Balsa wood what to do now?

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John in CR

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If you had this much balsa wood, what would you do with it ebike wise? I've got some ideas, especially using the portions of logs with gentle and uniform curves...like aero side covers to enclose batteries. Maybe some of you guys have ideas I can use. Note that the gallon milk jug is for scale.

Balsa1.JPG

Balsa2.JPG

Not that I kept the bark that is peeled off. It's about 1/2" thick and is a bit denser than the wood itself, but the inside of the bark is very smooth.

Some of the pieces made into lumber will have to go to something like a chair made with 4"x6" lumber for a super heavy and strong look that weighs just a few pounds, but that's a separate topic.

Whatever I make with the wood will get a coating of clear epoxy to seal it from water, as well as strengthen and harden the exterior. I'll hollow out the inside to get it down to a thin and light unit.

Any ideas?

John
 
One of my LBS's has literally a pile of bikes including a bunch of those tiny cromo tubed older road bikes. I could easily cover the frame in balsa lumber to make it look like a bike made of wood. Then just hollow out big sections of the balsa to hide strings of konions in the top, down and seat tubes. Hide the throttle and motor wiring in the balsa too, and add some aero balsa sleeves over the lower portion of the suspension forks, chain stays, and seat stays.

It might make an interesting stealth build.
 
Another idea I had was to use a normal head tube and bottom bracket. Then weld a basic frame using 1/2" square tubing with a bit a steel reinforcement in the critical areas. Then cover that frame in balsa using fiberglass+epoxy to bond the balsa to the light steel frame. The wood would give the frame it's rigidity as well as a place for batteries and hiding wiring.
 
Has the wood been complely dried? If not there is trouble ahead. Wood moves a lot in the drying process. It also can crack, known as checking. In hollowing one must be very considerate of the grain. It will not conform to any shape you can imagine. The grain is the issue. If you could sucessfully hollow it out on the thin side it will break with modest contact. It is not impossible but there are better applications. Perhaps battery boxes. Varnish it a lot. Look for varnish with uv protection. Avoid the center of the log. The grain tension is much different in the center of the tree then the rest of the tree. Most species waste the center of the tree.

ebent
 
I will second concerns about whether the pieces are truly dried out ie moisture content around 10%... not gonna happen if ambient air is humid already. I wood probably saw all into veneers to facilitate drying (home-made solar autoclave should be easy to fab), then laminate as needed. As veneers, easy to build up compound shapes later.
Lock
 
If you plan to build a "dryer" of sorts, BE SURE to get GOOD air flow. If you don't move that moist air out of the enclosure, you will have a slimy stinking mess in just a few days.

Wood down here will dry down to 14% just with air drying, and, that IS during the rainy season. I didn't believe it, so, I brought down a GOOD Moisture meter. I use it regularly to keep abreast of what the drying does.

We dry our laundry under the back porch roof, year round. We get 3 months of roughly minimal rainfall. Still, with the rain in the air, our laundry dries in a couple-3 days, usually. :roll: :roll: It's weird.
 
Lock said:
... I wood probably saw all into veneers to facilitate drying (home-made solar autoclave should be easy to fab), then laminate as needed. As veneers, easy to build up compound shapes later.
Lock
Click to expand...

Kinda ties into the carbon fiber concept which I saw here:
http://dragonplate.com/ecart/categories.asp?cID=58
 
I definitely won't do anything until the wood is dry. I may do some stuff with veneers some day, but not with this balsa. I'd go to the plywood factory and scrounge material before it becomes plywood for a multi-layer veneer, which would essentially be making my own compound curved plywood with epoxy as the glue and fiberglass as at least 1 layer (something in the back of my mind for a long time, vacuum formed of course). I've seen some beautiful kayak and canoe stuff with fiberglass over wood where the fiberglass is transparent, so that's a possibility, but carbon fibre is too expensive to waste combining it with the weight of wood.

Keep in mind that this is balsa, and once dry I can carve it easily with just a sharp knife. I have some nice broad curves to use already, and additional curves will come from carving (and if necessary gluing multiple pieces together. Then when I get the exterior like I want, I'll go to work removing material from the interior. I'll probably need to come up with tools to make removing the interior material easier...some kind of blade curved into a hoop or something. Who knows, maybe something like wire brush attachment on an angle grinder may make quick work of removing material.
 
One application I have seen in composites is to use end-grain balsa as a core material. It is very light (duh) and makes a thick core that weighs very little, allowing you to build a panel that is very rigid (due to it's thickness) but still very light.

How about a panel 1" thick, endgrain balsa core, skinned with carbon, home vac-formed, that you could put a car on, and weighs 454 grams?

Seriously though, since carbon is so expensive, you could use fiberglass and use the core to build thickness, and have similar properties. (Thin panel of Carbon is stiff, but thicker panel with fiberglass is stiff too)

Or you could make a raft and sail to S America catching flying fish for dinner. I loved that book.

Katou
 
While we're kinda on the subject of exotic materials, something I want to try is bamboo. In addition to use as a natural tubing, I'd like to try it as a composite fiber in place or in combination with fiberglass, and use vacuum forming. My machine shop buddies have a roller press, unfortunately too crude to flatten copper wire for me. My thought is to take freshly cut bamboo and run over it with the car lengthwise, run it through the roller press, whatever, to get it to a fibrous form. Then lay the fibers in a female mold with a thin layer of fiberglass cloth as the innermost material (strength insurance). Line it with visqueen and pull a vacuum, and then connect the vacuum to bucket(s) of slow cure epoxy and suck the epoxy into the mold to saturate the fibers with the minimum amount of epoxy for a very lightweight material that is hopefully extremely strong with an exterior that is already smoothly finished.
 
John in CR said:
. . . maybe something like wire brush attachment on an angle grinder may make quick work of removing material.
Click to expand...
99t2001s1c.jpg

http://www.leevalley.com/en/wood/page.aspx?p=42528&cat=1,130,43409,43424&ap=1
 
katou said:
One application I have seen in composites is to use end-grain balsa as a core material. It is very light (duh) and makes a thick core that weighs very little, allowing you to build a panel that is very rigid (due to it's thickness) but still very light.

How about a panel 1" thick, endgrain balsa core, skinned with carbon, home vac-formed, that you could put a car on, and weighs 454 grams?

Seriously though, since carbon is so expensive, you could use fiberglass and use the core to build thickness, and have similar properties. (Thin panel of Carbon is stiff, but thicker panel with fiberglass is stiff too)

Or you could make a raft and sail to S America catching flying fish for dinner. I loved that book.

Katou
Click to expand...

I want curves, not flat panels. I'm not sure I need that extreme stiffness, so grains running the length may be sufficient. The problem I see with end grain balsa is that it literally sucks up the epoxy resulting in too much weight.

Oh btw, I definitely have a lightweight hybrid electric catamaran mulling in my head. Wind would only be assist probably using a pair of windsurfing rigs. Electric would be the primary with a pair of small diesel generators, at least 10kwh of batteries and solar panels. I'm waiting a bit longer for the 10m version for solar panel and battery prices to come down further.

In the meantime I already have most of the thin plywood panels ready to go for a 4.8m beachcat. I'm going to modify the asymmetrical plan to make the hulls symmetrical and get more weight capacity by "torturing" the plywood side panels into a curved form, making the hulls more U shaped compared to the asymmetric V in the plan. I'm doing the mods to make it hybrid electric and wind.
 
bandsaw the balsa into thin ,wide strips i.e 1/4"...cross laminate[with slow dry epoxy??],like ply..... that will be stronger and should remain stable even when hollowed out... cut your shape and glass ...the light cloth is very clear... you can accent stain befor you glass
 
If you don't know what you are doing, end grain Balsa will "Print", meaning it will have the pattern of the end grains and the squares, in the surface of the finished layup. We used to use it for decks in our "go-fast" Boats, when I worked for Velocity, in Pompano beach, Fl. It came in squares, like bathroom shower floor tiles, all joined with a gauze type material. You have to slow cure the polyester or vinyl ester resins, to get past the "print" stage.

John, if you take those "half cuts", and dry them, you can shape the ends to get that air resistant curved effect, using the Electric Plane, and fair it all together as it meets the sides. THEN, hollow out the insides. Dry that stuff in the shade, and NO extra heat. Might even place it flat side up, so the water wicks UP to that flat surface, allowing the wood to NOT dry fast and split.
 
Harold in CR said:
If you don't know what you are doing, end grain Balsa will "Print", meaning it will have the pattern of the end grains and the squares, in the surface of the finished layup. We used to use it for decks in our "go-fast" Boats, when I worked for Velocity, in Pompano beach, Fl. It came in squares, like bathroom shower floor tiles, all joined with a gauze type material. You have to slow cure the polyester or vinyl ester resins, to get past the "print" stage.

John, if you take those "half cuts", and dry them, you can shape the ends to get that air resistant curved effect, using the Electric Plane, and fair it all together as it meets the sides. THEN, hollow out the insides. Dry that stuff in the shade, and NO extra heat. Might even place it flat side up, so the water wicks UP to that flat surface, allowing the wood to NOT dry fast and split.
Click to expand...

Thanks for the "printing" info. I planned to see how smooth I can get everything, and then seal it first with a thin layer of epoxy. If it seems like it needs more toughness, then glass the exterior. I think I need to experiment on a small piece first, before even forming a plan, because if I can't avoid the rough "printing" texture on exposed end grain, then all of my ideas are shot except the heavy looking but light chair.

That's exactly what I was planning with the half cuts. If I want to go something like velomobile width, then I was thinking of first joining the matching short pieces of 1/2 log at about 45° before shaping the curves.
 
kriskros said:
bandsaw the balsa into thin ,wide strips i.e 1/4"...cross laminate[with slow dry epoxy??],like ply..... that will be stronger and should remain stable even when hollowed out... cut your shape and glass ...the light cloth is very clear... you can accent stain befor you glass
Click to expand...

Yes, making a plywood is an option, though I'm not sure balsa is the best choice. There are some other quite light woods here that are significantly harder than this soft balsa. Time to start looking for someone with a veneer cutting machine, because for the big boat I'd really like to make my own plywood exactly in the manner you mention with the curves molded right into the sheets. Then I can start the cylinder mold construction process with a 3mm or 4mm plywood as the interior layer and vacuum form the multi-directional layers of DIY ply over that.
 
I can't remember the name, but, back when I was young :roll: , there was a molded plywood runabout shell that was sold on the East Coast. You needed to put the ribs and transom in it. IF you are good at searching the 'net, you might find info and a photo, to see just how much curve you can obtain. It DID have a name, but, it was 50 years ago, or so.
 
it was more than 50 yrs ago.... that molded ply was first used to build a canadian fighter /bomber. during the ww2.. VERY FAST cant even remember the name of the plane.... hah!! it was the mosquito bomber... i built one of those hulls... it lasted for over 20yrs
 
tritonwow said:
Shape it to the frame shape you want and skin it with cabon fiber. Voila!
Click to expand...

+1 only thing that should be done with it IMHO...with what you have left buy that outrunner you always
secretly wanted and build a park flier aeroplane to play with :)

BEst of luck with whatever you choose to do with it anywayz John...

KiM
 
I'm actually looking toward Kurt Hughes cylinder mold method for the big cat. The smaller one is Bernd Kohler's Duo 480 that I'm modifying for greater displacement with his input.
 
Balsa has a lot of strength already, so if I was made of money for something like carbon fiber, then to me the better "skin" for the balsa would be aramid fiber (kevlar) to greatly increase its toughness. When I'm ready to try something in carbon, it will start with a rigid foam core that is much lighter than balsa.
 
The resin-soaks-into-core problem is present with many core materials (e.g also foam cores). Two alternatives
1. Lighten first coat of resin with glass balls.
2. Make shell in a mold and glue in core with a controlled amount of glue; enough for adhesion, but not soaking the core.

For rounded cat hulls you don't need a stiffening core. E.g. the Hobie 16 cat with asymetric hulls, and a very flat hull outside has core, but the Hobie 18 with round hulls and cenerboards does not.

This is a classic book for how to make round symmetric hulls from plywood:
Gougeon Brothers on Boat Construction: Wood and West System Materials, 1979

John in CR said:
I want curves, not flat panels. I'm not sure I need that extreme stiffness, so grains running the length may be sufficient. The problem I see with end grain balsa is that it literally sucks up the epoxy resulting in too much weight.

In the meantime I already have most of the thin plywood panels ready to go for a 4.8m beachcat. I'm going to modify the asymmetrical plan to make the hulls symmetrical and get more weight capacity by "torturing" the plywood side panels into a curved form, making the hulls more U shaped compared to the asymmetric V in the plan. I'm doing the mods to make it hybrid electric and wind.
Click to expand...
 
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