Is Balsa really that bad ??

I have no issues with balsa cored material in my build - adhere to the designer's instructions and build as the material demands for a lightweight and strong vessel... I was told do not make holes unless they are necessary and that the nothing is allowed to penetrate the balsa... make a hole, refill with resin & cloth then put holes in the "glass/epoxy" part thus eliminating the opportunity for water to get at the balsa and soak/rot it... - That looks like drivel - but you should know what I mean... Do it right and it is worthy and appropriate for the task.... Look up the 'scrumble project', that is a meticulously detailed build project and that boat is balsa cored construction.... link in my link to Bob Oram designs, below...

 

OK Please elaborate.

 

Balsa cored DuFLEX panels can be an excellent build material ( www.atlcomposites.com & www.duflex.com.au and www.westsystem.com.au ) - High levels of quality control at ATL ensure a consistently superior product... also look at the Scrumble Project which is an excellent documentation of a build project http://scrumbleproject.wordpress.com/table-of-contents/ and follow some links in my post 232 here http://www.boatdesign.net/forums/boat-building/my-little-piece-peace-25962-16.html#post279166 ...

 

Some people in aerospace seem to agree with you on this as end grain balsa/Al skinned bonded panels are the most common cargo floor in big commercial jets.

Jimbo

 

Mas.

The trick with composites or balsa cores in fitting deck stuff is to drill the hole to be filled with epoxy, but then get a bent nail, put it into the drill and smash out some of the foam/balsa core between the laminates, then fill with epoxy, it seals the core and allows a great mechanical bond of the plug prior to redrilling for the fittings.

 

I am sophisticated - I use hex keys in a power drill - does that part neatly, Sadly the doc reckons I may be reacting to the epoxy (got my pancreas going no good, a while ago).... Bryan has been finalising (doing fit-out) his 44C and I have had ample opportunity to observe from the windward side a master craftsman at work (he was a teacher in the 'manual arts' and is an excellent welder in alloy and stainless, as well as carpentry and grp work).... I am 'just a dumb Johnny come lately' who can appreciate quality workmanship...

 

Keep that **** including fumes, and sanding dust off of you, including thinner.
West has a good basic technical safety read in their literature.
I've seen guys with poisioning so bad that when they come within 10 feet of a epoxy process building, their skin erupts in sores, right before your eyes.
Don't breath it while mixing, keep the skin covered while applying wet, and while sanding dry.
I wish for a prepreg that can be kept refrigerated, has a 2 hour working time, and will set / cure with a heat lamp. I've seen spar makers work w/ prepreg. The shop was so clean, it was amazing, and no fumes, no thinner, beautiful.

 

Okay, post-by-post. I know Ren Tolman (Tolman skiffs). He's got it bad (epoxy sensitization), now he has cancer. Don't know that the cancer came from epoxy but suffice to say epoxy's bad **** in which to swim. Pre-preg is in my future. See Eric Goetz's work.

 

When drilling holes, drill only until you get to the bottom laminate, epoxy fill and avoid pissing off the electrician working below...

 

Same hard spot technique applies to foam or other core materials, as well as balsa, and is even more important.

 

Lyam,

The proper way to bolt something to any coreed material is to:

1) drill a pilot hole from the outside of the boat (or from the side most likely to get wet)

2) from the other side using a Forstener bit ( http://www.mockett.com/furniture-hardware/wire-cable-management/forstner-bits ). Use a bit that is slightly larger than the size of the mounting hardware, I usually go up at least a 1/4 inch, but on a large bolt I may go up to 1/2 inch bigger. Just be careful not to drill through the second layer of fiberglass, it's pretty easy though since wood and glass feel completely different as you drill through them.

3) Tape up the bottom of the hole using clear packing tape, then fill from the top with thickened epoxy. Watch the epoxy fill the void and check for any voids.

4) once the epoxy is cured drill back through the epoxy and bolt the new hardware in place.

What this does is to leave as much of the wet side shell in place to try and minimize water intrusion. Then it seals the core in such a way that there is no path for water to follow into the wood. You also may get some penetration of epoxy into the wood wich will slow down water intrusion into the wood if water does get in.

As for the suggestions to just use an allen wrench or screwdriver to pull out the core... It is better than nothing, but that method has a couple of problems: First you can't control the amount of core taken out, and it is very hard to ensure that there aren't any loose wood fibers left in the hole. Secondly it is harder to make sure the epoxy fills the entire void since you can't watch the epoxy flow into void (I usually use clear packing tape to tape up the bottom of the hole. Third, it takes more time than just drilling a second hole.

 

Derek is trying to sell something

As to the initial comments by Derek Kelsall, I think they are way over the top. Derek basically says anything that isn't foam is just about to rot. He then goes on to talk about all the great foam boats he has built.

There is a reason why foam went out of favour in multis at least during the seventies and eighties. In fact Derek is involved in more than one. If you get your old multi books out you may find one by Rob James. In it he describes sailing Great Britain IV (I think) Anyway the boat was basically falling apart all the way around Britain. It had a large rig and so beat Phil Weld on Rogue Wave but in the book Rob James talks longingly of a structurally secure boat like Rogue Wave - she was built in wood. After sailing a few Derek boats both he and Chay Blyth use other designers for their next boats - not a show of confidence.

In Australia we had boats like Devils three and Pumpkin Eater that were falling apart after a decade of use. These light foam boats had gone soft and delaminated. Foam certainly was not fool proof. When Ian and Cathy Johnstone built Verbatim it was out of wood too so wood had lots of people who liked its stiffness and toughness when used in a composite situation.

At the same time there were good foam boats being built- Top gun and D Flawless - well she did break up actually! but there was certainly no monopoly by foam or wood on the best boats around.

Derek is trying to sell plans and ideas. He knows an awful lot but if he is not going to be generous enough to acknowledge the good things other cores have done his ideas must be treated with a fair bit of skepticism.

 

For those of us who don't read SAILING multihull magazines...hehehe

Would someone be so gracious as to PDF the article here, or a link by chance?

 

Master Captain, Admiral G. Rubin Esq.lll, Phd. PCP, STP, Any Tonneage, Any Ocean, Any Thing That Floats... Speaks; "Harumpf (Cough up phlegm), I say, and my title doth precede me, that the PROPER way to go about resolving the aforementioned conumdrum is to enlist the services of a borrowed Forstner bit. Because the things come so dear and smoke as to be rendered useless for the woodworking for which some misguided souls believe they shall be reserved, one is always a leg up by using one's mate's and reserving one's own for "later". Also, take precautions to ensure that the Forstner diameter is larger than the object to be attached by said twice-augered hole to demonstrate to the untrusting eye that, indeed, the core was replaced by a suitably aquaphobic resin.