View Full Version : Boom timbers spliting after shaping?

02-04-2009, 02:52 AM
Here's a problem I experienced after shaping my boom.

The stock sat round on the shed floor, on spacers, for several months (in the way).
I cleared the shed in preparation to move Ngatira out of the shed and was faced with a nice working space to shape the boom. Squared it up with tapers and then eight sided it and left the boom sitting on horses for a week.

Skill saw method of removing corners... and

traditional way by draw knife.



The temperatures can get high while it's closed up and over the course of a week the timbers split badly longitudinally.

Was this from the heat or was it from tension in the timber?

Unfortunately I deleted the shots of the cracks but needless to say they resembled canyons!!

I have since oiled the ends with linseed.

Pernicious Atavist
02-04-2009, 08:10 AM
Sure looks like continued drying due to the heat and lower humidity. Same thing happened when the new owner of my skiff took better care of it than I did! Others will wade in here, I'm sure, with reasonable fixes. 'Luck!

12-28-2009, 03:19 AM
Ngatira is in the water and awaiting boom and blocks. Final shaping of boom is under way and I still have this serious checking of the oregan problem to solve.

What is the best remedy for the splits. Leave well alone and varnish the spar, squeezing varnish into the splits, or oil the splits, or fill with epoxy and a mix of sanding dust?

My gut feeling is to leave it and just live with the checking and varnish over, but I have a niggle telling me to fill em with something.


12-28-2009, 04:17 AM
how bad is it
the size of the season checking on the tail end of that spar will not represent the depth of the checking midway or even a small fraction of the way into the piece
specially if its just starting to appear
but its really hard to tell
sometimes you can tell by the sound they make when struck by the tail end of a hammer but if your not real experienced at sounding for solid wood you might have a hard time interpreting what you hear
what you do is slowly move the hammer down the length of the spar wile slowly tapping away ans listen for changes in pitch. will tell you something about the changing charictoristics in the wood from one area without a split to another with a split ( Thanks grand dad for teaching me that one, I miss you )

how to fix it
Ild fill with marine epoxy that was about as soupy as you could safely make it and really pack it into those cracks. then seal the wood with something compatible, fast before you end up with two or three pieces of spar. I typically oil the living crap out of finish wood with tonge oil and I seldom have any continued season checking issues after initial drying, course I wait till Im ready to work the wood before I plane it off ( I hate planing lumber, gets to my back every time ) Im kinda funny about long deep season checks in structural timbers though, seems that season check can grow into something really really close to a full blown split if not dealt with

proper drying
you mentioned having left the timber lie for a few months
the general rule of thumb to air dry to ambient atmospheric humidity is 1 year for each one inch. looks like you have a 4 or 5 inch spar there so it should have sat for a bit longer than a few months to settle in after milling.
If Im mistaken and the mill cut then dried it for you then
but even just moving an untreated timber into the sun for a few days and then back into the shed can lead to season checking in an already dry piece so what a lot of old timers do is slather shellac on large timbers that have been dried and planed but not yet shaped to there final configuration.

that has a Douglas Fir look to it
tsk tsk tsk
Dougy has a hole slew of nasty habits and although Im sure there are a few fine upstanding citizens in here who disagree with me on this but IMHO it has few redeeming qualities
I could hit you up with article after article exposing Dougy for what it is.
please confirm my suspicion one way or another
I'd say thats either Dougy or Larch but probably Dougy

if you trash that spar try Sitka or one of the other closely related Spruces

You might try built up spars as well as they tend to have less of these kinds of problems
clamp the living daylights out of the lams between two full length heavy as you can get it pieces of I beam ( c channel is what I use for shorter stuff )
your glue up spars will turn out straight as an arrow and stay that way
or at least as straight as the I beams were that you clamped to

keeping down close to the concrete might have helped keep it cool but when you moved it up onto the horses it was now up in the heat
could have contributed
dirt floors in the wood shed is the ideal
material up on stickers at least three or four inches
that and always in the shade well under the roof of the shed

best of luck and nice looking boat in the background
got any more pictures of her

I just remembered
it may be posible to put some metal hoops on this spar and to some degree help its integrity some but thats kinda a long shot and that technique is typically reservedness for much larger pieces on much larger vessels and ones that have not split yet

personally Ild consider starting over with a decent piece of wood and this time shellac it soon as you get it
much as it will drink

12-28-2009, 04:35 AM
Here Oregan is the name commonly used to describe Douglas Fir. Plenty of doug fir spars around, so Steve just needs to solve the problem with this one. The boat is Ngatira, do a forum search for recent pics.

12-28-2009, 04:44 AM
Thanks Dave
must be one of those fine upstanding citizens I was referring to
oh and thanks for the confirmation
its nice to know I still got it in identifying the various wood species although Dougy is an easy one

Ill surely go look up Steve's boat

Ild still try filing it with soupy epoxy and then slathering it with a compatible sealer hardener
if it sounds good after that then do a few bench tests and Ill keep my fingers crossed for him

best of luck

Lucky Luke
12-28-2009, 05:32 AM
Hi Steve,

The first and last pictures show exactly the same radial cracks before and after the octagonal shaping. This very clearly shows that they do not come from the release of tensions in the wood! also radial cracks are typical of drying wood.
I also second Boston in his remark: this wood sat, as you say, close to the floor for months (and during winter and spring that was) it will have stayed close to the dampness of the soil/ concrete floor, and not drying much. The moment you had it sitting on horses, it went drying fast with the now summer heat.

Besides that, my opinion would be very much the same as "expert" Boston's here-above:

- glued spars much better than solid. It will not be too late yet. If this spar is already tapered at the ends with the same tapering (or not tapered at all) , you could cut it in four quarters and glue them back together the "diagonal" pieces being "head to foot". The reduction in size due to the cutting and planing would be compensated by the extra strength given by the gluing. At the same time: why not make this boom hollow a bit?
As the long radius of the growth rings show, this wood was quite far from the heart, where it splits the most, up to near complete separation!

- would you not want to go for splitting and gluing this boom: you need to repair it anyway, and not by letting some varnish go there and that's it. Epoxy filling the cracks (without saw dust and by gravity= one by one) is OK for the smaller ones. Bigger ones (but how bad is it???) would rather get a circular saw cut all their length, with wobbling blade if wider than the blade thickness - hope not!!! - and a slither of the same wood nicely glued in. If properly done, it will hardly show. I would however consider this bit shocking after such a wonderful restoration as what Ngatira has had: wonderful job done there!!!

wizbang 13
12-28-2009, 05:33 AM
Is that air dried wood to start with? Never been in a kiln? One third seems laminated (glue seam split) and 2/3 a VG beam. Best to know the full history of a spar, including time of year it was cut and how HARD it hit the ground! Only a boom.Set it and forget it.

Lucky Luke
12-28-2009, 05:37 AM
Here Oregan is the name commonly used to describe Douglas Fir.

"OregAn": sounds like very strong Kiwi accent from you both down-under mateys!
I am afraid Boston would spell it "Oregon"! ;)

Lucky Luke
12-28-2009, 05:47 AM
One third seems laminated (glue seam split) and 2/3 a VG beam.

Sorry, but it appears solid to me. The difference in the appearance of the wood on the end cut is that it has been cut with a circular saw not deep enough to cut whole timber, and then a second cut done. There just happen to be a radial split right there, but it's not not a glue seam split.:cool:

12-28-2009, 07:14 AM
I would go with your impulse and just varnish. Or oil and varnish. Anything you put into a check will either wedge the timber when it flexes or hold water inside. I owned a boat with checks in the mast filled with a wax mix (someone will recommend it). Water got in somewhere, ran down to chest height, and rotted the spar. It couldn't dry, the filling kept out fresh air.

12-28-2009, 07:39 AM
I think checks like that happen all of the time with relatively large spars, not to worry. Put the big checks pointing down so that they don't hold water and give the checks a dose of Borax and Antifreeze every year and they'll be fine.

Bob Smalser
12-28-2009, 09:51 AM
No biggie. It's summer there, right? Your wood continues to dry after milling, beginning with the end grain first. Those end-grain checks are likely only a few inches deep.

Rig an open-sided tent or tarp to store the spars and the remainder of your wood outdoors in breezy shade with natural humidity cycles where it won't overdry as badly. In summer your shed baking in the sun becomes a (tin?) kiln of sorts complete with a concrete floor that acts as an efficient moisture sink. How's the rest of the boat doing? It may also benefit from either moving outdoors or adding a couple yards of damp sawdust shoveled onto the concrete floor beneath it, and wetting down the sawdust daily.

Under no circumstances fill those checks with epoxy or anything that hardens. After you launch the boat the humidity will increase and the checks will close. If they close on a hard wedge like cured epoxy, the epoxy will become a fulcrum and the splitting will get worse, not better.

Last, this is about moisture content and too-rapid drying.....species has zilch to do with it. Airdried Sitka would have also checked. With a moisture meter you can anticipate and correct these conditions before they occur.

John B
12-28-2009, 02:13 PM
Don't swim it in that condition Steve.

Jay Greer
12-28-2009, 05:07 PM
It is not unusual to have solid timbers check and split after shaping, especialy, if one is using kiln dried stock. Kiln drying builds up tensions within the wood that do not have time to release as with air dried material. Shaping releases tension and often allows the wood to take on a mind of it's own. Painting the end grain with heavy paint or epoxy will aid in slowing the release of moisture and help to slow down checking. As long as the boom is still straight, there should not be great cause for alarm. The strength lays along the grain. Filling the checks should be done with some soft oil based putty such as Dolfinite or soft oil based seam compound. The reason for this is that the synthetic materials on the market today have a point of compression that will wedge the spare apart should it tend to take up in a more humid condition. The oil based material will squeeze out and can be skinned off with a glazing knife. If you are not alarmed by the open appearance of the checks, they can be primed with a mixture of bees wax and turpentine and left open. This way the wood can breath more easily until it reaches a state of equalibrium. It can then be painted or finished bright.

12-28-2009, 06:16 PM
my bad on the epoxy fill kids
if it is only a season check and not a full blown split then just slathering the whole thing with sealer/preservative would allow the piece to "breath" without further damage. If its a honest to God split then you have some decisions to make
I apologize for the epoxy suggestion and I stand corrected, if its only season checking ( more likely ) rather than a full blown split ( less likely )
if its only season checking then epoxy might exacerbate the problem. If its a catastrophic split, cutting it apart may not cut it along the split and you'd end up filling with Epoxy anyway assuming you had decided to try and salvage the piece.

I'd have to say though, Dougy does have a much higher inclination to splitting and season check in the drying process as well as general defects than most other species and there is typically a much higher waste consideration from the mill with this species because of it. I was just at the mill today buying some so Ive had some pretty recent experience concerning Douglas.

best wishes and cheers to a new year

Lucky Luke
12-28-2009, 09:17 PM
Unfortunately I deleted the shots of the cracks but needless to say they resembled canyons!!

This very much looks like a "bilge" thing! A hoax! :rolleyes:

Steve: you very well know what you are doing as proves the wonderful restoration done of Ngatira. Now I have the feeling that this is just a game where you come with a couple of rather meaningless pics, alarming voice, but (purposely) no indication of how bad it is, and sit there, not saying anything about what replies you've got, just watching the "experts" battle about something on which they have not got enough information.

You've been uncovered, mate!;)

12-29-2009, 04:38 AM
Thanks for the excellent replies everyone. And some good spotting there.

On the subject of the history of this lumber I know it sat at BBS Timber in Whangarei for several years. It would be more than 10 to hazard a guess. Stuff like this doesn't shift much in Northland. I believe it was ordered for spar timber and was rejected on the grounds of the knots. The school (that started to restore Ngatira) had to purchase the whole consignment otherwise the yard was going to chop it up into shorter more sellable bits! That's the pile sitting on the floor to the left in the second photo. 17 meters long was average length. Firstly I was concerned with the knots but am holding my opinions until we get sailing for a couple of years and wait and see.

The end radial cracks I'm not worried about and yes the ends were cut with a skill saw hence the appearance of being glued at the end grain.

My fault was shaping the mast and then leaving to weather for an extended period. It's had rain, sun and baking in a plastic bag. What was I thinking? The completion of the restoration really, and the boom just got left behind. I might add at this point that this is a boom not a mast. The checking is on the side perpendicular to the grain. The orientation of the grain will be vertical to give more strength to the direction of bend so all checks will be on the sides of the boom. The spar will spend most of it's time wrapped up with sail and cover so will be out of the weather once it is put to action on board Ngatira.

At present all spars are solid with the mast being the only spar glued together in two halves.

I always remind myself of the condition of the spars on a 50 footer (LOD) Ariki and rest assured that my spars look pristine in comparison even with knots and checks. Ariki's spars are a real eye opener! With no disrespect they look like old telegraph poles and I might add do the job admirably.

Thanks again for the informative replies. I will go with the leave and live with it direction, giving the checks a good varnishing.

Check restoration progress at... http://www.woodenboat.com/forum/showthread.php?t=84324

Water has slowed right down Daniel. First few days out on Christmas day and I forgot my camera!

12-29-2009, 05:51 AM
thanks for showing us whats up with you work for better or worse
I gained a little and gave a little as always on this forum
thanks again

Im digging out Dougy splinters even as we speak