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View Full Version : Balsa vs. Basswood


DaveR
04-20-2006, 11:42 AM
First post here. I have been using basswood instead of balsa on some recent scratch builds.
Basswood seems to be a bit stronger and has a tighter grain than balsa. The fins are easy to sand and finish, not requiring much filler. Basswood maybe a little heavier than balsa, but I am willing to sacrifice a little weight for added strenth. Have not flown a rocket with basswood fins yet, but will soon. Any thougts??

stefanj
04-20-2006, 01:17 PM
Basswood has one fault:

Because it is heavier and tighter-grained, surface-mounted fins made of it are more apt to snap off during hard landings and rough handling.

This is much less of a problem with through-the-wall mounting.

ghrocketman
04-20-2006, 02:26 PM
I have no problem with basswood fins snapping off even when surface mounted: I mount them the durable way; with good ol' EPOXY ala HPR construction. Heavier than titebond, but VERY strong.
I use this method for ANYTHING 24mm "D" power and above & never have fin breakage.

Phred
04-21-2006, 09:27 AM
This is a great discussion. I have tried both over the years, and here is my 2 cents for what little it is worth:

For a while I used basswood exclusively for my model rockets, but I have moved back to balsa for the ease of sanding, and the low weight. I have found basswood to be too brittle for my tastes, and have suffered not only the above mentioned fin 'snap off' on tough landings, but also a tendency to split along the grain.

I am picky about my Balsa however, and scour all of the hobby shops I visit (even while on vacation and business) for ' C grain' balsa. I find C grain balsa to provide the best of both worlds: strength, low weight, and a certain toughness due to the swirly grain. (My wife says: "You fingered every piece of balsa in this case and you are buying just two sheets???")

Lately I have been building BT-70 and BT-80 mid power models, and I have been using 1/4" balsa for the TTW fins. I typically will taper sand the fins to 1/8" at the outer edges, and then begin rounding the leading and trailing edges. What I am left with is an attrractive, tapered fin, with a 1/4" root that goes TTW, and is really strong.

My only problem is... I hate, hate HATE sanding... :eek:

Phred

stefanj
04-21-2006, 03:24 PM
Phred:

Do you have a Demel and/or a belt/disc sander?

I got a nice sander for under $100.

If you are really careful, and use extra-fine paper /drums, you can use these to work with balsa. Takes some practice, though.

Stefan

Phred
04-21-2006, 03:31 PM
Hi Stephan,

Yes, for 'big' sanding jobs like the fins for a BT-80 sized Screamer upscale, I use my belt/drum sander... but I still hate doing it!!

Thanks for the suggestion! :)

Ph

DaveR
04-24-2006, 11:08 AM
Interesting feedback. I hate sanding as well, but I find that I get a much better finish on basswood with a lot less hassle. I have tried using a Dremel tool to sand balsa, what a disaster, I try not to swear but on that particular day, if you would have written it down I would have signed it.
Actually flew my newest 2 scratch builts with surface mounted basswood fins Saturday, one under "D" power and the other under "E" power. Great flights with no adverse recovery effects. Ground softened by recent rain may have helped, but no sheared, cracked, or chipped fins.
This maybe a topic for another thread, but how do you cut a body tube for through the wall fin mounting? How do you keep the cuts at the correct locations on the tube? How do you keep the cuts straight? I just see piles and piles of worthless "swiss cheese" looking tubes on my bench.


When in doubt, get a bigger hammer.

ghrocketman
04-24-2006, 12:35 PM
You consistenly make the cuts in the correct location on the tube by using an automated machine using a laser ! (not practical for MOST)

Any other method I see as being extremely tedious at best.

DaveR
04-24-2006, 02:38 PM
I see, being that my laser is on the blink, maybe I should just stick to surface mounting for now. I just got the impression for earlier posts that cutting your own slots was common practice. Thanks for your input. Didn't mean to ask a stupid question. Ignorance is no excuse, but it is the only one I have.

Ltvscout
04-24-2006, 02:51 PM
I see, being that my laser is on the blink, maybe I should just stick to surface mounting for now. I just got the impression for earlier posts that cutting your own slots was common practice. Thanks for your input. Didn't mean to ask a stupid question. Ignorance is no excuse, but it is the only one I have. That is why I am the saddest of all mugs.
People cut their own slots all the time (although not myself). Someone will pipe in with an answer for you on tube-slot cutting I'm sure. No question is a stupid one here! :D

Phred
04-24-2006, 02:53 PM
I have tried to cut my owm slots as well. I ended up with a real mess.

Now, when I have a model that really needs TTW fins, I order a custom slotted tube from BMS:


http://www.balsamachining.com/

Phred

Ltvscout
04-24-2006, 02:59 PM
I have tried to cut my owm slots as well. I ended up with a real mess.

Now, when I have a model that really needs TTW fins, I order a custom slotted tube from BMS:


http://www.balsamachining.com/
Yes, that is an option. I've never slotted model rocket body tubes before, but the trick is to stiffen up the tube. If you're slotting a 13mm, 18mm or 24mm tube, you can stick a spent motor case in the tube to help support it during cutting. Any other size tube you'll want to stick couplers in to stiffen it up while you cut.

ghrocketman
04-24-2006, 03:06 PM
I would most certainly agree that there are NO stupid questions here ! :)
That was not my intent with the response.
I provided the laser answer as possibly a mis-guided attempt at humor....I still think it's funny though. :p
Many do cut their own fin slots, but I find it to be extremely tedious to do this accurately without at least some sort of jig.

Ltvscout
04-24-2006, 03:12 PM
I would most certainly agree that there are NO stupid questions here ! :)
That was not my intent with the response.
I provided the laser answer as possibly a mis-guided attempt at humor....I still think it's funny though. :p
I understood your humor, I just wanted to make sure that others didn't take it the wrong way. ;)

DaveR
04-24-2006, 05:21 PM
I would most certainly agree that there are NO stupid questions here ! :)
That was not my intent with the response.
I provided the laser answer as possibly a mis-guided attempt at humor....I still think it's funny though. :p
Many do cut their own fin slots, but I find it to be extremely tedious to do this accurately without at least some sort of jig.
No offense taken with your reply. That was my sad attempt at humor as well. I don't think it is possible to fly rockets and not have a sense of humor. I believe I'll stick to good ole' surface mounting, seems a lot less painless.
In all my years I have only had a few "incidents" regarding fin shear and cracking. After a through CSI (crash scene investigation) it was always my fault. Come to think of it, if you build it from the ground up and bad things happen (barring a motor related CATO) isn't it always going to be your fault?