Your opinion? Cruck vs Hammer Beam/Dutch Style bent

wkheathjr · January 30, 2010, 06:58:17 PM

I am planning to design a home in "T" manner and I am juggling decision for Great Room between Cruck bents vs hammer beam and dutch style bents. Ideally the great room would be from front to back. I would like to have dutch style on front so it could hold plenty of windows to beam sun down during the morning time because it would face east where the sun rise, and then it would be hammer beam bents toward the back end. I also like the idea of using cruck all the way from front to back.

So I am asking of your opinion based on your experience of working on cruck vs hammer beam and that includes the process of designing (blueprint), layout, cutting, and raising.. Cruck vs hammer beam?? (I guess what I am asking of is which is more easier and less complicated but still capture the interest of guests when they come to visit)

Thehardway · January 30, 2010, 08:02:24 PM

The Hammerbeam represents a much higher level of joinery skill and engineering capability while the cruck represents a much higher level of difficulting in sourcing material and in keeping everything in alignment.

The hammerbeam truss can be made from short timbers that are readily available just about anywhere and easy to transport. There are a lot of joints to make with a fairly high level of precision.

The cruck especially if using matched pairs must be sourced from large , unwieldy trees with the right arch or bend and are neither common nor easy to transport for distances.

If the room is to have a formal look then the hammerbeam is unmatched in its elegance and visual interest.

If the room is to have a natural look then the cruck is unmatched in its simplicity and sheer mass.

I have no experience in raising either a hammerbeam or a cruck frame. I have read of hammerbeam trusses requiring a lot of bracing in the transition from horizontal to vertical positions as there are no continuous members forming the bottom chord. I would think that the cruck would be an easier bent to stand up because of this fact.

Hammerbeams also require engineering in the way of thrust retention at the post or wall. Crucks are much simpler at retaining thrust.

I believe a queenpost truss would give the greatest opportunity for window placement.

moonhill · January 31, 2010, 07:09:27 AM

On a recent thread on the Guilds page drift was discussed, simply put, wood will sag over time. The post will bend over time. A hammer beam truss will bend the post if they are not large enough. How large does the post have to be?

A cruck on the other hand removes all the hinge points which exist through the hammer beam truss. I see them as the same system just one is weaker.

On a different note than Thehardway's perspective, I see the use of cruck blades as using local wood which would other wise be culled out and rejected as building material. On the "green" side you saved a tree ;D. There is less joinery in a cruck system equalling less time. When using sexy timber you don't have to apply lip gloss and such either, it has a natural beauty, no oils need be applied. Get out the axe. I had to add that in retaliation to the oil finish thread.

Tim

Thehardway · January 31, 2010, 03:13:55 PM

Ditto moonhills post. If you have the trees on site, I would go with cruck and mill or hew on site. River banks or north slopes often have natural crucks. If you have no trees on site then it is a different story, are you planning to build from trees on site?

moonhill · January 31, 2010, 05:46:21 PM

The cruck blades don't even have to have much sweep in them. If you are lucky as I am your timber stand will be full of crucks, mine is. They don't have to be matched either, but it helps.

Tim

Dave Shepard · February 01, 2010, 06:04:40 PM

I'd go with a cruck, without question, but that is just my bias. People have been building hammerbeams to attract attention for a long time now. There are very few crucks in this country. Hammerbeams are complex, crucks, not so much. ;)

Thehardway · February 02, 2010, 08:00:11 AM

Dave, that's some beautiful symmetry in those crucks. Were they hewn or milled?

Jim_Rogers · February 02, 2010, 09:00:01 AM

The ideal way to create cruck frames is to fine a very large tree and then cut it down the middle to create two book matched pieces.

To find such pieces you first can create a card board cut out the shape of the piece. Do it at a smaller scale, such as 1" = 1'. And then take this cut out of the cruck shape with you out into the woods and hold it up to the shape of the tree.

And also, remember that the piece can be upside down when it's standing in the tree, so be sure to rotate your pattern top to bottom when standing back and viewing special trees to be selected for the job.....

Jim Rogers

frwinks · February 02, 2010, 11:51:26 AM

Quote from: Dave Shepard on February 01, 2010, 06:04:40 PM
I'd go with a cruck, without question, but that is just my bias. People have been building hammerbeams to attract attention for a long time now. There are very few crucks in this country. Hammerbeams are complex, crucks, not so much. ;)

couldn't have said it better Dave. For me this craft is about expression...and the rectangular frames just don't speak the way naturally curved/bent/jagged pcs do... 8)
We just milled 2 of 4 blades for our cruck frame this weekend.... not bookmatched pcs by any means, but IMO, having two similar yet distinct blades make the crucks even more "against the (common) grain" :D

Dave Shepard · February 02, 2010, 04:48:15 PM

The cruck blades were sawn on a bandmill, then hewn to shape on the sides. Both pairs were bookmatched.

moonhill · February 02, 2010, 05:09:54 PM

Did they taper as well, Dave?

Tim

Dave Shepard · February 02, 2010, 08:12:18 PM

Not on this frame. Jack Sobon did an extensive slide show during the workshop, and a lot of the cruck work he has been involved with has had tapered blades. Crucks, crooked/natural wood, and scribed work is my answer to machine cut frames. I know a lot of people get bent out of shape at that statement, but there is no reason to try and compete with a CNC machine. There is room for both. I'll be the guy in the corner with a chisel and a hand saw, making a little sawdust, a bunch of chips, and maybe a little noise.

moonhill · February 03, 2010, 06:42:53 PM

Dave, sounds like you are dealing with an 800 pound gorilla, not as many in my part of the wood but they do show up once in a while.

Tim

routestep · February 03, 2010, 07:47:46 PM

I would go with the cruck also. Every once in a while the Heartwood school offers a five day school on building one. The picture that Dave Shepard posted looks like the one I helped on last summer. It had two bents but I think a three bent cruck would be pretty neat to build. Frame size was fourteen long and twelve wide. The blades were a bit over 14 feet long I think out of white pine. The taper was made with a supported chain saw. We used axes to rough out that long joint where the blade meets the wall posts.

Dave Shepard · February 03, 2010, 07:51:24 PM

That is the Heartwood frame from last summer. Where you in the Cruck class, or the Scribe? I was in both. Just got the new Scantlings today, looks like the Guild is going to do a Cruck with the VMI in March.

routestep · February 04, 2010, 12:30:05 AM

I was in the cruck class. I might be in that picture. Way over on the left just visible between the post, yellow shirt.

I saw that cruck build for VMI also, and hope to attend. I seem to learn something new at every VMI event, so I'm hoping to learn a little more on cruck building.

icolquhoun · February 04, 2010, 08:28:26 AM

Amazing.
Dave, that one picture has me re-considering my 14'x14' cabin project. I have always been arroused (should I be saying that online?) by the cruck, but for some reason, that one picture sealed the deal. I have never seen a cruck in person either.
I have a few questions. I am assuming there was a ridge beam on that frame due to the small rafters? I don't see a brace from the blades/small collar tie the the ridge beam if there is one? For the horizontal portion of the "A", those are three separate pieces instead of some sort of wacky lap joint as well I'd assume? What type of joinery was used for the lower long joint between the outer wall beam and the cruck blades? Do the beams/blades tenon into the flooring together, or just through the long blade section where it joins the sills?
I'm lacing the boots to go have a look-see in my woodlot ;)

Jim_Rogers · February 04, 2010, 11:23:59 AM

Quote from: icolquhoun on February 04, 2010, 08:28:26 AM
I am assuming there was a ridge beam on that frame due to the small rafters?

I was at that workshop for a short visit and yes there is a ridge beam.
It is held in place something like this:

QuoteI don't see a brace from the blades/small collar tie the the ridge beam if there is one?

I don't believe there is one in this type of frame, braces for the long way go to the plate at the eave wall.

QuoteFor the horizontal portion of the "A", those are three separate pieces instead of some sort of wacky lap joint as well I'd assume?

Well, I wouldn't call it a "wacky" lap joint, but I believe it is a lap joint as the horizontal portion is all one piece.

QuoteWhat type of joinery was used for the lower long joint between the outer wall beam and the cruck blades?

I could be wrong but I believe it is a very long mortise and tenon, with the tenon being on the cruck blade. But if I'm wrong, Dave or another FF member who was present will inform us.

QuoteDo the beams/blades tenon into the flooring together, or just through the long blade section where it joins the sills?

I believe the cruck is attached to the sill with a tenon so that the foot of the blade has something to keep it stable and in place, as most posts do.

QuoteI'm lacing the boots to go have a look-see in my woodlot ;)

Enjoy and now you know what to look for you'll see lots of them......

moonhill · February 04, 2010, 04:21:19 PM

I think it could be called a "wacky" lap joint, after two saw cuts you wacky it with the axe.

Walking through the woods looking for timber has to be near the top of the list of fun things to do, I truly enjoy that part.

Tim

Dave Shepard · February 04, 2010, 06:15:11 PM

routestep, I remember you, now that you've identified yourself.

The tie beam is one piece, with a lap at each cruck blade. The corner post and cruck blade each have their own stub tenon.

icolquhoun · February 04, 2010, 07:34:53 PM

thanks for the answers everyone, it's all much more clear now ;)

routestep · February 04, 2010, 08:53:17 PM

I'll look around to see if I can find some notes on this frame, but what I remember:

The frame was raised temporarily as it was to be sold and transported somewhere.

The cross piece was scribed in as a half lap to the crucks and two pegs were used, driven in at angles to hold the lap together.

There was no joint between the wall posts and the cruck blades, just the two long surfaces abutting to each other. Both cruck and posts had a snub tenon into the sill, I think there was about a one inch space between the mortices. All tenons and mortices were 1.5 inches wide, lengths were maybe six inches for the blades.

The rafters were 3 by 5 with a step lap into the plate and a half lap at the peak.

There was no bracing from the crosstie to the roof. There was a small collar tie near the top of the cruck pairs. I think it was dovetailed.

The sills were 8 by 8 and the door and window posts were fairly small, mortised and tenoned in to place.

Layout lines were put on the floor to get the cruck blades in to position and the crosstie placed on the blades. Then they were scribed, cut, fitted. Then the second set was placed on the floor and scribed etc. I don't remember the details but getting the cruck foot lined up with the sill was very important. We spent a while leveling and measuring.