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PostPosted: Wed Jun 01, 2005 3:55 am 
Hi Folks:

I would like to ask what you all think about aluminum vs. wood frames for ocean use. If you use a kayak extensively in salt water, would an aluminum or a wood frame survive better? Can you tell me about the advantages or problems with these frame materials? Many thanks...

Peter


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PostPosted: Wed Jun 01, 2005 5:38 am 
Brotherhood of the Golden Paddle
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Have you checked the Ralph Diaz book? He discusses this issue. Both aluminum and wood can work very well-- and both have their drawbacks, as well. Aluminum requires attention to th equality-- Feathercraft, Pakboats, etc. use good stuff, although it still requires a bit more attention than well-varnished wood vis-a-vis salt water. The former-Eastern-block boats have had issues with aluminum vs. salt water, but they may be improving.

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Chris T.
~'91 Klepper A2 w/ BSD schooner rig.
'64 Klepper Passat/Tradewind and T12 restoration projects.
Non-folding: '84 Hobie 16; early '90s Old Town Canoe.
Previously owned '04 Pakboat Puffin II and '05 Swift.


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PostPosted: Wed Jun 01, 2005 8:21 am 
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Both can be fine as long as you regularly rinse out the boat. For an extended salt water trip, through, I'd lean a little more towards wood. Maybe.

Feathercrafts, with their tight joint tolerences, are more prone to corrosion freeze-up than, say, Folbots, who rely more on metal-to-plastic joints, but they are certainly used a lot in the Pacific. (Folbots had problems in the past with rivet failures from corrosion but they've switched to different rivets).

In general, for short trips and regular maintenance, it's not an issue with quality boats.


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PostPosted: Wed Jun 01, 2005 9:16 am 
knight of the folding kayak realm

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Aluminum frames will have the tendency to lock-up on you if the joints come in contact with saltwater. If this happens, it's best to break it down shortly after the outing. Saltwater on the frame can be avoided with the use of a sea sock. Wood doesn't have these issues. Wood, however, must be kept varnished. With an aluminum frame you may have to break the boat down more often than you would with a wood frame kayak.

In terms of longevity I'd guess it's a toss up.


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PostPosted: Wed Jun 01, 2005 12:34 pm 
lord high faltbotmeister

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Paul Wrote:
Quote:
Aluminum frames will have the tendency to lock-up on you if the joints come in contact with saltwater. If this happens, it's best to break it down shortly after the outing. Saltwater on the frame can be avoided with the use of a sea sock.


I agree with your precautions, though my own water resistant sea socks do allow some water entry if I'm on the water long enough. Also, rolling a folder with zippers is a good bet to allow some water entry.

Not all aluminum tubing is created equal, with 6063-T832 ( Folbot and some FC models) being rated as "Excellent" and 6061-T6 ( some FC models and Atlatl) getting a "Good" rating.

A ounce of prevention is worth a pound of cure certainly applies in a salt water environment be it wood or aluminum. In fresh water only paddling , my FC Kahuna
( 6063-T832) remained assembled for over two years and no corrosion developed to hinder disassembly when I finally broke it down. ( Better lucky than good. ha!)

Regards,

Tom


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PostPosted: Wed Jun 01, 2005 2:28 pm 
knight of the folding kayak realm

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My understanding is that saltwater, as opposed to fresh water, is the culprit. Also, the effect will be worse in tropical climates.

Interestingly, while prelubrication of the joints is a good idea, I don't think it prevents the problem. My FC Java, which has exposed joints, showed me this. So, if you want to keep it assembled you'll need a very good sea sock, and even then as Tom pointed out, that may not be enough. If you plan on breaking the kayak down anyway, it's a mute point...unless you don't want to use a sea sock.

Tom--are you saying that Folbot uses a better grade aluminum than what's used on some FC models??? That would surprise me!


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PostPosted: Wed Jun 01, 2005 3:05 pm 
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Paul wrote:
Tom--are you saying that Folbot uses a better grade aluminum than what's used on some FC models??? That would surprise me!
Better in the sense that it is a corrosion-resistant alloy (I own two Folbots), but neither alloy is corrosion-proof. Both will lock up if allowed to sit for an extended period of time with salt water in the joints. I've gone many times for a two-week venture on the salt in my Folbots, with no disassembly until after my return.

But, I am careful to make sure the longeron joints are lubed before I go. I suspect the alloy referred to will handle longer exposure to salt water but functionally there is not much difference.

BTW, Mikeis comment about Folbot rivets is perhaps misleading. For a two- or three-month period back four years or so, Folbot got hold of a poor grade of rivets, and had to replace some assemblies, I believe. Before that interval and after, the rivets have been highly corrosion-resistant. Folbot will send Folbot owners some spares if you ask. Those rivets are miles better than most of the ones you get in hardware stores. I've never had a failure, in ten seasons of use, but I carry a dozen spares and a pop rivet tool in my repair kit.

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Folbot Kodiak, Cooper, and Edisto; three hardshells; Mothership: Surf Scoter the Bartender; dinghy Little Blue Duck.


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PostPosted: Wed Jun 01, 2005 7:03 pm 
lord high faltbotmeister

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Quote:
Tom--are you saying that Folbot uses a better grade aluminum than what's used on some FC models??? That would surprise me!


Dave is correct, not a better grade, just more corrosion resistant. My info is few years old so some changes in the alloy being used may have occured since.

Folbot and FC K-Light and Kahuna use 6063-T832
FC K-1 Expediion and K-2 used 6061-T6 as of a few years ago.
6063-T832 is a bit less expensive than 6061-T6, though the differences aren't that great.

Both alloys are very close in tensile strength at around 40,000psi. The non-annodized 6061 I use has a dull finish and tends to discolor over time. 6063-T832 has a polished look and appears to stay that way over time.

I started using 6061-T6 because it's what Feathercraft used on their more expensive boats, but I have switched to using only 6063-T832 . 6063-T832 is a bit softer and lighter in weight, but neither situation is a factor in frame strength.

On my homebuilts I use .055 wall thickness in 6063-T832, and .049 wall in 6061. The .055wall gives a tighter insert gap ( better in my opinion) in 3/4" ( .750in) tubes. Folbot uses 6063-T832 in .035 wall, so their tubes are quite light. I am not sure of Feathercraft's wall thickness, but it appears to be a bit thicker.

Attached is a pic of both tubes I've used showing wall thickness and gaps of inserts.(converted to metric) You will notice the different surface finish of the two grades and can see the gaps of each tube size.

http://yostwerks.com/Gap.html - 6061 / 6063 aluminum tubing

Regards,

Tom


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PostPosted: Wed Jun 01, 2005 11:04 pm 
peter wrote:
I would like to ask what you all think about aluminum vs. wood frames for ocean use. If you use a kayak extensively in salt water, would an aluminum or a wood frame survive better? Can you tell me about the advantages or problems with these frame materials?


Ralph Diaz in his "Complete Folding Kayaker" has dedicated 2 or 3 pages to point-to-point comparison of both materials, - there is a lot of myths and misunderstanding there. You should definitely read his book (the first 1993? edition is good enough). There are no particular benefits of one over another, - and Mike is right, for short trips, say, 1 week or less - no difference at all.

Both materials need rinsing in fresh water and then drying - aluminum needs rinsing more, wood takes longer to dry. Nobody is rinsing aluminum frames in wilderness ocean trips - no problem, it will not lock (in a quality boat), and you can rinse it later.

Some former East-block boats (namely, some Russian models) have extremely tight aluminum frames and are very difficult to assemble and dissemble, and they are difficult even if used exclusively in fresh water. They are relatively cheap, but are not "user-friendly", speaking of assembling, and - I think- not intended for ocean use. Even in these boats I'm not sure that problems with "frozen" frame joints after ocean trips were caused by corrosion of aluminum. Too tight tolerances are inherent to this design. Locking that I had (but not insurmountable) could have been caused by both small amount of grit and by initial stage of corrosion on aluminum. There are some low-grade steel parts in these boats (or, at least, they were - 2 years ago), but this has nothing to to with aluminum VS wood.

Feathercrafts have tighter tolerances than Folbots, but I never had any problem with F-craft Kahuna after 10 days of ocean paddling - frame didn't lock. I'm using the company supplied lubricant on some F-craft joints twice a season - it is also available in bicyle shops.

I wanted to comment on 6061 VS 6063 grades of aluminum, but this has been already done. F-craft website quotes T6061 grade for all it s models - which is apparently not true - Kahuna has more corrosion-resistant grade. I don't know what grade they are using in K1 now - there were big changes in 2001, prior to introducing Kahuna. If they still have T6061 on K1, - this shouldn't cause any failures due to corrosion - F-crafts have thicker wall in frame tubes (than Folbots). Locking due to lower corrosion resistance of T6061 - yes, may be - but very unlikely, especially if lubricated prior to long trips. Both these grades are very good, don't worry. The largest diameter tubes that I have ever seen, were in Russian Ladoga boat. Have no idea of aluminum grade, though.

Threre should be other criteria applied, choosing a boat for ocean trips - how often you need to assemble it, how long trips will make, would you prefer a lot of primary stability or narrow beam and roll-ablility, do you have sailing in mind, etc...


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PostPosted: Thu Jun 02, 2005 9:57 am 
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Alm wrote:
...
Some former East-block boats (namely, some Russian models) have extremely tight aluminum frames and are very difficult to assemble and dissemble, and they are difficult even if used exclusively in fresh water. They are relatively cheap, but are not "user-friendly", speaking of assembling, and - I think- not intended for ocean use. Even in these boats I'm not sure that problems with "frozen" frame joints after ocean trips were caused by corrosion of aluminum....


One person told me that the Soviet Military- for whom the folding kayaks were originally made- considered them to be disposable. They were one-way boats, assembled for a mission, and then sunk or abandoned afterwards.


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PostPosted: Thu Jun 02, 2005 3:22 pm 
mje wrote:
One person told me that the Soviet Military- for whom the folding kayaks were originally made- considered them to be disposable. They were one-way boats, assembled for a mission, and then sunk or abandoned afterwards.


Well, military often consider people to be disposable as well - if there is no other way to achieve particlar goal... They have their specific purposes and criteria. Sometimes it's one-way use, sometimes results at any cost, and sometimes durability. I'm only familiar with a post-soviet single kayak by Triton. Militaries probably use double and triple-seaters.


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