I'm about to drill my Mohawk Odyssey for bag cage lacing. I was going to drill 3/16 holes every 4 inches.
- How far below the lowest edge of the outer gunwale (essentially the lower edges of the rivets) should I drill? 3/4 inch seems a bit much. Is 1/2 inch enough?
- How do you assure symmetry when marking the holes? Do you use a jig of some kind?
- Can I use a regular, all-purpose drill bit?
Thank you for any tips
I'm about to drill my Mohawk Odyssey for bag cage lacing. I was going to drill 3/16 holes every 4 inches.
Plain spiral pointed bit is fine.
Drill far enough down that your drill chuck clears the gunwale so you can drill the hole straight. An angled hole has sharper edges which will either wear quicker on cordage or tend to oval out - depending on which material is stronger.
Masking tape over work area…measure (twice) and mark on tape…drill through tape.
the gunnel extrusion is square ? 90 degree corners ?
mark the upper hole from an edge...inner edge
draw a 90 horizontal line on a suitable rectangle of plywood with 2 factory sides...inside hull side and gunnel down side.
mark the hole point on the line and then moving keelward, mark the gunnel inside upper edge point.
measure the gunnel depth
place a second horizontal line below the first at the depth measurement.
on the second line mark outside gunnel and inside gunnel from the upper line inside gunnel measurement down 90 degrees.
the desired drill angle direction falls between the outside and inside gunnel on the second line
soooo if you extend that angle upwards, prob with a felt sharpie, this is the drill bit angle and whatever marking is effective on the drill body...expletive drill body deleted.
the plywood is laid on the gunnel then you place the drill on the hole point and look sideways down the gunnel matching angle of drill to angle on plywood
varnish the plywood and wall hang it
therefore if you want an gunnel underside sewable d-ring http://www.seattlefabrics.com/loops.html
the sewable needs fitting to the hole to the gunnel.
that second line hole would include a fitting for the sewable.
SF sewables have a lip on the tab adjacent the D where the lip fits a keelward bit off the gunnel facilitating ring movement.
8" is OK or 10" leaving room for drilling more holes when needed.
I have always used regular high speed jobber bits to drill Royalex and never had any problems. Just be aware that on some boats the inside and outside of the gunwale do not extend down to the same level. I do not believe this is true for Mohawks, but check to make sure that your bit will clear the low edge of the inwale part of the gunwale.
Exactly how far below the gunwale edge to drill does not matter too much. Hold up a 4 inch length of your bag cage lacing below the outwale and see what looks pleasing to your eye. Go with it. Having the cordage 4" apart is what I would recommend. I just measure with a ruler and make a mark in the Royalex with a scratch awl before drilling. You can usually tell if the indentation left by the awl is correctly placed or not. Sometimes the Royalex tends to collapse back inward a bit after the hole is drilled and an awl can be used to ream the hole a bit if needed. You can certainly make a spacing jig out of a little piece of wood if you prefer.
If you really have OCD here is something to consider. Because the gunwales are converging except right around the midpoint, if you drill holes spaced 4" apart at the gunwales along the sheer line, the individual strands of cord will be less than 4" apart. Since the gunwales converge at a steeper angle as they near the ends, the cord strands will be significantly closer together at the ends than they will be nearer the center. If you would like them evenly spaced, you need to adjust the distance between the holes you drill.
An alternative to drilling…
Would be to install webbing fabric loops on the underneath side of your thwarts and seats.
Easy to make your own webbing loops. 7 -8 inches of webbing, twisted once to create loop and then burn a hole in the end through which the machine screw would pass.
Get longer machine screws if needed.
There enough places on a canoe where this can be done that drilling holes is almost eliminated.
Enough lash points?
We’re talking about a solo boat with two thwarts. Your idea would provide two lash points at the end of each deck and two lash points at the end of each thwart. An X lashing would definitely cover a 48" bag and I don’t see how the bag would pop out of the four triangles the lashing provides.
Yet, most people seem do space their cordage much closer than that. Is there a reason?
Not so for a float-bag cage.
To eliminate the need for drilling the hull, you'd have to install attachment points at closely-spaced intervals along the gunwales, not just at thwarts and seats (and speaking of which, the thwarts and back edge of the seat aren't likely to be at the right locations anyway).
By the way, as has been discussed to death in the past, drilling the hull is the superior method, as there's virtually no loss in strength because the top edge of the hull provides virtually no bending resistance compared to the gunwale as it is. Drilling the gunwale weakens the only thing that's providing bending resistance to the top of the hull during side impact.
What I did
I didn’t want to spend a lot of time measuring, so I looked for a line-drawing aid of some kind. I found a wooden dowel that was roughly 5/16ths of an inch in diameter. I placed that flush with the bottom side of the gunwale and drew a line with a felt-tip pen along the other edge of the dowel. I drilled my holes on that line. “Close enough”.
Any water that enters your boat will do its best to flow underneath your flotation bags and will generally succeed. Since the flotation bag is not a rigid structure, the water will push up on the bag and cause it to pooch up between the individual cords of your bag cage. The closer together the cords are, the less tendency there is for this to happen.
If you use a simple transverse arrangement for your bag cage lacing, placing the cords 4" apart works pretty well. Six inches apart is not too bad but I would not go more than that.
Having the cords run straight across transversely is best if you are drilling holes since having the cords come out of the holes at an angle will cause the edge of the Royalex hole to fray the cord as Steve pointed out. If you want a bag cage that holds the bags down in better, you can rig a diamond-shaped pattern of cords in addition to straight transverse cords, but that generally requires some larger attachment point than a simple hole, such as a nylon inchworm or a webbing loop.
You can also run a couple of lengths of cord lengthwise down the bag cage either side of your center keeper strap or cord as shown in this photo:
watching a bag squeeze OUT of the cage coming out of the roll would burn you good…
drillling a #8
screw hole every 8" DOES NOT WEAKEN THE GUNWALE …
nor does the bag come out of a triangulated 8" spacing…
you show me bag or gunwale that does that and I’ll show you…
Depends on the gunwale
Personally I don’t think that the small holes required for the screws to mount nylon pad eyes such as these significantly weaken most synthetic gunwales, although it takes two screw holes per pad eye:
P-clips or webbing loops can, of course, be mounted with a single screw.
Wood gunwales can be a different story depending on how well the gunwales are cared for. Penetration of the wood grain by water is the most common mechanism for death of ash gunwales. Any hole in the wood is a potential entry point for moisture to enter the grain. This probably won’t be an issue for wood that is well cared for, but definitely can be for gunwales that are not. Having multiple holes in close proximity, such as the holes for the screws that hold the inwales and outwales together, the holes that the machine screws mounting the thwarts or seat hangers, and holes for mounting pad eyes, will significantly increase the likelihood of moisture penetrating the grain and weakening the wood.
Well, long before you showed up here,
… there was a big discussion about a boat that got pinned and one of the gunwales broke. Screw holes seemed to be the culprit. Even if there were no such examples out there of gunwale breaks happening at the location of screw holes, the other side of the coin is that you can’t show us an example of a hull that failed due drilled holes, simply because the top edge of the hull can’t break unless the gunwale also does. You preach incessantly about how bad it is to drill holes in the hull, but of all the people here who use float bags, you seem to be the only one who goes off on a rant about it. Do it the way you like and be happy.
That closer transverse spacing provides a more secure trap for the bag than a triangle arrangement.
Despite other advice I listened to, drilling lots of holes always made me feel uneasy. So I’ve triangulated my bags off loops. Using loops on thwarts/ seats I usually only need another pair of attachments, both fore and aft - that’s 4 holes, loops, worm/ inch eyes, etc for the lacing.
My bags are all clipped or tied in at the corners so the bag isn’t nt leaving the boat.
Put 2 loops on one machine screw if you need lacing running in two directions.
And despite my self confidence, I’ve been out of the boat on occasion and the bags stay put and do the job they’re intended to do.
And this is silly, but imagine during a sale to a newbie explaining why he needn’t worry about all those holes.
I’ll look for data…
hull holes are no problem for WW or W-WW ? as there's water in the boat.
but if you apply the drilled gunwale weakening theory then....?
jus' sayin' you know.....
The example is kinda murky as an example. We will find examples of hulls cracking from cordage holes...the stress riser.
I am guessing, but my guess is engineering data would suggest the reasonable hole(s) as #8 for the reasonable gunwale structure...that is a on the market canoe gunwale...would not cause structural gunwale weaknesses in reasonable use...like 99% percentile stress in canoeing.
'Drillium' common in post 10 speed and 10 speed bicycles spiderwebs metals with reasonable cracking failures from over drilling. Look up drillium in Google Images.
This is not a rant...only reasonable discussion. My caps are meant as humor...
Regarding the rant
I was just referring to the fact that you've previously referred to drilling holes in the hull as crazy, madness, stuff like that. To most people, drilling the hull and installing eyelets on the gunwales are just two different methods, and they don't adamantly preach that one of the methods is totally wrong and that anyone who does it that way is nuts. Yeah, you didn't do that this time, but it's happened, and not just once.
drilling holes through the hull
is definitely nutty when holes can be drilled in the gunwale.
Hull drilling being common practice doesn’t reduce the common nuttiness of it.
A reason that makes sense would be nice
That’s as logical as saying “What’s nutty is painting your canoe green when you could just paint it red.” After all, no one using the canoe is going to see a difference in how the two bag-lacing methods work. They work exactly the same.
Drill or clips
It really doesn't matter if you drill through the hull or use clips/pad eyes on the gunwales for the lacing. I have both and it works either way. Most people drill though the hull. Nobody has mentioned it, but you will also have to glue a couple of d-rings or loops to the hull. You can either tie the bag to these, or use them to hold a web strap down the middle. I like the Mohawk end bag lacing kit with the quick release buckle on the strap.
it makes it easy to get the bag out if you need to. I used it in my Yellowstone which is similar to your Odyssey since I usually paddle it without the bags.
I laced one side and it looks good. Pffff…I’m glad it’s over!
Thank you for all the helpful advice!