Corecell M for Stitch and Glue

[tunnels]

Originally Posted by Mr Efficiency

What are the implications of having the glassed side of the corecell to the inside of the boat, rather than the opposite way ? Either way, there seems to me to be a likelihood of problems obtaining a fair curvature where foam sheets meet one another. And it needs to be borne in mind that a core glassed on one side only is quite 'floppy' till the other side is laminated, much more so than ply.

Its because of Those very reasons you have discribed you glass one side of the foam only !! Glass has no soft and hard parts it 99% uniform from end to end side to side so you end up with a really nice fair curve in any dirrection .

[michael pierzga]

One of these days I need to get some foam and give it a try. The technique sounds logical.

[Mr Efficiency]

Originally Posted by tunnels

Its because of Those very reasons you have discribed you glass one side of the foam only !! Glass has no soft and hard parts it 99% uniform from end to end side to side so you end up with a really nice fair curve in any dirrection .

Are you talking sheet core, or the 'contour' following little squares with the scrim backing holding them together ? If it is the sheet, how are the joins achieved ? It is not uniform unless they transition smoothly from one sheet to the next.

[Herman]

The scrimmed version (blocks, as in my signature) are not of much use here. These need backing by a mould.

Sheets however bend relatively uniformly. The mating edges can be designed like a wave (sinusoide) to prevent a "hard spot". Amplitude of the wave could be some 10cm (4") and wavelength some 12" (30cm)

Pre-glassed inside or outside: Can be done both, but when the preglassed side is inside, you need some more sanding on the outside. I hate sanding....

[tunnels]

Originally Posted by Mr Efficiency

Are you talking sheet core, or the 'contour' following little squares with the scrim backing holding them together ? If it is the sheet, how are the joins achieved ? It is not uniform unless they transition smoothly from one sheet to the next.

i WOULD NEVER ADVISE ANYONE TO USE CONTOURED FOAM EVEN ON A TOILET SEAT .Use sheet foam with lots a bleed holes (perfirated ) one glass outside and foam inside . Keep the foam back from the edge 50 mm . The key is to make thin patterns and bend it to shape and cut etc etc almost perfect to the inside shape of the mould .Lay it on a bench and masking tape the line round the outside . Use the same thin material to form a recess for the glass joins about 100mm wide and peel ply the whole panel !!,Theres a nice triaxle availible either 400gram or 600 gram glass depending on the size of the panels ,good for the outside skin its fibre oriantation is 90/45/45 good for the bottom of the hull as well as the top sides . Wont interfer with the bending to much but will hold the sheet flater across and straighter than just a plain double bias . Turn the cloth over so the 90 is the outermost layer not against the foam I hear the questions why??? already ,because it will work better holding the panel flat !!Use the same triaxle glass when you glass the joins,!! 90 across the join as well as the 45/45 of the same cloth . so you have all 3 layers of glass holding across the join !!. simple ??

After you have made the sheet dont rip the peel ply off leav it there . The panels can be pressed firmly in to the mould frames and use a hot glue gun to tack them there and hold them in possition nice a fair . All being done nicely and sheets with the same amount of tension there could only be need for a minimal amount of stitching to be done !!,

Hot glue guns are magic for that type of work and we used to use them lots when fitting sheets for Vac bagging sheets of foam into a hull You can pre cut and fit tightly all your sheets !! Use a hole saw and take a plug out of the foam sheet in a couple of places then press the sheet down then hot glue only the plug onto the glass skin count to 100 and when its hard and strong enought to support the weight of a whole sheet on the side of a hull if the hull has a slight curve then use a small strip of ply and gently screw into the plug and use the ply across to hold the sheet perfectly in place then do all your bagging . When its hard and finished take the screw out and the ply and spot fill . simple !!!
,SSSSH dont tell cat builder !! its to simple for him to understand !!!

[Mr Efficiency]

Originally Posted by Herman

The scrimmed version (blocks, as in my signature) are not of much use here. These need backing by a mould.

Sheets however bend relatively uniformly. The mating edges can be designed like a wave (sinusoide) to prevent a "hard spot". Amplitude of the wave could be some 10cm (4") and wavelength some 12" (30cm)

Pre-glassed inside or outside: Can be done both, but when the preglassed side is inside, you need some more sanding on the outside. I hate sanding....

Interesting to hear about the "wave" joins.
Filed in the memory bank if ever I need it.

[Mr Efficiency]

Originally Posted by tunnels

i WOULD NEVER ADVISE ANYONE TO USE CONTOURED FOAM EVEN ON A TOILET SEAT .Use sheet foam with lots a bleed holes (perfirated ) one glass outside and foam inside . Keep the foam back from the edge 50 mm . The key is to make thin patterns and bend it to shape and cut etc etc almost perfect to the inside shape of the mould .Lay it on a bench and masking tape the line round the outside . Use the same thin material to form a recess for the glass joins about 100mm wide and peel ply the whole panel !!,Theres a nice triaxle availible either 400gram or 600 gram glass depending on the size of the panels ,good for the outside skin its fibre oriantation is 90/45/45 good for the bottom of the hull as well as the top sides . Wont interfer with the bending to much but will hold the sheet flater across and straighter than just a plain double bias . Turn the cloth over so the 90 is the outermost layer not against the foam I hear the questions why??? already ,because it will work better holding the panel flat !!Use the same triaxle glass when you glass the joins,!! 90 across the join as well as the 45/45 of the same cloth . so you have all 3 layers of glass holding across the join !!. simple ??

I'm still digesting all that Tunnels, I hope I'm not too long delayed in my understanding, like Captain Scott of the Antarctic " I'm just going outside and may be away for some time"

[CatBuilder]

Ok, I thought we were talking about real curves, like a tight bilge curves and doing that from a pre glassed foam panel that was already cured. That would be a bad idea. The foam snaps in half unless heated if you use corecell. Divinycell, I have found is a bit less brittle.

[tunnels]

Originally Posted by CatBuilder

Ok, I thought we were talking about real curves, like a tight bilge curves and doing that from a pre glassed foam panel that was already cured. That would be a bad idea. The foam snaps in half unless heated if you use corecell. Divinycell, I have found is a bit less brittle.

Its possible to bend 20 mm high density foam around a 80 mm radius cold . Took 10 minutes to get the technique sorted to do the wrap without any hassles . Had 8 boats to do both sides of the hull so had to get it right first off . And we never got any sort of print through to the shiney gel coated finish on the outside . i used to check every boat when it came out of the mould !!. as the glass skins were just 2 layers of cured glass .
i WILL do a sample panel tomorrow with single skin GLASS on the outside and 15 mm thick H80 foam on the inside and see what kind a radius its possible to get without any sort of straining or core damage of foam print through to the glass surface .

[CatBuilder]

Originally Posted by tunnels

Its possible to bend 20 mm high density foam around a 80 mm radius cold . Took 10 minutes to get the technique sorted to do the wrap without any hassles . Had 8 boats to do both sides of the hull so had to get it right first off . And we never got any sort of print through to the shiney gel coated finish on the outside . i used to check every boat when it came out of the mould !!. as the glass skins were just 2 layers of cured glass .
i WILL do a sample panel tomorrow with single skin GLASS on the outside and 15 mm thick H80 foam on the inside and see what kind a radius its possible to get without any sort of straining or core damage of foam print through to the glass surface .

H80? That's not corecell. It doesn't come in that designation. Just by naming the density I know you aren't bending Corecell. Corecell is brittle on tight bends even without glass. Snaps right In half when you stress it up much more than a deck camber level.

[tunnels]

Originally Posted by CatBuilder

H80? That's not corecell. It doesn't come in that designation. Just by naming the density I know you aren't bending Corecell. Corecell is brittle on tight bends even without glass. Snaps right In half when you stress it up much more than a deck camber level.

No we use Divinicell ! worked with it since it came on the dinosaur exspress long time ago could have been 1980s sometime .

[CatBuilder]

That's what I thought, when you said H80.

Now I can understand your bending better.

If you take a sheet of Divinycell and drag your thumb nail through it really hard, it leaves an indent. Corecell? Just barely leaves one.

Corecell, which the OP was looking at using is a bit stiffer and more likely to break in half on tight bends. Now I can understand your bends. I have been using Divinycell for some parts of my boat (hulls are all corecell) and found that the Divinycell bends more easily.

[tunnels]

Originally Posted by CatBuilder

That's what I thought, when you said H80.

Now I can understand your bending better.

If you take a sheet of Divinycell and drag your thumb nail through it really hard, it leaves an indent. Corecell? Just barely leaves one.

Corecell, which the OP was looking at using is a bit stiffer and more likely to break in half on tight bends. Now I can understand your bends. I have been using Divinycell for some parts of my boat (hulls are all corecell) and found that the Divinycell bends more easily.

Good boy !!
Being familiar with the product you use and understanding there limitaions of what you can do and what you cant do and what you shouldnt do is all important . Specially on a site like this . When people read they pick up on little snippets of information that sticks in there minds .This is what its all about is shearing and helping each other .
Have even tryed using two thin layers of foam and bending them but i feel better if it has a layer of glass between the foam as theres always that element of stress there .

[tunnels]

Bending a glass sheet with the thin foam inside the curve and glass outside you are less likely to delaminate the foam off the glass ! .
The thick ness of the foam would naturally be determined by the size and the amount of curve you are trying to work within . For a dinghy size id also look at using Double bias 400 gram with 3 mm Core matt on the inside for stitch and tape . Made a complete new deck for a 20 foot open boat , Just used 450 csm and 5 mm core matt laid in sheets and trimmed to shape over a light plywood frame Then glassed the other side till i got the right amount of glass for the deck that size . If you work carefully and neatly you dont have much grinding of sanding to do .
Stitch and tape method if you use glass roving as used in a chopper gun and a sack needle through the drilled holes then its all glass and easy to work with .
I have along side of me one bundle of strands from a glass cheese roll about a meter long wet out with just good old everyday polyester resin . It has lifted 6 adults so far and showed no signs of breaking .
Am going to try it with load cell scales and the crane in the work shop after the Chinese new year holidays and take it to breaking point just to see what one strand bundle will actually lift .will lash it to the end of a hull mould and slowly lift with the crane and a chainblock with load cell attached . I HAVE THE FEELING THE RESULTS COULD SURPRISE THE LOCALS AND MYSELF !!
Used to make fenders for beach buggies and laid 6 bundles of strand of glass roving lightly twisted all round the edge of the fender . Never ever had one break or crack even when it had been hit quite hard and done other damage . winding glass rovings around a bolt parly buried in glass is pretty strong and if you weld a small strip od steel across the head of the bolt the you have tons of strength and will hold really well .

[rberrey]

I think the poster may be refering to the ST21 sticth and glue plan on the Bateau web site. You might look at the plans and offer advice based on those plans alone. I dont see how he can build with standard sticth and glue methods. To gain the desired weight savings with foam on a boat that size I think he should go the Catbuilder route and infuse. In the over all cost factor of the build he would be closer to getting the weight savings by ponying up the pennies and buying carbon and kevlar. Rick