do I need to "fill the weave" in fiberglass cloth?

[RichKrough]

On the Kayak I am building, I am trying to keep the weight down where possible.
In the cockpit area I am going to put 4oz Eglass cloth on the floor to both protect the hull from sandy shoes and for a little extra stiffness in the bottom. After wetting out the cloth and letting it harden do I have to put on another coat of epoxy or can I just leave the texture?

[Steve Miller]

You could do either really. Try a little test in an area like under where your seat will be to see if another coat fills it in too much to retain the less slippery texture you want. If you decide to do another coat a roller will do it thinly and maintain most of the texture.

[ssor]

If you have coated the wood beneath the glass then the water won't go through. The primary reason for filling the weave is ease of cleaning.

[Steve Lansdowne]

Normally one fills the weave on the bottom (facing the water) to give a smooth surface on the exterior, but often the glass on the interior of the boat is left with some weave showing so the interior is not too slippery when wet.

[JimConlin]

It makes no difference structurally.
One guy's non-skid surface is another's 'hard-to-clean'.

[George Roberts]

RichKrough ---

Is this a plywood or strip kayak?

For a plywood kayak it does not matter.

For a strip kayak I would think it might.

[Cuyahoga Chuck]

In terms of strength a sq. yd. of 6 oz. 'glass that is wetted with 6 oz. of epoxy gives max strength if the 'glass is tight against the wood. You will see the weave with this layup.
Anything beyond that is cosmetic. Filling the weave is necessary on the outside to present a smooth surface to the water.
If you don't care about weight you can pile on as much epoxy as you like. But epoxy is the single heaviest material you are dealing with.
Charlie

[RichKrough]

thanks for the replies. It is a plywood kayak . The first kayak I made a few weeks ago.I made with 5mm luan and polyester resin. I slathered over 2 gallons of resin over 6oz cloth inside and out. It made it smooth and pretty but it also weughs close to 60lbs. This one is for SWMBO and I want to get it under 50#. I used 3mm ply for the sides and top. I am making the outside of the hull smooth but inside I just want to use enough to hold it together .

[Cuyahoga Chuck]

Now that you have your feet wet, consider this.
You could have built this hull out of 4mm BS1088 okoume, a gallon and a half of epoxy and only enough 'glass to cover the seams and the bottom and had a boat that would be 15-20 lb. lighter.
Plenty of 16-17 foot designs come in at 40-45 lbs. But they have to be built with high quality plywood.
Quality 4mm ply doesn't need 'glass sheathing at all. Most builders sheath the bottom to ward off gouging.
You are fighting the weight battle from the wrong end. You're cheating on the wood and compensating with a lot of 'glass and resin. Resin is the heaviest component, wood is the lightest.
I hope you can wean yourself off of polyester resin. In boatbuilding it left the scene about the same time as disco dancing. Epoxy cost a lot more but it is far superior.
Charlie

[George Roberts]

Cuyahoga Chuck ---

(I have been in my shop sweating all day long. I am not a happy camper. I try hard to not correct people up here but ...)

By your number I see you are a recent arrival.

I usually let people use the resin of their choice. Unless they are building 20-25# 17' kayaks it does not matter.

You mentioned:

"In terms of strength a sq. yd. of 6 oz. 'glass that is wetted with 6 oz. of epoxy gives max strength if the 'glass is tight against the wood. You will see the weave with this layup."

There is a great deal misleading and/or wrong about those statements. Both in general and how it relates to plywood boats.

[George Jung]

I built a S&G from CLC; they recommend a second coat on the interior to fill any 'pinholes' that might allow entry of water, and the subsequent 'black ick'. That said, less is more; if you run this question past the forum at CLC, or kayakforum, suspect you'll hear the same. One fellow does a second coat 'rubdown' to fill said pinholes; avoid the endpours (wasted weight). My boat weighs about 45#; it has been built by those in the know at less than 40#, just as strong structurally.

[Nick C]

I'd guess your kayak will actually be faster with the weave not filled. It is actually a good thing to have a surface that createds little air bubbles around the hull. This seperates the water flow from the kayak. Too smooth of a flow of water actually makes the hull sticky in terms of flow.

You will really notice the difference if you race someone in a similar kayak for 50 miles. You will have a half mile advantage!

[Richard Smith]

Well . . . kinda

See:

Golf Ball

Submarine

[ 08-29-2005, 12:55 AM: Message edited by: Richard Smith ]

[RichKrough]

I used okoume this time except for the bulkheads. that alone should save about 10 lbs. Polyester weighs 11% more than epoxy .It will add maybe a pound. not enough benefit for me to break into the stash of epoxy I have squirreled away for the Hartley 16 project
I only did an end pour this time on the stern to give some solid support for a rudder, I mixed a smaller amount of resin with saw dust to make it lighter.

[ 08-29-2005, 11:59 AM: Message edited by: RichKrough ]

[Nick C]

Great sites on the golf ball and submarine. Although, the submarine site didn't really get into details that well.

I hadn't heard of the Reynolds # before, but it looks like if I stamp the right size hexigons in my hull I can reduce the drag from my flat transom.

[George Jung]

I'd love to hear from some of our engineer friends on this one, esp. those in boat design (Wild Wassa out there?). I don't believe the statement :

I'd guess your kayak will actually be faster with the weave not filled. It is actually a good thing to have a surface that createds little air bubbles around the hull. This seperates the water flow from the kayak. Too smooth of a flow of water actually makes the hull sticky in terms of flow.

You will really notice the difference if you race someone in a similar kayak for 50 miles. You will have a half mile advantage!
--------------------------------------------------------------------------------

is correct. Too much effort has been made by those in the know, achieving a very smooth surface, for me to believe otherwise. But I'm willing to stand corrected.

[Cuyahoga Chuck]

All anyone has to do is get a look at a high peformance paddle boat. Something like an Olympic class flatwater canoe or kayak. If "bubbles" or frog skin or anything else will make a boat go faster than these boats will have it.
Charlie

[George Roberts]

George Jung ---

Racing has rules that corrupt the design process. So don't look there for an answer.

Looking for a better design is more fruitful than trying to change the surface texture.

[jzeigler]

I think it was America3 that had the longitudinally grooved vinyl below the waterline. Before that, they "roughed" the surface with 220 wet or dry sandpaper.
If you sand out the "waffle" you have lost some of the intended strength of the cloth though.