Frames notched into keel or not ?

[Peter Jacobs]

I've been building my boat over and over in my head for the past few weeks (Folkboat) and one of the decisions I having trouble making is if I should notch the frame ends into the keel and lower stem, or not.

Each book I read has a different opinion. My latest read was in WB # 93, page 70, "Painting for Longevity", an article on the importance of painting pieces during assembly, while they are still reachable. It shows a diagram (page 75) of the frame ends cut off slightly above the keel to allow future re-painting. My concern is that if the ends of the frames are sitting in pockets there's going to be a danger of water getting at them, and subsequent rot.

If I understand correctly, the floors are the binding link between the keel and frames (and the garboard, at least part way). I can see it might be easier to bend them in during installation, but other than that what's the attraction for notching them into the keel?

Any thoughts on this one ?

Thanks.

-Peter-

[Noah]

My Folkboat has the frames notched into the keel. The frame ends still seem like they are in good shape with not rot, so that is a good sign. I'm not sure that they are actually fastened into the keel with anything though. I really don't know enough about this issue to offer a good opinion based on what the better practice is.

Noah

[Matt J.]

Our Saga had frame ends socketed into the keel, and I won't be doing so with the new frames in the new keel. Nearly all socketed frames were rotted at that location. Another builder, and forumite, suggested the strength gains from socketed are offset by the problems of frame ends sitting in water that can't go anywhere.

Of course, I'll also be looking at other options for the frame-floor-keel connection as our frames are nearly all kerfed...

Good luck.

Nearly forgot, our frames were screwed into the keel with rather heavy (no 14 or 16) screws. In removing the keel, we found that the screws, large as they were, had lost any use, as they all turned easily in softened wood. I wondered why we'd create a pocket for water to sit in at the time...

[ 06-12-2002, 11:25 AM: Message edited by: Matt Joyce ]

[Ken Baker]

Hi Peter,

Sounds like a fun project.

Dave Gerr's Elements of Boat Strength recommends not notching the keel for the frame ends and apparently feels trimming the frames one frame siding above the keel will not present any structural issues. While I tend to agree, one does need to be careful to provide enough landing space for the garboard to lay and a place to locate screws to properly tie it all together. With frames on a Folkboat being sided only about an inch it's not a big deal but on a larger boat I would think this guideline through some more.

On my Folkboat (1956 vintage) the frames are notched into the keel (no current rot problems)and a screw passes through the garboard plank, through the end of the frame and into the keel effectively tying it all together. The frames are not tied to the floors.

If I were to build a new Folkboat, I would follow Mr. Gerr's advice and trim the frame up probably an inch above the keel, tie the frames into the floor and screw the garboard into the frames and the floors to keep it all together as much as possible.

Hope this helps and good luck on your project.

[Dave Fleming]

I dunno folks, it may be fine for lighter scantlings but, when you get up to something like this, In My Opinionated Opinion, I want the frame heels boxed into the keel.

[mmd]

IMHO [img]smile.gif[/img] If you consider what strength the notches are providing to the backbone structure, you will arrive at the point that the only gain is to prevent movement longitudinally. Out of six possible axes of stress, pocketing resists only one, and that at considerable cost to longevity. A much more efficient method to gain longetudinal strength (albiet with a slight gain in weight) is to land the frames on top of the keel, tie them together with the floors which are in turn fastened to the keel, and fit blocking between the floor/frame assemblies. The blocking will resist longetudinal stress on the frames and if bedded properly and bevelled 'thwartships, will shed any water in the bilge into the garboard valley and thus out through the limber holes toward the bilge pump. The additional weight of the blocking is minimal (about 150 lbs in a 45-ft yacht) and is very deep in the boat where extra ballast is a boon. The price to pay is labour - it takes time to fit & shape each block. But if you happen to be in the position to either afford the cost of this detail, or you are your own labour and the payroll is your personal beer supply, this may be a detail to pursue.

[Dave Fleming]

MMD,
In the case I cited the garboard was 2 inch thick Doug Fir does that affect your view?

[Ruaridh]

The frames in my folkboat are notched in, I think its this way in most of the older clinker ones - I think they did it mostly to make the frames easier to steam in?. Don't think there are screws purposefully through mine, athough garboard fastenings are bound to have caught a few.

No problems with rot at the ends of the (otherwise rotting!) frames I replaced this winter, but mine's always been a saltwater boat.

Not qualified to say whether you should do it or not in a new build but with steamed frames it might make them easier to fit. Perhaps you could seal them into the sockets with a modern glue / sealant?

Best of luck,
Ruaridh.

[mmd]

Dave - no, my view remains the same. I agree that with large scantling planking the frames must be very secure so that the planking stress won't move them, but the stresses created by the garboard plank are mostly vertical and 'thwartships, with a bit of torque in the ends, all of which are not resisted very well by the boxing of the frame ends unless there is a substantial keelson fitted. (Note that in the size of vessels you are describing, keelsons are pretty common in all but light racers.) IMHO, the notching of the keel exposes too much end grain in the frames and keel too deep in the bilge to be adequately dealt with using bedding compounds, and that it creates pockets between the frames where moisture can collect against the keel/garboard (limber holes usually don't drain all the water and expose further end grain of the frames & floors). If the frames are landed on top of the keel, their ends are above the small bit of water that always seems to be present in the bilge, and the keel remains a homogeneous timber presenting longetudinal grain to the bilge water. The blocking on top of the keel and between the frames presents longetudinal grain to the bilge water and their ends are bedded and fitted against the floors/frames and thereby relatively protected from soaking in water. In the worst case scenario in which you are the proud owner of an old boat with rot in the frame ends, with the method I propose you will have to replace the frames, floors, and blocking, but the keel is likely to be sound; if the frames are pocketted, the rot in the ends of the frames has easy access to the end grain of the pockets cut in the keel timber and will most likely attack it, too, necessitating replacement of the keel - not a task for the financially- or experience-shy folks. I believe that the practice of pocketting frame ends evolved in commercial boats because it was fast and economical for the shipwrights to do it thusly and longevity was not an issue because most commercial boats of the late 19th century were only expected to last twenty or thirty years or so. Yachts were constructed in this manner due to habit, speed and ease of construction (as Ruaridh commented, it is easier to bend in a steamed frame if the end can be fixed in a "socket"), and weight reduction. I personally believe that the great yacht designers like Herreshoff, Fife, etc. rationalized their designs for speed, handling, beauty, strength, etc, but that the notion that their boats be constructed with an anticipated lifespan of a century or more was not a factor in their design.

[Art Read]

Those of you with Bud McIntosh's book might want to re-read what he had to say on this subject. He makes a pretty good case for socketing. That being said, the exposed end grain, "rot pocket" arguement makes sense too. I suppose if my boat had frame heels that were going to hidden away down in some inaccessable nether regions, I'd be more concerned, but as my bilges will be pretty much open to the air, I suppose I'll just have to make sure I try to avoid standing water collecting there unnoticed. Oh, and I made very sure that all those sockets were fully sealed and bedded with Sikaflex when the frames went in. We'll see...

[Dave Fleming]

MMD,good point about commercial builders and carry over to yacht construction. Like to see a sketch some time of large size frames ie: 2'x 4" set on keelson with that blocking in between.
I envision the frame butting on top of the keelson and, some how attached to the floor?

[Ken Hall]

Wouldn't limber holes in the bottom of the frames next the keel reduce or solve the rot problem, assuming you keep the limber holes clean enough to allow water movement?

[Dave Fleming]

Ken, depending upon the design, those frame heels can be pretty deep down and a limber chain might do more harm than good abraiding the heels or if the frames are boxed into the keel where is the chain to run?

[mmd]

Ken - I also don't think much of drilling limber holes in frames right at the edge of the keel 'cause this tends to weaken the frame at a critical point. "Tis better to place the limber holes inboard of the frame/floor bolts.

Dave - I'd love to oblige, but I haven't figgered out how to post photos of "Elly" in here yet, much less than posting an AutoCAD drawing. If I can get the ol' bean to accept new knowledge in the next little while, I'll see what I can do about a sketch.

Art - I have the highest regard for MacIntosh's book and refer to it and quote from it regularly; I just don't agree with everything for every application everytime. The method that I have proposed is not infallable, either, but primarily referring to big boats with sawn or laminated frames. Good air circulation and due diligence is a sure-fire way to longevity of a boat, regardless (almost) of construction method.

[Sconnell]

Peter
Being a backyard amatuer, I can only offer a point of reference. I'm building Sally Rover which calls out socketed frames. It was fairly difficult to do the sockets and some are a bit off. Having them there was great for bending in the frames and what a nice stable surface the frames in conjunction with the rabbit present to the garboard now. It seems to me that a working hull especially one that is clinker with light frames is going to flex the garboard/keel rabbit joint to some degree and having the frames anchored is a good thing. Anywhere gaps were available in the sockets, especially the not-so good ones, I squeezed 5200 into them. I treated sockets and frames with wood preservative too. I will be filling the bilge to the limbers with boat pitch (another controversial issue). It just looks so solid and there is plenty of wood surface for garboard screws. Everytime I fit my template garboard and look at how it's going to tie together I have to grab my wife to show her -she's had enough of that by now.

Steve

[Peter Jacobs]

Thank you for your opinions/information, gentlemen. You have inspired me to look a little deeper
Here are some opinions from the library:
McIntosh: "... maintaining steadfastly that direct fastening of the frames to the keel is a fine thing, adding tremendously to the strength of the boat, and fully justifying all the time it takes."

Chapelle: "...The heel fastening of the frame to the keel is of little importance structurally and only serves to hold the frame in place during construction. The use of boxing, therefore, is largely a matter of personal preference."

Herreshoff: "...One of the commonest mistakes made with frames is to box them into the keel... This is a very bad practice, for the chiseled-out cavities in the keel weaken the part where the garboard fastenings come and very much encourage rot. The whole strength of the frames should be transferred to the floor timbers by proper bolting or riveting, so it is not of much consequence if the frames do not even touch the keel."

Pardy: like Herreshoff.

Steward: ?

It seems to a matter of personal preference in small, lightly built boats whether to 'knotch or knot'.
Below is the sketch from WB #93 article on painting before assembly... hopefully I won't get jailed for copyright violation



Folkboats have a tall skinny bilge, with the bottom ends of the frames almost vertical, only a few inches apart at the keel. The construction plan shows limber holes on each side of the floors, inboard of the frames.

My problem is that there is only one floor every second frame, so the frames between floors are only attached to the planking (if they're not notched into the keel). Which leaves me with the typically Canadian solution (compromise) of doing it both ways: not notching the frames that are attached to floors, and notching the frames between the floors into the keel. That way at least I'll be right 50% of the time [img]smile.gif[/img]

Steve: Tell us more about Sally Rover. What materials are you using, and how far along are you? She's a beautiful design.

-Peter-

[ford]

for my 2 bobs worth my 1962 [img]smile.gif[/img] 30' has all frames notched into the keel and secured with 12 gauge monel screws, adequate amount of red lead was also used at the time.
Although my boat had a serious case of galvanic corrosion that weakened all the copper nails, to date I have repaired 43 frames with about another 26 to go, not one end of the frames was affected in any way whatsoever by decay, all and I repaet all the ends were in excellent order.
So there you go make of it what you will.

[lallone]

In the boat I'm going to build, not all frames are in contact with floors. If you don't notch them into keel, what is the structural function of these stand alone frames? Thanks

[warwick]

on my 30' all relevant frames were notched into the keel, all were screwed with monel 12 gauge and copious amounts of red lead, none of them have suffered rot and all screws and timber were in good condition. She was built in 1962.

[Ian G Wright]

John Parker who was in charge of the building of my Vertue favoured steamed frames let into the keel and so that's what Patience has and that's good enough for me. White lead paste with a dab of grease keeps the water out.
And anyway are rabbetted frames that have rotted off any weaker than frames that were cut off by the builder?

IanW.

[Mrleft8]

If you just drill a few drainage holes through the bottom of the boat, no water will accumulate, and you won't have to worry about rot...

[Dan McCosh]

For what it's worth, Nevins practice was to not notch the frames. They bolted them to the keel floors, and used bronze floors where stressed. Aside from creating a water trap, any fastening ends up too close to the end of the frame to add any strength. Of course the rot issue is less important when the keel stays in salt water.

[Malcolm Henry]

I suspect that the frames are notched in to make the steaming job easier (i.e. quicker).

The two folkboats that I have worked on (one clinker, one strip-planked) had them notched in but only by c.1", which would add negligible structural strength to the keel/frame join.

If you bed the frame ends in some nice poisonous goo you'll not get any rot.

[mark ward]

Interestingly enough, the solution John Alden proposes in the Triagle I'm building, hasn't been brought up on this post yet. Perhaps Thad (the Triangle expert of the world) can speak of the solution's longevity. 90% of the frames in the Triangle are continuous athwartships, with a sharper bend in the frame where it turns from garboard to keel. This allows for a very solid connection to the floors, no end grain exposed for rot to scurvy into, and a gradual decrease in surface connection to the garboard (results in less localized stresses). As with frames cut short of the keel, the primary connection to the garboard is at the floors. This solution does require the frames to be twice as long as typical, but one person can stand on the steamed frame in the middle over the keel and two others, one on either side, can clamp the frame into place simultaneously. In all my readings I have yet to see this solution discussed, and am interested in everyone's feedback. If there's enough interest, I'll post a drawing of the detail with respect to the floors and limber holes.

BTW, I'm several years out from bending frames as I'm only just now laminating my keel.

Best,
Mark

[Dave Fleming]

Lets see now how many folks would it take to stand on a 2 inch x 4 inch net White Oak frame hot from the steam box and bend it to the hull of a 18 or 20 foot beam vessel???
Funnin' ye lad, sorry.

I like the idea for smallish stuff though.

Some places had a 2 part box. One part could be bolted up to the main and longish planks and pieces could be fed in but in others the end with the worst bend was put in the box and all around was packed with rags to keep the steam in. This did work but seemed to take longer for the steam to do its job and as the rags sopped up the wet steam they would become sodden and more rags had to be added to keep the opening plugged tight.
Steaming hot rags ain't no fun to have to handle, let me tell you.

[imported_Conrad]

Rot, rot, rot, unless done perfectly with lots of red lead at birth. My preference would be no sockets, and a bit of extra attention to the fastenings from frame to floor. Any boat with sockets should probably be pitched to permit perfect drainage.

[Peter Malcolm Jardine]

Hmm.. as a rank amateur here, the only way I have learned is to top bolt the notched floor into the keelson, and rabbet it for the garboard plank. steam bend the frames if they are smaller than 2 1/2 inch square, and bolt them to the floor. Floors to be 1 to 1.25 larger than the frame, and depending on the hull as long as reasonable amidships. Does this make sense? Seen lots of frames not attached to the keel too, but always thought that was considered MUCH lighter construction...? all of this slathered in red lead of course

[ 02-07-2003, 05:17 PM: Message edited by: Peter Malcolm Jardine ]