding novices like me...............when the guys who are obviously experienced builders join in they are really great!  Thanks to all of you!

[Miyot]

Fishman38, your staple idea may yet work. I did some research and found they have been used on thinner veneers. Perhaps with the modern guns to drive them they may work. Howards nails have also been used, at least where driven into structural members. If the plys can be pulled down and fit nicely, the staples may be strong enough. It would be a bonus. No holes to fill or screws to remove.