Adding Support to Gunnels
 

23' Tsunami - I'd like to add additional support throughout the length of my gunnels without creating any 'hotspots' ( while the topside is attached and the boat upright ).

Has anyone done this or have experience with adding structural support?

I'm trying to tighten up this area a bit. I was thinking to either add core ( it's straight up roving/mat ) or, adding more glass 1808 etc in structurally supportive way.

No matter what, working upside down seems like a PITA !

The hull, liner, topside joint is thru-bolted already.

I have posed this question awhile back with the same results. Crickets. Seems like unexplored territory. Can anyone recommend another site where I could learn about this type of project. I have searched online with no real luck ( a lot of canoe stuff ).

Thx

I built up under the gunnels on a 18' SeaHunt; do you have access to the underside?
Because of the liner, I had to remove the rod holder locker and work from inside. One layer of 1708 stiffened up the hull a lot and Coosa board backing and another layer of 1708 under the rod holders.
Boat is very solid when running now.

Glassing upside down- wet out the underside of the cap and your fiberglass, I used Epoxy and 1708 and let it get a bit tacky and then laid out the glass.
I also taped over with Blue masking tape, and it held fine.
You could use a quicker setting hardener and use a support board and brace; cover the boards with plastic tape.

Even simpler, you could add a vertical stiffener, like a 1"x2" piece of board, under the cap.

I did this for my deck. I made foam hat channels then bonded them in place with thick VE resin. If you look at my bass relief thread, you can see the carbon and glass and foam trapezoid stiffener I made. I'll see if I can link it.

http://www.classicseacraft.com/commu...t=25405&page=9

Installing the piece

Here is an underside view of the port gunnel looking aft. I want to add support to make it much stronger and structurally sound. The blocks of wood are supports to the hardtop and you can see all has been thru bolted.

As this site is all about taking a classic and making even better - I'm hoping to get sound advice as this is not an area I'm familiar with. I think adding core all around including the curves will tighten it up ( what a PITA !! ) but want some insight.


http://www.classicseacraft.com/commu...1&d=1438813600

This is different view - same side, but aft looking forward

I think if you made a core with skins like mine on a laminating table or atop the cap to achieve the desired compound curvature then you can build them right side up then bond in place?

Hmm. Not exactly sure what you;re describing. Are you saying to use the topside as a mold - a female plug ?

Once solid, add wax/ mold release on inside of that female plug, glass in core material, then pop that out, cut and use cored pieces as needed ?

Not a plug, per se, but a curved surface. If we assume that the core in the cap is a constant thickness, then if you were to wax/pva or just polyethylene sheet the cap, then you could lay down a layer of mat or even 1708 and a layer of core and a layer of mat, or even 1708 on top.

That way you make a sandwich core that conforms to the curvature of the underside of the cap. But you lay it up right side up.

The bottom layer of mat/ 1708 would be the underside of the core. Once that all kicks you could flip it over, cut a 45 degree bevel around the edge and put more glass over the bevel. Then you have something like the inverted trapezoid I made for a "hat channel" stiffener for my deck, except it should follow the underside of your existing cap nicely. Of course you want it to be less than full cap width. Then you sandblast the underside of your cap, wash with acetone and bond the additional core in place like an oreo. Or grilled cheese sandwich. I'd use VE or an epoxy thickened with some cabosil and structural thickener. You will need a bunch of C or bar clamps or welding clamps.

I hope this makes sense. I haven't tired this, but it is a variation on the deck support I made.

First - thx for the input - been tough finding info ANYWHERE online to tackle this.

I would want to not only capture the flat cap, but also the the (2) radius' on either side of the cap. So, if I used a sheet of plastic on top of the cap and along both sides ( to avoid gumming up the nonskid ) and layer it up as you described - once it kicked, that pc would not fit under the gunnel as it would be too wide. That's why I was thinking the female mold idea.

I do like the sandblast idea as the idea of hand-sanding that area under the gunnel made me want to puke ! My goal is to have glass and core on all the surface of under the gunnel to really tighten things up.

This has all stemmed from the fact that the hard top I recently put on attaches to vertical surfaces ( not horizontal - which I think is a better idea ) of the topside/gunnel and this topside/gunnel structure is not built for this - so the gunnel flexes.

When I figure this out, I will share...

Could you build on top of the cap with a foam core, drape down the vertical sides, then trim.

Just a single layer top and bottom, but maybe more on the vertical sides.

Then pop them off the cap. Then freehand rip up the middle with a router. Maybe 3/8" wide? Then reassemble and patch the rip. The part should be narrow enough to slip inside the cap now. You could even use G-10 skins for the patch. You might have to space the patch off the cap with 4x4s so that the vertical parts don't hit the existing cap when you patch up the rip with the 3/8" kerf. (So as to help maintain the compound curvature)

Then bond the inserts inside the cap with thickened resin.

Maybe that will work?

I was at the dentist today getting a crown. He was making splash molds of my teeth all morning.

Inspiration.

I think the best way ( at least the way I can envision ) is to buy balsa core with the 'cloth' backing. Pre-cut it to fit under the area I want to stiffen. Pre-cut mat - saturate it well and in small sections, glass the balsa in place. Continue this process till its all covered - then glass on top with roving or bias roving.

You could also use Contour Cut Divinycell or NidaCore; the Divinycell is made up of smaller squares, so it should follow the curves better. Both have a scrim glass layer and glassing upside down will work.
You'll still need to add backing plates for rod holders, TTop, etc.

Any fix is going to be a pita.
Flip it and foam it....or dam up the bottom of the gunnel and foam it from the top. I've noticed some builders of new boats are doing this now (foaming the gunnels while in the mold).
Good luck.