chine bars

Steel and aluminum boatbuilding. See: "Boatbuilding Methods", in left-hand column of the Home page, for information about alloys.

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mwga
Posts: 5
Joined: Mon Mar 16, 2009 3:55 pm

chine bars

Postby mwga » Sun Mar 29, 2009 7:22 am

I am building the jet setter and need a little info on chine bars. I think because there called bars they are solid, not pipe? how much of them can you see, on the outside, before you cover them with the 1 1/4 split pipe. Im having trouble with there position. Why can they be 1/2 or 3/4? and what do i need? Any one ever build a jet setter or any kind river jet sled?

thanks murray

Kevin Morin
Posts: 664
Joined: Thu Jan 24, 2008 11:36 am
Location: Kenai, Alaska

Re: chine bars

Postby Kevin Morin » Sat Jun 27, 2009 5:10 pm

mwga,

You've probably finished the boat, so I'm not going to be a lot of help but I'll make some remarks about chine bars.

Lots of designers of owner-built boats have to accept the fact they can't control the skill level of their clients so one way to help critical seams to be stronger is to make the seam contain a huge bar that will accept heat and stay put.

So one main reason for chine bars is joint strength when the welder may not be as experienced as a full time builder or someone whose trade is MIG welding.

Next, and this is along the same vein, chine bars help inexperienced builders to 'find' the line. If you put up frames and add chines then using door skin ply or other thin plywood you can take of patterns for the metal by tracing around the chine bard when your pattern hull piece is in place.

They can help 'back up' the weld depending on where they are located in relation to the two sheet edges (bottom and topsides- or topsides and reverser chine flat's outer edge). IF a chine bar is inside the weld zone then it can act to improve the outside hull weld by accepting a higher amperage and therefore increasing the fusion of the two adjacent plates and the bar.

If the chine bar is in the middle of the joint, then there are four welds at the chine- left and right of the bar and inside and outside of the both the previous welds. This make for some more effort and heat build up, but the result is the all four welds can be a bit more tolerant of less skillful operators.

After construction and welding the thicker material can take a bit more beating before it bends, caves, deflects and the welds around it crack less- potentially.

So the good side of chine bars is they help to make construction easier in the early stages of learning to build welded aluminum skiffs. They result in a thicker seam and that is a point of impact in a jet sled as it slides sideways in the white water and hits a rock at the chine.

The down side is they're not necessary once you have the skills or work methods to avoid them. But remember someone designing a boat to be built by others whose skills they don't know and can't predict safely- can't design welded joints that would suit the more experienced tradesman.

They take up more welding wire, and if not done correctly they act as a chill bar. This means the heat of fusion of some of the three parts in the chine bar seam may be cold lapped. For example many beginning MIG welders find 0.035" wire to be more controllable than 0.045" wire because the smaller wire will weld at lower amperages making travel speed and burn through or drop-out less likely. But the smaller wire can't make a decent weld of a 1/4" plate, 3/16" plate and a 3/4" round solid bar -unless you preheat with a temperature crayon- and that is another weld procedure that designers can't control.

In most river boats there is an extrusion over the chine, like and angle welded to the bottom and topsides 'around' the chine bar. So the bar is not used by full-time builders because it won't add to the joint strength if there's already going to be an angle cap rail.

I've built sleds that were pump and inboard powered and didn't use chine bars and instead used the angle extrusion covers and the boats are still banging around after 30 years so I'm pretty sure they're not needed.

But then neither are transverse frames needed in welded aluminum boats, after all none of the fulltime large scale builders rely on transverse framing- they use longitudinal framing more extensively. But frames do provide a good method for the new or first time builder to build a controlled shape and end up with a nice fair boat their first time.

Chine bars can be various sizes because they are there to provide different benefits to different boats and builders. They can be half exposed or act as back up bars, and the sheets can lay butted to them or some amount of tangent when the three parts are viewed in cross section.

Cheers,
Kevin Morin

Wearl
Posts: 27
Joined: Sun Jul 01, 2012 12:27 am

Re: chine bars

Postby Wearl » Wed Jul 11, 2012 11:33 pm

Kevin,

I took my chine bars out and used a half round on outside at chine. Grinded weld for looks. Bad idea? Shall I add some added support inside?

Hope this find you.

Thanks

Kevin Morin
Posts: 664
Joined: Thu Jan 24, 2008 11:36 am
Location: Kenai, Alaska

Re: chine bars

Postby Kevin Morin » Thu Jul 12, 2012 9:31 am

Wearl, sanding off or grinding down MIG welds is not usually accepted as good practice in welded aluminum, but on a case by case basis, it can be done without problems. If you've welded the chine inside and out, bottom to topsides, and then covered that chine seam outside with a 1/2 pipe, then welded that shape continuously over the seam, you've created a composite 'shape' (in cross section) along the chine. The shape is a V inside the 1/2 pipe.

If the outside seams of the half pipe to the plates were sanded/ground off, it will probably still do its job of covering the chine as a protection during impact. Further the naturally formed V of the edge of the extrusion half to the plates formed a small fillet V and that would be left intact even if the top of the weld was faired down.

I'm not sure of the boat, the material in either the topsides or bottom so its hard for me to say anything knowledgeable about further structural elements. If you have a picture or two we'd all be able see what you're dealing with.

cheers
Kevin Morin
Kevin Morin

Wearl
Posts: 27
Joined: Sun Jul 01, 2012 12:27 am

Re: chine bars

Postby Wearl » Thu Jul 12, 2012 10:58 am

Hi Kevin, Scrambler is the boat. I attached this picture. This was 1/2 rounds tacked. I did continuous welds and now ground. I will try and get more pics.




Image
Untitled by wearl2012, on Flickr
Last edited by Wearl on Thu Jul 12, 2012 11:10 am, edited 1 time in total.

Kevin Morin
Posts: 664
Joined: Thu Jan 24, 2008 11:36 am
Location: Kenai, Alaska

Re: chine bars

Postby Kevin Morin » Thu Jul 12, 2012 2:16 pm

Wearl, that confirms what I 'assumed' (my favorite form of [ILL]logic) and yes this will hold fine, as the inner two welds between the sheets are the real strength of the joint.

I'd suggest you get some acid or Scothbrite (tm) pads to continue cleaning the mill scale off the rest of the boat like you did along the welds you've already cleaned/dressed/faired.

cut/sand/grind the ends of the pipes back so they're very sloped (3:1) and put caps on of plate to keep the ends from filling with junk and making a corrosion cell of each chine. Drain them aft or if you seal them then make sure to pressure test the welds and float the leaks; much easier to drain aft.

If you post a pic of the insides we could see if you need more structure- did you use the plans for framing and structure?

cheers,
Kevin Morin
Kevin Morin

Wearl
Posts: 27
Joined: Sun Jul 01, 2012 12:27 am

Re: chine bars

Postby Wearl » Thu Jul 12, 2012 5:34 pm

Kevin, yes used plans and frames. Planning on taking them out a putting inside stifner as shelf. A couple of new pictures. The weld is inside chine. Other is G shaped round top of deck. Not welded yet not sure if I should do continuos weld or every 5 inches? My first time. Reading lots but still a bit blind on what is the preferred way and the garage way? Godd fun and good experience so far. Trying not to rush. Ok ant thoughts are welcome.


Wayne

Image
Untitled by wearl2012, on Flickr

Image
Untitled by wearl2012, on Flickr
Last edited by Wearl on Thu Jul 12, 2012 6:12 pm, edited 1 time in total.

Kevin Morin
Posts: 664
Joined: Thu Jan 24, 2008 11:36 am
Location: Kenai, Alaska

Re: chine bars

Postby Kevin Morin » Thu Jul 12, 2012 6:07 pm

Wayne, first a few notes about MIG in aluminum, you may already know this so I'm just reviewing these details based on the photo of the chine weld.

First you lead aluminum MIG, if at all possible so the gas cleans off the scale and other puddle 'scum' that floats up. That means you'd end up with a clean zone or white tracks near the weld. These, clean tracks near the finished weld, show #1 there is enough argon flow (40 to 60 cu/ft hr) #2 the lead is not sucking in atmosphere (blackened puddle top) and finally #3 the top of the bead is usually very clean showing there were no permanent contamination(s) in the weld zone that the hot gas and arc could not remove- so the 'salt and pepper' (centerline stream of bead) you show in your weld indicates something needs attention.

I don't see those clean tracks so: #1 maybe you're dragging the weld instead of leading? #2 you may need more argon flow ? #3 you may have sources of contamination you are not eliminating before welding.

Aluminum weld zones should be wiped with acetone or some other solvent that completely evaporates with clean rag; before wire brushing. This gets to the oils from gloves or hands, and also removes the oil that is left on some sheets by storage and handling in steel suppliers' environments.

Don't use turpentine/paint thinner(s) as its just an oil. You don't need to use acids but there are methods where that will work- not for the faint hearted!

Next you use a ss wire brush either a hand brush or a power brush to remove the mill scale but this can be done with a Scotchbrite (tm) buffing wheel (not as controlled as brushing). But as long as the mill scale is gone you're ready to weld. Further experienced welders will always use a hand brush just before they light up to help break the oxide- just before a weld (using MIG).

Aluminum oxide forms in about 4-6 seconds to a thickness of about 2-3 mills. So when you clean with an SS brush you'll have an oxide that will melt at much higher temp than the underlying aluminum. That means brushing the surface so the oxide is grooved by the sharp ss brush bristles and then lifts' and floats on the molten puddle and then is blown off by hot argon.

I know all that sounds like a bit of work, but that's the way its done by everyone that does it for a living in case you hadn't already been told these details?

The weld is just a little too hot, the amperage is too high for the travel and puddle width. Each individual movement is pointed and not rounded so the puddle is just a little hot for that width and travel speed. Fusion along the top and toe is nice, but the clean zone is too narrow so you may not be getting solid welds? Can't tell until that clean zone is at least 1/16" wide.

Black soot that close to the weld is likely water vapor left in the mill scale that does not appear to be removed with power brush prior to welding. Not sure what the corrosion looking stain is the right of the image? [I'm assuming 5356 wire on 5052 alloy?]

Have you done break bend tests? I'd be a little hesitant to weld more on the boat until you had confirmed your weld's performance. I think you're on the right track but there appear to be a few details that may need attention before spending lots of time doing seams?

G extrusion on the gunwale is often continuous welded but some builders do stitch them on. Production builders like to get all the labor and production time down to the least possible - other builders focus more on full boat integrity. If it's seal welded there are fewer locations to begin trapping contaminates that may lead, in some cases, to corrosion sites.

Cheers,
Kevin Morin
Kevin Morin

Wearl
Posts: 27
Joined: Sun Jul 01, 2012 12:27 am

Re: chine bars

Postby Wearl » Thu Jul 12, 2012 6:51 pm

Thank you. I appriciate your help. I have read some of your other post and have read up on it a bit. In the book building aluminum boats by Pollard. This is a good and fun learning experience getting better as I go. More argon flow and acetone may be part of my problem. Turn down heat got it. I did bench test weld. Seemed dang strong I also good a weld sample to weld supply store.

So a Continuous or stitch is preference to builder.

Thank you!

Wayne

Ps. so more support on chine?

That is not a stain but a bad tack weld on bar grind off when removed chine bar from boat!

I am a very visual learner dive in and go. Using picture below I thought I have been accomplishing a Good weld, as shown 3rd weld "good". Kevin maybe you could attach a picture to what it should look like. Thanks.



Image
Untitled by wearl2012, on Flickr
Last edited by Wearl on Thu Jul 12, 2012 11:33 pm, edited 1 time in total.

Wearl
Posts: 27
Joined: Sun Jul 01, 2012 12:27 am

Re: chine bars

Postby Wearl » Thu Jul 12, 2012 9:49 pm

Hope to see picture of MIG aluminum weld. Smiles.

Kevin Morin
Posts: 664
Joined: Thu Jan 24, 2008 11:36 am
Location: Kenai, Alaska

Re: chine bars

Postby Kevin Morin » Thu Jul 12, 2012 11:23 pm

Wayne all the weld examples are substandard.

when I go to the shop tomorrow I'll try to get some photo examples and mark them up for a post here.

I usually only show TIG welds as that's the method most people have the most trouble learning, but I looked at my library of images and have not taken any aluminum MIG so I'll set some up and try to get back.

Did you do a break/bend test? something may be strong until its bend back and forth a bit.

More tomorrow or the next day when I can edit photos and post.

Cheers,
Kevin Morin
Kevin Morin

Wearl
Posts: 27
Joined: Sun Jul 01, 2012 12:27 am

Re: chine bars

Postby Wearl » Fri Jul 13, 2012 8:12 am

Kevin,

Thank you. I look forward to seeing your examples.

Wayne

Wearl
Posts: 27
Joined: Sun Jul 01, 2012 12:27 am

Re: chine bars

Postby Wearl » Sat Jul 14, 2012 1:36 pm

Image
a Little better by wearl2012, on Flickr

A little better. Working on controll with mig. Not pretty like tig

Kevin Morin
Posts: 664
Joined: Thu Jan 24, 2008 11:36 am
Location: Kenai, Alaska

Re: chine bars

Postby Kevin Morin » Sat Jul 14, 2012 3:10 pm

Wayne the clean zone looks much better, the weld is more fused top and bottom and overall it seems better than the previous welds shown. I'm going to start another topic to give some MIG procedures so we can talk just about that subject and not have the chine bar listing at the top.

Cheers,
Kevin Morin
Kevin Morin

Wearl
Posts: 27
Joined: Sun Jul 01, 2012 12:27 am

Re: chine bars

Postby Wearl » Sat Jul 14, 2012 8:41 pm

Thank you! Shall i do anything different to my chine?

I am tagging on to cbrammer scrambler board My progress!

Thank you!!!


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