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Luan boatbuilding


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  #1 John Stevens

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Posted 11 December 2005 - 01:27 PM

I asked a question about using non marine plywood for building a 15' minuet and got some good answers.

My next question is: Can I build a boat out of luan if I cover it with a few layers of glass? I think the boat calls for 3/8 on the bottom. Just trying to look at ways to save some money. Thanks.

John

  #2 Greg Luckett

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Posted 11 December 2005 - 01:53 PM

I take it you mean an exterior grade?

In any case, the answer is yes. The qualifier is: how long do you want the boat to last and where will it be used? Covering the luan with several layers of fiberglass is a form of "cold" molding.

The little bit of money saved on substandard plywood will be way offset by the added cost of fiberglass as well as later repairs and/or structural failures.

  #3 Barry Pyeatt

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Posted 11 December 2005 - 02:49 PM

I'm in agreement with Greg and of the opinion based upon a rather large number of boats that have been built using Luan that the savings is false economy. Particularly in anything larger than a one sheet skiff. If you don't care about how long it will last, how much maintenace it will need or how sound the boat will be then go right ahead.

A few layers of glass means just what to you? A better grade of plywood will cost you 2-3 times what the Luan will cost. From a life expectancy pont of view, how much glass and what resin are you planning on using that you hope will make up the difference? Total encapsulation with glass and resin? It will cost you a lot more in glass and resin than better quality plywood for the structure not to mention labor and you still end up with a lower quality end result.

I'm a maintenance person, I understand that wood boats require a lot more than plastic boats and that rot and deterioration can be a major problem in a wood boat. The unknown wood at the heart of most Luan plywood is anyones guess for the most part. Voids are common and plentiful. No rated standards for most Luan makes for its low cost and most common use as packing grade plwood. Some of the exterior grades are suitable for underlayment in a home but that isn't the same as marine use by a long shot.

Its only advantage in my experience is that it is cheap. And in boat building that makes it a lot more expensive

Having said all of that, we used a lot of Exterior grade Luan for patterns, mockups and non structural components that would be totally encapsulated.

But then it is always builders choice and builders decision.

  #4 PAR

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Posted 11 December 2005 - 06:22 PM

Lauan is troubled by a number of issues, that aren't helpful in the boat building process.

The hull planking accounts for a surprisingly small amount of effort, materials and time in the over all build picture. On larger boats, the planking of the hull is typically less then 10% of the total output necessary for a boat. In smaller craft this percentage may reach 15.

Considering this fact, it wouldn't be much of an advantage to cut corners on the most important wood in the boat (the planking) As a general rule, the planking stock is some of the highest grade stuff you put in the boat.

Lauan has limitations in construction that cause problems too. The outer veneers are usually quite thin, often being paper thin and cosmetic in application. In a 1/4" sheet with 3 layers, the two outer skins provide 90% of the longitudinal strength of the panel. If the outer skins are thin, you're left with a very weak sheet and it shouldn't be relied on for stressed loads, like is common in stitch and glue (tape and seam) construction. In lightly constructed, very small boats the panel loading is small and many have had success using lauan, but in heavier, more stressed boats (cabined sailboats in particular) this type of product will fail quickly.

Lauan is a pine (it's not mahogany, not even close) and a weak one at that. This coupled with the low ply count, thin outer veneers and other lesser construction practices, makes it a poor choice for planking or other structural members. It does have a place and takes a nice finish. It's reasonably light weight can be used in shelving, drawers and many of the other things that count toward the completion of the boat. After the hull is built, you still have 85% or more of the yacht to complete, many of these things can use a skin of lauan or be totally of lauan.

To directly answer your question, a kayak, yes. In a more substantial craft it shouldn't be recommended.

  #5 Charlie Jones

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Posted 11 December 2005 - 09:39 PM

John- the most expensive thing you will spend on the boat is your own time, and when you are finished you will want something you can be completely proud of. The cost difference in the long run will be not that great, compared to the total cost of the boat.

Use good plywood.

I did use Luan on my Minipaw- I built it in a hurry, used left over glass cloth to sheath it and really didn't expect it to last long. We needed a dinghy quickly, so I used the luan and built the boat in a couple of weeks.

I wouldn't use luan on a larger boat- it's just false economy.

  #6 Ken_Potts

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Posted 12 December 2005 - 10:20 AM

Back in March I helped a friend build a little boat to putter around in and fish from. Before building the boat I told him to consider using marine ply but since it was a small boat that we wouldn't expend much time building (it took us 20 hours over two weekends) he decided to go the cheap route. As soon as the boat was finished enough for him to sit in he said "you know, I think we should have used marine ply." :lol:

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