Building first aluminum boat

Discussion in 'Metal Boat Building' started by Kemmer, Aug 23, 2020.

  1. Kemmer
    Joined: Aug 2020
    Posts: 2
    Likes: 0, Points: 1
    Location: Holland

    Kemmer New Member

    Hi! I’m building a small aluminum boat at the moment. The dimensions are 4,8 by 1,8 meters. The boat is Designed all by ourselves with the intention to keep it as simple that we could because its our first time that we are building a boat. Butt this has a down side. The sides (well the entire boat) of the boat are made out of a singel plate
    4mm thick aluminum. Because of this there is a lot of welding distortion visible on the outer side. Small design flaw..... i had hoped that it would be less. Maybe some tips to reduce it by heating??

    The next boat will be designed differently with double hull also on the sides of the boat. then it will be much easier to reduce the welding distortion on the outer side of the boat I think?

    i am curious about the opinion of you guys. The intention is to start a side company with support of mine own company. I own an metalshop in holland also started out of a hobby. Im hoping that this also will grow. But could use some good tips and tricks ;)

    Here is some additional information.
    - double bottom. With insulation for noise reduction.
    - self draining.
    - it will be fitted with a outboard engine.
    - motor support is 15mm thick.
    - it is designed for small lakes, rivers and city canals. (There are al lot of them here in Holland)
    -steering on console.
    -see additional pictures

    Hope to hear from you guys.

    Attached Files:

    Last edited: Aug 23, 2020
  2. bajansailor
    Joined: Oct 2007
    Posts: 3,463
    Likes: 1,430, Points: 113, Legacy Rep: 37
    Location: Barbados

    bajansailor Marine Surveyor

    Welcome to the Forum Kemmer.

    The quality of your aluminium work is impressive - I am less impressed though with the actual design of the boat itself.
    I am sure that you could have used much less transverse framing in the hull double bottom structure, especially as it will only be used on flat water.
    Re the hull topsides plating (which you say is subject to welding distortion, but it is not really visible in the photos) - will you be fitting any additional framing and / or a capping rail on the gunwhale, in addition to the stiffening provided by the seating shown in the last sketch?
    Why do you want to create a 'double hull' on the sides of the next boat that you build?
    If it is sealed / airtight, then it could provide useful reserve buoyancy if you get swamped, but otherwise it will just be extra weight / expense.

    How much power does your outboard motor have?

    Here is a nice design for a 16' aluminium garvey which is a similar size to your boat, but a very different hull design.
    15'-9" Jimbo AL - garvey hull with center console-boatdesign

    Re the next boat that you design, may I suggest that you look on line at the hundreds of boat designs that are available, find one that you really like, and then use this as a basis vessel for your design rather than 'starting from scratch' as you appear to have done with the boat in the photos above (or is she based on another, similar type of boat?).
    Or simply buy a design that is already proven - it will be well worthwhile doing this.

    Edit - another thought - dare I ask if you have made any calculations re the weight of aluminium in the boat, and the buoyancy available?
    Have you worked out roughly where the waterline might be when she is floating?

    Have you done an estimate as to where the longitudinal centre of gravity of the boat might be in the anticipated load condition (with passengers sitting on the forward seats?) in relation to the longitudinal centre of buoyancy?
    You might well find that she will trim 'bow down', especially if you have all your passengers 'up forward', as she appears to be much 'finer' in the bow than the stern..
  3. Kemmer
    Joined: Aug 2020
    Posts: 2
    Likes: 0, Points: 1
    Location: Holland

    Kemmer New Member

    Thank you for the respons.

    -the double bottom design is quite a overkill indeed. But we just said we wil start the boat and learn by trail and error.

    -the gunwhale will be fitted with a capping rail for some extra support and finishing like the model.

    - the reason for a double wall is that it looks more luxurious. And on the other hand if it collaborates with the interior design we can place the seating on the inner sides of the wall so that there are less welts necessary on the outer side of the boat what causes the weld distortion.

    -the power of the outboard will be around 30hp. It is tested last week with 10hp outboard and that went quite good actually.

    -We 3d printed the model to have an idea how it would behave in the water. It still needs some trimming by adding some weight. It floats quite high on the water at the moment.

    Attached Files:

  4. Mr Efficiency
    Joined: Oct 2010
    Posts: 10,390
    Likes: 1,039, Points: 113, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    With little to no "flam" or outward flare of the topsides, and especially right forward, this looks likely to be a wet boat, at the very least, it would be wise to have a longitudinal "knocker", or step, half way up the sides all around. If travelling at some speed, and encountering a wake, the occupants could get an unwanted shower.
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.