FZR

Muha, you are very polite. Thanks for your patience in reading all that! Sorry for the long winded answer. I am an engineer and any advice I give becomes my personal liability. I have many colleagues in court for years because they gave a partial answer based on unqualified assumptions and then they were sued. Not saying that you would do that but I can't control who is reading this nor do I have control of the work. A frame that fails and folds up could result in injury or death under the right circumstances. I could not live with that and I don't want the grieving family members looking for the guy that told him how to do the faulty repair. That makes things complicated. Good luck with your repairs.

Hello muha, There are too many variables at play to give you a simple answer. This is complicated by the fact that the original equipment manufacturer's design or quality processes were not adequate for the service. You have alluded to this fact by suggesting that welding over the old weld is likely not a sustainable solution. I agree with that observation and suggest that you are on the right track by trying to modify the construction at the joint. I cannot tell you exactly how to do that. Instead I will offer you some steps to determine the correct repair method. First, contact the manufacturer and see if they will share some technical information. You need to figure out how to weld the parent material to the repair without compromise to either material. To do so you will need to know the tubing chemistry and dimensions. That is normally provided by stating a material class (ASTM or some other standard) and a statement of outside diameter and wall thickness. Next you should ask them for a recommendation for a weld procedure. Finally, you should know if the joint was stress relieved (PWHT = Post Weld Heat Treatment). With this information in hand you can visit your welder and select the materials and welding method to provide an appropriate repair. That said I can suggest a couple of things to consider for the repair. Once the old weld is ground out (you don't put a new bandage over an old bandage) then the hole will be bigger than the cross bar. So some method of patching the hole is necessary. A reinforcing pad rolled to suit the outside diameter of the main tube could be fashioned with a short length of tube attached that will form a socket to receive the cross bar. The fit of all the parts should be close tolerance so that they are tight before welding. The pad is then welded to the main bar and the cross bar is welded into the socket. Alternatively I would think about replacing the section of the main tube with one of a larger diameter. I would make it long enough to capture at least both cross bars and maybe longer if some other members might impart a torsion on the main tube. The front and back frame parts could be cut and inserted into the new main frame tube segments and socket welded in place. In all cases the final fit up must be true and square to avoid introducing racking or twisting under load. Don't forget to prime and paint the raw steel to avoid rusting. Or if the new frames are only $150 then buy two and throw them away each time they fail. Or maybe upgrade to a higher quality product? That seems easier to me.

Thanks Don, I have two Outcast 800 boats and an Outcast 8D. They have not given me any trouble but I do not get as many days on the water as you do. My previous boats did have steel frames with smaller diameter tubes and I always thought they were too flexible. If I take anything away from this conversation it is to look for larger diameter tube so the stress concentrations at the welds are reduced. I agree with you that aluminum is generally less ductile than steel. However, with tube products, the alloys and manufacturing methods make a huge difference on how they perform. It is tough to say what to expect for failure modes. In any event I agree that these failures are a fault by design or poor welding practice. It seems new frame parts are less expensive than the cost of upgrading to a boat with larger tubes. So it might still be worthwhile to save money by going with smaller tubes. That is if the safety issue is not considered. That is not for me so I am happy you shared this information.

Thanks for the heads up Don. Aluminum does not rust. That frame is steel. The welds failed in the heat affected zone of the parent metal, probably in fatigue. Did you ask Outcast for help? Frank