Fiberglassing Shearwater 17 Hybrid

Builder's Forum
1

I pride myself in understanding this building process, but this time I am a bit uncertain.  I find that the instructions for glassing the hull exterior of the Shearwater Hybrid are a bit unclear.  I presume that each layer of glass gets wetted out with some curing time between each layer, and that the additional coats of epoxy to fill in the weave come after all three layers of glass are on.  This is not spelled out in the manual and could lead one to trying to wet out three layers of glass all at once - seems like a major mess to me.  What ever the answer, I presume the same will apply to the multible layers on the underside of the deck aft of the cockpit.

Just as a side comment, I found the MC manual to be very detailed and easy to follow.  (Boat Building for dummies - even professional Naval Architect dummies)  In comparison, it seems to me that many details are glossed over in the Shearwater manual and I find my self referring back to the MC book as a refresher.  It's all a bit of a challenge and that's a good thing.

Paul

2

Hi Paul,

I had that same question about 4 months back:) I think the manual is saying to do all three layers at once. And some people indicated they had done it that way. Since I was working by myself, and not in any great hurry, I did the layers one at a time. Especially the first layer that covers the entire hull is a bit of a job to get all that epoxy mixed (will need to be mixed in at least 2 batches or it will get too hot), out of the cup (as fast as possible!) and spread evenly before it starts setting up on you. So if working alone, I'd play it safe and concentrate on that first layer especially, without the added complication of trying to wet out 3 layers and keep everything from sliding around at the same time. If I had helpers mixing and spreading, and was in a hurry for some reason, I might feel more comfortable doing them all at once. And someone with a lot more experience working with epoxy and fiberglass than I might very well have no problem doing it all at one go. But one layer at a time works well and make things a little easier.

 --

Ogata (eric)

3

Are there really three (3) layers of glass (I take it that means glass cloth) on a Shearwater Hybrid?   I intend this to be my next project and have already ordered the plans for preliminary studying and 'thinking-about-it', although for the S&G model, not the Hybrid version.   Surely - unless I misunderstand - three (3) layers of cloth plus all that epoxy would be overkill - plus overweight?   And "multiple layers on the underside of the aft deck"...?   Or am I getting the wrong end of the stick...?

A slightly concerned Lol from Oz

4

lol, the SW uses 4 oz glass, some others use 6.

The 3 layers on the outside of the lower hull you do all at the same time. It turns out to be only 1 on the side, 2 to protect the chine and a 3rd thin just strip for extra keel protection.

The underside of the deck gets only 1 layer and you do not need to fill the weave on this piece.

The place underside the deck right behind the cockpit gets a little beefing up because this flat area is a place where a person can sit on top of the boat at times when getting in or out of the boat.

Then only 1 top layer on the deck and overlapping onto the sides of the boat to strengthen that hull to deck joint.

It may sound like a lot but the 4 ounce glass is very thin. Very easy to work with. the 3 layers on the bottom I did all at the same time and it went very well, no wrinkling or other problems.

http://shearwaterkayak.blogspot.com/

shearwater

5

Fishbuster,

So, forgetting the keel strip for the moment, are you saying that you lay the full layer of glass, then the bottom layer, all dry and then start wetting out or do you wet one layer out and then put the second layer into the goo and keep wetting?  Do you see anything wrong with one layer at a time as described by Ogata above?  I do all of this alone so I need to keep it manageable.

I appreciate all comments.

Paul

6

Wow - it still sounds like a lot of glass and epoxy to me - but thank you all for the clarification!   Why does the Shearwater differ so much from the Chesapeake, I wonder, which has only one (1) layer of cloth on the hull?   I have just completed this step, BTW, on my Ches 17LT, and chose NOT to use the suggested/ recommended method of pouring the epoxy onto the glass cloth draped dry over the hull, then squeege-ing the resin into the weave.   Instead, I applied the resin with a thin disposable foam half-roller, thinly, but not obsessively so, then squeeged off the excess.   I was surpised at how little excess actually came away on the squeege, but it has left a very nice even finish, with just slight weave showing through, ready for the second and final epoxy coat using the same approach (after washing-off carefully to remove the amine blush).   The whole process took a little over one hour until I decided to 'leave well alone' as it seemed fruitless to keep squeege-ing away with no effect!

Looking forward to receiving those Shearwater plans now! 

Lol from Oz

7

Memo to self: 'always engage brain before putting typing fingers into gear!'   In the above post I should have included a prior step, before laying on the glass cloth.   After fairing and sanding the bare hull, I rolled on a coat of epoxy thinned with the addition of about 10% of proprietary thinner/ diluent.   This gave the mix a consistency of water.   This was quickly and easily rolled on, again using a disposable foam half-roller: it very quickly soaked in, and was left to cure.   After a very light sanding - all it needed - the steps above were taken.

Now - what other critical thing(s) did I omit...

Sorry - Lol from Oz

8

Paul, yes I put all 3 pieces on the hull and wet them out all at once. With the hull dry and smooth, the glass slides easily, so I could position each piece exactly where I wanted it. Some people do 1 at a time. It is a matter of preference. You can clearly see 2 layers in the enclosed pic. The 3rd keel strip is maybe only a foot long on both ends of the boat, this is another preference, you can run the entire length if you want, which will depend on a persons intended use. Some people only launch from a boat slip while others do a lot of beaching in the sand and want a better protected keel.

Lol, you have to remember the Chesapeake uses 6 ounce glass and the Shearwater uses only 4 ounce glass, it is much thinner, so we build up only exactly where we need/want the extra protection. This uses less epoxy and saves weight.

hull glass

9

The instructions are for 3 layers of glass but you will find it much easier to lay the smaller pieces down first and let the largest piece hold the 2 layers below.  Professional glassers do it this way so you don't get uneven edges and glass strings everywhere.  To build a light boat always unroll Toilet paper to soak up all the excess epoxy.  You can lighten your boat 3-5 lbs by doing this. 

10

Darryl, I’d be interested to know what you mean by "unroll tp to soak up all the excess epoxy". How the hell do you do that? SEEYA Jack

11

I followed Darryl's suggestion but used paper towels instead of toilet paper and it worked great. Basically, for either, you just lay the paper down onto the fresh layup, let it sit until the wet spots stop growing (10 to 30 seconds) and pull up the paper. Darryll is absolutely right, it sops up all the extra resin that's on top of the glass. It's especially good for interior layers of multi-layer layups. It leaves just enough resin to thoroughly wet the glass, but not enough to add excess weight. It gives a result closely approximating vacuum bagging.

And speaking of weight and vacuum bagging, doing all the layers at once is something best left to those who have vacuum bagging equipment. With that gear, all the extra resin is pulled through and away from the layup. With a hand layup, there's a very good chance of excess resin use. Not only is it likely that you'll end up needing more resin than what came in the kit, but the boat stands a good chance of coming in overweight.

I've layed up three layers of glass at once, but only on small (2x4 ft) flat pieces. It was after I'd been glassing for the better part of 10 years. Everything worked, but I was glad that it was not my first time out. First-timers would do well to stick to the instructions in the manual and do one layer at a time.

Laszlo

 

12

Good to hear this works for some.   A roll of paper towels would work too but I prefer a full roll of TP.  The TP really soaks up the epoxy.  I think Laszlo may have understood what I was trying to say but I will clarify in case.  You are to "unroll" the roll of TP while pressing the roll down firmly.  With TP you can go about 2-3 feet at a time before the 2-3 foot piece of TP starts to soak up too much epoxy and you may not get it off.  Keep a garbage can nearby.  My one & only kayak (Shearwater) came in at 42 lbs using this technique.  (A technique used by R/C modelers & a large aircraft manufacturer here in the NW).

13

Isn't this TP technique the same - basically - as the use of Peel Ply?   I've never had occasion to use it, but believe it works miracles in terms of eradicating excess epoxy and therefore excess weight.   Has anyone used PP on kayaks?

Lol from Oz

14

3 layers of glass plus a coat for sanding will take a certain amount of epoxy whether 1 at a time or all 3 at one time. The epoxy and glass do not know the difference, the first coat is very dry after using the squeegee. A physical height must be achieved. Wetting out glass and then soaking it up on the deck of a hull, only to have to then add more epoxy for sanding doesn't make a whole lot if sense to me. It really isn't 3 sheets either, it is only 2 sheets and it is only 4 ounce, not 6 ounce. The 3rd is just a smappl strip at bow and stern for abrasion protection.

Most often I hear that more epoxy dos not make a stronger boat than less epoxy. This is false. In a shallow river, paddling at full speed, a sharp tree branch will penetrate most places of the hull, less likely at my cockpit that has an extra sheet of glass and epoxy inside. But the bow and stern, with their end pours are virtually indestructible. More epoxy does make for a stronger boat.

The paper towel trick would be GREAT though inside the bottom of the hull, where some epoxy does slide down and accumulate and you can't squeegee too hard, needing to protect the still soft fillets. That definitely would have save me a pound or two, but no loss I suppose when we load the boats up with all of our heavy gear for the day and head for the water with the boat on a dolly. I will try out the paper towel trick on my next build inside the bottom of the hull, an Oxford. Good idea!

15

LOL, It's very similar to using peel ply, except that peel ply is left on until the epoxy cures.

Fishbuster, that depends on the definition of strength that you're using. Normally, when talking about composite layups, strength is taken to mean the resistance to tension, torsion and/or shear. In that case, a 60/40 ratio by weight of epoxy to glass is usually optimum. More epoxy is simply weight that contributes no resistance to those forces.

The reason more is less is because, while epoxy is very strong in adhesion and compression, compared to glass it sucks in tension, torsion and shear. So if you have too much epoxy on the inside, the shear resistant layers of glass are separated by a relatively easy to shear layer of epoxy and the layup becomes more liklely to fail in shear. Same for torsion and tension.

Your cockpit is more puncture-resistant because the glass on the inside and out, in combination with the wood, forms a true composite. The wood resists the compressive force of the branch trying to penetrate it, while the inside glass resists the tensile force of the wood trying to bend inwards. The outer layer of glass doesn't actually do all that much in that case except to resist surface abrasion. So yes, more epoxy is good, but only insofar as it's part of a good layup.

As far as endpours go, they're a tremendously inefficient use of epoxy in terms of strength. Wood actually resists compression much better per unit weight than thickened epoxy does. The great virtue of endpours is that they are easy to fabricate and rotproof.

Finally, 3 optimally wet out layers will indeed take a certain amount of glass, regardless of how the layup was done. The issue is whether the layup technique used promotes excess epoxy between the layers. Epoxy usage is more difficult to control for 2 or more at a time, unless something like vacuum bagging is used. Blotting works best when used while putting down 1 layer at a time for a multi-layer layup. Normally you'd only use it on the interior layers if you're finishing bright, but if you're painting you could also blot the outer layer and fill the weave with lightweight fillers like microballoons.

Hope this clarifies things,

Laszlo