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Red Columbine - A Rocket Based On A Flower

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lakeroadster

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Steamed Basswood.... mmm yummy. It appears this is actually going to work.

I cut some 1" thick plywood material into strips 8" long, one of which is about 3/8" thick. That's the inside thickness of the fins. These will act as the fixture to hold the basswood after it's steamed, while it dries.

Then I cut a piece of 1/16" thick Basswood 7-1/4" long x 2-1/2" wide.

I soaked the cut piece of basswood in a pan of hot water for an hour.

Next I steamed the basswood standing on it's edge for 20 minutes. It still seemed to stiff.

So I layed the piece flat on the bottom of the steamer and steamed it for another 20 minutes, flipping it over about every 5 minutes.

It still seemed pretty stiff but I decided to try to form it over the fixture anyway. What I found was the basswood is stiff but tends to bend well with pressure and patience. I slowly applied pressure and bent the basswood over the fixture, with just my hands.

Once it was close to the correct shape I placed the side supports and top support over the basswood and then clamped them in place.

Worth noting, I formed the piece with the longitudinal wood grain. This is referred to as forming it the "easy way", with the grain.

I'll let it sit for 24 hours and then release it from the forms.

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neil_w

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I love me some good wood-bending.

I have found that basswood is extremely bendy with the grain, but I'm still surprised it was able to make that tight of a radius. I am *most* curious to see how well it'll hold shape when dry.
 

mbeels

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Wow, very cool! That's impressive. Opens up some interesting possibilities.
 

lakeroadster

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Released the bent basswood from the restraints this morning and it was still damp. To allow air flow around it to help it dry I re-clamped it but just by the outer edges.

There was a crack in the center so after I let it the wood dry for 3 hours I added some wood glue to the full face of the radiused area.

Just as Neil predicted the part still wants to open up and flatten out if unrestrained, but it was still pretty damp. I'm surprised how springy this part is at this point. But I can always add some internal spars if needed.

So far so good.

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lakeroadster

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My second attempt at steaming basswood failed miserably.. split right down the center. I didn't soak the wood prior to steaming... didn't think it was needed.

I'll try again... and follow my own instructions :angiefavorite:
 

Greg Furtman

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@lakeroadster You might want to try gradually drying the bent piece or at least keeping the outside radius moist. Since it is being clamped around the form the outside will be drying faster than the inside which might cause the splitting.
 

lakeroadster

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@lakeroadster You might want to try gradually drying the bent piece or at least keeping the outside radius moist. Since it is being clamped around the form the outside will be drying faster than the inside which might cause the splitting.
Good idea Greg. I'll lay a damp paper towel over the formed edge on the next one to keep it damp.
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Here's the first piece, fully dried. It maintains it's shape and doesn't spring back open. It slides right over the fixture and is actually slightly snug.

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lakeroadster

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And trial #3 fails miserably also. Could it be that the first piece was beginners luck?

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Thoughts:
  • The piece needs to be steamed longer than 30 minutes? Next time I'll try an hour.
  • The first piece I formed slightly askew.... if you notice the center line I drew before steaming (see below). That might be the secret... that way the crack can't propagate straight down the part with the wood grain?
  • Wondering if I should place the piece in a zip lock bag first, with some window cleaner that has ammonia in it, and let that soak for a day before steaming? That should help to break down the wood fibers. I'm not sure though what steaming ammonia would do to our steamer.
In any event it'll be a while before I can try again. I need to buy some more basswood. I'll get some balsa too.

We'll know more later!
Any comments or suggestions will be sincerely appreciated :computer:


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neil_w

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Or break out the ammonia... or just make the fins solid balsa. I'm actually not sure what the objective of the basswood skin is, although as I said before I love to see some wood bending.
 

lakeroadster

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Or break out the ammonia... or just make the fins solid balsa. I'm actually not sure what the objective of the basswood skin is, although as I said before I love to see some wood bending.
I mentioned ammonia, not sure if you saw that or not?

As for the objective: 1/2" thick fins, with a nice round leading edge that are lightweight yet durable enough not to break at landing.

It's a challenge... you know, basically the same reason we're scratch builders, instead of kit builders. To boldly go down paths and worm holes.... where you have never gone before.
 

BABAR

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Any chance placing some vinyl tape over the outside curvature pre bending may help? Would even out the stress. Would also take a lot longer to dry, on the negative side.
 

boatgeek

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This is a little counterintuitive, but maybe also try bending it perpendicular to the grain. That should resolve the problem of breaking between the grain lines, though possibly at the cost of adding other problems. I also have a vague memory that it’s possible to oversteam wood, making it brittle. Checking how flexible it is every so often helps with that until you have a good time mark set.
 

jqavins

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I keep thinking more and more that ammonia might be the way to go. But that's from someone who's never done it, only seen the amazing results. Maybe I'll try a sample.
 

BABAR

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@Rktman might have some ideas regarding bending basswood.

Eric?
 

lakeroadster

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Question:

Please provide your thoughts on using the one formed basswood fin I have as a form to build some multi-ply card stock fins?

Basically wrap the basswood fin with wax paper, then start laying up card stock, with wood glue between each layer?​

Since the fins are u-shaped my mindsim speculates that a card stock version should be structurally sound for this size rocket?

If after laying up the card stock it seems flimsy I could include an internal boxing plate to close the u-shape.​

As always... comments are sincerely appreciated.

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jqavins

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That sounds like a plan. Using the bent basswood as the form will give you a bigger end result, if you're forming around the outside, or smaller if you use the inside. You could make a dedicated form out of sheet metal, aluminum or brass.

I'm going to assume that the floor is open, and presume to offer another plan.

I would start with a 3/8" sqare piece of balsa or basswood. Glue 1/8" by 3/4" strips to two opposite sides to make a piece of channel with a very thick base. Then sand in the inside and outside curves.

Bending is still the coolest, and probably the structurally best way, if you can work out the techniques.
 

lakeroadster

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That sounds like a plan. Using the bent basswood as the form will give you a bigger end result, if you're forming around the outside, or smaller if you use the inside. You could make a dedicated form out of sheet metal, aluminum or brass.

I'm going to assume that the floor is open, and presume to offer another plan.

I would start with a 3/8" sqare piece of balsa or basswood. Glue 1/8" by 3/4" strips to two opposite sides to make a piece of channel with a very thick base. Then sand in the inside and outside curves.

Bending is still the coolest, and probably the structurally best way, if you can work out the techniques.
Yep... all options are on the build table...

I guess it makes sense to just use the wooden buck that I made.. that way I can maintain dimensions that match the drawing.

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Rktman

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1/16" contest grade balsa will easily bend widthwise and conform to your wooden buck if soaked in ammonia for 10 minutes (or Windex with ammonia for 20). It may need to be supported inside with foam or balsa cross-bracing.
 

lakeroadster

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1/16" contest grade balsa will easily bend widthwise and conform to your wooden buck if soaked in ammonia for 10 minutes (or Windex with ammonia for 20). It may need to be supported inside with foam or balsa cross-bracing.
Bought some ammonia, and some 1/16" balsa.
Soaked it for 15 minutes.. still to stiff,​
Soaked it for 30 minutes.. still to stiff​
Soaked it for 45 minutes.. still to stiff​
Soaked it for 60 minutes.. tried to bend it around the form... the balsa snapped clean into two pieces.​
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So now I'm laying up some 11 mill paper, making paper-ply fins.
Started with (4) pieces of paper.. will evaluate for stiffness and add paper ply's as needed.​

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Rktman

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Bought some ammonia, and some 1/16" balsa.
Soaked it for 15 minutes.. still to stiff,​
Soaked it for 30 minutes.. still to stiff​
Soaked it for 45 minutes.. still to stiff​
Soaked it for 60 minutes.. tried to bend it around the form... the balsa snapped clean into two pieces.​

So now I'm laying up some 11 mill paper, making paper-ply fins.
Started with (4) pieces of paper.. will evaluate for stiffness and add paper ply's as needed.​

Has to be contest grade balsa (much more flexible) and must be bent across its width.


 

lakeroadster

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Has to be contest grade balsa (much more flexible) and must be bent across its width.
Thanks Eric. I'm going to give the paper ply a try for this small LPR rocket. But I'm toying with getting back into control line airplanes so the data you provided is very interesting.

My initial success on the 1st 1/8" thick basswood fin lead me down a rabbit hole... :facepalm:
 

lakeroadster

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Here's the first paper ply fin as pulled from the form. It's 4 layers of 11 mil paper glued using Gorilla Wood Glue. It currently measures .055" thick. I'm guessing it'll get thinner, and lighter, as it dries.

It seems dimensionally stable and stronger than I expected.
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I'm clamping it lightly to another piece of 3/8" wood to allow better air flow for drying and to keep it straight.

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Looking forward to cutting it to size once it dries.

Red Columbine Dwg Sheets 6 of 7 Rev 00 Modified.jpg
 

mbeels

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That cardstock looks really good from here. Probably too early to say, but I bet that'll be the ticket.
 

lakeroadster

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Nose Cone:

Turned the nose cone today out of a piece of pinion pine we cut down about 4 years ago here at our home. Came out pretty nice too.​
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Formed Cardstock Fins

I've been forming up the cardstock fins too. Not to exciting. I need five, ended up forming 6 of them. One came out pretty bumpy looking, it's the one on the upper right in the photo below. I've learned they need to stay in the clamped jig for about 3 hours minimum or they'll move around after released from the form. Probably longer in a more humid environment. It's been crazy dry here.​
The formed fins are heavy little boogers... actually weighs more than equivalent balsa or basswood. I guess that makes sense after thinking about how heavy a container of 8-1/2 x 11 printer paper is.​
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