when adding a crossmember to an aluminum boat....

Discussion in 'Boat Modification Journal' started by JEFFRODAMIS, Jan 25, 2010.

  1. JEFFRODAMIS

    JEFFRODAMIS New Member

    Messages:
    2,537
    State:
    TEXAS
    ok..if i take all my seats out and build it like i want it..what is the best way to attach wooden crossmembers to a boat?


    i figured something like this

    http://web.ecomplanet.com/BULL2958/ServerContent/MyCustomImages/BULL2958CustomImage1839496.jpg

    but side to side then build off of it, but i am putting a flat floor in it and would be bracing whatever crossmembers to the floor.

    what should i use to attach it to the boat? seems bolts and nuts would be a sturdier, more secure way to go about it then screws,

    i do plan on treating the wood and/or glassing it..whatever seems to work best.


    the goal in a nut shell is flat floor add seats and storage and INCREASE the rigidity of the boat.

    any tips would be greatly appreciated
     
  2. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    I would find me some square metal tubing either alum or iron. Those 2x4 are gonne get heavy at some point and then the trouble starts, Use 3m 5200 to seal all screws and bolts.
     

  3. What kind of seats are in the boat now? Are they the built in aluminum cross benches with the floatation in it?? Don't take those out hoss. I don't understand about the cross braces, just put the floor right on top of the cross ribs and secure with short stainless screws. Put that cheap white 1" foam sheets in between the ribs then the plywood. If the floor has a "belly", then rip a 2x3 or whatever to the correct height to support the floor in the middle the length of the baot, You can then build off that. You can cut "bulkheads" out of 3/4" to fit the inside floor and walls of the boat to build up to the height you want and attach it to the sides with a light flexible angle of aluminum or thich sheet metal with rivets and washers or 1/4" bolts nuts, nickel plated. Here are some ideas homie....

    1rst pic is a middle floor support if ya need it, a john boat should be pretty flat though...

    2nd pic, notice the aluminum light guage angle riveted to the sides the the top deck will screw into...

    3rd is the bulhead I made. I actually doubled up 2 pc of 3/4" for that one. It is also held to the floor with the angle material....
     
  4. JEFFRODAMIS

    JEFFRODAMIS New Member

    Messages:
    2,537
    State:
    TEXAS
    well if ad a 1 x 4 or 1 x 6 down the length of the boat i can make it where i can move the seat any where i want to easily..if i do aluminum id probably buy some 100% argon and weld it in there..be a lil more difficult to move. as far as weight..im nto real concerned..going to gain a few lbs overall but with all i am taking out it wont be noticable
     
  5. JEFFRODAMIS

    JEFFRODAMIS New Member

    Messages:
    2,537
    State:
    TEXAS

    It does have the flotation filled alumnum bench type seats..but i do plan on taking them out... thats why iw ant to be sure and add mor reinforcement. your pic gave me a better idea of how to do the floor..with the runners on either side....i may just add a reall strong brace in the rear welded and braced to the floor and transom.. amke it out fo aluminum tubing and add something simular up front where i know i will not be trying to walk around..trying to make it easier to get around in. are there special "marine" rivets? and if so will the work in a hand held riveter ? i have apneumatic but no air at the house..got plenty at the shop
     
  6. Handheld riveter is fine, just seal up the pin hole when yer done. So you want the inteior all open like a sea ark is designed then. It can be done......
     
  7. Here is my first boat. Somebody took the built in bench seats out before I got it. I just htrew in a floor, a front deck/storage, and a center console and it was fine for 6 years, and it's still running today close by. Wish I had better pictures....:wilt:
     
  8. karaep

    karaep Member

    Messages:
    268
    State:
    Greenville, NC
    Jeffro, I added a floor to my Alumacraft MV1648 NCS by ripping treated 2x4's to match the angle of each rib. Then countersinking stainless screws through the 2x4's and into the ribs. I added the foam insulation you see stacked in the third picture between each rib. It makes for a quieter ride. The rep at Alumacraft told me the only difference between the marine insulation/ floatation material and the stuff you get a Home Depot is it's resistance to gasoline. A 4x8 sheet of plywood topped it off. It was screwed down with stainless screws then carpet. I have three friends with the same boat and floor modifications, one has been down for over 12 years with no problems. We all keep our boats covered so they don't get wet very much. There are some pictures of the finished boat in my profile.

    You can then add seat bases directly to the floor by srewing them in, just be sure you have enough depth under the floor to clear the seatpost.

    If your talented enough to use aluminum I would. It is lighter and will last longer. I would still put the insulation between each rib.

    Hope this is helpful.
     

    Attached Files:

  9. JEFFRODAMIS

    JEFFRODAMIS New Member

    Messages:
    2,537
    State:
    TEXAS

    thats my boat! lol cept mine is bare aluminum cept on the back...and mine has no captains console...or anythign like that haha..same shape..thats bout it lol
     
  10. Nice work there buddy.:handshake:
     
  11. lmao....
     
  12. JEFFRODAMIS

    JEFFRODAMIS New Member

    Messages:
    2,537
    State:
    TEXAS
    from what ive been looking at it may be a lonestar..closest thing ive found anyways..been havin hell with the TPWD trying to get the title paperwork figured out..got 12 pages to persouse tonight... basically./// no hull id # = sol
     
  13. DANZIG

    DANZIG New Member

    Messages:
    6,672
    State:
    West Virginia
    If you remove the seats you have to keep the sides of the boat together. You don't want that puppy "unfolding" on ya.


    If I were going to do that I would build "supplemental" ribs out of aluminum square. Thicker the better within reason. Use the ribs(like in your picture) as a guide and run them up higher to where the seat attached. Put 'em where the seats were and you can use the holes where the seats attached.


    Might be a good idea to run a couple bow to stern for "stringers" too, or tie the new deck together in one piece so it becomes structural.

    You are peckering around with the structure so, short of having an engineer look at it, more is better if you can keep the weight down.

    For 2 seats imagine something like this # . Maybe 2 "supplemental rib braces" per removed seat, and 2 bars front to back connecting all 4. Basically building a stiff internal frame for the hull to hang off of.

    Did any of that make any sense??

    If we were sitting at the bar with a pen and a piece of paper it would be easier to explain.
     
  14. Now yer talkin hoss, I'll get the first round. ;)
     
  15. That's a whole other mess. That boat I posted had the ID missing off the hull. They'll bust yer stones and make ya jump through hoops, but they should eventuallly assign a new one for you to use. Just got to stamp a pice of metal with the numbers and mount it on the back of the transom. That's how they did in PA here....
     
  16. DANZIG

    DANZIG New Member

    Messages:
    6,672
    State:
    West Virginia
    "Jeffro, I added a floor to my Alumacraft MV1648 NCS by ripping treated 2x4's "

    If you did not seal that treated wood very well it is going to end up eating your aluminum.

    Copper treated wood is evil to a tinboat!!!
     
  17. DANZIG

    DANZIG New Member

    Messages:
    6,672
    State:
    West Virginia
    BTW Do not mix metals! Stay with aluminum as much as possible, even SS with eventually cause problems.

    When two or more different sorts of metal come into contact in the presence of an electrolyte a galvanic couple is set up as different metals have different electrode potentials. The electrolyte provides a means for ion migration whereby metallic ions can move from the anode to the cathode. This leads to the anodic metal corroding more quickly than it otherwise would; the corrosion of the cathodic metal is retarded even to the point of stopping. The presence of electrolyte and a conducting path between the metals may cause corrosion where otherwise neither metal alone would have corroded
     
  18. DANZIG

    DANZIG New Member

    Messages:
    6,672
    State:
    West Virginia
    "Now yer talkin hoss, I'll get the first round. ;) "

    LMAO!! All the World's problems can be, and have been, solved over a beer in a bar! :biggrin:
     
  19. Catfishboy1995

    Catfishboy1995 New Member

    Messages:
    3,104
    State:
    Council Bluffs
    Do ya mean napkin..lol
     
  20. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    What I did to reinforce a jon-boat that I took a seat out of, was to install an eye bolt just below the deck elevation I was installing, on each side. Cut your bulk head to fit the area that's going to support the deck. Run a plastic coated cable from eye bolt to a turn buckle, and pull your sides back in to tighten up to the bulk head.

    The eye bolts go just in front of the bulk head so all the cable , eye bolts, cable clamps, and turn buckles are hidden by the decking .

    On the outside of the eye bolts, I used rumble washers. That's those washers used in metal roofing or siding with a bonded rubber washer. I also first installed a jam nut on the eye bolt threads. You can use those type washers on both sides of the threads.

    I also used self locking nuts ( Nylock nuts), on the outside. Turn them on so just about one or two threads stick out of the nut, then crank down on the jam nut.