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Old 21 November 2016, 14:47   #1
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A-frame thickness?

Hi guys,

Just a quick one...

What thickness is recommended for an 2" diameter a-frame?

I have the option on both 2mm and 3mm thickness.

I'm planning on having it similar to nicks on his SR4 and potentially tow from it also.

Fitted to a SR4 with the transom mounts and floor mounts.

Thanks.
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Old 21 November 2016, 15:07   #2
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if your going to tow off it go thicker cant understand why your asking
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Old 21 November 2016, 15:23   #3
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Because the weight difference between the two is pretty big so I suppose my question is, is the 3mm necessary?

What thickness are other a-frames?
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Old 21 November 2016, 16:19   #4
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Is it a single or double "A" frame? Either way 2mm will be plenty strong enough, the weak point will be the attachment point to the boat.
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Old 22 November 2016, 01:00   #5
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Typically, what weight would a double A frame be in 2mm stainless? 5.5 to 6 m rib. Just wondering. Nik
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Old 22 November 2016, 02:08   #6
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Quote:
Originally Posted by mwb.wright View Post
Because the weight difference between the two is pretty big so I suppose my question is, is the 3mm necessary?

What thickness are other a-frames?
ah sorry
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Old 22 November 2016, 04:30   #7
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8m x 50mm x 2mm = 19.11 kg
8m x 50mm x 3mm = 28.17 kg

strength will be down to design & bracing my A frame was 2mm 60mm dia assumed length for calcs off google hope that helps

cheers
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Old 22 November 2016, 04:48   #8
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Thanks for the replies.

The link below is what I'm wanting to have made.

http://www.rib.net/forum/f8/new-aframe-for-my-sr4-42705.html

I'm guessing 2mm would be fine but just thought I'd double check first.
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Old 22 November 2016, 09:17   #9
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I'm guessing 2mm would be fine but just thought I'd double check first.
Save yourself some more weight and money and go with 1.6mm. 50mm dia with 1.6mm wall will be more that strong enough. Something to bear in mind though, stainless tube is surprisingly springy and stainless welds are prone to cracking if they are flexed - good design is essential.
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Old 22 November 2016, 11:43   #10
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stainless tube is surprisingly springy and stainless welds are prone to cracking if they are flexed .
Yer! Watch the video:

A Frame
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