Why not balsa?

[Kolar]

I've been reading a-lot of posts over the last six months and have noticed nobody uses this. Instead opting for ply but why? I use to work in a FRP plant, we would make everything from yellow iron parts up to nacelles for wind energy (that's the part which houses the motor and such). These same parts would be in the elements 24/7 and under a-lot stress and I mean a-lot. We used to encase a lot of metal brackets or more accurately called stiffeners but never ply. The cost and weight ratio was always a problem. I always wanted to ask that question when I worked there, but all the old timers where either retired or dead from the era when they used to make boats. Any ideas?

Regards

 

[NSBCraig]

Re: Why not balsa?

You can use balsa.

Lots of boats are made with balsa cores.

I'd still use ply for your transom if your replacing it though.

 

[Yacht Dr.]

Re: Why not balsa?

Hello Kolar..welcome to Iboats..

I think the Scare about balsa is absorb rate of water.

End Grain Balsa is lightweight and strong in the applications that require compression.

I have no clue why Ply would be used for replacement of balsa .. other than cost and availability.. ( Or other custom mods being added to the OEM part of the structure ).

Its good stuff when used right. I like it..

What would be your application for EG balsa ? .. or are you just asking ( No problem with that bye the way ).

YD.

 

[Kolar]

Re: Why not balsa?

Thanks for the reply. I'm gutting my 87 Regal this winter and was wondering what the trade off would be? Examples; decking, bulkheads, dash and so forth.

But what would be the negatives in using it in a transom? I have a feeling it would be cost wise. As building flat sheets of glass is expensive and time consuming (we always bought are flat sheets and angles from other companies)

We used balsa all the time, along as it is saturated right and all edges are sealed with glass there was no problem. Matter of fact the only problems I have heard of was an air pocket that was not ground out and re-glassed (with a production pace there is bound to be errors).

I have A-lot of ideas bumping around upstairs and it would be easier to make cheap molds with say 2 or 3 inches of run off to wet knife. Many of the angles and radius would take way to darn long with wood. That's the nice thing about glass the tools are cheap and the end result is left to your imagination.

Regards

 

[erikgreen]

Re: Why not balsa?

Lots of folks here don't use it because it can be hard to get. I'm up in the Minneapolis area and I only know a couple of places you can buy sheets one at a time.. other shops will only sell in pallet or package form.

Plywood, on the other hand, is available just about everywhere, and is cheaper than the end grain balsa.

If I had to pick two reasons more balsa doesn't get used in the repairs documented on this board, they would be availability and cost.

For a transom, the only advantage balsa has over plywood is the weight savings and maybe ease of installation.

You could use it if you are very careful about letting water get to it and you engineer your glass overlay layup to be strong and stiff enough. A plywood transom supplies a lot of the stiffness from the plywood, a balsa cored transom would need almost all of it to come from the skins.

Erik

 

[sasto]

Re: Why not balsa?

Coming from one that has never built a boat using wood.....except a cold molded sportfish....I can't answer your question.

Ericgreen has has a good answer as for availability, cost, etc.

Balsa is a preference in sandwich construction of decks, soles, or cockpits with most builders. Racing to hard core offshore fishing. They take a beating.

The reason for any sandwich construction is for thickness...which builds strength. Around here boatbuilders reley on composites and balsa core. We are not releying on any core to add strength by itself. but to add thickness. I wouldn't rely on a piece of plywood anymore than I would on a piece of balsa or foam. The laminate lay-up shedule is the most important factor to us.

good luck in your findings and decisions.

 

[Yacht Dr.]

Re: Why not balsa?

Before the petrol crash in the 70's I think.. the FRP boats were built like tanks ( they just didnt know what glass and resin without wood would do ).

I had a 67 30' Catalina that was at least 1.5" at the keel and 3/4- 1" on the topsides..

But then builders descovered that they can build within the margin with cores ( balsa/foam ). The only thing not considered was water..

FRP boats Dont need wood at all.. just very expensive using glass instead of build of core..

YD.

 

[barbosam]

Re: Why not balsa?

Another reason a lot of people on these forums use plywood instead of balsa is because it holds its form without a mold while the glass is applied. With balsa you need some type of mold to define the shape then you can start laying the glass followed by the balsa and then more glass. Then you pop it from the mold and put it in the boat. With plywood you can do all these steps right in the boat without a mold. Is it the best way to do it?..no but its cheap, easy, fast and if done properly can create a good sturcture.

If you have the skills and know how to use balsa then more power to you! go for it. Creating a mold for a deck, transom or other flat panel is pretty simple. This is a boat and it is emersed in water A-LOT so take extra precautions to keep water from getting to the balsa. Try to plan ahead and ommit the balsa in areas you know you will be drilling a hole in later just put an extra layer or two of glass in those areas with no balsa to maintain the stiffness.

 

[Last Mohican]

Re: Why not balsa?

Balsa is used all the time in performance boats. I have seen many jet boats and V-drives with balsa in the floor and transom. It is expensive though.

 

[Shife]

Re: Why not balsa?

Another reason a lot of people on these forums use plywood instead of balsa is because it holds its form without a mold while the glass is applied. With balsa you need some type of mold to define the shape then you can start laying the glass followed by the balsa and then more glass. Then you pop it from the mold and put it in the boat. With plywood you can do all these steps right in the boat without a mold. Is it the best way to do it?..no but its cheap, easy, fast and if done properly can create a good sturcture.

If you have the skills and know how to use balsa then more power to you! go for it. Creating a mold for a deck, transom or other flat panel is pretty simple. This is a boat and it is emersed in water A-LOT so take extra precautions to keep water from getting to the balsa. Try to plan ahead and ommit the balsa in areas you know you will be drilling a hole in later just put an extra layer or two of glass in those areas with no balsa to maintain the stiffness.

Who told you this???? Honestly.. where do some of you get this stuff?

This is way too complex of a question to simply try to state why some boats use balsa, plywood, foam, nomex, aluminum honeycomb, etc... Substituting one core for another is not straightforward as the laminate schedule changes for each core material. Some basic engineering is required when swapping to a different core to prevent underbuilt or overweight results.

The simple answer is cheap boats use cheap core materials. As the core materials advance, so does the engineering along with the price.

A low performance boat (Bayliner, Cobalt, Four Winns) gets low performance materials. A medium performance boat (Dorado, Albemarle, Fountain) gets medium performance materials. A high performance boat (Wally, Swan, Cookson) gets high performance materials. See the pattern? Polyester and plywood = generic production boat. Vinylester and balsa/foam = premium production boat. Epoxy and carbon/nomex = high end custom build.


Anyways... Isolate your fasteners from the core material. The original builder didn't and that's why most people end up on this site.

 

[Mark42]

Re: Why not balsa?

Who told you this???? Honestly.. where do some of you get this stuff?

This is way too complex of a question to simply try to state why some boats use balsa, plywood, foam, nomex, aluminum honeycomb, etc... Substituting one core for another is not straightforward as the laminate schedule changes for each core material. Some basic engineering is required when swapping to a different core to prevent underbuilt or overweight results.

The simple answer is cheap boats use cheap core materials. As the core materials advance, so does the engineering along with the price.

A low performance boat (Bayliner, Cobalt, Four Winns) gets low performance materials. A medium performance boat (Dorado, Albemarle, Fountain) gets medium performance materials. A high performance boat (Wally, Swan, Cookson) gets high performance materials. See the pattern? Polyester and plywood = generic production boat. Vinylester and balsa/foam = premium production boat. Epoxy and carbon/nomex = high end custom build.


Anyways... Isolate your fasteners from the core material. The original builder didn't and that's why most people end up on this site.

FYI... Bayliners are Vinylester. Just like high end boats. And they have some of the best designed hulls going. Much better than the competition for the money.

 

[Shife]

Re: Why not balsa?

FYI... Bayliners are Vinylester. Just like high end boats. And they have some of the best designed hulls going. Much better than the competition for the money.

I'm sure they're great among the generic production boat stuff, but they are nothing like a high end boat. Bayliner having superior hull design is VERY subjective, eh? I was just trying to paint a picture; not detail the exact production methods used by each builder and the dates they implemented those particular methods. A 2010 Bayliner and a 1990 Bayliner are about as similar as a dog and a cat.

Kinda like saying a Lamborghini Murcielago is just like a Chevy Malibu. They're both technically cars, but they are very different animals.

I'm not aware of any high end builders using vinylester. Then again my definition of high end is probably somewhat different from many here. At at that price point epoxy is expected and usually required to meet performance goals.

You're not going to see any of this stuff at your local boat show, but this is what I consider "high end":

http://mcconaghyweb.com/newsite/mainsite/mbinc.asp

http://www.gunboat.com/technology.php

http://www.wally.com/default.asp?bflash=1

 

[NSBCraig]

Re: Why not balsa?

Hey mark they only use it for one coat as a barrier, it's not like the whole boat is made of vinylester.

It's just to keep the GP resin from blistering.

(I love when people argue which econo boat is better. They are still cheap cause they are built that way. One company (especially within one parent company) doesn't have any secret special magical way to make something cheaper then others. They cut costs in the boat that you buy.

Shife is referring to companies that make racing sailboats (and one that makes real ugly powerboats) when he says high end. Builders that use carbon fiber, epoxy and sandwich cores.

That's where his reference of a Lamborghini Murcielago comes from. Although I personally think a Nortech or OuterLimits would be more accurate.

But either way he means super big money, like bust out your checkbook and don't ask questions.

Then his reference of medium is what most would consider a high end boat. Fountain, Velocity, Everglades...

Then comes boats most of us buy. Production boats. Which really vary a whole lot in construction and quality of construction (doing the work). There could be a whole nother scale in this category of which cores, resins and technologies are used to manufacture the boat.

Do you see where he was coming from?

And yeah superior hull design is just Bayliner marketing B.S. Come on there is nothing superior about a Bayliner except they are cheap and one can afford them easily either new or even cheaper used.

 

[NSBCraig]

Re: Why not balsa?

FRP boats Dont need wood at all.. just very expensive using glass instead of build of core..YD.

What? Are you seriously stating that they use cores for cost?

I can't believe I just read that!

No not even close it's a matter a weight not cost. Using cores makes the hull stronger for way less weight then a just glass hull.

Who wants a 10,000# boat when it only has to weight 5,000# and will be stronger?

 

[proshadetree]

Re: Why not balsa?

I dont care about cost Baylinners are some of the best riding boats I have ever been in. I have rode in everything from 70s jets to 35 foot Rinkers. Baylinners are built cheap and require a lot of work to keep them from falling apart but they ride excellent just my opinion and not necessarily the opinion of WSMV

 

[barbosam]

Re: Why not balsa?

Your right shife, this is a very complex issue, but we are talking about back yard boat building here not top dolar yacht design. He asked why people around this forum (most of which are average Joes not boat builders or yacht designers) use ply instead of balsa. I think everyone here has made a valid point and has kept it simple.

We could talk about this issue for months if we wanted to be scientific about it. If you want to have that type of discussion start a new thread or go to a boat builder/designer's forum.

Lets remember he's not asking why boat builders use balsa or other types of cores.

 

[barbosam]

Re: Why not balsa?

Just on more thing, he also never mentioned that he was actually looking to substitute ply for balsa. He may have been asking why not substitute balsa for ply? I mean probably 85% (just throwing a number out there) of the boats restored on this forum are ply wood cored decks, stringers and transoms from the factory. If your boat came with a balsa core deck would it not be suitable to replace it with a new balsa core deck? yes it would. Same thing goes for a plywood deck. Just another reason why someone would use plywood instead of balsa.

Kolar do you know what core materials are used on your boat now?

 

[Yacht Dr.]

Re: Why not balsa?

What? Are you seriously stating that they use cores for cost?

I can't believe I just read that!

No not even close it's a matter a weight not cost. Using cores makes the hull stronger for way less weight then a just glass hull.

Who wants a 10,000# boat when it only has to weight 5,000# and will be stronger?

You didnt read that as I never said that core was for cost..

I said Glass only boats are more expensive as compaired to cored..

It is a matter of weight..however ITS a matter of materials also .. Prepreg for example..and I have done it without core and lighter then a conventional Poly lammed boat .

I would also agree if you took balsa out..you should put it back in if its a patch repair..just me though..

YD.

 

[Shife]

Re: Why not balsa?

You didnt read that as I never said that core was for cost..

I said Glass only boats are more expensive as compaired to cored..

It is a matter of weight..however ITS a matter of materials also .. Prepreg for example..and I have done it without core and lighter then a conventional Poly lammed boat .

I would also agree if you took balsa out..you should put it back in if its a patch repair..just me though..

YD.

Prepreg what? Carbon? If so, why wouldn't you use an advanced core? Here is where all the confusion comes from. Are you talking about a FRP panel, or a small part? Building a hollow part such as a bike frame from autoclaved prepreg carbon is waaaaaaaay beyond the scope of pretty much anything on this site. Most of the folk here scratch their heads a bit trying to understand why balsa is used in boats, let alone prepreg carbon. I don't know what your background is, but a cored panel is going to be far lighter than a solid FRP layup at an equal level of strength. Solid glass boats are durable yes, but extremely overweight and poor performance is the result.

The short answer to the original question is that the average DIYer doesn't have the knowledge to swap core materials. The laminate schedule needs to be changed to take advantage of different core's properties, and most folks here just want to fix their boat up so they can use it. Shedding hull weight usually isn't on their radar.

 

[NSBCraig]

Re: Why not balsa?

FRP boats Dont need wood at all.. just very expensive using glass instead of build of core...

I read that cause you said that...

Now if you mean to say that's not exactly want you meant then that's one thing, but You said that it is "just very expensive using glass" as in all glass as opposed to building with a core.

Feel free to explain yourself but stating that you didn't post something so out there makes no sense at all.

But saying "You didnt read that as I never said that core was for cost.." is just out there because that is what you said. "it's JUST EXPENSIVE.... instead of using core"

I read it, you typed it. It pretty much is the entire point of your post.

Man you post some crazy things on this forum which is really out there what with being a self professed yacht doctor.

I mean for real there are some people on here that are real close to being experts and they don't claim it but you do and some of your posts don't back up that claim even remotely.

How about you take it down a notch.