Boat Building Forum

Find advice on all aspects of building your own kayak, canoe or any lightweight boats

Re: Material: alu-tube rigidity
By:Brian Nystrom
Date: 11/15/2012, 7:18 am
In Response To: Re: Material: alu-tube rigidity (Bill Hamm)

: All aluminum tubing is not created equal, what grade and hardness
: is the material you bought? There is a giant difference in
: strength between one of the common soft aluminum tubes compared
: to one of the marine grade or aircraft grade materials of the
: proper hardness. The difference can be as much as 300% or more.

While this is true, strength has nothing to due with stiffness (a.k.a., "Young's modulus) and all aluminum alloys have very nearly the same stiffness, regardless of differences in their strength. The diameter and wall thickness of the tubes are what determine their stiffness. The 30mm (~1 3/16") tubes in question should be MUCH stiffer than the 3/4" tubes that Tom specs in his boats.

However, the description indicates that the fit at the joints is loose and he's using tape to fill the gaps (2mm), which is going to result in a frame with a lot of flex at the joints, regardless of the stiffness of the tubes. That's a MAJOR flaw, in my opinion. If the joints need to be shimmed, it must be done with a hard material. It shouldn't be hard to find 1mm aluminum or steel shim stock, or tubing with 1mm walls that can be split and reformed to make proper shims.

Messages In This Thread

Material: alu-tube rigidity
CarstenT -- 11/14/2012, 3:26 pm
Re: Material: alu-tube rigidity
Marc Upchurch -- 11/14/2012, 6:55 pm
Re: Material: alu-tube rigidity
ancient kayaker -- 11/15/2012, 12:06 am
Re: Material: alu-tube rigidity
Bill Hamm -- 11/15/2012, 2:03 am
Re: Material: alu-tube rigidity
Brian Nystrom -- 11/15/2012, 7:18 am
Re: Material: alu-tube rigidity
Bill Hamm -- 11/16/2012, 10:22 am
Re: Material: alu-tube rigidity
Brian Nystrom -- 11/16/2012, 12:31 pm
Re: Material: alu-tube rigidity
CarstenT -- 11/16/2012, 5:32 pm
Re: Material: alu-tube rigidity
Marc Upchurch -- 11/16/2012, 9:22 pm
Re: Material: alu-tube rigidity
Bill Hamm -- 11/17/2012, 1:39 pm
Re: Material: alu-tube rigidity
Marc Upchurch -- 11/17/2012, 3:53 pm
Re: Material: alu-tube rigidity
Bill Hamm -- 11/18/2012, 12:35 am
Re: Material: alu-tube rigidity
Marc Upchurch -- 11/18/2012, 9:40 am
Re: Material: alu-tube rigidity
Bill Hamm -- 11/19/2012, 1:16 am
Re: Material: alu-tube rigidity
Mike Savage -- 11/17/2012, 3:54 pm
Re: Material: alu-tube rigidity
Marc Upchurch -- 11/17/2012, 7:07 pm
Re: Material: alu-tube rigidity
Bill Hamm -- 11/18/2012, 12:38 am
Re: Material: alu-tube rigidity
Mike Savage -- 11/18/2012, 12:42 pm
Re: Material: alu-tube rigidity
Yostwerks -- 11/15/2012, 11:06 am
Re: Material: alu-tube rigidity
CarstenT -- 11/15/2012, 12:22 pm
Re: Material: alu-tube rigidity
Yostwerks -- 11/15/2012, 1:42 pm
Re: Material: alu-tube rigidity *PIC*
Yostwerks -- 11/15/2012, 2:02 pm
Re: Material: alu-tube rigidity
CarstenT -- 11/15/2012, 3:04 pm
Re: Material: alu-tube rigidity
Bill Hamm -- 11/16/2012, 10:26 am
Re: Material: alu-tube rigidity
Jeff Buyer -- 11/15/2012, 11:11 am
Re: Material: alu-tube rigidity
CarstenT -- 11/15/2012, 12:51 pm
Re: Material: alu-tube rigidity
Bill Hamm -- 11/16/2012, 10:32 am
Re: Material: alu-tube rigidity
CarstenT -- 11/16/2012, 5:53 pm
Re: Material: alu-tube rigidity
Bill Hamm -- 11/17/2012, 1:42 pm
Re: Material: alu-tube rigidity
Bill Hamm -- 11/16/2012, 10:29 am
Re: Material: alu-tube rigidity
Jeff Buyer -- 11/16/2012, 11:21 am
Re: Material: alu-tube rigidity
Bill Hamm -- 11/17/2012, 1:44 pm
Re: Material: alu-tube rigidity
Jeff Buyer -- 11/17/2012, 3:53 pm
Re: Material: alu-tube rigidity
Bill Hamm -- 11/18/2012, 1:45 am
Re: Material: alu-tube rigidity
Jeff Buyer -- 11/18/2012, 1:56 pm
Re: Material: alu-tube rigidity
Bill Hamm -- 11/19/2012, 1:19 am
Re: Material: alu-tube rigidity
CarstenT -- 11/16/2012, 6:53 pm
Re: Material: alu-tube rigidity
Marc Upchurch -- 11/16/2012, 9:29 pm
Re: Material: alu-tube rigidity
CarstenT -- 11/17/2012, 5:30 am
Re: Material: alu-tube rigidity
Yostwerks -- 11/17/2012, 10:40 am
Re: Material: alu-tube rigidity
Bill Hamm -- 11/17/2012, 1:47 pm
Re: Material: alu-tube rigidity
Jeff Buyer -- 11/17/2012, 4:07 pm
Re: Material: alu-tube rigidity
CarstenT -- 11/17/2012, 4:34 pm
Re: Material: alu-tube rigidity
Jeff Buyer -- 11/17/2012, 5:40 pm
Re: Material: alu-tube rigidity
Bill Hamm -- 11/18/2012, 1:50 am
Re: Material: alu-tube rigidity
Jeff Buyer -- 11/18/2012, 2:10 pm
Re: Material: alu-tube rigidity
Bill Hamm -- 11/19/2012, 1:22 am
Re: Material: alu-tube rigidity
Bill Hamm -- 11/18/2012, 1:51 am
Re: Material: alu-tube rigidity
Jeff Buyer -- 11/18/2012, 2:07 pm
Re: Material: alu-tube rigidity
Bill Hamm -- 11/19/2012, 1:25 am
Re: Material: alu-tube rigidity *PIC*
Yostwerks -- 11/19/2012, 10:14 am
Re: Material: alu-tube rigidity
CarstenT -- 11/18/2012, 4:31 am
Electrolysis
CarstenT -- 6/2/2013, 6:39 am
Re: Electrolysis
Jeff Buyer -- 6/2/2013, 7:39 am
Re: Electrolysis
CarstenT -- 6/2/2013, 9:46 am
Re: Electrolysis
Tom Cooper -- 6/2/2013, 10:35 am
Re: Electrolysis
CarstenT -- 6/2/2013, 12:57 pm
Clogged up hinges. Solution
CarstenT -- 6/26/2013, 4:43 am
Re: Material: alu-tube rigidity
JohnAbercrombie -- 11/18/2012, 3:03 pm
Re: Material: alu-tube rigidity
Bill Hamm -- 11/19/2012, 1:33 am
Re: Material: alu-tube rigidity
Yostwerks -- 11/19/2012, 9:48 am
Re: Material: alu-tube rigidity
CarstenT -- 10/17/2014, 5:31 am
Re: Material: alu-tube rigidity
Bill Hamm -- 10/17/2014, 9:56 am
Re: Material: alu-tube rigidity
CarstenT -- 10/18/2014, 6:00 am