re-using old mahogany

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Joris
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re-using old mahogany

Post by Joris »

in my search of a woodsupplier i ran into someone who has an quite large stock of mahogany planks but since i'm new to wood-working i'm trying to figger out if they could be used for boat-constructing.
planks are 50-60 years old and were probably used as floors as there are two small holes on each side (nails not screws), some with small splits at these holes.
they are all the same dimensions 3/8 rough x 4" x 8'.

I bought 50 of them thinking that if they are no good to construct frames or a hull, they might be usefull as interieur or i can use them for the terras in yard i've been promising to my wife for years... If any kind of mahogany can be used to build decent frames i would cut them to 1/2" thickness and laminat them together to get the required thickness for frames and maybe thinner pieces for the final layer on the hull and to build the deck.

If it is important to know what species this is, i can get it analysed by the Royal Museum for Central Africa but i much rather spend my money on planks...
I cut of a small piece and sanded it smooth hoping there is anyone who can recognise this.

Thanks,
Joris
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pamelalynne1
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Re: re-using old mahogany

Post by pamelalynne1 »

Many boats have been built using reclaimed lumber. As far as I know, as long as it is in good condition, there should be no reason not to use it.

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Bill Edmundson
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Re: re-using old mahogany

Post by Bill Edmundson »

Definately :!: NOT Usable :!: Bring it to my house. I'll get rid of it for you. :wink:

Bill
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Joris
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Re: re-using old mahogany

Post by Joris »

Bill, i'm sure DHL knows a good way to make these planks a lot less attractive :mrgreen:

So if i understand correctly, the differences between all the different sort of mahogany (and i found out there are a lot...) are no reason not to use these planks for frames and hull?

I noticed i posted this in the outboards-section, not really sure how i did that, can one of the mods move this topic?

Thanks,
Joris

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Lowka53
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Re: re-using old mahogany

Post by Lowka53 »

8) well from my days as a cabinet maker I would almost bet that to be the real stuff I would love to find that many in that good of condition. i would not have any trouble using them to build with :wink: 8) a few passes though a thickness planer would clean them right up and you would probably not lose as much of them they look pretty straight and i didn't see any cupping in them :wink:
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Joris
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Re: re-using old mahogany

Post by Joris »

This morning i went to see the guy that lets me use his saw and planner, he's a woodworker but admitted he's not really into tropical woods. It's pretty light and dense he said, and if it's good for boatbuilding he thinks it was a good buy.
So, i guess it's time to decide what boat it's going to be. I've started out with the biscayne 18' in my mind and have spend some evenings reading books that were recommended in differents topic on this forum. (topics themselfs have also been very helpful!)

What i'm struggling with it that every build close to a 18' runabout has a huge engine while i regularly run into old designs that originally were intended for 40-50hp, sometimes 100hp max.) With fuel costing approx. 2Euro/Liter or well over 10USD/gallon, and speedlimits on lots of rivers, this is something to consider.
Is the difference between, lets say a 250hp Biscayne '18 and a 50hp runabout design from the 40-ties (that was intended for 25hp), that the first one will be constructed for more power and that is will plane while the other one wont? All help is welcome!

If anyone knows about a design that is 18-20' , looks like a Gar Wood speedster or a Hacker runabout, and it will plane with 80hp, give me a shout :D
2L-diesels with 100-120hp are so cheap overhere that it's hard to go for anything else...

Joris

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jamundsen
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Re: re-using old mahogany

Post by jamundsen »

Most of the early Chris Crafts were powered with what we would view as small moters. The specs for the Biscayne 18 actually call for a 120 to 200 cubic inch motor. I would think a 120 hp to 150 hp would work fine. Build as light as you can. Dont add too much extra stuff
John Amundsen
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Roberta
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Re: re-using old mahogany

Post by Roberta »

WOW!! Great Buy!!! It look's a lot like dark red Philippine mahogany or possibly Honduras. That stuff will be great for planking on any classic design. A bit thin for framing, but you could laminate it.

Roberta :D :D :D
Roberta "Queen of the Boat Builders"
Built Zip "Oliver IV", Super Spartan "Jimmy 70", and Torpedo "The Glen L".

Joris
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Re: re-using old mahogany

Post by Joris »

John,
Thanks, although i'm not sure i will go for the Biscayne, it's good to know the modern 2L and 2.5L diesels are an option. :wink:

Roberta,
The plan is to make frames from these planks after shaving them to 1/2" and each frame would me made twice but having the joins in a different spot so when i glue them together, they will hopefully be as strong as a full inch plank. I'm not sure if i will need to add plywood gussets as i still need to do a lot of reading on the subject :?

You mention planking; i stumble across a methode called "Ashcroft"-planking. Since i have 18mm planks and i dont think doing full planking on my first experience, could this Ashcroft be a possibility? I was thinking to plank the hull with 1/4" planks, sand it smooth and epoxy the whole surface, then add a second layer and epoxy that too.
Maybe the same in three layers for the bottom? Crazy idea or worth doing some more research in that direction?
(btw love the colours and finish on your boat!)

Joris

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Roberta
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Re: re-using old mahogany

Post by Roberta »

Not sure the 4" planks will be wide enough for all the framing on a larger boat, but certainly some of them. Laminating will make a strong, stable frame member. The problem might be landing screws in the lamination. They might not hold as well as solid wood. Not familiar with Ashcroft. Most builders just use 1/8" ply for the cold mold double diagonal planking and use a nicer solid wood for the last finish layer of planking that will be finished brite. 1/4" could be hard to bend on some designs. Best of luck in the build. BTW I would want to use as much of that pretty wood on the sides and deck and finish brite.

Roberta :D
Roberta "Queen of the Boat Builders"
Built Zip "Oliver IV", Super Spartan "Jimmy 70", and Torpedo "The Glen L".

Joris
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Re: re-using old mahogany

Post by Joris »

I will be laminating a few pieces together next week to get a feel for the proces (i only have experience with Carbon and Kevlar laminating) That should give me the chance to check out the strength and see how good the screws hold.
I'm a long way from any planking so i will stick to what clearly has been proven to work well. Plywood it is :D
For the final layer in Mahogany, how thick should they be? Can you saw such wood to 1/8" and them bend them in the tight sections without splitting the wood?

Joris

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Bill Edmundson
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Re: re-using old mahogany

Post by Bill Edmundson »

Joris

I'm running a Yanmar 4JH3-DTE 125 hp diesel in a 20'-6" Tahoe. Will make 38-39 mph.

Bill
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
Tahoe 19 Build

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jamundsen
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Re: re-using old mahogany

Post by jamundsen »

1/8 or 4mm is what I used for the ply. I often wonder if 3 mm would have been better
For the mahogany I resawed mine with a band saw and planed it to 1/8. It went on very nice
John Amundsen
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Joris
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Re: re-using old mahogany

Post by Joris »

John,
thanks, for the info. It's kinda hard to get the good plywood overhere...

Bill,
any idea on weight for that engine? 35-40mph seems like a nice speed. Any idea at what speed is needed to plane?
I'm looking at 2L and 2.2L diesels that are giving 140hp at 3500rpm.

Joris

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Bill Edmundson
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Re: re-using old mahogany

Post by Bill Edmundson »

Dry Weight of engine 229 kg (504.8 lbs)
Reduction Gear ZF25A 31 kg (68 lbs)

I used a ZF45A which has a 1.23:1 gear ratio

The 4JH3-DTE will turn 3800 rpm. Continuos 3700 rpm.

Bill
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
Tahoe 19 Build

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