Balsa Core?

My plans call for a balsa core, but I am thinking of having the builder use a different core material, such as Nida. Since the plans were desiged for balsa, what would this do to the vessel? IE - could it cause stability issues or ??

 

Do not make such a change without speaking with the Designer who prepared the plans--

 

I doubt of stability issues but all scantlings must be recalculated, plus other things. Never make changes on a plan without the written assent of the designer, or better ask the designer to make the changes.

First you can run into deep trouble and build an useless boat.
Second you free the designer from any reliability if you modify the plans and specifications without his consent.
Third if you're using old "free" plans, hire a able person (architect, engineer) to recalculate. it may be a matter of life or death.

 

I did not think that nida core was used in hulls or parts requiring significant strength.

I am all for avoiding balsa, if you really want the problems associated with timber in general then go for it but I think sticking with pure plastics(PVC), polyester/viynelester or epoxy resins etc is far safer.

 

It won't change anything about stability or maybe increase it a little cause your hull must be lighter . For structural point of view there is probably no issue, the only critical point is the utlimate shear strength cause Nida or other honeycomb and foam have lower characteristics but in most case Nida can easily replace balsa. If your boat isn't a high speed craft or 60ft racing boat you don't have to worry too much . Once more if your sandwich isn't more than 15-20mm thick the low shear properties of your core won't be an issue. So if you're not in these case you should thanks the builder cause he used more expansive materials and built you a lighter boat, just check is familiar with this core cause it's a bit harder to use than balsa.
If you ant be sure ask an architect but don't pay too much cause it's just an half an hour calculation if you give him dimensions&lay-up of your boat.........

 

I should have been clearer in my original post. The hull is not to be cored, the decks and house are supposed to be cored in Balsa. I would really like to avoid this.

 

Im sure Nida-Core would be OK, but consult with the designer for the appropiate thickness and scantlings.

 

I have used Nida-Core for the hulls of small racing dinghies, but with the knowlegde I have now, wouldn't use it for that purpose anymore. I would also avoid it on deck, unless you have a lot of framing.

Nidacore produces a more flexible laminate, compared to balsa. This is not desirable on a deck.

Personally, I would not use balsa as well in a deck. You should be very carefull with drilling holes, making sure the balsa is protected from water ingress. an unknowing worker could easily install something on deck, thereby ruining your balsa core in a couple of years time...

 

If you have the $$$ AIREX is probably the best material for light weight boat cored construction.

FAST FRED

 

So what core then...

OK. this thread seems to have morphed into a good core material debate. I suspect this has been discussed in the past, if so pointers to the thread would be appreciated. If not, then recommendations would be appreciated.

So far we have Nida - not the best, Airex tons of $$$, gotta be other ones out there that will work fine.

 

I expect that there are lots of issues that are being ignored here.

We have a core and a couple faces. The usual loads include distributed loads, concentrated loads, point loads, and impact loads.

The "best" core depends on the composition of the faces. To select the "best" of either is wrong. You want to select the "best" combination.

 

Definately.

For a hull, personally I would choose a more ductile core, such as Core-Cell A foam. The hull receives plenty of pounding and abuse. second demand is panel stiffness, in which Core-Cell is still OK.

For a deck, I would choose a cross linked PVC or Core-Cell T foam. This is stiffer than A foam, so sagging of the deck when walking on it is less. (sagging is an unpleasant feeling, and can create unexpected nice little problems). Point loading is an issue, but can be addressed by the top laminate.

Also a consideration is how much abuse will the boat receive, and how long should it survive? a lot of sailing boats just sit in the harbour for 30+ years. I know plenty of boats that will just dis-integrate if used actively for a year. Not my idea of boatbuilding, but it happens...

Above is my opinion on a cabin cruiser / daysailer. For a die-hard racing boat, other options come in mind.

 

Airex may be one of the better foams out there, and I personally like the stuff (thousands don't), BUT... it is almost impossible to sand it. Core-Cell, developed from the same criteria, has all of Airex's good qualities, but can be sanded.
Herman recommends Core-Cell "T" foam, but this is only neccessary if you are cooling the part ("T" for "Thermal"). If no cooking, then the "P" foam is cheaper and just as good (but moves under heat and vacuum)

Steve

 

Ummm... COOKING... Aargh - I've got to stop getting up so early...

 

T is also stiffer than P and A. One can need the stiffness...