method question

I have a question about making the frames in my wooden boat. First, a little information. I am building a 18' glued lap double ender that is a derivative of a nomans land boat, similar to a peapod but is overall larger and more heavily built. The hull will be 9mm marine ply. It has a yawl type rig with a 1029q ft gaff main and a 22 sq ft st lug mizzen. It will be timbered out similar to a trad boat and I want to use something like a sawn frame as opposed to steam bent frames simply because I like the clean and uncluttered look of sawn frames. They also make it easier to clean, and keep clean, the boat. I am doing a laminated stem and a solid stern post(it is just a straight member) so I am thinking about laminating the frames as well. but I also want the frames to be jogged over each lap(again, just a personal preference and my designer specs either sawn, laminated or steamed) so I would like to know if I can laminate and then still cut the frames to fit over each lap. Will I be loosing any strength by doing this?

 

Welcome to the forum.

My personal preference would be to laminate the frames. It uses minimum timber and means there is very little stress in the stucture. Also avoids moisture (from steaming) so is more suitable if you are using epoxy. There are other slightly more moisture tolerant adhesives that will do the job too. It keeps grain integrity through the frame so is a true structural rib. Thats's why the old larch on oak hulls have lasted pretty well - lots of ribs to keep strength and weight down. Unfortunately thay are a pain to maintain but give them credit - in their day, light and quick to build.

9 mm ply is quite stiff to bend and the shape of those Nomans boats are fairly curved, still a bit of careful planning, and it should go. Again personal, I'd build onto the frames whilst upsidedown, it should let you get good joints all along. Minimise stress in the build to get an accurate result - if you start to fight it, stop and think about laminating or using smaller sections (just more of them).

I note that there is a strip plank version of this type of boat on Youtube. That has to be the cleanest interior you could get.

 

Why would you want to put frames in a glued lap build? Any reasonable designer would pick one or the other (traditional lap or glued lap). Simply put, you don't need frames in a glued lap build. Who's design is this? Obviously you've miss typed the amount of area in the gaff mainsail, maybe 102.9 sq. ft., for roughly 125 total sq. ft., including the mizzen?

I disagree in that sawn frames make it easier to clean and framed lapped build. With the frames jogging at each lap, they create natural moisture retention areas, on each lap/frame interface. With bent frames, you can just hose out behind the frame, at each lap, but more importantly, moisture can run down, along the lap, until it gets to the low point and drips off. With sawn frames, you just create lots of places where water will pool, especially low in the boat.

I also think notching laminated frames for the laps is asking for stress risers at each lap, which will require larger dimension frames, defeating the purpose of building a lapped boat in the first place. Lap strakes are the lightest of all the traditional build methods. The fairly burdened shapes of the nomans land boat could be refined to produce a much better sailor. These boats where haulers first and sailors second. I hope you don't mind going slow.

If you must have the notched frame thing, do it in to stages. Glue a ramp looking sort of thing at each frame location, filling the gap behind laminated or steamed frames. Then bed frames over these, so they can act independently.

 

PAR, yes, I obviously mistyped the sq ft of the main, I thought it was 102 but went and looked at the plans and saw that it was 109 and I guess I didn't delete the 2 as planned.
Why would I not put frames in a glued lap boat? If it is a sailing boat wouldn't you want something framing the boat for strength? I see many designs out there from reasonable designers that are glued lap construction that also have frames in them, Walter Simmons has several, his Matinicus double ender, Ducktrap wherry, Christmas wherry all have steam bent ribs with the option of sawn frames. Iain Oughtred, a very prolific designer of glued lap boats, specs frames of some sort in many of his designs and there are many others. Paul Gartside, Thomas Hill, all reasonable designers.... I could go on but you should be getting the point by now, if not, let me know and I will give you more names.
Also, I stated that this boat is a Nomans land derivative, so it means that it is based on a NML boat and it was drawn by Kees Prins, another reasonable designer and a phenomenal builder who refined the sections of the Beetle boat as drawn by Chappelle to give the hull some kind of rowing qualities and improve the sailing aspect of the hull, which as stated by Chappelle, this hull (he lists several of this type) is the hull is the stronger type designed to sail well, page 168. This was drawn to be a little narrower than the original and as I said, for what that's worth, had the sections shapes reshaped and tweaked a little. Kees Prins was recently in woodenboat that highlighted his personal boat, FETCH as well as his other new design, LOON, a cruising sloop he drew while at GLBBS last year, as an instructor. The Townsend Tern is another of his, he has also built many Oughtred designs that Iain has incorporated into his own catalog, just like the modifications he made to Iains own Fulmar design. He has also built several NML boats previously.
As far as the sawn frames being cleaner, having 8 frames to clean around sounds a lot better to me than having the entire interior of the hull covered with little steam bent ribs and every one of the little nooks and crannies to clean out. Besides that damn it, its my boat and I want them there, I like the look, also, this design is going to need some weight in it .Im not a naval artichoke like you so please don't argue all of the technical points that go along with your point of view, Im just a guy trying to have fun building a new boat.

 

Sukisolo, thanks for your reply and thoughts on the frame construction, definitely something to ponder. I have a few weeks to think this all over.
About twisting the planking, Kees drew the shapes to be a little more friendly to my planking material and Im going to go for 8 or 9 strakes per side and this should help a little too I hope.
Ive seen the strip version you speak of and she is very beautiful.

 

With respect to PAR, there are quite a lot of framed lap strake (clinker) dinghies in the UK, many using the 'frames' as a bulkhead for in built buoyancy tank. One reason for frames is to maintain stiffness athwartships, until the thwarts are put in to stabilise the shape. It eliminates a cradle or jig if you want good accuracy. I am referring to post 1950 glued lap strake builds. Older multi rib boats are more stable - so many ribs and copper rivets...and yes I have repaired a few. In structural terms there is a trade off between the number of athwartship ties you need and spacing - in practice how many thwarts and how many frames. The c/board case will need fair support for starters.

Par is right about letting the water run to its natural bottom level. If an open type boat, it is important to put a limber hole through the frame at the bottom of each plank. In combination with a local bevel, water then drains, this is important. The ammount of extra frame is no more than the thickness locally of a couple of planks and I would not be concerned about a stress raiser personally.

Agree with PAR on the shape, these boats look like the curve of areas is pretty extreme, and that is without looking at the Cp which will be poor. It would not be difficult to get a more efficient nicer hull shape which would be more pleasant to sail. Would be mighty interesting with over 1000 sq ft...

Any sketches? or frame set up shots?

 

Just so you can see what Im working on. Sure, there will be some hard spots in the planking but all will be fine in the end. I work at the Chesapeake Bay Maritime Museum and am surrounded by a lot of very experienced and ingenious builders, just wanted to get some opinions from elsewhere to get some other points of view.
About them not being good sailing boats, Tom Jackson built The original hull which was recently was on the cover of woodenboat mag and he really loves it.

 

Of course PAR is right, just as you are, about the water drainage and that has all been accounted for as you can see in the construction details. Limber holes are all there as is a pump well at the rear of the hull, which because of the pronounced drag, is the lowest point of the hull and I know to put limber holes at the laps where the frames cross the laps.
Now, before there is anything said about the bodyplan, this is before the boat was lofted(for the first time) and the lines all corrected and reconciled so station 2 has been faired and corrected to its correct shape and the same goes for all the lines. Kees and I drew this last year over the very long Northern Michigan winter so it is a new and unpublished design, one that I wanted to build.

 

Thanks for those shots Arko. Be interesting to see your faired lines. Particularly where the CB is as percentage, it looks a little forward on the original lines. Also I do not particularly like diagonal A, and would like one drawn just beneath it, as I think it would change dramatically. Not quite convinced in that area, and I suspect that Diagonal A or just underneath it is hiding something I would investigate.

The bilge looks quite moderate for that type of boat, she'll heel pretty easily then become more stable. Personally I would put more buoyancy low down at both ends - straightening the waterlines shown (the set below LWL), a bit. Not completely mind. Probably fill out Station 1 a little low down, and probably tweak 7 and 8. Bit hard to tell without drafting it properly, or these days 3D modelling.

I would also increase the C/board size and especially depth so the case inside is also a little longer. Again personal but at least 40+" would not be unreasonable. To give you some idea 12' boats here (UK) use 1200mm ie just under 4' or more where allowed for upwind efficiency. As she is moderate V she will go even better upwind with a slightly deeper (and likely wider towards bottom) foil. You get quite an improvement with a much smaller increase in depth and area than you might think.

Extending the case aft slightly would not be a problem, you seem to have plenty of sideways strength to the case. BTW I usually glue and screw these kind of joints rather than just glue. If you want to hide the screw holes better than plugs, try laminating a thin layer of solid timber in situ afterwards. Works a treat visually. Also you cannot get too much strength into the mainsheet block area. It is very important to really secure the timber down ie glue and screw and then to bolt through the block retainer whatever type. It gets a fair whack when gybing in breeze and there is a strong upward pull when on the wind. I've seen a lot of screwed in ones fail....
That area requires a little local detailed thought, but will repay you by not failing. Be prepared to laminate thick timber as one option, ie have two bits at 90 deg as top capping. Just depends a bit on the timber used.

 

An example of modern glued lap. Not a single frame, so it's nearly half the weight of a traditionally framed boat of the same dimensions.


Sawn frames in a modern glued lap. There are 4 frames in this boat, three hold up the thwarts.


This is the Oughtred Arctic Tern and a perfect example of the ways of a modern glued lap. Athwart stiffeners, in terms of partitions and bulkheads, leaving a clean, uncluttered, considerably lighter boat.

The Chapelle drawing and what appears of the revised drawings, still suggest a fairly burdened boat. If you compare these lines to a similarly sized Oughtred, you'd see a huge difference in volume distribution. I too have some issues with the diagonals, but these are typical of the boat's intended use, therefore require this volume distribution. The modified lines will not hold as much Cod in her belly as the original, but she'll still prefer a healthy load, to immerse those bilges some (possibly a reasonable justification for the weight of the frames). In it's defense, I've sailed this type a number of times (not in recent decades) and they feel initially tender to most modern skippers, but firm up nicely once heeled over say 12 - 15 degrees of so. It's an easy sensation to get used too. With a fair bit of mass down low (like several bushels of Cod), they hunker down and become very solid feeling underway. Lightly loaded they're tend to be a tad "corky". This is something that Oughtred designs are really good at. His designs tend to take the corkiness out of the seemingly antique, traditional looking designs, while still producing a light, modern structure.

You can build how you like, in the fashion you like, though slightly modified digressions of antique hull forms, usually just produce slow, if salty looking antique(ish) craft. I'm not trying to insult you, just suggesting there are easier, lighter, more waterproof techniques and designs to consider, than attempts to semi modernize antique designs. Simply put, you can have the look and rig of the era you want, but with modern weight expectations, better performance and with easier/cheaper build techniques.

 

Nice examples PAR. Please note them Arko, and how the athwartship stiffness is maintained with combinations of the inherent stringer effect of clinker/lap strake and thwart or higher bracing.

Concur with PAR about volume distribution ie ease through the water. We have learnt quite a bit over the years, and I am not knocking Herreshoff, Fife, Watson at al who were all masters of their craft. A few modern twists to these old shapes does improve them. Check out the English Salcombe Yawl as an example of a 'traditional' development class....

http://www.stonesboatyard.co.uk/the_yawls.html

When you have Ian Howlett and Phil Morrison and others designing these beasts you do get more speed!. These do have transoms and despite their not inconsiderable weight (bronze c/board) actually do plane.....
Beautifully built with khaya garboard, then all Sitka planking with the densest tightest grain next after garboard slowly transitioning to moderate grain at gunwhale.

 

Yes, I like old, antiqueish looking hulls, I work at a museum for cryin out loud, and, that is exactly what I wanted when I first talked to Kees. I initially wanted an enlarged peapod but the conversation morphed into this hull. Fast was the least important criteria on my list and it remains so, so I should be satisfied in that area. We both thought the boat would be corky as you say which is why there is 200 to 300 lbs of ballast specified in the plans and the gaff main, all 1029 sq ft of it, was decided on, because of its low center of effort, to help alleviate some of the heeling at least. Also, yes, that is why the framing was decided upon, to add some weight. I am even using meranti ply instead of occume, its heavier. I know it doesn't bend as well but I have thoughts on that as well. If it works or not, I don't know yet but Im about to find out.
With all due respect to IO, I do not like his designs all that much, certainly not enough to build one. Yes, I know, his boats are prolific and all of that and Kees has built several of them and even sails one himself and he tried to get me to just build one of them instead but I opted against, I just don't see me in one. I DO like old antique boats.
OK, I already said I am certainly no designer so, if it is not beyond the scope of our method of communication, please explain what both of you are talking about with diag A and what is wrong with the volume dist. PAR says it is normal for this type of boat? What is normal?
I thank you both for your input.

 

Well, most of the previous discussion is now moot, as you want an old school, antique boat, which is just fine and these types should be "preserved", so folks can see how it was done. Thank you for "reviving" the type, we need many more of you, willing to do this, as we have more then enough canoe body hull forms floating about.

Double enders have some "quirks" about them, if you want them to go uphill in a blow. Your designer tried pretty hard to get the buttock angles as low as practical, considering the shape of the stern, but for this reason (maintaining the general shape of the old hull) his inboard most diagonal and buttock show a lot of "sweep". This causes the boat to be "cranky" up wind, when she's in a fresh breeze and worse in a hard blow, she'll struggle to get upwind. On a double ender, you need a fair bit of overhang aft to let the buttocks "lay down" at a reasonable angle to prevent this trait, but the type doesn't permit this luxury. This is also partly because hull volume aft, forces the buttocks and in turn the diagonals to make a significant upward turn, just where you'd prefer them to be as straight (subtle) as practical, for good handling characteristics. Given the limitations of the hull form in general, he did a good job of "sweetening up" the run on this boat, working with in the "box" he had. In short, she'll do much better then the real antiques, just not as well as we modern folks are used to (comparatively).

 

PAR, I want to start by saying I wish I had 1/10 of the understanding of design that you have and that I really have respect for you and other good designers. I wish I could do it, I wish I understood it, but I cant and I don't. The advances made in hull design and the understanding gained in the years since this (original) hull was conceived have been enormous no doubt but really do enjoy the boat that I do like, i. e., old, smallish, inshore fishing craft of the northeast coast of the US. They have to be my alltime favorites. They worked for the fisherman for a good number of years. They fed them and other people as well.
Ill let you in on something. I wouldn't know the damn difference in the sailing performance of this hull and the performance of the absolute latest most technologically advanced miracle hull because.....................Ive never sailed a boat before!! There I said it. Yes, this will be my first sailboat. It was just not something I grew up around. Ive had boats, yes, but they either had motors or oars(something else I really enjoy). So will I be happy with the performance of this hull? Im sure of it. Could it be better? Im also sure of that. For now though, it will serve me just fine.
So, about those frames.......................................................................