Building a single scull

[singlescull]

yea i can buy a boat for 10k. i dont mind if the boat comes out 18kg or so. there is a 25 year old german boat at our rowing club and that is about 16kg.
do you think 2mm coremat is a good idea they say it uses around 1kg of resin per m2 so it would be stronger than foam but much heaver?

[Guest625101138]

Originally Posted by singlescull

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do you think 2mm coremat is a good idea they say it uses around 1kg of resin per m2 so it would be stronger than foam but much heaver?

I have not used it but anything that gets thickness for less weight than glass is suitable for a spacer providing it has some shear strength.

One issue with any core is ensuring it conforms nicely to the shape. The 3mm Klegecell can be heat formed but it cannot conform to a compound curve. It has to be cut into pieces. I do not know how well coremat will conform to curves.

Rick W

[singlescull]

yea apparently this stuff is real easy to form once wetted out. I can get it for $11 m2.

[Guest625101138]

With any layup that you have not used before it is worth the effort of doing a test. Make measurement of the amount of resin used in the test so you can mix the right quantity for the full mould.

Also allow to cure properly. A couple of days in the sun is good. The epoxies I have used all get some level of amine blush - it will be an issue for fitting bulkheads so needs to be cleaned off before epoxying bulkheads. Unless you know about amine blush you think there is a problem with the curing. The degree of oiliness increases with the humidity.

In fact I use 25mm thick blue foam for bulkheads and glue in place with a water curing polyurethane glue. It gives slight expansion as well. However the blush still has to be cleaned off.

After the test piece has cured load it to measure the stiffness and then take it to destruction to see what fails and where. Also check for any voids. You can bet with a curved mould you will get more voids in the full hull than a test piece so it gives an idea of how well you need to set up for vacuum bagging.

Rick W

[Guest625101138]

The most important aspect for the test piece of course is the weight so you can do a better estimate of the the final hull weight. However it is easy to underestimate all the little things that go into a working boat like a bit of reinforcing here and there; a mounting point or two, a little rudder tube and so on. All adds up.

Rick W

[Herman]

Working clean helps in that respect. (keeping weight down)

About amine blush: 10:1 water : ammonia solution works very well to remove it.

Make some test panels. One thing not to worry about: The coremat will conform to your shape with ease.
The 1000 gr/m2 might be a bit optimistic for the coremat. Do a panel with 3mm PVC foam as well, to see what the differences are.

[singlescull]

i have been looking at cores and now think foam is proberly a better idea.
is it possible to have a core too thick?
i have found a quite lightweight 10mm polyurathane foam

[singlescull]

after some research i found that polyurethane degrades over time so scrap that. i finaly found a new zealand supplier of 8mm honeycomb and am waiting for a quote. hopefully it wont cost an arm and leg.

[Herman]

I hope so, it is quite expensive, and it has a learning curve, so produce and destroy some samples first. Luckily a scull does not eat up that much honeycomb.

PU foam is crap. Good for insulation though, so it has a use in boating: For DIY refrigerators only...

[singlescull]

yea 4m2 will easly do it. it will only need one join in the middle. i hope it is quite easy to work with bending into curvs and such.

So Rick, You get these flat bottom things on plane? Could a strong rower maintain plane through the glide?

Coremat XI is about 12€, Aramid paper honeycomb 1,5mm is about 26€ m² in W.Europe.

Richard

[Guest625101138]

Originally Posted by mark775

So Rick, You get these flat bottom things on plane? Could a strong rower maintain plane through the glide?

Mark
I can get mine to lift as opposed to sinking that you see with typical low rocker rounded hull. They are not on the plane but are starting to lift. I think a strong cyclist might get enough lift to say they are planing. This would be in sprinting at about 1000W.

With rowing the drive is too variable to maintain the steady lift. In rowing they would rise and fall at very high power stroking but typically a strong rower only maintains about 500W so there would not be a lot of lift. However it would lift and would be better than sinking.

Rick