affects of seat height and ballast/gear load on stability

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LesForgue
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affects of seat height and ballast/gear load on stability

Post by LesForgue » Mon Apr 15, 2019 8:35 pm

My JEM Trapper 15.38 is built without permanent seats per tradition. I built a temporary bow seat for a tandem outing with my sister. The bottom of the seat is 9 plus inches from the canoe floor per recommendations for smooth exit of tucked under feet. When sat on this seems very high. Barely a handbreadth lower than sitting on the thwart.
If this adversely affects stability,
Would adding ballast to ride lower in the water restore any lost stability?
(I realize riding deeper might make the canoe slower than it already might be.)
But first time out it was November 2018 the canoe was fast enough for me!
But I'm concerned about the high seat eroding stability.
Thanks in advance for replies.
Les
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OnkaBob
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Re: affects of seat height and ballast/gear load on stability

Post by OnkaBob » Wed Apr 17, 2019 6:38 am

Howdy Les,

I have no experience with the Trapper but the design specs - ie designed as a tandem, 38" beam, 660lb capacity- all implies that you should be OK even with high seats. However, to answer your question I doubt that there would be any significant advantage in having it ride lower in the water. The stability improvement from ballast comes from it moving to the opposite side of the balance point as the hull heels. It needs to be low and fixed in place so that it is always pulling the keel down. If it is loose so it can roll or tilt then it could be a liability.

If you do capsize remember to post photos for us :D .

Seriously, good luck, hope it goes well.
Cheers, Bob

Laker 13 - christened and slimed (just).
Laker accessories underway.

LesForgue
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Re: affects of seat height and ballast/gear load on stability

Post by LesForgue » Wed Apr 17, 2019 1:50 pm

Thanks Bob!
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jem
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Re: affects of seat height and ballast/gear load on stability

Post by jem » Thu Apr 18, 2019 6:14 pm

You'd have to add 50+ pounds of ballast to begin to have an impact.

Is lowering your seat an option? Even an inch would help.
-Matt. Designer.

LesForgue
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Re: affects of seat height and ballast/gear load on stability

Post by LesForgue » Thu Apr 18, 2019 11:41 pm

Well Matt I have two six gallon plastic water containers purchased mostly for solo outings for trim and or strong head wind bow or tail wind stern weight for tracking help.
I might never use them filled up to their fifty four pounds each, but if I ever want to ride deeper one or both might help then in that regard.
The only problem with lowering the seat an inch or so is I would have to buy four new bolts😓😃. But that's what I'll do if some mitigation is needed.
Probably I could have bought some kind of bean bag thing for my sister to sit on instead of making the seat, but it was fun to make and it looks pretty nice.
Hopefully I'll get my photos into the builder log and out & about forums one of these days.
I surely do thank the Lord as well as you Matt and those on the JEM forum for allowing / helping me to have gotten this far!👍😊
Les Richard Forgue

LesForgue
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Re: affects of seat height and ballast/gear load on stability

Post by LesForgue » Thu May 02, 2019 6:09 pm

turned out the seat height was no problem. my sister she loved the seat. she served as bow paddler with no problems as to stability eve tho we had waves rockin us somtimes abeam . they were little breaker waves about halway up toward the gunnels. the waves were caused by combo of high winds and too shallow water. definitely more than "chop". One advantage to the breakers was it showed us where was the too shallow water (too shallow for any power in our paddle strokes) I wsa afraid she would break the featherweight cedar paddle i had made for her by prying or pushing but it seemd surprisingly strong enough. If the winds we encountered had been present when we launched well we would not have launched at all. there was just enough difficulty with the wind etc to constitute an Adventure, but not enough to be crowned Miss Adventure.
Les Richard Forgue

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