Thread: What timber for Boat frames

Originally Posted by mcchaddy

What do other people think.

I think we're going to see the birth of a lovely boat

Doug fir is Oregon if that helps. As for the rest of it, I'll let people who actually know what they're talking about answer you

Richard

I'm not an expert, but two considerations come to mind:
1) how durable do the frames need to be? especially in relation to moisture? I'd be trying to match the durability rating of the three suggested woods.
2) weight. 40mm thick silky oak frames are likely to be about 2.2 times as heavy as 25mm thick ones made from Sitka Spruce. This could affect the trim of the finished boat and how easy it is to move through the water.


hope this helps

ian

Since I come from the land of Sitka Spruce, that would be my first choice. It is a long fiber wood with very good torsional and shear strength. It is an easy wood on your power tools, much more so than oak. It is relatively rot resistant, more so than Doug fir but not as good as Mahogany. I am not familiar with the silky oak but if it is like red or white oaks, it is very hard and can be a bit brittle. Some oaks are failry rot resistant but others are not, so I'd watch out for that.

That classic ChrisCraft sounds like quite an undertaking. Good luck.

jabar

Hi Mcchaddy,

How are you going to build the boat.

Traditionally where you rely on fastenings or are you going the full epoxy method.

Both are nice approaches.

If you are planning to glue everything up with epoxy and coat all parts of the boat then both strength and durability are not so critical. The gluing of all parts to each other makes the boat so much stronger than the original the timber doesn't have to be quite as strong. So if you pick a timber of similar density with reasonably straight grain all will be well - because the boat will come out at around the right weight.

You could even use lighter timbers like Paulownia for a fair bit of the structure and easily get away with it (not engine bearers or keel structure if there is a big donk going in her - or the floors the engine bearers intersect with). Also if the piece of timber is only glued to the structure along one face (stringers, frames) I would suggest increasing the depth dimension (from glued surface to opposite face) by 6% but not changing the width. see an elaboration at http://www.woodworkforums.ubeaut.com...ad.php?t=36099

The durability of the timber is also not so important using epoxy to seal. The timber will never get enough water and air going in and out to start rotting if the job is three quarters decent.

If building traditionally then there are others here that can give better advice than I can about timber substitution. Viking, Dingo and a number of others are much better with Australian wood knowledge than I am.

The important thing is to pick timbers that have a similar density to those specified and will hold fastenings to the same degree - as well as durability as suggested by Ian.

Hope this helps

Michael Storer

Sitka Spruce might be a little expensive and mahogany, well probably more than a little.
If you are going for traditional methods then try the following. Celery Top pine, or Huon pine. Huon is getting scarce due to no trees being felled but Celery Top is still cut as a bi product to the chippers in Tassie and is a bit stronger than Huon, also takes epoxy better than Huon. It is still available in Boat grade although you may have to chase it a bit. KevM should be able to help you there.
Good luck with the boat
Scotty

Howdy Scotty,

Can you tell me more about epoxy behavior with huon - I was looking for that sort of information a year ago. What do you know?

Cheers

MIK

I have only word of mouth to go on but all my advice from my Father who is a carpenter in Tassie is that Huon it doesnt take epoxy well. I am pretty sure it is the oil that makes it such a great timbr, makes it let go of the epoxy. I may be corrected on this one but it is just something I have always avoided.
I am sure that there should be someone with some hard data, so hopefully we get some help on this.
Scotty

Hi Boatmik,

My cousin has just built a 14ft carvel hull sailing boat. He used celery top for the frames and huon for the hull planking. I know he used west system epoxy on some of it but to what extent i'm not usre. I will be speaking to him in the next few days and we ask how he went with it. I know he bedded all the screws in using epoxy and it apparently worked really well.

mcchaddy, History is of course geographic when it comes to boat building but the primary boat framing material in the US during the Runabout Hay day was white oak. DEFINATELY NOT RED OAK. This is easily verified by reading some of the older plans by people like John Hacker. White oak has very different properties than red oak, primarily its ability to flex and it will not darken with moisture. This is also one of the reasons you will see white oak used in gunwale applications so often. Mahogany is a good wood to use but it is more brittle than white oak and a bunch more expensive depending on where you are from.

All of this of course assumes that you are building a hard chined runabout as opposed to a round bilged hull. If you are building a round bilged hull and do not have serious bending jigs then the douglas fir or spruce is definately easier to work with. They are much softer and consiquently easier to bend.

Epoxy will seal pretty much any wood that is not particularly oily or sappy. When you seal members of a boat, mix up what is called an epoxy primer. This is simply an low viscosity resin with a slow hardener and about 10 to 15% denatured alcohol. Because of the chemical properties of epoxy, the alcohol will thin the epoxy mixture allowing it to penetrate the wood deeper and the alcohol will evaporate as the epoxy cures.

If you need specific info on epoxy, I encourage you to call the help line at MAS epoxy. You will most likely talk to a man named Tony if it is during the day. Tony is the founder and chemical engineer who invented the goo and probably one of the nicest guys I know. I have certainly never been able to stump him with an epoxy question and he will give you enough info to make your head hurt.

Hope this helped....

Jackbat

Hi All,

Thinned or not thinned epoxy will stick to timber.

WEST don't recommend thinning their epoxy. Here are the reasons.

http://members.ozemail.com.au/~store...ervative2.html

Best wishes to all

MIK

Any links to the Chris craft you are going to build???? PLEASE

Hi Sinjin,

It is a Chriscraft replica, based on plans by Ken Hankinson(no longer available unfortunately). Have a look at www.glen-l.com in the boatbuilders forum under the heading Hankinson & Associates. There are some links to people who have built similar craft. As far as I know this is the first of this type in australia. Please correct if I wrong. I would love to talk to other people who have built or are building this boat.

I see everyone is talking about what kind of wood to use for the frame. The true version of a Chris Craft Barrelback Runabout, was all Mahogony frame and all. Section on the Deck had Oak for alittle decorating to offset the rest of the boat. Very nice runabout, I still love them, but my father is going to kill me when he finds out that I am weeks away from starting my second building of a boat. He keeps telling me about the upkeep on the wooden boats, ( WHAT ) This is 2006, those boats built back in the 1940's didn't have the materials we have today. The outside of the Hall has a 3/16 layer of fiberglass to presurf the wood. Finally, we can now enjoy the histery of the old wooden boats that we are so admired by.