Perfect Laminated Skids

I'm foregoing my usual Title of "Passagemaker Plans Build" because I think this may be of interest to builders of other boats. 

Let me preface this post by saying that when I made the skids for my EP, they were out of solid white oak.  This was before I discovered oak's resistance to being epoxied.  Regardless, I was barely able to wrestle a pair of solid oak skids onto the bottom of my EP, following the rocker built into the bottom panel and secure them in place with silicon bronze screws long enough for the wood flour thickened epoxy bedding to cure.  I actually needed some help from a friend to make this happen.  Since I'm building my PM solo, in a foreign country, I thought I'd try to think outside the box for this attempt.

I took the basic dimensions of the skids and rough cut out 1.5" x 48" strips out of some of my left over 6mm marine grade plywood.  This would leave plenty of room after the glue up to trim the edges for the final size.  I laid down some wax paper on the bottom panel and started applying silica-thickened epoxy to the strips.  I then used some spring clamps to line them up horizontally and put some weight along the curve to compress the lamination.  I laid up 2 sets of 4 strips for 1" thick skids.  Because of the damage I incurred on my EP, I wanted them to be substantial enough to handle the PNW beaches, which can be rather rough.  Because I laid them up on the bottom of the boat, other than a little spring-back, they should fit the bottom perfectly.

Tomorrow, I'll remove the clamps and weights and see how much spring-back I get.  I'll also either run them through the table saw or across the jointer to clean up the edges.  Then I'll shape them with my Shinto rasp and soak them with CPES.  After that cures, I'll be ready glue them down to the hull with some more "mustard" and then put a large fillet around them.  I may or may not glass over them at that point.  Either way, they'll then be ready for several coats of graphite epoxy.

I'm hoping this works out and just wanted to share my approach.  At this point, it's no harm no foul.  Since it's not readily obvious how to post pics on this forum, I'll find that info and do so tomorrow...


8 replies:

« Previous Post       List of Posts       Next Post »

RE: Perfect Laminated Skids

As promised...

Slight amount of spring-back.  Nothing that can't be filled with a little goop.  Overall, I'm very happy with this attempt.  I may add one more strip for clearance.

   

RE: Perfect Laminated Skids

   

RE: Perfect Laminated Skids

Skully,

Before you glue those to the hull, I'd like to make a friendly suggestion that you call CLC and discuss this substitution with them. To me, it looks as if you're heading for trouble. If I'm wrong, you'll get to hear the experts say that I'm full of it. If I'm right, you could save yourself some damage to your boat.

I'm basing this on the photographs in the PMD construction gallery, especially this one:

In your other post, Pippy replied that the skid dimensions were 3/4"x1/2". That looks like a good match to the picture. In the picture, it's dimensional lumber, not plywood. Note that it's also placed on the narrower side (3/4") with 100% of the grain running fore/aft.

Comparing that to what you described, using plwood means that half the grain is in the lateral direction so you have less grain in the fore/aft direction than the skid in the picture. You also have the wider side against the hull, losing the dimensional stiffness provided by orienting the narrower side down. That will result in your skids having less stiffness than the ones in the CLC construction gallery. Will that be an issue? I don't know. Maybe the PMD doesn't need all that stiffness, maybe your skids (while not as stiff as they could be) are stiff enough. Either way, it might be worth a call to CLC to make sure.

Another concern is that while you mentioned glassing the skids in the original post, now you're saying you may just go with graphite/epoxy. If it was my boat, I'd put a couple of layers of at least 6 oz glass on the top of the skids before the graphite. The entire weight of the boat and all its contents will be ending up on those skids. That'll be a lot of pounds/square inch, especially since the curve will prevent the entire surface area of the skids from being used. Add in the fact that I believe you mentioned in a previous post that you're using okoume, that's awful soft wood to try standing up to abrasion across, say, a concrete ramp with a fully loaded boat. If you glass it, you'll have the wood providing compression resistance, the glass abrasion resistance and the graphite/epoxy making it slippery so that sharp points won't get an easy purchase.

Good luck,

Laszlo

 

RE: Perfect Laminated Skids

   

RE: Perfect Laminated Skids

   Weird... my post disappeared...

Anyway, I was just saying that after reading your post Laszlo, I panicked and had to go check my manual and skids...

According to the manual, the WIDE (3/4") side of the skid goes against the hull (phew!), and as such the skid rises 1/2" off of it.

Interestingly, although they seem like very good ideas, there's no mention of fibreglassing the skids in the manual and it even remarks that fillets are not necessary.

P

RE: Perfect Laminated Skids

Glad to hear that. Sorry about the panic. That's why I was suggesting that Skully call CLC, there's only so much information you can get from a small picture. Thanks for posting what you found.

The reason that glassing the skids is not in the manual is probably because they are considered sacrificial. I was suggesting the glass because okoume is so much softer than even pine. It might be too sacrificial.

Laszlo

   

RE: Perfect Laminated Skids

Thanks for the sanity check on this, guys.  Ironically, I read Laszlo's original response immediately upon coming into the house AFTER gluing the skids to the hull. 

One thought I had was that once the veneer gets scraped through, the next layer is the boil-proof glue they use to make the marine grade plywood, which is pretty tough.  I've done some informal destructive stress testing on the marine grade plywood and it's much tougher than regular 1/4" plywood.  The five layer lamination is super strong, stiff and heavy as a baseball bat.  The fact that it fits the rocker perfectly, I belive, relieves stress in the final boat.  My EP was under a lot of strain with the forced oak skids.

I will be soaking the skids with CPES, which will penetrate the top veneer and into both sides.  I will also be doing a large fillet on both sides to add stability and to smooth out the "bump".  This will be in addition to a large radius round over around the entire skid.  This will create a shape that will be very easy to add a couple of strips of glass over.

I even had another thought.  I could theoretically route out all the wood once the fillets are in place.  This would then create a negative which I could then fill with more thickened epoxy.  This would make the skids entirely out of epoxy with no actual wood product.  I doubt that I'll do anything that extreme, but I thought it was an interesting concept.

I'll post more pics here in a bit.

RE: Perfect Laminated Skids


« Previous Post     List of Posts     Next Post »


Please login or register to post a reply.


 



Follow us on Instagram: @clcboats & @clcteardrop