snapdragon rubbing strake replacement

[zak]

Hi

I wonder if anyone could share their experience of snapdragon/mirage rubbing strake replacement please? I might need to replace the rotten rubbing strake replacement on a 29' Snapdragon. I have no problem with the wood or fitting it where there is access inside but there are a few areas where access seems difficult if not impossible without some surgery.

The problem areas for access to the back of the rubbing strake seem to be

-- both port and starboard in the middle of the saloon. Looks like removal of a narrow wooden strip will provide a very slim slot for access if the pop rivets (??) are drilled out.

-- Cockpit both sides, seems that an access panel might need to be cut in the back of the locker wells?

any advice appreciated

rgds

zak

 

[sjchilde]

Hi Zak,

My Invader 22 is identical to a Snapdragon 670, it could be similar construction to yours.

I have replaced a section of wooden strake - mine was just screwed on from the outside, into the GRP which is really thick at the join. Rather than having to get pieces of wood 22ft long (or more) I went to the mouldings display in a diy shed and bought some hardwood strips, 42 x 8 mm I think. Two thicknesses matched the rubbing strake exactly. Buy doing it in two layers I was able to overlap the top one over the old wood to make a stronger join. I bedded them on some white sealer and joined them together with Balcotan glue, all in one messy operation (but i kept it all off the paint). And having thin strips means they are easy to bend to the curve. And I marked the screw holes first, although I don't think it would hurt to drill new holes there. When it had gone off I was able to plane the square edge off top and bottom and it was all tidy before the tide came back in.

Let us know how you get on!

Steve

 

[zak]

Thanks Steve, I'm also thinking I will have to do this from the outside where access inside is not easy. Had a good suggestion of machine tapping into the two layers of grp, hopefully that will be stong enough to hold the 2" x 1" D section.

I wonder if anyone knows of a marine grade Rawlnut or some other blind cavity fixing that might be stronger than machine tapping the grp?

rgds

Zak

 

[Searush]

I did half the port side of my W25 after it chafed away when a warp broke. I used bolts & steamed it to help it bend. I also found I needed a Spanish windlass to pull it in far enough at the bow to get the bolts home. For the scarfe joint I used brass screws (Yeah, OK bronze would have been better) to pull it in tight.

 

[sjchilde]

Hi Zak,

It looks as though mine is thinner wood, but I doubt if you need tapped holes. Mine is just stainless self-tapping screws into the GRP. The heads really don't show unless you are looking for them, and you could always countersink and fill over.

About thread taping, one thing I have done on other jobs is to file or grind away a thread or two at the point of a self-tapper, on the right hand side as the screw faces away from you, leaving the thread on the left untouched. This makes an edge that cuts a thread as the screw turns. (I don't believe ordinary self tappers actually cut a thread, they just find their way through wood fibres, and they can jam a bit in GRP).

I also have a deck winch that has no backing plate and the bolts are just tapped into the GRP. It's from a previous owner and I have meant to alter it for the last ten years or so, but it takes plenty of weight, I use it for a main halyard and for raising the mast.

Searush, do you know anyone who sells bronze screws? I do have a bronze plate I would like to fix with them...

 

[zak]

thanks guys

I might be being a bit paranoid but I'm worried that self tappers, or drilled, tapped and screwed fixings in grp might pull out under the strain of a 2 x 1 rubbing strake trying to straighen out or under collision.

Others suggested ideas I have rattling around in my head
- drill out the holes, fill with epoxy putty then redrill and tap etc
- stick foam soaked with epoxy in the hole then drill/tap etc
- Rawlnuts but dont know if there is a marine grade version
- Trying to jiggle bighead.com nuts into a slot and pullng in place with wire

any thoughts anyone?

Zak

 

[PetiteFleur]

For Bronze screws try Anglia Stainless nr Bury St Edmunds Tel 01359251414 - they don't seem to have a website.

I replaced the rubbing strips on a Vivacity 20. I bolted the wood to the boat with bronze screws & nuts and bronze screws where it was innaccessible. I also found a ¼" diameter hole, doing nothing, under the old wood - which explained where all the water came from when on port tack!(obviously been there from when built in the 60's.

When fitting the new strakes start at the bows ands work your way to the stern with the overhang pulled together with rope then cut off surplus after bolting.

 

[dam747iam]

rubbing strake

on my 747 i removed the rubbing strakes to refurbish them, they were fittited with self tapping screws and thats how they went back with a wood plug to cover screw.
as the originals were there for 34 yearsi feel this method to be th way to go.
i only had to replace the strip on the transon and i laminated this from 3 strips of oroko screwed and glued (balcotan) and shaped to suit.

 

[zak]

Thanks for all the suggestions

Zak

 

[[448]]

I have a similar job on a Macwester 27.
I think if you can secure the bow end with a through bolt, and find a place to position the scarf (if any) where a through bolt can be placed, and through bolt at the stern, then decent stainless self tappers would be good enough for the middle bits.
Anyway, that's what I intend doing.
I think stainless throughout would be best.
Dave