God Is Made Of Aluminum...

[FAST FRED]

Aluminum seems a great material , but the older cruisers we have seen get all the tin boat hassles.

Dents , the starved horse look , and gouges from pilings that are too deep to polish out.Sure a ton of filler and a few weeks of fairing might improve the look, but the Joy of aluminum for a cruiser is the LACK of care needed to maintain a finish.

I think the sheet GRP system that Kelsall uses would be as cheap and perhaps even lighter for a one off , and certanly GRP construction does not take 5 years to learn.

The Kelsall system is limited to simple curves , not compound , but thats usually the limit on most aluminum designs too.

FF

[Brent Swain]

Alumium and the equipment to weld it is just to damned expensive.
My alumium dinghy was getting a lot of holes corroded thru the bottom before it got stolen by a metal thief and turned into scrap. I now have a fibreglass one , to ugly to be sold as a dinghy , quickly recognizable if someone does, and scrap fibreglass is as worthless as a conservative election promise.
Now I get to use antifouling paint on her, something that's getting much harder to do with aluminium.
Brent

[Sean Herron]

Hello...

What a bunch of poo...

I have no idea what you are talking about - I thought this was the Lynda Carter and Lucy Pinder site...

Or shall I share my favourite sandwich recipe...

SH.

[Brent Swain]

With rising oil prices FG is probably even more expensive.
The steel for a 36 footer is around $9500, still a fraction the cost of aluminium or especially FG. Tougher too, and much simpler to build.
Great pictures.
Brent

[lazeyjack]

now you are really talking nonsense, will listen as long as you dont exaggerate, Al Al is 6000 a tonne, it goes three times as far as steel, it works out cheaper cos you dont paint, it works 3 times as fast, and the only expensive item to build is the power pac and true pulling gun I can rip a 6m plate with saw, so accurately that it is like laser cut, and so fast that laser cutting or plasma our whatever is a waqste of time and money however I will not argue with you, you are totally blinkered

[rwatson]

Lazeyjack - I have noticed you have had a lot of experience in aluminium, and the points you make make a lot of sense to me.

I have designs for a 28ft trailer sailer in progress, and I wondered if you have come across successfull aluminium versions of craft this size and purpose ?

From what I picked up off the grapevine, we are probably look at 6 mm plate do you think?

The final straw is whether I could teach myself enough Mig welding to build it myself. I have done a bit of ARC stuff, which got a lot better after I bought an 'instant' mask - but the science of Alu welding still seems a bit daunting.

Any thoughts welcome

[kach22i]

I have NOT read this whole thread.

I have found a site with some good comparision tables, slighted toward composite/fiberglass though they be (nothing about stress cracks in fiberglass skin).

Sample:
http://www.airlifthovercraft.com/Hov...5/Default.aspx

Corrosion

Even marine grade Aluminium is subject to corrosion and must be monitored carefully throughout it's lifetime for signs of corrosion. Aluminium hovercraft typically use very thin sheet and it does not take long for corrosion to have a debilitating effect on the whole hovercraft. Typical problems are:

* If moored alongside a steel vessel and inadvertently electrically connected (touching metal), the hovercraft will act as a sacrificial anode to the steel vessel and suffer accelerated electrolysis damage.
* Tools inadvertently left in the bilge's can corrode through the floor plate in very short time (weeks), a copper coin dropped in the bilge will corrode through the Aluminium plate very quickly.
* Interaction with dissimilar metals belonging to the hovercraft equipment. This is unavoidable and can only be kept under control by scrupulous maintenance procedures.

I've seen other such charts and claims, but I think this is a nice collection, click the link if you have some time to burn. Click Hovercraft Information at the top and explore.

[SheetWise]

"I have found a site with some good comparision tables, slighted toward composite/fiberglass ..."

Slighted? That's downright biased.

[lazeyjack]

Originally Posted by rwatson

Lazeyjack - I have noticed you have had a lot of experience in aluminium, and the points you make make a lot of sense to me.

I have designs for a 28ft trailer sailer in progress, and I wondered if you have come across successfull aluminium versions of craft this size and purpose ?

From what I picked up off the grapevine, we are probably look at 6 mm plate do you think?

The final straw is whether I could teach myself enough Mig welding to build it myself. I have done a bit of ARC stuff, which got a lot better after I bought an 'instant' mask - but the science of Alu welding still seems a bit daunting.

Any thoughts welcome

sorry mr Watson, I did not see this post
6mm is very very strong, typically we use on the bottom of fast powerboats at that length,
i have built 45 footers with 6mm, so depends, if round bilge 4 -5 five will do, if chines 6 will make it easier for bottom, 5 on topsides, 4 deck, do you have a plan?
mig? well its not hard, with a pile of scrap you can learn, and I can always help you here
You really need a good pulling gun, push/pull as they are commonly called, , but the only true pull gun was the hobart Linear, No longer made, all the others are assist guns, Hofftiger, Binzel Cobra,
, Binzel would be my pick
You can drive yourself completey nuts using just a push system, as soon as you try bending the gun cable, the wire slows and the volts stay up and you get burnback

Au is not the bestest place to buy good used power packs, but on ebay USA you can fing grunters, millers, hobarts and Lincolns
I have yet to see or find a single ph power pac(230 vac THAT WILL WELD 6 PLATE, You need reserve power, that means a 300 amp welder min
sorry for delay

[Boston]

funny
I thought God floated

[rwatson]

Thanks for the advice and encouragement lazeyjack. I have done enough building to know that the right tools are the main game. I imagine if I looked hard I could probably track down a good value secondhand unit, but I dont mind paying for the best.

Re the fibreglass V aluminium debate - the hovercraft info is spot on, but more applicable to the high velocity, high vibration noisy hovercraft world.
They do say about aluminium "Cost of materials is less than good quality composites. Also there is less need for stringent quality control in the construction process as the aluminium quality is controlled by the metal manufacturer."
Generally, mixing the goo, keeping it in the mould and curing it properly is a very laborious and unpleasant experience, that may go wrong in big lumps. Its easier to know what you are getting in an alloy boat because most of the damage is on the outside, where you dont know what is going on inside composites (especially balsa). Likewise, repairs in aluminium require proper tools, but have a read about the traps in repairing fibreglass, usually requiring a vacuum pump for infusion to get a really good repair.

For out of the water, tow it around the country, build it yourself jobs - I am heavily biased towards god of aluminium.

[kach22i]

Originally Posted by rwatson

I am heavily biased towards god of aluminium.

I like aluminum, it's all shiny.

The additions and alterations to my hovercraft involved aluminum from the local hardware store. I go with what works, and I'd rather work with aluminum 75% of the time.

http://s184.photobucket.com/albums/x...ch22i/?start=0





EDIT: With the price of fuel/oil/gas boat builders may soon be building to light-weight hovercraft standards.