capt jake Posted May 1, 2003 Report Share Posted May 1, 2003 OK, I haven't packed the 'puter up yet; I will be tearing it down in a few hours though. I took the tarp off of 'Escape yesterday in prepartation to drag her to her new location. After hooking up the lighting, etc, I did a walk around to check things out. Mush to my dismay, I noticed that one of my rub rail scarfs had failed (mind you, they We glued with thickened epoxy over 6 months ago). The whole joint had separated!!! :( I fussed and cussed for a bit and then broke out (after I unpacked it) the industrial strength super glue (CA). With a bit of accelerator sprayed on it, i was able to force the joint back together, of course now it had to be re-sanded and varnished! Yes, they were cut at 8:1 . I walked around in an attempt to find the rest of the 4 joints. Yup, 2 more are just beginning to give way! The only thing I can figure is that it was caused by the 'slight' increase in temperature caused by being outside (though the joint that failed was on the North side of the boat). The one joint that is holding solid has a screw though it at its extreme end of the joint (the end that would be showing on the outside of the rail). The two that are starting to fail have a screw though the joint near the middle of the joint. The joint that failed had no screw through the joint. I assumed that epoxy would hold fine and layed out my screw pattern in a symetrical fashion, without regard for running them through the joints. Anybody else ever had this happen to them??? Quote Link to comment Share on other sites More sharing options...
Craig Posted May 1, 2003 Report Share Posted May 1, 2003 Jake it is a shame that that happened to you super nice work. However, with that out of the way go on to enjoy her and don't worry about the little stuff. :wink: Quote Link to comment Share on other sites More sharing options...
capt jake Posted May 1, 2003 Author Report Share Posted May 1, 2003 It just maked my wonder; how many more joints might fail?? I had them so smooth that they were very hard to detect. Quote Link to comment Share on other sites More sharing options...
JTam Posted May 1, 2003 Report Share Posted May 1, 2003 Jake, Ditto on my rubrail scarf joints. But mine didn't last 6 months. Only 6 weeks in the summer sun. The fault was mine. I positioned the scarf joint where the bend, and the stress, was the greatest. And, since epoxy will soften when heated, the summer sun in combination with the stress on the joint cause the scarf to begin to separate. Luckily I was inject more expoxy into the joint, push the ends back into position. Then I drilled and pegged the joint ... it's held so far. Quote Link to comment Share on other sites More sharing options...
High C Posted May 1, 2003 Report Share Posted May 1, 2003 A scarfed rubrail joint does want to open up. It's under constant pressure to do so. Hopefully you can pull them back in tight with screws, maybe #12s. And more glue, of course. Best of Luck! Quote Link to comment Share on other sites More sharing options...
waynemunro Posted May 1, 2003 Report Share Posted May 1, 2003 hmm, A timely posting, just did two rubrails last night, going down now to make sure that there are some screws through the scarfs... cheers. Quote Link to comment Share on other sites More sharing options...
Andrew Posted May 2, 2003 Report Share Posted May 2, 2003 Whoa! whats this I hear - epoxied scarf joints failing! I was looking at Phil's 'Aloha' and was planning on scarfing the hull bottom and sides in the same way he did. Does this mean that this is not a good idea anymore? Here in Canberra we have cold winters (below freezing) and hot dry summers (over 100 Degrees F) - will my hull sides split? - This is the first I've heard of epoxy failing. Here I was thinking that it was fantastic for just about any application!!! Is anyone else having the same troubles??? Quote Link to comment Share on other sites More sharing options...
Guest Posted May 2, 2003 Report Share Posted May 2, 2003 Scarf joint failures 101, in my little world. Starved resin, too thick with thickening agent, in thickened glue mixes, fast cure harderners, not allowing for resin saturations of ingrain woods. Cure, soak joints with unthickened epoxy, to wet out and don't clamp to tight, to squeeze out the thickened glue. my .02 cents worth. Also, some woods have a oily residue, if not cleaned, will allow for the wooden cells to be closed to receive the resin for complet satuations. Quote Link to comment Share on other sites More sharing options...
tdrown Posted May 2, 2003 Report Share Posted May 2, 2003 Tomorrow I am going to pick up the wood for my rub rails. I found 1x12"x16' premium oak for $100 (with a discount, $118 norm.) I am going to have to very carfully rip this, but the wood is simple beautiful. It is going to be a significant cost but had someone look at the car today, finaly. Avioding scarfing on the rub rails is something that I was aiming for, I just hope I will be able to rip, bend, route, and not mess up with this wood. This just solidifies my decition for nice 16' wood on the rub rails. Quote Link to comment Share on other sites More sharing options...
Andrew Posted May 2, 2003 Report Share Posted May 2, 2003 Thanx for that Oyster, Does the addition of unhardened resin on the joints add to the curing time? (while the hardener osmosises through it) Quote Link to comment Share on other sites More sharing options...
Barry Pyeatt Posted May 2, 2003 Report Share Posted May 2, 2003 A couple things to consider when you are doing scarf joints. The longer the scarf the greater the strength of the joint. 7:1 us about the minimum and on something the width of a rub rail a 12:1 would be much better. Check the grain in the area being scarfed as well, too much run out can cause a weaker joint. You can't squeeze all or even most of the epoxy out of the joint. Too much pressure on the joint and you remove too much of the epoxy and the joint becomes weaker rather than stronger. Sometimes the clamps are just a little too tight when holding it together. Scarfing rub rails is a different breed of cat than panels of plywood. The Rub rails are under a lot of stress on the forward bend of the hull. If you have to place a scarf joint on a boat like the Weekender or Vacationeer it is better placed in the rear quarters, there is less stress on the joint in that area. I would still try to plan to place a fastener thru the joint to help hold it at that point though. The ply joints running the width of the boat are under a lot less stress than the rub rails are and are a lot less likely to have a problem. Likewise the front to back joints on the sides of the bottom panel. You are also dealing with a lot thinner material that has a greater flexability than a 3/4" thick piece of solid wood. Phil had some challenges when he tried scarfing the side panels. They really need to be laid out and the overlap accounted for before they are scarfed together. I think he had to scarf on additional material along one edge to make it cover. And I don't think the length of the two pieces of ply are sufficient to scarf them together and have a long enough side panel so you are going to have to make two scarf joints in each side panel. That is fine, just think about where the joints will fall and how much stress will be on them at that point. Properly done, without forcing too much of the epoxy out of the joint itself and the wood will fail before the joint will fail, even in 100+ degree weather. I would also try to use a really good quality epoxy for this rather than finishing resin as I have seen some try to use. Using finishing resin to bond these types of joints together can cause all kinds of problems down the road. So I say read up on scarfing and then go for it. Only one other thing to remember, don't sand it too smooth on the joint before glueing it together. Quote Link to comment Share on other sites More sharing options...
Guest Posted May 2, 2003 Report Share Posted May 2, 2003 In my little world of scarfing, unthickened resin on raw joints should be mixed resin. Pure resin is oily at best. Some people have used just resin to fill the grain, but I have never had a failure from wetting out with mixed resin and thickened glue joints, with minimal clamping of either sheetrock screws or deep throat clamps and solid wood pressure across the seams. Quote Link to comment Share on other sites More sharing options...
Frank Hagan Posted May 2, 2003 Report Share Posted May 2, 2003 I planned for the scarfs to land in the aft section, cut them at a 12:1 I think, but still worried about them splitting apart. I cut the 1 x 2s on the table saw using a home-made tapering jig and used Weldwood resin glue to glue them up. I waited 48 hours or so before applying them. All the right advice has been given ... don't sand the edges smooth and close off the wood cells, don't clamp too tightly, and spill some for Neptune and it will probably work out OK. Capt Jake does great work, you can tell he's taking a lot of care in finishing his boat, and I suspect it may have had something to do with the wood itself. Quote Link to comment Share on other sites More sharing options...
P Doug (WA) Posted May 2, 2003 Report Share Posted May 2, 2003 This looks like a place to insert a question I have been wanting to ask. Has anyone used Gorilla Glue on their boats? It is too expensive to use extensivly, but would it be good for the rub rail joints? Is it as strong as they claim? I used it to put together my ships wheel but I don't know how it will hold up. It is doing fine hanging on my wall! Quote Link to comment Share on other sites More sharing options...
Phil Gowans Posted May 2, 2003 Report Share Posted May 2, 2003 As mentioned scarfing plywood is much better than scarfing rub rails. There is so much more surface area for the glue to hold and so much less stess on the joint of a large panel. I would still recommend scarf joints on the plywood dispite my side little problem :oops: . BTW for rails I used 18' mahogany benders that I had cut the day before so they would be fresh. I wet them well and still had 1 break. It was a good thing I bought 2 extra. There really is a lot of force on those rails. Quote Link to comment Share on other sites More sharing options...
Knut Posted May 2, 2003 Report Share Posted May 2, 2003 Hi, I am not quite sure I understood it all correctly when somebody wrote about pre-soaking the scarf surfaces etc, but let me emphasize one thing to make sure: Epoxy resin is system where hardening depends entirely on the right quantity of resin to hardener + that it has to be properly mixed. Any deviation will lead to lower strength of the hardened resin. There will be no migration or osmosis of hardener from one area to the other; it has to be there in the right amount and properly mixed in to take part in the reaction. Quote Link to comment Share on other sites More sharing options...
High C Posted May 2, 2003 Report Share Posted May 2, 2003 A boat builder friend of mine uses Gorilla glue on his boats. He's built a 48' and a 57', and has quite a fine reputation around these parts. I'm going to use it on the rub rails, toe rails, etc. of my Weekender. I've already used it on the framing of the seats, and it seems pretty good so far. The excess that squeezes out looks like that expanding foam stuff, easy to clean up. Here's one of his Gorilla boats: Quote Link to comment Share on other sites More sharing options...
Chris Potts Posted May 2, 2003 Report Share Posted May 2, 2003 Knut, I have heard some people recommend that you put properly mixed epoxy on both pieces before clapping them together and allow it to dry (you could probably just wait until the epoxy was green). Then apply thickened epoxy resin on the joint and clap it together. That way the end grain does not absorb the epoxy from the joint and leave it to dry. Chris Quote Link to comment Share on other sites More sharing options...
MikeStevenson Posted May 2, 2003 Report Share Posted May 2, 2003 Great looking boat! That's a serious hoembuilt...I suspect you'd actually need a boatyard to build in, but maybe not. A note about the scarfing of things: We have never built our boats this way. I know a lot of you are doing this, but be careful. The boats work fine with the joiners. I just don't trust that scarfing actually works, and to some degree the rubrail failure justifies this feeling. Mike Quote Link to comment Share on other sites More sharing options...
tdrown Posted May 3, 2003 Report Share Posted May 3, 2003 Just bought and brought home my future rub rails. A 1x12"x16' premium oak board. Looks great, probably the best wood I will get my hands on for a long time. I am just going to have to be careful ripping this though. With this sized board I have the opertunity to make the rub rails a slightly thicker, but I most likely will not. Should a route these before I attach them? I also read in a book that rub rails should have a drip grove to allow water to quickly run off these rails. Would anyone advise these as good ideas? Quote Link to comment Share on other sites More sharing options...
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