Inwale Question, How do you like yours?

[Lowell Bernhardt]

What are the difference in inwales? I have seen both a solid type wrapped around the boat, and I have seen the staggered type common in canoes. The solid type is pretty self explanatory, as to the how to and why. But, the type that appear to be off set by wooden blocks at regular intervals, what is the purpose of this? Does it add more strength to the gunwale?

I was thinking about the interior of the Diablo and I really like the way the second type looks over just the plain wraparound type.

Any questions comments or suggestions are welcome and aooreciated as always.

Thanks
Lowell

[Steve Lansdowne]

In both canoes and traditionally constructed boats the "staggered type" reflects the vessel's construction -- the inwale goes over the top of the frames. On my Whisp as I understand it the "staggered type" helps the top of the sheerstrake maintain the curve you want it to have. I figured that if the spacers were not there, and thus the inwale attached directly, and solidly, to the inside of the sheerstrake, the curve of the sheerstrake would be less stable. Perhaps on a boat with thicker strakes the need for "staggered type" would not be so great. The designer of the boat likely considered this, thus I'd not experiment with this. The "staggered type" does come in handy to allow one to tie lines to the inwale for various purposes, though.

[G. Schollmeier]

The open spaces also allow for water to run out when a canoe is turned on edge, on land. But I think Steve is right, the spaces originated when the inwales jumped from rib to rib on some types of construction.
Gary

[imported_Conrad]

The open type would be stiffer for the same weight since it's thicker in the across dimension.

[Bruce Hooke]

The terms I've heard used for these two types of gunwales are 'open' and 'closed'.

On canoes and on most small craft that use the open type of gunwale, the 'blocks' are just the heads of the frames. This, of course, only works if the frames are close together. In terms of comparing an open gunwale with a closed gunwale that wraps over the frame heads (basically an open gunwale with a cap), the closed gunwale is certainly stronger. A big weakness of this sort of closed gunwale is that if you try to tip the boat on it's side to empty out any water in the bilge, the water, and any grunge with the water, ends up going into the cavity under the gunwale.

On the other hand, on Diablo I expect that a closed gunwale would not have any cavity under it because there are no frame heads (true?) so there wouldn't be this problem. In that case, if it was engineered correctly I'd guess that you could make it a little stronger (or lighter for the same strength) than a closed gunwale, however, I'd guess that the strength difference would be pretty small. On boats without frames I think the primary reason for going to an open gunwale is because you like the looks. Purists might argue that it doesn't make sense because there are no frame heads, but if you like the look, who cares what the purists think.

[Paul Scheuer]

Strength, drainage, and "sheer" beauty ! (couldn't resist).

When I see an unnecessary open gunnell, (with spacer blocks), I think of the builder paying homage to the traditional techniques.

I'm no artist, but I know what I like. I think that the open gunnells in Diablo are a pefect touch to an otherwise spartan design. Certainly, no one here would object.

You could even put the blocks in with the end grain showing, for a more traditional look (and finish problems).

[On Vacation]

Keep in mine the complex refinish work involved in the open rails for down the road especially if you are painting the rails. Also make sure your pieces are not too large. this will create hard points in the curved areas and will need to be eased on the ends upon installation. If not the fit will not be that swell.

[Scott Rosen]

I agree that the open ones are pretty, but I've always wondered about the added maintenance burden, as Oyster points out. Sanding and painting in those tight spaces will take a lot of time and patience.

[Bill Perkins]

Lowell I think you should go for the open rails . They add visual interest and would make the boat more your own . I built a canoe that's got them and have had no maintainance troubles so far . The parts that are hard to reach- the holes- aren't subject to mechanical or UV damage .Varnish over epoxy seems to be holding well . The boat spends most of her life in a shed tho .

[ 09-20-2002, 10:40 AM: Message edited by: Bill Perkins ]

[DavePulaski]

This thread's giving me some serious food for thought. I had always sort of figured I'd just go with the open gunwales (being clinker ply construction, it's purely an aesthetic choice in my case). But now you've got me thinking about the hassles of maintaining the finish on such a structure.

A simple, closed, three-piece "sandwich" gun'l is looking better and better...

Speaking of gun'ls, how exactly does one affix the rope into a cove routed into an outer gun'l, for that other popular "traditional" look? Just Epoxy it in?

[mmd]

Boats by the numbers:

Assume gunwale 3/4" thk, planking 1/2", frames or blocks 3/4" thk on 6" centres, and inwale 3/4" thick.

Section modulus for side impact: 7.622 in^4 with blocks, 4.000^4 without blocks and inwale laid up on the inside of the planking.

Conclusion: sheer structure is 190% stronger in side impact with blocking than without.

Caprail omitted on many small craft for a.) light weight, b.) cost & labour savings, and c.) regular maintenance is expected.

"Nuff said? :D

[ 09-20-2002, 05:20 PM: Message edited by: mmd ]

[Lowell Bernhardt]

Thanks guys, once again yall have helped me through another decision. And as always I feel more educated about the subject.

I think I'm gonna go for the traditional "open" rails, and chance the extra maintainance.

[On Vacation]

Keep in mind that the open rails requires a heavier wood for the open stretches than lamination or solid rails.

[DougC]

I went for open inwales on my Swampscott dory, contrary to the plans. I took my cue from another John Gardner boat, the Chaisson Dory Tender, which had open inwales and looked great. Since my boat doesn't have a lot of ribs (the real origin of the open gunwale) I cheated and used spacer blocks as well as the frame heads. I'm glad I did, it makes the boat easier to empty out and is less prone to hold water and promote rot. Painting and varnishing it was a bit tedious, first I taped off the inside plank area and then varnished the inwale/rubrails, removed the tape and carefully painted the inside bit of plank. Will try and post some pics (if I ever figure out how). Greg Rossel Has some great info on this subject in his book "Building Small [wooden] Boats."
Doug

[EdenRose]

Doug C... I am just about to do the inwale on my
own Swampscott Dory and plan on using spacers, contrary to my plans. My sheer clamp outside is
3/4" x 2"
What size of block (length and width), inwale and
spacing did you use? I will probably use 1 1/2" material on the inside.
Do you have photos? I can direct you to some of my
building process.

[ 09-21-2002, 02:01 AM: Message edited by: EdenRose ]

[EdenRose]

DAVE,
I have been researching rope inset on gunnels
for a while and photographed and probed
about a dozen or more at the Port Townsend Wooden Boat festival. I saw several techniques:
BEST: wide gunnel (up to 2") routered with a core
bit to accept 3/4" or 1" rope. The prettiest and most secure was one laced into the
gunnel with cord. Small holed drilled in gunnel
top and bottom to lace cord through. The rope held
at the ends with leather or bronze fitting.
The ones that seemed the best had the rope stretched very tight, maybe shrunk in place. Also
it seemed to work best as one continuous piece and wrapped around the stem or drilled through stem.
BETTER: Same as above only unlay rope and use hidden screws or nails to attach.
NOT SO GOOD: Glued to boat. They were falling off.
If someone could tell me how to attach photos, I
would scan some in and put them up.

[Tar Devil]

Asthetics, Lowell. All the Diablos I've seen had closed inwales, but I've always liked open. When I built my 1/6 scale Diablo I used open, and to me it just doesn't work well visually with that boat. What WOULD look good, IMHO, is a nice little bow deck, flowing back to a caprail just wide enough to cover the flat section on top of your transom. I'll show you as soon as I modify my model.

I tend to associate open inwales with more traditional vessels, and the Diablo doesn't portay any "traditional" boat appeal, again IMHO (doesn't mean I dont' like the boat by any means!)

I think I mentioned to you once before... there is incredible value in building an exact scale version of your boat. That way, you can try out all these little variations without spending a "boatload" of money. When I built my 1/6 model, I used the exact techniques from the plans to get a feel for how the boat goes together. I learned a few shortcuts (but not many) that work well, and a few that would be costly. I also learned (as in the inwales) what will look good on the finished boat before I have to redo it. The colors, for example... that's the third variation before I settled on those colors and scheme.

For what it's worth.

Later,

Phil

PS. Plus, building the scale model is just plain fun, and you'll have miniature version of your pride and joy to set on your desk!

[ 09-21-2002, 12:44 PM: Message edited by: Phillip ]

[On Vacation]

http://www.imagestation.com/picture/sraid33/p46957b58ee9f3c882604896f55d43c68/fd40509c.jpg
We are incorporating both types into a lightweight hull for structural integrity.

[DougC]

EdenRose, I used 3/4" x 1-1/2" white oak for both rubrails and inwales. I notched out the sawn frames on top to receive the inwales. This left a space of about 3/4" - 1/2" depending upon the frame location. I put a strip of oak between inwale and sheer plank at the oarlock stations, these are about 11" long. That still left some areas that needed reinforcement. Here I put in spacers about every 6", these are 1-1/2" X 1-1/2" by a depth tapered to accomodate the curve of the sheer. The spacers get progressively smaller toward both the bow and stern, so at either end the inwale meets the breasthook or transom cleat with no spacer. Since my boat is glue lap construction with a solid riveted sheerstrake, I wanted to keep the construction of the rails reversible. I screwed the rubrail into the frames and strake. For the inwales I screwed down through them into the frames' timberheads (seemed stronger than screwing into the notched out frame heads sideways). I epoxied the spacers to the inwale, but not the sheerstrake or frames (so I can remove the inwale and spacers if need be). I also put some screws through the rubrail and sheer strake into the spacer/inwale assembly. This makes a real sheer clamp -- very solid. Will try and get some pictures up. Doug

[EdenRose]

Doug, Thanks for the description of your inwale.
Quite different to make the blocks progressively
smaller towards the ends.

[DougC]

EdenRose, You're welcome. I will try to get some pics up. How's your dory coming along? What plans and construction technique are you using? Mine is based on John Gardner's 16 ft. Modified Swampscott Dory, which I slightly modified further. Trying to get it in the water before the season's over. It's all just details now.
Doug

[EdenRose]

Doug, I am building a glue-lap Swampscott 16 from
plans by Paul Fisher at Selway-Fisher in England.
Original plans were for s&g, but he drew up mold shapes for a lapstrake for me. The boat is planked, flipped over and I am doing the interior
joinery. His design is for plywood bulkhead frames and a one piece inwale, but I am making
solid dory style frames, and the spacer block inwale... for looks, but also to have a place to pick up boat, tie on fenders etc.
I have pictures of construction at the Yahoo
Group for Selway-Fisher design under
"Swampscott" folder. I don't know if you have to
"join" group to see pictures.