:lol: Hi I'm installing a davit to pull crabs in a 1997 22' angler and need to attach hardware holding up davit pole to gunnel which is single thickness fiberglass and looking for ideas on how to reinforce the gunnel to support this bracket as it will have quite a bit of pressure pulling on it thankyou for any suggestions you may have :wink:
strngthen gunnel
- Thread starter wanna-be
- Start date
Most davits I have seen installed on boats our size have two points of contact with the boat. For example, Bob Austin installed his with an attachment point at the gunnel and at the side of the cabin. I've seen others installed with an attachment point on the cockpit sole at the base and one at the gunnel. These types of arrangements reduce torque overall. That said, I have installed and Ace Line Hauler on a standard Scotty downrigger baseplate. I backed my install with large ss fender washers (about 1-1.5" in diameter). Others have used "backing plates" made of aluminum, stainless, starboard or even epoxy coated, wood. Typically one cuts the desired material to the appropriate size and pre-drills holes in it for the mounting pattern of the device. That hole pattern is transferred to the gunnel and the device is through bolted with the backing plate below and fender (or other) washers behind that. Usually, you have to over drill the holes on the backing plate just a little to allow enough slop to get the bolts all the way through. Also, be aware that almost nothing on a boat is square and the underside of the gunnels have fillets where the hull and other pieces of fiberglass meet them. Thus to get a backing plate to sit flush, it needs to fit inside the fillets - either by making it small enough or by rounding over the corners of the backing plate.wanna-be":3ke7dnpo said:
rogerbum":1zfjbz6a said:
A couple of additions to Roger's excellent comments:
1) Another material that can work well is fiberglass. One can lay it up one's self, or purchase pre-made "board stock" from places such as McMaster-Carr. The latter is my preferred backing material, although you do have to deal with some dust when cutting it (I suit up and get it over with).
I'm not in favor of Starboard or "cutting board" plastics because they can creep under load, and they also don't take any caulking or epoxy (doesn't stick). That doesn't mean they wouldn't do anything to help the situation, but just that if I'm choosing from scratch, and there are better materials...
2) One way I like to take up any gaps in mounting (because, as mentioned, the surface is often not perfectly flat), plus bond the plate, is to mix up a paste of thickened epoxy, then use that to mate the backing plate with the underside of the deck. If you leave a couple of spots bare (after "buttering" the plate with epoxy), and then put dots of hot glue on them, that can serve as a "clamp" to hold things in place while the epoxy cures. A fillet around the edge can be made. When using this way, I usually don't pre-drill the backing plate, but rather start with the holes in the deck and then drill down through the backing plate after the epoxy cures.
Sunbeam
AstoriaDave
New member
wanna-be,
If you have to pull a stuck pot, the torque across the davit mounting plate can be pretty high. You might consider adding a stainless plate inboard of the backing/stiffening material, perhaps extending close to the edges of the backing. OTOH, if you will be tending pots soaked only an hour or two, unlikely they will be sanded in significantly.
Sunbeam's glue dot trick is a good one, if the mating surfaces are flat or mate uniformly. OTOH, if the gunnel area is concave on the inside, setting hardware to hold the backing in place during glueup will allow you to deform it for good contact over the whole surface. A bonus is that the squeezout will probably be ample for a structural filet, formed using gloved fingers. I would use epoxy mixed with milled glass fibers as well as a thickener, Cabosil or equivalent. Avoid cranking down on the fasteners. You want to leave some epoxy mix in the joint. Finger tight plus an eighth of a turn is probably OK.
Waxed paper under the hardware washers and or bolts and nuts is a good idea. A very thin coating of light oil such as WD-40, wiped well into the threads of the bolts, will allow you to pull the hardware after the resin sets. If it is stubborn, a little torch action on the bolt head will release it.
If you have to pull a stuck pot, the torque across the davit mounting plate can be pretty high. You might consider adding a stainless plate inboard of the backing/stiffening material, perhaps extending close to the edges of the backing. OTOH, if you will be tending pots soaked only an hour or two, unlikely they will be sanded in significantly.
Sunbeam's glue dot trick is a good one, if the mating surfaces are flat or mate uniformly. OTOH, if the gunnel area is concave on the inside, setting hardware to hold the backing in place during glueup will allow you to deform it for good contact over the whole surface. A bonus is that the squeezout will probably be ample for a structural filet, formed using gloved fingers. I would use epoxy mixed with milled glass fibers as well as a thickener, Cabosil or equivalent. Avoid cranking down on the fasteners. You want to leave some epoxy mix in the joint. Finger tight plus an eighth of a turn is probably OK.
Waxed paper under the hardware washers and or bolts and nuts is a good idea. A very thin coating of light oil such as WD-40, wiped well into the threads of the bolts, will allow you to pull the hardware after the resin sets. If it is stubborn, a little torch action on the bolt head will release it.
AstoriaDave":32r1x6zv said:
I maybe didn't describe it very well: I don't put any hardware in place until after the epoxy is cured. But I also don't pre-drill the backing plate (because then you have to line up the holes perfectly).
If the deck holes already exist, then I tape around them (to contain spillover) and then "moosh" the un-drilled backing plate on from underneath (fillet optional depending on situation). Air and some thickened epoxy comes out the deck holes onto the tape and I clean that up. Then after it is cured I (re-) drill the holes down through from the top, this time including the backing plate. Then I bed and fasten. If the deck holes don't exist yet, I do it the same way, but nothing to tape over (up on top anyway).
Usually I also overdrill the deck holes (if through a cored area), but leave the top deck skin intact. So, those holes get filled with thickened epoxy at the same time as I install the backing plate (I paint them with neat epoxy first, as I also do the underdeck surface; then I thicken it and continue).
Probably could have said that better the first time.
Sunbeam
