# Aluminum vs. Wood for framing (Am I missing something?)



## Sayre32 (Dec 7, 2010)

I have planned all along to do an aluminum deck frame for my conversion. I thought that it would be much lighter and last forever even though the price would be much higher. However, after a few calculations I found that 1 ft. of T6 aluminum 1x1x.125 tubing weighs .5132 lbs. so 100 ft. would weigh 51.32 lbs. An 8 ft. 2x2 stud weighs around 4 lbs. So 100ft of wood bracing would weigh 50 lbs. Just on the framing you would save around $150 using wood after considering spar urethane sealant for the wood. So the only really benefit is longevity. Does somebody else have a different calculation? I am using numbers from suppliers.


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## FishyItch (Dec 7, 2010)

Sayre, I'm looking forward to a good answer to this question as well since I'm trying to decide how to frame my boat in the spring. I think I'm probably going to go with wood since I'm more comfortable working with that than aluminum.

But to (sort of) answer your question...Some of the framing jobs I've seen done on the forums with aluminum have not been done with _tubing_ but aluminum _angle_. My guess is that would cut the weight you've calculated by about half. Can someone back me up on this? It's just sort of a half guess.


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## bassboy1 (Dec 7, 2010)

You weighed it with 1 x 1 x .125. Try a larger tube, say 1.5 x 1.5 x .125, or 1 x 2 x .125. Now, you aren't comparing apples to apples, as even though the larger tube is heavier, a deck can often be built with larger spans, and overall, less weight. On some deck layouts, on some boats, it is where the weight gains will be. However, on other deck layouts, and with some boat hull designs, it isn't practical, which is why we go back to the 1 x 1. One more thing to look at is 1 x 1 x .063. You definitely can save some weight there.

For the boats I work on, the aluminum is used primarily for the longevity, and for lack of maintenance needs. I never have to worry about a cover not working properly, that is, if I even bother covering it, and rain, leaves, etc left in the boat during storage are no real issue. Aluminum will never warp as it gets wet and dries out, and won't develop soft spots. Pretty much the same reasons as choosing an aluminum jon boat over the equivalent plywood boat. More to do with durability than weight.


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## FishyItch (Dec 7, 2010)

There we go, that's a much more thorough answer.


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## Sayre32 (Dec 7, 2010)

Yeah, I definitely see the longevity benefits of aluminum, but I think that the weight will be close in the end. I agree BassBoy, I guess you could go a little further with the supports. However, I would think 1/16 would be pushing it pretty far. It feels weak to me, but you have much more experience. Anyways, just kinda caught my attention doing some calculations.


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## Sayre32 (Dec 7, 2010)

Oh I forgot to talk about the aluminum angle. It would def decrease weight, but it seems hard to keep everything flush. I haven't really seen one on here that keeps everything flush using angle, Im sure there is some though but it seems a lot harder. Looking at Bassboy's aluminum tubing builds everything if flat and in-line. Most using angle is all over the place, therefore I would think it would sag to the lowest support.


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## perchin (Dec 8, 2010)

Sayre32 said:


> Oh I forgot to talk about the aluminum angle. It would def decrease weight, but it seems hard to keep everything flush. I haven't really seen one on here that keeps everything flush using angle, Im sure there is some though but it seems a lot harder. Looking at Bassboy's aluminum tubing builds everything if flat and in-line. Most using angle is all over the place, therefore I would think it would sag to the lowest support.



I didn't use 1/6" thick materials.... I also had no issues with keeping things flush.... I don't really follow what your getting at with it sagging to the lowest support :? 
Come stand in my boat... I weigh in at 220lbs, and my fishing partner is larger than me. We have no sag issues at all. :wink:


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## BassChasin (Dec 8, 2010)

Ok this is an interesting subject here I have been thinking alot about this on my build as well as far as the weight but as far as the strength I am almost positive if you lock either one down with plywood neither the wood or aluminum would be weak the plywood on top of both of them makes them solid Its only my opinion from being a carpenter in residential and commercial projects. If anyone has ever used metal studs they are week until you secure something to them it makes it really strong same concept just my 2 cents


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## poolie (Dec 8, 2010)

As Bassboy said, it's more about durability than weight savings.


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## perchin (Dec 8, 2010)

BassChasin said:


> Ok this is an interesting subject here I have been thinking alot about this on my build as well as far as the weight but as far as the strength I am almost positive if you lock either one down with plywood neither the wood or aluminum would be weak the plywood on top of both of them makes them solid Its only my opinion from being a carpenter in residential and commercial projects. If anyone has ever used metal studs they are week until you secure something to them it makes it really strong same concept just my 2 cents



huh??? the studs you mention are paper thin tin... the aluminum angle most use is 1/8" thick, and most can't even bend a 2 foot piece.... kinda a huge difference there. :wink:


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## bassboy1 (Dec 8, 2010)

Sayre32 said:


> However, I would think 1/16 would be pushing it pretty far. It feels weak to me, but you have much more experience.



Take a look at the Yazoo in my sig. All the tube in it was 1 x 1 x .063. Also, the decking was all .090, as opposed to the commonly used .125. That was my personal boat for a few years, and never had any issues with 300 pound coanglers, nor did I ever have any problems stacking 500 pounds of concrete block in it, for service projects on Allatoona. It does depend on deck design. I have a handful of times that due to the desired designs, larger spans and thicker material is more desirable. 

I use .125 primarily these days primarily due to availability in my area, and the fact that a 21' stick of the stuff is often within 2 bucks of the thinner. 

The way to make it lighter is to loose the angle and tube, and work instead with formed sheet (thinner stuff). Not to say that the extrusions should be eliminated in entirety, but instead of building a frame with extrusions, then sheathing them with sheet, use a combination of sheet and extrusions. Take a look at many factory built boats. Many of them have entire decks and all built with just brake bent sheets. On a factory boat, this is very cost effective, as once the designs are made, and the specific tooling (various brake dies, etc) acquired, it is pretty simple to shear and brake the same part over and over, and a decent deck can be built quickly in mass production. _However_, unless weight savings are the primary goal, it isn't necessarily cost effective to make the patterns for one off boat builds, and the equipment needed to properly form such often costs much more than the small shop can afford, and is too big to be practical in a small shop.

I've been getting a local shop to do some brake work for me these days. When I finally get the shareaproject page made for a customers 1648 Alumacraft I'm working on. In certain places, I've used formed sheet as opposed to building up extrusions. In this particular case, even though it was a one off, the simple design did allow for time savings, and eliminated about 40 inches of welding, which results in cost reduction for the customer, even though the weight probably remained the same.


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## bobt (Dec 8, 2010)

To add to the framing discussion; my son and I recently completed modifications on his 1448 mod V to extend the front deck and add a rear deck. We used 6061T6 aluminum angle framing for the rounded corners and added strength, most of it being 1" x 0.125 and one larger/thicker piece for the main crossbar at rear of the front deck extension. 8' of the 0.125" weighs 3 lbs per Metal Supermarkets web site. Then used 3/4" marine plywood for decking material. The 500 lbs between my son and myself yielded no flexing or sagging anywhere on the decking.

We used all pop rivets or thru bolting making the install relatively simple and no problem in keeping the surfaces flush. We added some flat bar on cross beams to make surface flush with the horizontal beams. Tools needed: Drill, hand rivet gun(don't buy a cheap one), hack saw.

One additional benefit not previously mentioned is the space saved by using the aluminum angle vs 2x4's for framing.

So the pro's we encountered using aluminum were 1)saved weight, 2)easy to install with hand tools, 3)better yield of storage space, and 4)certainly less maintenance.

We were able to get our aluminum from the Tampa Metal Supermarkets store and that gave us a price lower than that listed on their website.


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## Sayre32 (Dec 8, 2010)

Ok, I do understand the other benefits of aluminum, just don't entirely believe the whole "much lighter" thing. Bassboy is right, I don't guess you would use the same footage on aluminum as you would wood. So it would be a little lighter, I just don't think it is as much as people think. 

Perchin, I usually see people overlaping aluminum angle and the results are that the plywood sits on the highest piece and sags to the lower piece. I know it is only an (1/8") or whatever thickness used, but there still will be sag from highest to lowest angle. Probably not a big deal at all, but I would rather have everything flush. Didn't mean to down anybody for using angle, I thought about it myself, just didn't like the whole overlaping thing. 

Bassboy, the Yazoo build looks good so I guess you can use .0625" I guess it just doesn't feel that strong in the store, but once you get everything together it really is.


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## 89Suburban (Dec 8, 2010)




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## BassChasin (Dec 9, 2010)

yes Perchin you are right but the plywood gives either wood or the metal strength I was using metal studs as an example when tied together properly.


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## Jr Branham (Dec 9, 2010)

Not to hijack this thread, but, Bassboy when are you going to post the shareaproject 1648 you speak of?? I'm anxious!!!

jr. b


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## PartsMan (Dec 9, 2010)

If I could work with aluminum like Bassboy I would use it for everything.
But I can not. I will be useing wood if I add anything to my boat.
I have the tools and know how for wood.


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## FishyItch (Dec 9, 2010)

Pardon the pun, but I'm in the same boat as you, PartsMan. Plus, I don't plan on building a raised deck, just a flat floor and turning the benches to storage, so I think I'm fine with just wood.

Also, I know that aluminum has an advantage of longevity and durability, but what's the limit on wood if it's got a few coats of spar varnish and it's taken care of? (i.e. no standing water in the boat, all wood under marine carpet and sheltered under a boat cover or roof) I mean, I would imagine the wood would last just as long as the carpet on top of it. 5 years? 10 year? 15?


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## perchin (Dec 10, 2010)

FishyItch said:


> Also, I know that aluminum has an advantage of longevity and durability, but what's the limit on wood if it's got a few coats of spar varnish and it's taken care of? (i.e. no standing water in the boat, all wood under marine carpet and sheltered under a boat cover or roof) I mean, I would imagine the wood would last just as long as the carpet on top of it. 5 years? 10 year? 15?



Far too many variables to answer that question... where is it going to be stored? how much use will it see? do you ever fish in the rain? how often will it be out?

typically though wood, if properly sealed and under carpet, will last a good many years. :wink:


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## perchin (Dec 10, 2010)

BassChasin said:


> yes Perchin you are right but the plywood gives either wood or the metal strength I was using metal studs as an example when tied together properly.



I understand your point....I just think that its a moot point in regards to how a boat mod should be properly framed while using aluminum. 8) 
During my build, at no time would the framing have been loose or moveable or weak, before I laid down the deck.... call me going overkill I suppose :roll:


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## BassChasin (Dec 11, 2010)

I can agree with you on the overkill Perchin its the only way I know how to do things too I just started my boat mod and I am using wood gonna paint it with fiberglass resin before carpet I am just trying to rip 2X4s in half where i can to save a few pounds 3/4 plywood is where most of the weight comes from but its solid.My boat had 1/2" on the floor and it was flimsy between the supports.this is a good thread and gives you something to think about


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## perchin (Dec 11, 2010)

BassChasin said:


> I can agree with you on the overkill Perchin its the only way I know how to do things too I just started my boat mod and I am using wood gonna paint it with fiberglass resin before carpet I am just trying to rip 2X4s in half where i can to save a few pounds 3/4 plywood is where most of the weight comes from but its solid.My boat had 1/2" on the floor and it was flimsy between the supports.this is a good thread and gives you something to think about



Heck yeah... everytime I'm out in the shop building something... In my head I'm doing the Tim Allen Oaahh, Oaahh, Oaahh


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## Brine (Dec 11, 2010)

Sayre32 said:


> Perchin, I usually see people overlaping aluminum angle and the results are that the plywood sits on the highest piece and sags to the lower piece. I know it is only an (1/8") or whatever thickness used, but there still will be sag from highest to lowest angle. Probably not a big deal at all, but I would rather have everything flush. Didn't mean to down anybody for using angle, I thought about it myself, just didn't like the whole overlaping thing.



If you wan't to use angle and have it flush, you simply use flat bar in the same thickness you are using for your framing. There is a pic somewhere early in my build that shows bassboy holding some scrap together that demonstrates this.

So, if you use 1.25 x 1.25 x .125 thick angle, you would use 1.25 x .125 flat to have everything flush. 

Hope that helps.


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## benjineer (Dec 15, 2010)

I agree with what you are saying about the overlapping angle. I couldn't get over that either. I did mine flush by using little angle brackets to connect the angle. It used more rivets and added some extra cutting, but the floor doesn't sag at all. It is plenty sturdy.


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