Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 14-04-2008, 08:29   #61
jzk
Registered User

Join Date: Jun 2006
Posts: 639
Why would I consider a balsa core? Because the two boats I like, the Gulfstar 60 and the Leopard 47 each have balsa cores.
__________________

__________________
jzk is offline   Reply With Quote
Old 14-04-2008, 19:22   #62
cruiser
 
BigCat's Avatar

Join Date: May 2007
Location: Everett, Washington
Posts: 765
Balsa in a new boat

Quote:
Originally Posted by jzk View Post
Why would I consider a balsa core? Because the two boats I like, the Gulfstar 60 and the Leopard 47 each have balsa cores.
I am knowingly putting balsa in a brand new boat, everywhere except below the DWL. It is just as strong as the strongest foam, (which is SAN) weight per weight of the finished laminate. See the composites thread for supporting evidence. Infused balsa core has resin between the squares, especially if it is infused flat and horizontal on a laminating table, so the idea of any water in the core spreading far is very unlikely, IMHO. And since I am building my own boat, I know the bolts will all be placed in either solid laminate (which mine is near the deck edges on deck) or in putty plugs made by reaming out a bit of core. The balsa costs 1/2 as much as a good foam, and won't soak up resin because I am using pre-coated.
__________________

__________________
BigCat is offline   Reply With Quote
Old 18-04-2008, 15:37   #63
Registered User
 
cat man do's Avatar

Join Date: Aug 2006
Location: Brisbane Australia [until the boats launched]
Boat: 50ft powercat, light,long and low powered
Posts: 4,409
Images: 36
Quote:
Infused balsa core has resin between the squares, especially if it is infused flat and horizontal on a laminating table, so the idea of any water in the core spreading far is very unlikely, IMHO

If you are infusing it flat, why use contour balsa?

All you are doing is adding weight and wasting resin.

Dave
__________________
"Money can't buy you happiness but it can buy you a yacht large enough to pull up right alongside it"...............David Lee Roth
Long Distance Motorboat Cruising It Is Possible on a Small Budget
cat man do is offline   Reply With Quote
Old 18-04-2008, 16:14   #64
cruiser
 
BigCat's Avatar

Join Date: May 2007
Location: Everett, Washington
Posts: 765
Unh, so you can have resin between the squares and prevent any water that gets to the core from spreading? So you can have end grain balsa? (I don't know if end grain balsa comes in a laminated product, but haven't heard of one.) So it will infuse better?

Also, I want perforated, grooved, pre-coated balsa. I'd be surprised if that were available in anything but contour.
__________________
BigCat is offline   Reply With Quote
Old 18-04-2008, 18:51   #65
Registered User
 
mark_morwood's Avatar

Join Date: Jan 2007
Location: Cruising (Atlantic -> Med -> Carib -> Pacific)
Boat: Vancouver 36, Hobie 33, Catana 48, now all with new owners
Posts: 206
End-grain balsa comes in flat sheets or scored sheets from both Baltek and NidaCore. Both have pre-coated as an option. I don't believe there is any advantage to using scored balsa for a flat panel.

http://files.alcancomposites.com/dow...data_sheet.pdf
http://www.nida-core.com/pdfs/pds/ni..._balsalite.pdf

I had this info to hand as I'm currently building a hard bimini for my catamaran, which does need the scored stuff as it has a curve to it.

Mark.
__________________
mark_morwood is offline   Reply With Quote
Old 18-04-2008, 19:19   #66
Registered User

Join Date: Dec 2007
Posts: 340
confused? infused?

Quote:
Originally Posted by cat man do View Post
If you are infusing it flat, why use contour balsa?

All you are doing is adding weight and wasting resin.

Dave

To infuse both the outer and inner skins and bond the core in the same process it is necessary for the resin to pass through the core some how. This can be achieved by punching closely spaced holes through solid sheets or using contour foam. We have had the least grief using contour foam, but it is necessary to fold all the sheets in both directions first to make sure all the cuts go right through the sheets. If not dry spots will result. Even with 25mil squares the resin only just reaches the centre of each square.
__________________
cat skin hat
catty is offline   Reply With Quote
Old 18-04-2008, 19:55   #67
cruiser
 
BigCat's Avatar

Join Date: May 2007
Location: Everett, Washington
Posts: 765
Grooved, perfed, contoured balsa?

Hi, Mark

My goal is to start with a dry layup of glass / core / glass, and infuse it all at once on a melamine surfaced laminating table. The resin has to pass through the core for that, as Catty describes. For this to work, you need holes every two or 3 inches right through the core, and grooves on both sides about 1/8" deep and wide connecting the holes-aka perfed and grooved.

So, I wonder if that product is available in balsa that isn't contour through cut. There are two potential benefits to what is admittedly a heavier laminate through using contour balsa on a flat laminate, and that is that it provides isolated core cells so that any water can't travel, and it makes the panels stronger. I posted a link to a study of various panels on the 'composites' thread on this BBS that makes the 'stronger' claim.
__________________
BigCat is offline   Reply With Quote
Old 18-04-2008, 21:10   #68
Registered User
 
mark_morwood's Avatar

Join Date: Jan 2007
Location: Cruising (Atlantic -> Med -> Carib -> Pacific)
Boat: Vancouver 36, Hobie 33, Catana 48, now all with new owners
Posts: 206
Sorry, I don't know the answer on the perforated stuff. I'm simply vacuum bagging, not resin infusing.

Mark.
__________________
mark_morwood is offline   Reply With Quote
Old 18-04-2008, 22:05   #69
Registered User

Join Date: Dec 2007
Posts: 340
infused??

Big Cat, I hear what your saying and wonder weather infusion is the go for flat panels. Potentially a lot of room for expensive stuff ups, for practically very little gain ( theoretically big gain ). If youve done it before, well no worries, you no what to expect . Gee laying up panels hands down on a flat table is pretty easy without trying to complicate it too much, with infusion. Just my opinion. Have you worked out the volume of resin contained in your 1/8" x 1/8" grooves compared to plain contour product?


Found this on proa forum............

Hello,
There is no reason to use epoxy ! Vinyl ester resin can be used and is comparable to epoxy in the overall composite laminate. Derek has talked about this many times and the subject has been discuss on the KSS forum.

http://groups.yahoo.com/group/KSSBoat/

Yesterday on the ProBoat virtual trade show and conference, the subject of using vinyl ester resin instead of epoxy was discussed and even for such items as a carbon fiber mast. Rob Schofield (Naval Architect) gave a talk on "Determining Laminate Properties", he also echoed Derek 's opinion that vinyl ester resin was structurally as good as epoxy for boat construction. As he explained it most of the strength comes from the fiber reinforcement and if you compare the strength of the resin to the fiber reinforcement you will see that the difference of the epoxy is insignificant. The resin is only used to hold the fibers together. I believe the presentation will be available on the ProBoat web sight for a month or two.



George Kuck
Chestertown, MD

PS; When you add in the adverse health effects of working with epoxy I do not think there is any reason to consider it.
__________________
cat skin hat
catty is offline   Reply With Quote
Old 19-04-2008, 00:58   #70
cruiser
 
BigCat's Avatar

Join Date: May 2007
Location: Everett, Washington
Posts: 765
Resin infusion on a flat table, carbon fiber masts with VE

Hi, Catty

It would take a lot of guys to vacuum bag a panel 65' x 7' without RI. With RI you can lay everything out at your leisure, test your vacuum for as long as you like, and open the valves and watch it flow. If you want to speed things up you just raise the bucket. I'm going to use a squeal detector to find small leaks.

I have my resin infusion links online at a Yahoo group at:
Yahoo! Groups

This is Derek Kelsall's preferred method now, and I have seen lots of videos and photo essays of this. I haven't done it, but I'll start with a hatch, then a bulkhead, and do big panels like topsides and decks later. No moving on to larger panels 'til I get the smaller ones worked out with no problems.

You can see a long photo essay of a Kelsall workshop here:

KSS Workshop Colorado 2006

I already have the engineering on my unstayed masts-each mast holds 1200 sq. ft. of sail, is 17" in diameter at the base, and 8.5" at the mast head, with a wall thickness of .55". The layup is vinylester / carbon fiber uni, with some +45-45 glass against wringing strains. The USCG has accepted the engineering. The masts are 70' long, with 7' below deck to hold them up. The current cost of the carbon fiber for two of these masts is @ $30,000 (not each, between them.)
__________________
BigCat is offline   Reply With Quote
Old 19-04-2008, 01:12   #71
cruiser
 
BigCat's Avatar

Join Date: May 2007
Location: Everett, Washington
Posts: 765
RI adds how much weight?

There are, if my estimate is correct, about 3.2 cubic inches of resin per square foot in the chanels and perforations. I used these figures: Each channel is about a half of 1/8" diameter circle, and placement is every 2.5" Each hole is about 1/4" in diameter. Resin is something like 72 pounds per cubic foot. Divide by 1728 for cubic inches per cubic foot, and you get .042 pounds per cubic foot. Multiply this by, say 5000 square feet, and resin infusion is adding 208 pounds for a 65' boat 35.5' wide. I can live with that. This is in addition to whatever seeps through the slits between the chunks of balsa, but it is clearly the only extra penalty for RI.
__________________
BigCat is offline   Reply With Quote
Old 19-04-2008, 01:49   #72
Registered User

Join Date: Dec 2007
Posts: 340
It sounds so easy

Sounds like you've given it a great deal of thought Big Cat. It will be interesting to hear how you go. Can you keep us posted on the final laminate weight. Maybe weigh an off-cut and extrapolate. It will be interesting to see what resin / fibre /core ratio you actually achieve. If you can grab yourself a vacuum gauge so you can pierce the bag and actually measure it on the panel itself ( an upside down cup with gauge mounted through the base arrangement). Once the resin has wet out you'll be surprised at how hard it is to actually achieve good vacuum on the job.

"It would take a lot of guys to vacuum bag a panel 65' x 7' without RI"

There's no need to do the whole lot in one go. The most benefit from the bag will be sticking the foam down which can be completed in a few goes.

Good luck.
__________________
cat skin hat
catty is offline   Reply With Quote
Old 19-04-2008, 12:15   #73
cruiser
 
BigCat's Avatar

Join Date: May 2007
Location: Everett, Washington
Posts: 765
Vacuum / RI issues

Hi, Catty

I would think that you would have to have your core attached by a secondary bond if you didn't do it all at once. I would also think vacuum problems would be due to vacuum source insufficient, not enough vacuum tubes, or leaks. I am choosing my equipment by making an estimate of the area to be vacuumed and choosing vacuum pump equipment that can empty it in less than 1/2 an hour.
__________________
BigCat is offline   Reply With Quote
Old 19-04-2008, 17:46   #74
Registered User

Join Date: Dec 2007
Posts: 340
Sounds good Big Cat . The smaller panels and bulkheads will give you lots of chances to experiment. If you do get a chance, it certainly is worth comparing the vacuum reading at the pump to that on the actual wet out job. A bit of bagging tape around the bottom of the cup will provide a good seal for this gauge.

Regards
__________________
cat skin hat
catty is offline   Reply With Quote
Old 20-04-2008, 14:34   #75
Senior Cruiser

Cruisers Forum Supporter

Join Date: Feb 2008
Location: Eastern Seaboard
Boat: Searunner 34 and Searunner Constant Camber 44
Posts: 949
Quote:
Originally Posted by BigCat View Post
"An epoxy, rather than a polyester or vinylester, hull is technically more moisture resistant when correctly applied." Nope, all the cool kids are using vinylester these days. It's used as a water barrier layer by a lot of manufacturers who use poly for the layup. Vinylester is just as strong and elastic as epoxy--as I demonstrated once I finally got Gideon to post the properties of the epoxy used on African Cats...
This has been good thread BigCat (et al), I’ve really enjoyed it.

But I have a few questions and a couple of comments

The questions--

BigCat:
Quote:
If I were making a cold molded boat, or a cedar core boat, I'd use epoxy, but balsa doesn't need epoxy.
Why do make the exception for epoxy for for these two cases?

Gideon:
Quote:
Most fiber is basalt and carbon and on the inner hull we use twaron/kevlar for impacrt resistancy
Could you go into the properties of basalt, I’m not very familiar with it.

The comment:

Several years back at university, I was speaking with a materials science PhD candidate. He was working in steel. I am somewhat familiar with the crystalline structures steel from like ferrite and cementite so we spoke for while on his area. Later I asked him about alloys of steel. What he said surprised me: we don’t know that much about alloys of steel and, fact we don’t understand everything about plain steel (as in iron and carbon). You would think this wouldn’t be the case since we have been working with it for a long time and know adding chromium helps with rust and staining. So that high-carbon chromium molybdenum vanadium steel is basically a decent guess, based on some generalized principles but is less than fully understood ... even less so for all temperatures and quenches.

This from a material we have been studying for 250 or so years.

I suppose by now you see my skeptism in the “which is better debate”. But I do find the accumulation of knowledge part is not only interesting but useful as it gives a good sketch and illustrates what we don’t know.

My .02 cents
__________________

__________________
Regards,

Maren

The sea is always beautiful, sometimes mysterious and, on occasions, frighteningly powerful.
Maren is offline   Reply With Quote
Reply

Tags
core

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Admiral 40 Balsa Below Waterline laser Construction, Maintenance & Refit 28 08-06-2010 17:01
different core types (foam pvc, divinicell vs balsa) schoonerdog Multihull Sailboats 56 22-07-2008 10:56
Core Material ksmith Construction, Maintenance & Refit 8 05-12-2007 12:27
Core sample repair Jacana Construction, Maintenance & Refit 11 01-10-2007 07:13



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 02:16.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.