Balsa core lamination

[tunnels]

Attachment 346661Attachment 346660
Here are a few pics of the transition and fillet work on a core.
This is h60 but it will be the same for balsa.
You can use a grinder to do the tappers and then very little fillet needs to be done.
You don't want any sharp transitions or gap for air to build up in as you do the final cover layup.
The better the cloth lays on the core the better the load will spread threw the matrix.
Sand the whole core like you where going to paint it. This makes for a smooth surface to do the lay up on and strait even thickness to the skin on top.
This is and important step as it will reduce the air pockets.
Spend the time on the prep work it will make it go easier when it comes time to do the final layup.
The small details are what make it all work.

Just from a point of interest why did you use contoured foam sheets instead of perforated flat sheets ?? Only asking that's all !! That's a job well done !!
H 60 density is a bit low for bottoms in fast boats ,H 60 is what gets used for decks and the like mostly !.What thickness ???
H 80 or above gets used normally, even in Racing yachts
Another point of interest what glass did you use for the skins over the top ??

[dwilfong]

[QUOTE=tunnels;2867825]Just from a point of interest why did you use contoured foam sheets instead of perforated flat sheets ?? Only asking that's all !! That's a job well done !!
H 60 density is a bit low for bottoms in fast boats ,H 60 is what gets used for decks and the like mostly !.What thickness ???

Don't want to clutter this tread with what I did. Just giving some pointer to help with his project.
You can find the full build up here http://www.screamandfly.com/showthre...r-Resurrection
The sheets where sanded to look like that. That is the point you can just sand the tapper on the edge after the core is set in place. Then use some fillet to complete the tappers to the outer skin.

[tunnels]

As a general rule of thumb is better to use a harder foam in the bottom of boats !! specially power boats and the faster they go even more so ! if the bottom panels have any flex or movement then the core is having to do a lot of work from the lower and upper surfaces wanting to pull in opposite directions minutely , Core shear is something that's not a pretty site , not to common these days but was long time ago when foams were just bought onto the boating screen and not much was known about them ! CONTURED FOAMS that get all and each individual blocks completely surrounded with resin is less prone to the penetration of water as well if done properly !!

[Gmcviper]

Little update. I have the outer core layed to the bow, chamfered and sanded. I will cover with mat when I get back from vacation.

[tunnels]

Little update. I have the outer core layed to the bow, chamfered and sanded. I will cover with mat when I get back from vacation.

That looks pretty good and that's a really good chamfer along the edge ! So your next step is ??
and what glass laminate you looking at using ???

[powerabout]

Hi Tunnels
Whats your take on balsa versus foam for fast boat hull cores?

[tunnels]

Hi Tunnels
Whats your take on balsa versus foam for fast boat hull cores?

To begin with its just two things !

First is bond of the core to the hull skins ,next the bond of the glass over the core !!

Second is Shear strength within the core its self ! this is where foams fell and fall down badly and was something that had never been seen till foams came into being in all there various forms .
Core cell is possibly the only exception in all this !! When a outside skin and core are damaged and water gets in at hi speed the peel ability of the skins off the core is abysmal and this is another place where foams are scary specially if the density of the foam is not hard enough . General rule of thumb is always use a denser foam than you think you should be using !
Core thickness also plays a big part in all this as well , thicker cores means stiffer , stiff doesn't want to bend and does not absorb shock so the bond lines of skins and shear of cores is much higher plus the hull rides really hard and pounds badly !.

Something that's recently new and taking its time to be accepted But the concept is really old are hulls bottoms that move and flex and are made to absorb shock and give a softer ride and out last there stiff solid counter parts !
I personally have been preaching this concept in the fiberglass industry for over 25 years since working making surf life saving IRBs .
Fiberglass Boats built that were soft riding ,had hulls that were flexible and had twist were faster more maneuverable and the personnel had way less injuries than then crews in convention IRBs .

Think back to the old Viking ships nothing could match there speed in any and all conditions !!

Want to see which boats damage easily go do fiberglass repair WORK for a while and see boats built with the same materials ,one falls apart yet the other is built with similar materials and the damage is no where as bad as the other boat ,WHY ??

[powerabout]

Thanks for all that BUT how do you work out what flex a certain hull needs?
Spend money with High Modulus to work out what will flex but you still need to know how much you want?
Of course speed generally means stiff as

PS yes I have seen racing tunnel boats destroy themselves due to small crack

[tunnels]

Thanks for all that BUT how do you work out what flex a certain hull needs?
Spend money with High Modulus to work out what will flex but you still need to know how much you want?
Of course speed generally means stiff as

PS yes I have seen racing tunnel boats destroy themselves due to small crack

Call it instinct ,gut feeling , knowledge and common sense is all that's needed ! Take the frame work out of any hull and naturally it will flex so if you use a better glass to build your hulls and us it to get the most from its properties ,Make Framework and stiffeners that are capable of moving also supporting and helping the newer flexible outer skins . Boat designers are another problem they have the capabilities of designing much better riding boats than whats out there but are caught in the don't want to be seen to be different mode !! they are just like sheep and follow what everyone else does !!
If you mention what I been saying to any boat builder or designer they will rush to the fridge to get a beer and go and hide some where till you leave !!
When I started with this the first comment was they will never last !! BUT 15 years later the same boats I built were still in use and had out lasted 6 inflatable tubes and who knows how many out boards !! The boats were inspected every year and never once did they show any signs of gel coat cracking and stress marks at any time. That's another small secret as well how to stop gel coat from showing stress marks !!
We are so set on the ways everything is made that with a little thought and simple product knowledge it could be made much better ,with glass its the orientation of the fibers that's the key . We don't need as much as 30% of the materials that get used to make a boat its just there as ballast and serves no useful purpose ! If better materials are used differently the strength factor goes up, weight goes down and we use less materials !! And all this is just for starters !!

[powerabout]

The last Americas Cup mono's didnt have any frames, I guess FEA taught that?
I wonder if any Powerboats have had that kind of design engineering in them?

[Gmcviper]

I am going to put two layers of 1.5oz csm up to the dash from there on only 1 layer. Once I get the core covered I will pull stringers out and the small amount core on the sides of them and start on replacing them.

[tunnels]

The last Americas Cup mono's didnt have any frames, I guess FEA taught that?
I wonder if any Powerboats have had that kind of design engineering in them?

I have over the years worked with some very clever people including designers and a couple of composite engineers , in general when they don't have answers the rush for the books they have buried away . I get sick of forums and there armchair know it all's That have little to no practical hands on experience and have read truck loads of books and all the crap written during the 1940/50/through to the 70s . its was rubbish when it was written back then an should be burned !!
A lot of boat companies I have worked I have had a free hand at changing things and tossing out woven glasses and copious amounts of csm and changed to more modern fabrics and built boats quicker , stronger and lighter . One 48 foot boat I totally changed the whole laminate for the guys in the workshop all said it would never work but when the deck was finished at sat on the hull the whole crew walked around the deck kicking and shaking there heads at how much stiffer the deck felt and how much lighter it was !!simply by changing to different materials cores where they should be and increased thickness with better glass over the top . AND I MIGHT SAY this was achieved using a chopper gun but mostly as a saturator gun to spray resin only !! some parts were sprayed with the chopper gun but very few !!. LIKE I have mentioned the orientation of the glass fibers and using as longer lengths of materials as is possible every where and eliminating joins and over laps any where possible !! this adds significantly to the strength of what ever . Glass manufactures are working behind the screens as well and no one notices what they have been doing !! Fabrics had sprayed on csm glass that had binders , now more recently that same glass is stitched and has no binder at all so wets quicker and is heaps better and adds strength because of it !! Here in china its possible to get glass specially made any width you want ! so for big boats eliminates longitudinal overlaps and rolls can be made and cut to the lengths you need as well , this is a really big saving when making boats 100 foot long and no joins ! the same boat had 3 different thickness of balsa core throughout so changed to just 40 mm for everything hull topsides cabin sides and side decks all vac down onto 2 x 450 csm glass then reduced the number of layers of csm significantly through out the lay ups . Plus reduced the amount of glass over foam framing by 50% and introduced 2 extra layers of Unidirectional glass running athwart ships at 5 degrees to each other and that achieved better stiffness in the bottom and took a week off the build times .
I showed the guys how to use the glass in steps and wet and roll out then roll more glass out another 8 feet and sit the glass rolls on plastic sheet and carry on one more step at a time but all done in one long length with no joins I use this technique when glassing boats with just a small crew and a chopper saturator gun its a breeze and the jobs are done and finished before you know it !!

[tunnels]

I am going to put two layers of 1.5oz csm up to the dash from there on only 1 layer. Once I get the core covered I will pull stringers out and the small amount core on the sides of them and start on replacing them.

2 layers of 450 csm and reducing to just 1 layer ?? Tell me which way is the panel likely to bend ? inwards of outwards ?and to reduce that bending what's needed ?

In reality its the inside of the bottom cored panels that's the most important part !! its the part that takes all the stress and stretching of the laminate from the bending and needs strength !!, CSM has little strength It needs a good glass over it all way across and length ways !

[Gmcviper]

Thanks everybody for the insight! I "finished" the boat about 3 weeks ago and have had it out 4 times. There is no "floor" but to supplement strength I added bulkhead and the stringers are 4" tall. It is a completely different boat. Here are a few pics of it done.

[W2F a V-King]

Looks really good!!

I like the grey finish on the floor.

Lots of hard work, but worth it..

Safe Boating!!

James