Anyone lengthen a boat?

[Slimm]

Has anyone thought about (or succeeded) in lengthening a boat safely? I have been involved with the chopping of roofs on many different shapes and sizes of street rods and have some ideas that I think are not only plausible but very possible even for me.


Slimm

[XstreamVking]

Have done it and also made them wider. Used to build plugs and molds for boat co's. We would take the boat, cut it up, and often pieces from the mold the boat was built from and glass them together. Also jigged the hull pieces up on a frame and made an insert mold to add to the hull. Then glass up on that, overlapping onto the existing hull. I ran the boats as plugs, made more mods, and then made molds from them for production. Not fun or easy. But can be done. I have a 26'x 8" boat that I am considering stretching to 30' x 10'. Still undecided about it. By the time all is said and done, it might be the same amount of work just starting from scratch.......

[afr]

its done all the time and been done for years

[Smoking Joe]

I have done a number but boats in the 35ft to 45ft length. Two most important things to consider. Bouyancy/weight distribution at both rest and at speed. Don't consider redistributing weight using fuel or water as these are both variables. On boats this size no more than 3ft or you will have to move engines etc. Before doing this take a number of photo's of the boat both at rest and speed. I have seen many done which result in a boat with too much aft buoyancy. Absolutely kills resale if you don't get it right. The boat in my Avatar is my own and it has 3ft added to transom.

[Slimm]

Thanks everyone, the boat I am wanting to lengthen is my 1977 Cobra bass boat. It is a 17 foot and I want to make it a 20 footer. When you make the first cut, do you just cut a straight line through the boat and then add a piece in or make a sort of zig-zag cut along a seam or body line so the pieces could be slid apart yet stay in alignment.


Slimm

[XstreamVking]

Honestly, you will be better off selling the 17 and buying a 20. There's a lot more to it than just cutting and sticking it back together. If you want to do it as an experiment, and can live with maybe less than the expected results then go for it. Cut straight lines. Jig it up first on a frame that will slide apart.

[Smoking Joe]

I appreciate that the boats I do are considerably larger but I will share what we do. We don't cut the boat, rather we add the desired length as a new build which is stitched to the existing hull. We cut slots in the transom and stitch stringers to the existing ones. By not cutting the hull then we negate any issues about keeping the hull straight. In your case the existing transom could be cut down to become a bulk head after the added section is structurally complete. Fair the new section into the existing hull then paint.

[FUJIMO]

Having done my share of boat mold tooling/manufacturing, I wouldn't even think about it. Sell what you have, and go buy the hull that you want it to be. Major time & dollars & aggrevation will be saved. Not to mention resale.