different core types (foam pvc, divinicell vs balsa)

[44'cruisingcat]

Originally Posted by fastcat435

When Balsa is infused the resin absorbtion is almost triple as much as with closed cell foam so unless somebody wants to produce a very heavy boat it is a no go item
With the exact same laminate of 1200 grams glass 20 mm foam or balsa 300 glass and 400 kevlar the weight for the foam laminate came out at 5.9 kilo per squire meter and the balsa version at 10.2 kilo or a added weight for our FastCat 455 of 1660 kilo.
A bit much for our taste.

Greetings

The idea is to use a pre-coated balsa which won't absorb anywhere near that much resin. Also because balsa has superior engineering properties to foam, as well as better impact resistance, you can use less of it, and lighter glass laminates, to achieve the same result.

As Nordic cat has said, ATL make balsa cored panels with very high glass/resin ratios which are very light. ATL have also done resin infusion tests using balsa cores and have found resin absorbtion not to be an issue.

[fastcat435]

Originally Posted by Nordic cat

I find these figures for Balsa a bit high to say the least.

Take a look at the specifications below for composite panels from ATL.

25 mm of 80 kg/m3 foam with 600 g/m2 each side and 66% fibre weighs 4.0 kg/m2.

19 mm balsa of 150 kg/m3 (the heavy stuff) with the same fibres weighs in at 6.0 kg/m3. This is also much stronger than the 25 mm foam composite, that is why I chose a thinner balsa than the foam.

Using the better Balsa of say 120 kg/m3 would get the weight difference down to around 35% heavier.

Your statement says around 100% heavier.

Your figures for foam seem right, so what did you do with the balsa layup?

There are lots of nice lightweight cats in Balsa core, see the Barocka thread

Regards

Alan

Hallo Alan

with infusing straight panels for bulkheads using 20 mm divinycell foam and 800 grams of biax glass each side we come to a total weight of 4.8 kilo the foam has a weight of 1.6 kilo per m2
doing the same exercise with balsa , the balsa weights 2.4 kilo per squire meter so one wouls say with the same infusion the total weight would be 5.4 kilo but the resin consumption is actually 900 grams higher so the total weight came out at 6.3 kilo
With a straight sheet of divinycell we infuse 700 gram just for the foam and with balsa it is 1600 gram so it is actually more than double the resin used for the core.
The balsa we used has the same infusion grad as the foam used so the difference is not in there
Greetings
|Gideon

[Whimsical]

Originally Posted by fastcat435

When Balsa is infused the resin absorbtion is almost triple as much as with closed cell foam so unless somebody wants to produce a very heavy boat it is a no go item
With the exact same laminate of 1200 grams glass 20 mm foam or balsa 300 glass and 400 kevlar the weight for the foam laminate came out at 5.9 kilo per squire meter and the balsa version at 10.2 kilo or a added weight for our FastCat 455 of 1660 kilo.
A bit much for our taste.

Greetings

Giden I am getting a little confused.
The difference here is 4.3kg per meter

[quote= fastcat435]
with infusing straight panels for bulkheads using 20 mm divinycell foam and 800 grams of biax glass each side we come to a total weight of 4.8 kilo the foam has a weight of 1.6 kilo per m2
doing the same exercise with balsa , the balsa weights 2.4 kilo per squire meter so one wouls say with the same infusion the total weight would be 5.4 kilo but the resin consumption is actually 900 grams higher so the total weight came out at 6.3 kilo
With a straight sheet of divinycell we infuse 700 gram just for the foam and with balsa it is 1600 gram so it is actually more than double the resin used for the core.
The balsa we used has the same infusion grad as the foam used so the difference is not in there
[\quote]

But here the difference is only 1.3kg per meter. The difference doesnt depend on the skins as there the same in each comparison.
I think to be totally fair the two samples need to take into account the different strength of the complete panel, thus the balsa would be thinner and have less laminate applied. Then a wieght comparrison is valid.
As to the greater resin adsorbtion, did the balsa have grooves and holes drilled as per the foam you use. Without sealing this may be where the excess resin is getting into the core.

Mike

[fastcat435]

[quote=Whimsical;178933]Giden I am getting a little confused.
The difference here is 4.3kg per meter

Originally Posted by fastcat435

with infusing straight panels for bulkheads using 20 mm divinycell foam and 800 grams of biax glass each side we come to a total weight of 4.8 kilo the foam has a weight of 1.6 kilo per m2
doing the same exercise with balsa , the balsa weights 2.4 kilo per squire meter so one wouls say with the same infusion the total weight would be 5.4 kilo but the resin consumption is actually 900 grams higher so the total weight came out at 6.3 kilo
With a straight sheet of divinycell we infuse 700 gram just for the foam and with balsa it is 1600 gram so it is actually more than double the resin used for the core.
The balsa we used has the same infusion grad as the foam used so the difference is not in there
[\quote]

But here the difference is only 1.3kg per meter. The difference doesnt depend on the skins as there the same in each comparison.
I think to be totally fair the two samples need to take into account the different strength of the complete panel, thus the balsa would be thinner and have less laminate applied. Then a weight comparison is valid.
As to the greater resin adsorption, did the balsa have grooves and holes drilled as per the foam you use. Without sealing this may be where the excess resin is getting into the core.

Mike

You should get confused so did I , the total difference is the 600 grams added for the balsa and the 900 grams added resin for the infusion of the balsa or a total of 1.5 kilo per squire meter and not 4.3 kilo per meter.
That is what you get after trying to answer a mail after a flight of 18 hours from Amsterdam to Durban
The basalt we used was grooved and perforated the same as the foam and it is not possible to get this presealed since the Little holes clog up.
Using presealed balsa ads about 150 grams per squire meter for the sealant but these are
sc ( scrim blocks and that ads about 1.5 kilo,s of resin per squire meter extra.
I think the use of balsa is fine as long as it is not infused since that creates a high resin absorption.

Greetings

Gideon

[Whimsical]

[quote=fastcat435;178953]

Originally Posted by Whimsical

The basalt we used was grooved and perforated the same as the foam and it is not possible to get this presealed since the Little holes clog up.
Using presealed balsa ads about 150 grams per squire meter for the sealant but these are
sc ( scrim blocks and that ads about 1.5 kilo,s of resin per squire meter extra.
I think the use of balsa is fine as long as it is not infused since that creates a high resin absorption.

Greetings

Gideon

I presume you meant balsa not basalt
I think the balsa would need sealing before adding the grooves and holes. I can see why there would be a great increase if you used blocks on a scrim in curved areas with infusion.

I am not very keen on balsa unless it is used as a premade sheet such as Duracore, Duflex or infused. I don't like the idea of bedding it to the inside of a mould, to much room for waterways. I do think it has better properties in many ways and if finished panels of like strength and stiffness are compared it will probably be lighter.

Mike

[fastcat435]

[quote=Whimsical;178969]

Originally Posted by fastcat435

I presume you meant balsa not basalt
I think the balsa would need sealing before adding the grooves and holes. I can see why there would be a great increase if you used blocks on a scrim in curved areas with infusion.

I am not very keen on balsa unless it is used as a premade sheet such as Duracore, Duflex or infused. I don't like the idea of bedding it to the inside of a mould, to much room for waterways. I do think it has better properties in many ways and if finished panels of like strength and stiffness are compared it will probably be lighter.

Mike

Yes Off course it is Balsa, we have chosen to go all the way with Foam core for many reasons
1.weight on the material and the higher resin absorption
2.No rot possible with foam
3.Better acceptance in Europe , customers do not like to have balsa core
4.Foam can be preformed with heat to shape better
The cost is higher for foam but that is no problem for us.

Greetings

Gideon

[Zach]

This thread has been a great read. Thanks everybody that has contributed...

I had been leaning toward foam, and now I don't know any more.

[BigCat]

Unfortunately for the South African / Dutch boat builder who often criticizes technology that his competitors use that he doesn't, I found the links below in less than 5 minutes, by googling: europe balsa core boat . One may note that many of these boats below, including some very large, very expensive boats use the balsa / vinylester combination which the aforementioned boat builder criticizes. He doesn't criticize his competitors boats, he just criticizes what they are made of. That isn't the same thing at all. Or is it?

European Boatbuilder

Europe's Infusion Pioneer Simplifies Process With Bottom Up Approach: COMPOSITESWORLD.COM

Sailing Magazine : Boat Test

JEurope, JBoats History

http://www.multihullworld.co.uk/PDF%...0BROADBLUE.pdf

CNB 104 German Frers Sloop - Racing Boat Sailing Racer Sailboat Sloop Super Yacht - Boats for Sale

Lagoon 380 – Boat Reviews, Tests & News - BoatPoint Australia

Open 50 Designer's Comments

[fastcat435]

Originally Posted by BigCat

Unfortunately for the South African / Dutch boat builder who often criticizes technology that his competitors use that he doesn't, I found the links below in less than 5 minutes, by googling: europe balsa core boat . One may note that many of these boats below, including some very large, very expensive boats use the balsa / vinylester combination which the aforementioned boat builder criticizes. He doesn't criticize his competitors boats, he just criticizes what they are made of. That isn't the same thing at all. Or is it?

European Boatbuilder

Europe's Infusion Pioneer Simplifies Process With Bottom Up Approach: COMPOSITESWORLD.COM

Sailing Magazine : Boat Test

JEurope, JBoats History

http://www.multihullworld.co.uk/PDF%...0BROADBLUE.pdf

CNB 104 German Frers Sloop - Racing Boat Sailing Racer Sailboat Sloop Super Yacht - Boats for Sale

Lagoon 380 – Boat Reviews, Tests & News - BoatPoint Australia

Open 50 Designer's Comments

I do not criticise other boat builders or other manufacturing techniques , I just have my preferences as you have yours, Maybe if I was building a big cat like you I might also choose for Balsa and Maybe even vinylester becasue of the cost issues of Foam and Epoxy.
When your cat is ready I would love to be invited to sail with you

Greetings

Gideon

[Pblais]

He doesn't criticize his competitors boats, he just criticizes what they are made of. That isn't the same thing at all. Or is it?

It's not the same thing but making criticisms of people is. It's not anything that adds to the discussion. Most people recognize name calling for what it is and don't need it explained. The protracted debate about it furthers none of either of your objectives and has grown tiresome. Putting personal differences aside is the action we all would applaud. The spirit of cooperation could be a moving experience for us all.

If that becomes intolerable you also have a second option. Go to member profile and find user names of those members you can not read without great pain to your personal "ignore list" located to the right of Add to your buddy list. Then poof! Your view of all their postings will be cleared in all parts of the system. They will no longer exist in the alternate universe. This is the one feature members have that the staff do not have.

Settling differences or ignoring each other totally are very acceptable solutions with the same positive result desired. At this point you both have the oppertunity to make your own choices. Getting on with it is the point.

[neelie]

I for one really appreciate the debate.

I also really appreciate Gideons opinions - he does usually back these up with documented outcomes from his factory. That he is a commercial vendor and has his own interests at heart is irrelevant as long as he is factual - which to date he has been.

Equally I also value dissenting arguments from Big Cat, he too has a lot to offer.

Material choice like design choices are always a compromise - as the rest of us scramble in search for the Prophet of Cores - to tell us what the truth path really is.

[BigCat]

I think foam and epoxy have their virtues, but I strongly disagree about the alleged flaws of the alternatives, vinylester and balsa. Balsa and fire retardant vinylester are just as strong, pound for pound, as epoxy and foam, and far, far safer from a fire standpoint. Foam is much more flammible than balsa, and unlike balsa, it produces toxic fumes when burnt. Foam, in the weight usually used is in fact not as strong as balsa, and the epoxies usually used in boat building are, in fact, not quite as strong as the vinylesters in actual use by boat builders. Claims to the contrary might have the unfortunate effect of making people reluctant to invest in these materials, when in fact they are very often used in, for example, Europe. It would be unfortunate if slanders made some people choose an expensive, and from a fire standpoint, dangerous, combination of alternatives. Contrary to what has been implied in this BBS, vinylester never blisters, and is in daily use by scores, perhaps hundreds, of boat builders and boat repairers for just that reason. Rot cannot spread in balsa if it isn't delaminated, and if it is delaminated, you have worse problems than rot. Balsa does not soak up resin if it is precoated by the companies offering balsa, and this precoating is readily available and inexpensive. When claims to the contrary are made by those in a position to know better, I have to ask myself why they would say things that they surely know aren't true. It is not having a different preference that concerns me, it is systematic misrepresentation of the alternatives that gives me pause. In the construction and equipping of commercial vessels, far more attention is paid to fire prevention and control than it is in yachts. Fire is responsible, dollar for dollar, for about 1/3 of vessel damage and losses.

See: http://www.uscgboating.org/statistic...stics_2004.pdf