plywood vs balsa deck construction?

[matalag]

Dear friends, I've been costruction a sailboat with WRC(strip plank) and just finished the hull.I thought I could construc the deck easily with plywood but my designer want me do it with balsa.Since I am a real amateur I am afraid of handling balsa cored composite construction.So I need your advices.
Thank you

[cyclops]

Are you paying him to help you? Or is he paying you to do what he orders and you do not feel comfortable doing it? The person paying should have the final decision.

[PAR]

I usual agree with Cyclops and his replies, but I'd would pay attention to the designer in areas where structure and weight can play a critical role in the outcome of the vessel's qualities. A heavy deck can over burden a craft, particularly if it is under 10 meters (LOD) raising the CG to an undesirable point.

I do question the need for cored deck construction on a strip built hull and will double the question Cyclops posed with; is this the boat's designer or some other person? If it is the craft's designer, listen up, if not, hand him the plans and ask for a more accurate assessment, keeping your building skills in mind.

Strip plank methods are amateur driven, because of the few skills necessary to complete a hull. Composite construction is a completely different set of skills and typically are not in the realm of the average backyard builder, who doesn't have much experience. A plywood deck will be a good bit heavier then a balsa cored deck. Since strip planked hulls aren't the lightest things in the world, I'd suspect a plywood deck would be fine, but would first check with the true designer of the boat, before making a decision that could alter her handling qualities.

What design is it and who drew it up?

[matalag]

Thank you both for your replies. I paid for the plans. It is a 12m cruser-racer. So I'll ask him again a good solution for me since I am an amateur.
Mehmet(retaired M.D.)

[gonzo]

Why did you start building a boat and then decide you didn't like it? I firmly believe the designer should have the last word. It is pretty common on amateur built boats to have disastrous modifications. Only an experienced professional should deviate from the plans.

[FAST FRED]

A very simple method of using balsa is to lay it out on any flat surface and glass ONE side to the balsa.

After it cures cut to fit as you would plywood .
Use a tape "shelf on the underside.

Then glass the upper surface of the balsa.

Have built many an item with cores this way , as the fresh "green" glass will take a huge curve (if necessary) in the first few days.

Epoxy paint rolled on COTTON coarse screen material makes a great light weight no skid.

FAST FRED

[Capt. Mike]

Fast Fred, I'm trying to decide on what to use for non-skid. What do you mean by "course cotton screen"? Do you mean window screen?
Thanks

[Oyster]

Strip plank methods are amateur driven, because of the few skills necessary to complete a hull.

Ouuchhhhhh!!! THe shape of a hull, strength and stabilty or even avaliable woods stands on top of the list. Bulking up thickness can also be at the top of the lists, in solid planked boats when contortion comes into play.

That was painfull to read.

Knowing after the facts with balsa cores, give me the worse wood, and proper sealing methods and materials anyday.

[Tynaje]

There are two issues to consider.you will need a plug or large solid surface to build a composite deck.You need an open area the size of the boat to build such a plug,unless you use the boat as the deck plug strongback.
The second issue is Balsa's constant ability to absorb water.I have never seen a balsa cored deck that didnt have water damage.( I just removed the balsa deck from a performance boat I own and will replace it with Plywood and glass,this from an advanced composites builder with 30+ years experience.)The costs of tooling a plug and lack of experience with the materials,you would do well with high quality plywood.
I developed and built the Cape Fear 38 ,which started life as a 33ft sport boat and accidently morphed into a confused cruiser/racer ,all without a single drawing.I would not allow any balsa in the laminate,only balsa is in the baltek panels used to build the interior.Each and every fastener is a potential leak with balsa.
The result:balsa cored is a deck soaking water ,getting heavier by the moment.Rotting balsa also means delamination.......
High end marine plywood,not fir,with a glass skin will do well and eliminate issues due to lack of experience with the composites.Bonding the balsa is another post issue on its own,humidity,dealing with warped panels etc.Balsa's great performance features are heavily out weighed by the water absorbtion issues.
I know there will be much arguing this,but I can see a balsa deck/hull from a mile away.Just look for the black goo............Bruce Marek made a convincing argument about coring hulls,while I was building the 38 and considering methods to bond the(Corecell) core in Vinylesr resin(YUK),non cored hulls are lighter and dont suffer from lack of proper core bond.
Properly frame the deck,go with plywood glassed both sides and enjoy your deck in half the build time..........SO ends my rambling balsa rant.

[gonzo]

Non cored hulls are lighter? Is your claim that all racing hulls are heavier than the cheaper consumer type?

[Oyster]

Gonzo, what is it with you that you feel the need to be sooooooo rude. Why can't you reply with some substance to address the issues that you deam to be incorrect, or do not agree with, in the context of which its written? You rudeness over shadows any substance that you may add into your mush.

I will not address the Balsa core issue as anyone that has been around the horn a bit knows what happens in too many cases after a boat ages.

[gonzo]

I corrected my post. Balsa or any other core will last indefinitely unless there is water intrusion. Well bedded hardware doesn't leak. Plywood will rot faster than end grain balsa because water will travel along the grain and affect a larger area faster. As for the claim that there is no balsa cored deck without damage, I find it farfetched.

[Oyster]

You know yourself that the chemical makup of polyester resins or ester resins are friendly to moisture causing a lot of natural satuation with aged gelcoat and skins, especially in hulls that are not properly maintained, even without any leaking fittings. This is also an unknown factor with the consumer that buys or bought those shiny hulls filled thinking they are bullet proof.

Many of the true racing hulls live a very limited life pushing the envelope, where the resulting issue of weight or issues that create added weight rarely comes into play. There are so many alternatives of liteweight and great cores avaliable now, for deck and hull cores, since balsa came to life, that yes there are other alternatives to it. my ,02, otta here.

[Tynaje]

I agree with gonzo on his racing hull positon and well bonded fittings and core.Panel stiffness speaks for itself,but I have also been on older composite hulls that have become spongy with age.My response was to a post about an owner built deck.The chance for poor bonds is high in this case ,it is not an easy process to master and failed parts hurt the owner builder(not that they dont hurt a others too )
I own a 1986 built race boat,it's displacement in 86'was 2,500 lbs(approx1134 kg )
I carefully weighed the parts I removed from the boat,hull,cabin, cockpit,"grid",and other liners,leaving only two bulkhead,mast step and keel floors. The debris totalled 1,680 lbs,the dry hull,with keel and rudder in place weighed in at just under 2,000 lbs.That boat gained at least 1,000 lbs,in its balsa parts,not to mention the total delamination of the outter skin.The crazy thing is it is a boat that was advertised to be built entirely of foam,I found balsa in the transom!!!! but the hull is indeed foam and dry .
This boat was owned by very attentive owners who kept it in top condition but sold it due to its lack luster performance( the boat was a fast light air boat in its day)Now this is a racing example and is no way an example of offshore application as fittings may have been relocated several times thru years in raceboat deck.
I like a cored hull,because I build from inside out off a hard plug .I laminate inside skin,bond core fair core and limit as much as possible,the need for fairing putty on outter laminate.
Cape Fear Yachtworks has had great success with their noncored hulls,the boats are fast and no bond issues,I prefer core for stiffness,but longevity is not I go with no core.

[gonzo]

Have you tried end grain balsa panels that are already laminated? The manufacture them with vacuum bagging and are of consistent quality. If the deck is flat, all they would need is tape on the seams.