Baltek Core As Planking Material?

[c-cat]

I'm Planning A Build Of A 28-30ft. Performance Cat And Would Like Any Info On One-off Fiberglass Construction.i Was Thinking Of Sheeting Traditional Frames And Battens With Baltek Core-fairing-and Glassing With Epoxy Laminate.then When Outside Is Complete Rolling Over And Glassing Inside.is There An Easier Method?has Anyone Done This?

[grantn]

should work in theory!

actually a lot of performance cats and racing boats are built with composite cored hulls. hatteras is also starting to build their hulls that way. using sheet composites should eliminate the need for batten strips unless you have some serious compound curves to span. the thing to keep in mind is that wooden hulls get their strength from the wood. cored hulls get their strength from the distance between the two frp panels. (i-beam effect)

[c-cat]

After Some Research I've Discovered That It Has Been Done.i'm Now Curious To Know If I Leave A Gap Of 1/8 In. Between Planks That Are 4in. Wide, Fill That Gap With Carbon Fiber Cloth Then Apply Outer Lam's (followed By Inner Lam's Later) This Should Yeild A Stifffer Panel For Say The Bottoms.kind Of An Internal Stringer System To Keep The Hull Light. I Plan To Lay Up S-glass Throughout With Some Carbon Fiber Here And There.

[captainjsw]

Not sure of how well that would work. I mean think you will have a problem 1- getting the carbon in a small gap like that and 2 wetting it out. Just glue the planks together. That works. I am building a 17.5m catamaran from DuFlex and gluing as we go. I did think of a similar approx to the gluing where you leave a gap and force the glue through when the planking is complete. But decided against it in the end - was worried it might cause too many voids

[c-cat]

After extensive research Iv'e decided to eliminate the cf between planks.Foam core will only be used in the sides and deck,all remaining will be balsa core. One of my big concerns was rigidity when only half laminated (outside).Would like to body work while upside down which involves walking on tunnel. That will be the strongest portion of the plug I quess.

[Kaptin-Jer]

I built a 78' mono as a one-off with a balsa core 15 years ago. Even then new and better technology was coming out. There are much better core composites that fare easier, are less costly and bound better to the 'glass. Do your research and get more familiar with the many foams on the market. The salesmen will be eager to try to sell you their product, and at the same time you will be getting an education. That's how I learned.

[c-cat]

Thanks Kaptin, I'm not sold on one foam or the other as of yet.I do however have some boat building experience with both,balsa being the majority.I like the idea of foam due to it's workability,its easier to sand and shape if needed compared to balsa.How long did it take you to build a 78ftr?

[Kaptin-Jer]

It took two years to turn-over working on the week-ends. I logged the hours, but don't have it around anymore. Since you are only going to +- 30' why don't you do a search and try to find a female mold that you can use (either buy or rent). You will get better results faster. A one off takes forever to fare and you will spend a lot off time and money building a mold that is a throw-away. Hopefully you will build it strong enough to use twice.

[c-cat]

I,ll probably spash a mold off the finished boat.I schedule commercial const.for a living and figure the plug at 2 wks.(after cutting frames & etc.)Sheating with foam 2-3 days.And glassing at 4 days.Fairing and finishing @2wks.I,m not accounting prep time like cutting glass,battens,I figure 1-2hrs.daily for that.I,m tooling a 1/6 scale model currently for mental clarity while my shop is being prept.Any secrets on the foam I should know?

[waikikin]

C-cat, are they like man weeks your using or do you have plenty of labour on tap to meet that kind of schedule on the "plug" hull, typically mold production costs are quite high with figures of around $1600-2000 per meter squared common(most goes on labour esp in finishing) & can go higher but of course there's cheaper options such as molding off melamine sheet/laminate/glass formwork might be a good option. All the best from Jeff.

[Kaptin-Jer]

--and C-cat multiply those numbers by 3. Everything on a boat takes 3 times logger than "normal" construction. I'm also in the construction business. (I'm an architect) I have gotten caught estimating time on boat construction too--3X!.

[c-cat]

I,ll admit that I plan to prep through the weeknights,assemble on weekend.Then probably rip the foam and apply over a long weekend.Fair thrugh the week,and glass on weekend again.Then slow it down to finish everything nicely.Logistics are fun when working by ones-self.

[Pericles]

Read Gougeon Brothers book. http://www.westsystem.com/

Pericles

[c-cat]

After research and discussions with alot of helpfull people I'm going to explain what the procedure will be.First,cut up and assemble frames.2nd,build lofting table unsheeted.3rd,Assemble frames on lofting table then apply battens spaced @8" apart.4th,apply foam core sheeting (thru tunnel and flats).5th,apply foam core planking on sides virtically-across battens.6, fair anything that needs it(should be minimal at this point).7,apply laminates to foam and fair,of coarse followed by body finishing and painting. Roll over, remove wood batten plug and repeat #7 less bodywork. Bulkheads stringers are added then deck construction begins, only foam-planking is laminated one side first (underside) so that when outside laminating is done laminating upsidedown will be slightly easier.

[AndrewK]

C-Cat

I have a friend that is building a 12m catamaran the way you are suggesting over a male batten mold but stripped in foam longitudionaly. I am also building a 12m catamaran and I chose to build the hulls split down the centre line in a female batten mould and strip the foam verticaly on the flatish topsides and narrow longitudional strips in the tight turn of the bilge. I then hand laminated the inner laminate and installed all of the bulkheads to lock in the shape before removing from the mold and storing away suspended from the roof. Next I produced another half the same way. The mold is then reversed to produce the oposite side, and then one of the first halves is put on top and locked together by taping along the centre line and bulkheads.
The outer laminates I vacuum infused.
Looking back at the two tifferent approaches my friend and I think my way produced a fairer and lighter hulls. The big flat underwing like all other flat panels I make on an inexpensive malomine covered MDF table by infusion.

The other advantage with this method is if your hulls are symetrical then you only need one set of half hull forms; ie one quarter of materials my friend and your proposal requires.

If I was to build again I would still chose the split verticaly down the centreline way but would actualy prepare molds made from striped MDF so that the whole structure is infused and fairing is reduced by half.