Stiffening a Royalex Hull??????

I have a royalex canoe that has a very flexy hull that oil cans easily on waves. Annoying.

What do you think of this…

What if I were to lay long strips of fiberglass down the inside of the hull in an effort to provide some stiffness and rigidity?

Seems like it would work I think as long as the epoxy would make a good bond with the plastic hull and would not add much weight I don’t think.

I just find the flex of the boat on the water to be annoying.

What do you think???


Not an uncommon problem
What hull is it? Some are fairly easy to address.

Steam bend approximately 65 northern white cedar ribs and install in the hull.

(or buy a wood canvas canoe and solve problem).


Mad River
Boat is a Mad River Freedom Solo. Really, really flexy compounded by a flattish bottom.

So what are these “easy” ways to address???

Tandems are easier
The Wenonah solo plus is easy (BMO makes a minicell thing for under the seat). But a Freedom Solo that is meant to be kneeled … I don’t have an easy fix that wont interfere with kneeling.

Perhaps a narrow minicell pillar between the seat and the hull?

Fiberglass strips probably won’t help
For strips of fiberglass to be effective, you would need some kind of spacer material between the strips and the inside of the hull, to create a situation where the strips would need to stretch in order for the hull to bend inward (and they won’t stretch much since the material has good tensile strength, and therefore the hull won’t bend much either). Applying the strips directly to the hull only requires them to bend when the hull bends, not stretch, and since fiberglass won’t resist bending very well, you’ll have essentially the same hull flex as before.

This principal (separating two layers with a spacer material) is well illustrated by the way a foam core allows the bottom of a very lightweight Kevlar hull to be extremely stiff, even though the fabric itself bends extremely easily. There are also some composite canoes with ribs to stiffen the hull, and in those cases the ribs are only effective because they have a foam core within them creating the situation where the inner and outer layers must change dimensions relative to each other for the rib to bend. Maybe you can find a way to make similar ribs yourself.

Actually FG strips would help, but why?
Why add all that weight?

I have a MR Guide (Freedom Solo) which has a Mohawk minicell saddle installed under a thwart. Voila ! No flex. I have a seat suitable for sitting or kneeling, a big bunch of floatation if I spill, and a support to hold the Royalex bottom in place. The same setup pertains in my MR Synergy.

Royalex does stiffen with time, but why wait? Putting support between one or more thwarts and the bottom of the boat is a very efficient solution. Doesn’t weigh as much as an equivalent FG rib job, and won’t make your shins itch either.

Good advice
… I just want to highlight what you said about using a long saddle that allows you to sit comfortably as well.

Yeah, ironically, Mohawk probably
sells the best long saddles right now. Most saddles are set up for kneeling only. Of course, back in the 70s, I glued up my saddles from Ethafoam scavenged from packing.

working with Royalex…

– Last Updated: Jul-24-09 4:56 PM EST –

Think I read something about a ww-style of's my choice(fwiw)..THE most comfortable and efficient.
I had a ww boat a couple years ago that I wanted to stiffen up. With a thin hull...anything stiffer can, as mentioned, create stress fractures with time. I bought thin polyethylene from , cut/glue thin, well-spaced soft-foam rectangles..glue onto hull & then glue to polyethylene.
1/8" thickness worked well for me(~175lbs). Contact cement is fine(foam to hull)..but polytheylene to foam blocks requires special stuff(3M's #90 spray cement..others online HERE and on "")..polyethylene isn't friendly to apply glue to...HAVE to get all the air bubbles out..I don't think it likes air!..cuz just a little air space underneath & contact will weaken (weird). Foam to hull w/contact cement(Weldwood..etc)THIN Layers(1 or 2), but remember to let dry thoroughly!! w/each layer, re-heat, THEN press together...then using 3M's or other glue..connect to poly layer. The procedure works well.. You'll be surprised how solid it becomes, yet the foam will allow "give". And because the polyethylene/foam is a little less dense than the Royalex = no fracturing. My halacious 90min of just pure fun...LOL..LOL.


See Alice. Will have you up in no time.

So for the rest …

– Last Updated: Jul-24-09 8:22 PM EST –

of those who own Freedom Solo's/Guides...Do they oil can as well? I'm just so used to both of my boats oilcanning, I've gotten used to it. (Solo Plus,Spirit II RX) BTW Matt, I'll be emailing you tonight/tomorrow about the FS.

Can’t tell about mine, because it has
always had a Mohawk saddle supported by a thwart. But my opinion is that the boat would not oil can. The Royalex seems pretty stiff, perhaps partly because of the age of the boat. Probably made in the mid 90s.

Not too much flex
I’ve had my FS (05 model) set up with a saddle and a traditional seat, and there isn’t much flex there. I just recently removed the saddle and put the seat in and that has stiffened the boat even more.

No erl-cannin’ on mine…

– Last Updated: Jul-25-09 5:33 PM EST –

But ah' gots de old Vermont made MR Guide ca. 1997 vintage an' ah's always kneel so thaar always be a opposin' force on de hull.


So, your boat beer cans instead.