Wood type

[LandLubber No More]

I have a 1967 Pacemaker with several planks needing replacement. The original specs, as far as I have been able to determine, say she was planked with mahogany. I have two questions:

1. How do I determine for sure it is mahogany?; and
2. Do the replacement planks have to be mahogany or can I use something else? (I do have access to some white oak)

[Bruce Hooke]

Mahogany should be fairly easy to recognize if you can get down to some reasonable clean wood. Here's a picture I found on the web.

http://www.edromanguitars.com/resources/images/Mahogany-swietenia.jpg

It should be noted that there are a number of varieties of mahogany that look fairly similar but that are in fact totally unrelated. What is usually considered best for marine uses is "Honduras" or "Central American" mahogany. There is also a group of trees from SE Asia that are sold as "Phillipine Mahogany" and there is yet another species that is sold as "African Mohagany". Looking at fresh samples it's not too hard to tell the difference between the three. It is likely to be harder on old planks. However, on an older boat built in North America I'd guess that if it's mahogany then it's Honduras Mahogany -- but that's just a guess on my part.

White oak does not strike me as a good substitute for mahogany planking. Oak is harder and heavier and so may strain the frames and related parts and it also moves around much more with changes in moisture content so you are likely to have more trouble with seams opening up.

[LandLubber No More]

7/8" Phillipine Mahogany Carvel Construction.
Oak Keel and Frames.

The only spec I have says Thiokol type sealer used for bottom seams. I intend to google it but does anyone know what the hell that is?

[Keith Wilson]

"Thiokol" is also known as polysulfide; 3M #101 is a well-known type. It's sticky, hardens to something resembling rubber, and smells like sulphur out of the tube.

[paladin]

The "Philippine mahogany" in use in 1967 was a variety called tangulle which was close to honduras mahogany....forests literally depleted by Marcos and Chris Craft...luan/philippine Mahogany/African Mahogany/red meranti sold out of S.E. Asia today is a cheap tropical cedar.....

[BRobinson]

The "Philippine mahogany" in use in 1967 was a variety called tangulle which was close to honduras mahogany. The Philippine Mahogany, used by Chris-Craft at least, is for the most part the same Phillipine Mahogany you can buy today. Yes, is is not actually Mahogany, it is in the Cedar family, but Chris-Craft has used this "Cedar" on their cheaper boats since 1927, and began using it on all of their boats in 1932 to cut costs. Originally they had to call it "Phillipine hardwood" as to not false advertise until the term "Phillipine Mahogany" was accepted.

If you were to replace a plank with Tangile or Honduras mahogany it would stick out like a sore thumb (I've seen it done).

Chris-Craft also used Spanish Cedar from 1946-1948 when their wood supply ran out after the war, which is why so many of the boats built then were painted.

[LandLubber No More]

The planks needing replacing are below the waterline. I am not worried about how it looks. I want to make sure the new plank will expand or contract at least in a similar way to what is there. I live in an area where this boat will be hauled out every fall for about 6 months. Should I replace it with cedar? or Mahogany. I have a very good mill very close so I can get whatever I want (as long as the cash holds out).

Scott,

[paladin]

Not to start a negative discourse with mr. Robinson....but the two species are not the same...they look pretty much the same...and the loggers even screw up once in a great while and cut down a missed tanguille tree and do not know the difference...but it definitely ain't the same wood..lived there too long and cut up too much of it........

[werner]

think Sipo would be a reasonable choice for replacing mahogany planking. I had to make the same decision for my boat.
But for the shelf of my boat (4cmx9cm 10m long)wich was originaly in honduras mahogany I do not think Sipo is a good choice.What is?....I haven't made up my mind yet.
a good quality douglas perhaps ?

[LandLubber No More]

Guys, I wouldn't know the difference between the two trees your are discussing if someone hit me over the head with them. I do know enough to not want a replacement plank to expand and contract greatly from those around it. I can get Honduras Mahogany locally so I may go with that.

[LandLubber No More]

Thanks Mike (and all). I am slowly absorbing all the advice. I think I have turned into a wood boat information sponge. I bought "Frame, Stem and Keel Repair" wooden Boat Series.... I think that is the name of it. It has some great material in it. I intend to acquire more of that series of books. I have always been a - Get out the manual and learn how to do things properly - kind of guy, so I am hoping that the more questions I ask and material I cover the fewer major problems I will have. Thanks for the advice!
While I am at it, can anyone recommend a good book on Transom work/replacement for bigger boats (30 footer)? I have been unable to find much.

[LandLubber No More]

Here I go again. For planking, are quartersawn boards the norm, better, not so good....?