Questions on cutting out frames, layout board and jig/base

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North
Posts: 280
Joined: Mon Jul 15, 2013 6:29 pm
Location: Nova Scotia

Questions on cutting out frames, layout board and jig/base

Postby North » Thu Aug 15, 2013 5:42 pm

Hi folks,

Sorry to have posts on a couple of differnet sections, but I think these questions belong here.
Have plans for the 23' Double Eagle in Aluminum, and may have missed something on the plans, but I am a bit foggy.

I see the patterns for outside dimension / edges of frames, to transfer onto layout board, or large plate for cutting, but:
- how thick are the frames, or how do you know where the inside edge is, so I cnb trace them out onto a 1/4" alumium plate?
- are the frames made up of several pieces, and welded togther, rather than cut as one piece from a large plate?
- what did you folks use for a layout board in your metal builds?
- what did you use for the jig/ base - I am thinking of just using scrap steel, but not sure what size and thickness would be adequate for rails / sides, etc in angle or other common shapes.
- If I use steel for the base, what is the common way to temporarily attache the frames to the jig, at the corrent intervals (ie drill and bolt, etc) Could tack weld if I used aluminum for the base but scrap aluminum in large lengths / sizes not easily found - of course, if using aluminum for the jig/base realy makes sense, I could likely rig something up.

Hopefully some of you experienced folks can take pity on a newcomer and fill in some of the blanks.
Thanks!

Cyclone
Posts: 60
Joined: Sun Jan 08, 2012 7:26 pm
Location: Barrie, Ontario

Re: Questions on cutting out frames, layout board and jig/ba

Postby Cyclone » Fri Aug 16, 2013 5:32 pm

Well my build is in wood so there is only 1 of your questions that I can say something about. My plans only provided the outside lines as well. There were a couple places on the drawings and in the information package I received with my plans where it listed the moulded minimum width of the frame members. I used a straight edge to create the line for the inside of the frame member and positoned the inside edge so that at no point did the distance from the straight line go below the minimum width listed in the plans to the exterior lines. I tried to keep the frame members as light as possible to reduce the material used, weight of the frames, and to maximize the space inside the hull while not going below the minimum. I would look over your plans carefully and look for where the minumum moulded width is given. Perhaps you could run a search on the posts to find a site member who also builds in metal and send them a message about your other questions.

North
Posts: 280
Joined: Mon Jul 15, 2013 6:29 pm
Location: Nova Scotia

Re: Questions on cutting out frames, layout board and jig/ba

Postby North » Sat Aug 17, 2013 6:08 am

Cyclone - thanks for the help. After looking at the plans again, I did find a reference to a 4" minimum width for all frames, so that answers one big question. Also noticed the minimum overlap for frame gussets, where the side and bottom frame pieces are joined together, so that answers my question on whether they should be cut whole or pieced together.

As well, in the aluminum boat building guide, it mentions that in general metal building, frames can be made from flatbar or cut from plate. But on the plans it always references 1/4" PL.

My main two questions are:
1. I don't think there would be a huge price difference between FB and plate (ie maybe about the same per pound)so I would think that I would use 4" flatbar wherever possible to have avoid so much cutting and have nice (factory) straight lines. Is this what others have done?

2. I see that some frames look to be the same "width" on the bottom as the sides (where the minimum 4" reference is marked) while others incorporate internal tank sides/bulheads into the bottom frames, and these are "wider" than the others. They come up to within a couple of inches of the DWL (presumably to the underside of the deck plating), but I have not found a note that says how to measure this - ie how many inches below DWL on full size patterns.

Again, thanks for help so far and hope to hear from some of the steel or aluminum builders as well.

Cyclone
Posts: 60
Joined: Sun Jan 08, 2012 7:26 pm
Location: Barrie, Ontario

Re: Questions on cutting out frames, layout board and jig/ba

Postby Cyclone » Sat Aug 17, 2013 11:00 am

I used to work in a custom shop where we fabricated large items from steel and aluminum and we used to change between flat bar and plate all the time. The flat bar and Plate were the same material as far thickness, grade / mechanical properties anyway. For some jobs we had flat bar at a width that would save some cutting time and less waste rather then cutting a piece out of plate that was basically the shape of a long flat bar (which we did in a pinch if we ran out of flat bar). For other parts that did not suit the shape of flat bar we would nest all the parts in a plate and figure out how to nest them to gether to keep waste to a minimum.

For your frame members that have wider sections, such as those that form internal fuel tanks, if there are no dimensions for the area beyond the minumum frame width requirement they may be leaviing these dimensions up to the builder. They may say somewhere in the plans what is the recomended location and capacity for fuel tanks. So if you determined a length and width for the tank then the height would be the distance required to get the volume you want. Some builder might want to minimize the fuel tanks to have more interior room while others might want the biggest tanks possible. I think they would want some clearance between the top of the tanks and the deck surface. Just my thoughts, I am a little out of my element here, being a wood builder. I have viewed a book written by David Gerr, Naval Achitect, on Mechanical Systems for boats. He has written a series of books that are available at my Library that are are a good source for general questions such as fuel tanks and fuel systems requirements. I have found these books helpful.

Hopefully some guys with metal boat build experience will have some feedback.

North
Posts: 280
Joined: Mon Jul 15, 2013 6:29 pm
Location: Nova Scotia

Re: Questions on cutting out frames, layout board and jig/ba

Postby North » Sat Aug 17, 2013 4:37 pm

I think you may be right about the width of frames adjacent to tanks, wenibe compartment ,etc, as that would vary based on the builder's choices.
I looked a few pics that BillyZ has in the gallery, of his Double Eagle in aluminum. The pics are small and get fuzzy when I try to enlarge them, but it looks as though the frames are all the same size. I hope to hear form him or some other metal builders tp o see what they did. For example, the tank side which doubles as the frame bottom seems to call for 3/16" plate, rather than 1/4", likley because it would be significantly wider(higher actually) than the minunum 4" frames.
I think I could juts make all frames 4" on the bottom and then later weld on extensions for the tanks / engine well ,etc, but it would reduce chances of leaks, etc, if the bottoms are cut from one piece.

North
Posts: 280
Joined: Mon Jul 15, 2013 6:29 pm
Location: Nova Scotia

Re: Questions on cutting out frames, layout board and jig/ba

Postby North » Wed Aug 21, 2013 2:52 pm

Noticed on the full size frame patterns, that the frames sides and bottoms are (of course) not straight, and have a slight curve to them. I think it would still be worthwhile to use flatbar, imnstead of plate as at least the inside edge could be left straight (I think), and I would just take off what is necessary on the outside to make it fit the plan / layout board outside line.
But, it state a minimum of 4" for frame width, so I guess 5" flatbar may be more appropriate than 4", so I stay abpve the minimum when I shave some off to fit the pattern.
Or, should I use plate and use the good edge of the plate for my inside edge, where possible and cut the "outside" sedge of the frame out from the plate.

If others could let me know what you did (or would do next time...) I woudl really appreciate it!


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