Keelsons/Ice Runners

[Ben M]

I've nearly got my Spira Marsh Rat ready for planking. Hopefully, I can get going on that this weekend. Once the hull planks are on, I'll want to install keelsons for protection. Keelsons aren't spec'd in the plans--this is just my minor addition.

Here's a link to the design where you could get an idea of the hull: http://spirainternational.com/hp_mars.html

A few questions:

1) The hull is more of a semi-V than a traditional round-chine, feather edge. The center of the hull along the keel will get the most abuse, so it needs protection the most. How should I install the keelsons? Putting one straight down the keel seems best, but the hull has a slight V and a keelson won't sit flush on the keel. Carve out the back side of the keelson to fit? Mount 2 keelsons to either side of the keel?

2) What material should I use for the keelsons? Oak? I read here that someone used Ipe? What about that plastic Trex deck material?

3) Dimensions?

4) How should I mount them? I don't think I want to put screws through my hull. But if I simply glue them, how do I clamp them properly without them wiggling or getting inconsistent clamp pressure down the whole piece?

5) Is there a better solution for protecting the hull? A buddy suggested I just put a piece of aluminum sheet down the keel. Kevlar tape?

This boat will be armstrong powered, or pushed by a low-horsepower outboard. It's kind of a semi-displacement hull, so I'm not worried about "turn-on-a-dime-at-speed" kind of performance. Tracking under oar power is reasonably important, but I'm more concerned with just getting as much life as I can out of this hull in the shallow, rocky rivers I typically hunt. Oh, and it would be nice to keep it light enough to carry/drag through a pasture field to open water when the feeder creeks are locked up.

 

[Chris S.]

For the runners on my BBSB I used mahogany I used thickened epoxy and stainless bolts to attach em. As far as holding them in place while the thickened epoxy dried for 3 days I used 4 ratchet straps. I did a dry fit marked everything with a sharpie and drilled my holes then took them back off and sanded the hull to make a nice tooth in the epoxy for the thickened epoxy to adhear to then painted unthick epoxy on the runners an let that soak in for like 20 min then put thickened epoxy on each runner and lined em up put the bolts back in one at a time and putting one ratchet strap on at a time working my way down the hull one bolt and strap at a time and tightened the bolts up and let dry for 3days then filled the bolt holes with thickened epoxy aswell. The runners are 9'6 long 1" wide and 3/4" high I will be putting a 1/8 by 3/4 inch strip of aluminum on the runners as well check out my BBSB REBUILD for some pics as far as what to do on the "V" I am not sure but someone here will know what to do.

 

[Dennis Johnson]

I built a Devlon "Mallard" & it has the V bottom too.
1~ if the 2x4 is left inside for a keel, I'd screw the external keel,from the outside, bedded in thickened epoxy& put small fillits where the keel/hull joint is. Counter sink the screw heads a bit& fill with thickened epoxy. Then cover the keel with a strip of alum. 1/8" thick by the width of the keel you use. Paint the bare wood both sides of keel with unthickened epoxy first, then the thick stuff.
2~I used Dug. Fir old thght grain stuff. Mahogany is traditional, WHITE Oak works well too(not red oak). I'd stay away from the Trex stuff, but I don't know about the other stuff.
3~I used 3/4"thick X 1"wide for the keel on mine, & 3/4 X3/4" for the bilge keels, covered with 1/8"thick alum. bedded in 5200& screwed to keel. 3/4 X3/4" would work for you also.
4~As Chris said, ya can strap them down& weight them down too. I'd screw them to the inner keel, makins shure the screw point didn't go thru the keel inside. the epoxy will seal the screws& holes& is stronger than the wood.
5~ There is paints that some put on the bottom that help. One I have read about is Frog Spit, others may chime is with more details, I'v never tryed it. I'v broke ice over 1" thick with the setup I have & had no problems. The 1/8"thick alum. over the wood protects the bottom very well.
I hope I have helped ya some, post away with any more ???? Thats what this place is for. Enjoy your build.
Dennis

 

[Ben M]

Thanks, guys! Huge help!

 

[Ben M]

Anybody else have an opinion on that Trex material? I know one reason people love plastic canoes is that they have a tendency to slide over/off rocks rather than "sticking" like aluminum & fiberglass. I wondered if the Trex stuff would just be a simple, low-drag choice for rocky stuff?? Tradtional? Absolutely not. Effective? Idunno . . . It DOES seem like it would get chewed up. But replacing it seasonally doesn't seem like too terrible a chore. But I don't know anything about this sort of thing . . . which is why I'm asking YALL!! Hahaha . . .