Carbon fiber 42” bar

[slackinoff]

Wow nice work!!

 

[cus_deluxe]

yeah thats sweet david, nicely done!

 

[davidwyby]

Just gotta change the design to keep the ends in.

 

[MG2186]

Looks good for sure! How are you holding the carbon fiber in the bar?

 

[davidwyby]

Looks good for sure! How are you holding the carbon fiber in the bar?

Right now, epoxy and those tiny screws. Future designs will probably at least have islands un-milled or rivets in the ends.

 

[Czed]

Probably will not be the final design of the bar, but I added some tiny screws in the ends of the panels to help retain the ends.
View attachment 361790

Are the bar's without any insert too weak to use?

Could the same area that you cut out simply be ground down on each side to reduce weight and hold rigidity?
Maybe leaving a vertical full thickness section to act as a brace in the middle.

 

[MG2186]

Right now, epoxy and those tiny screws. Future designs will probably at least have islands un-milled or rivets in the ends.

The insets on the Oregons had a tendency to come loose in the middle where they are glued. I’d fix them by riveting them in the middle.

 

[davidwyby]

Are the bar's without any insert too weak to use?

Could the same area that you cut out simply be ground down on each side to reduce weight and hold rigidity?
Maybe leaving a vertical full thickness section to act as a brace in the middle.

They would be kinda flimsy and chips would get stuck.

 

[Czed]

They would be kinda flimsy and chips would get stuck.

One of the guy's on here used to have a big dolmar with a skeletonized bar
But I think it was 20"

 

[Squareground3691]

Just wondering if ran a small T - cutter at bottom around perimeter into side wall like .05-.075 , to provide a lip for the carbon fiber to hold on to , just a thought ?

 

[davidwyby]

Just wondering if ran a small T - cutter at bottom around perimeter into side wall like .05-.075 , to provide a lip for the carbon fiber to hold on to , just a thought ?

That is part of the plan. I think the main issue with popping out is that when the bar is bent, the outside of the bar gets longer which separates the epoxy on the ends. Probably same in the middle on the inside when it gets shorter. I think a large part of the cure is posts left unmilled in the center of the pocket that are swaged like rivets after the panel is laid in. Or like @mettee said, trellis the bar and pour the CF so it is all integral. I think @SOS Ridgerider didn't have as much trouble because he did two sections of CF that could move independently and not pull so much, but I think this makes the bar less rigid. I thought about milling key slots or notches around the perimiter of the bar so the CF panel would interlock, but that will create fracture points in the steel.

 

[Hundred Acre Wood]

I think @SOS Ridgerider didn't have as much trouble because he did two sections of CF that could move independently and not pull so much, but I think this makes the bar less rigid.

I think this consideration is why you see many lightweight bars (e.g. Tsumura) using several small staggered ovals in their design. It spreads the twisting stress out so no one piece is affected so greatly that it separates from the bar. Staggering them minimizes the lost rigidity.

Effectively they're trading off some amount of rigidity for increased durability.

Just my guess.

Edit: to add image of example

 

[Squareground3691]

Tsumura Black Edition 36” have a separation probably for that reason are good looking bar , but are very hard to come by.

 

[davidwyby]

I think this consideration is why you see many lightweight bars (e.g. Tsumura) using several small staggered ovals in their design. It spreads the twisting stress out so no one piece is affected so greatly that it separates from the bar. Staggering them minimizes the lost rigidity.

Effectively they're trading off some amount of rigidity for increased durability.

Just my guess.

Edit: to add image of example

Yes. The epoxy is just there so the pockets don't fill with chips. CF with full pockets will be stiffer and lighter if I can get it down. Another option would be to make the pockets larger and fill with CF, which would be lighter, but not sure it would be any stiffer, and less durable.

I think I posted somewhere back in the thread that the 30" CF bar (previously heavy Cannon) and 28" Tsu LW balanced the same.

 

[davidwyby]

The end goal is a LW 42" - they are heavy, and at that length, the design must add rigidity or it will be floppy.

 

[davidwyby]

Progress

 

[davidwyby]

$550 worth of different CF remnants for testing. Gonna have a few 32” .063” bars to sell/test.

 

[davidwyby]

 

[ferris]

Oregon Bars?

 

[Shane¹]

$550 worth of different CF remnants for testing. Gonna have a few 32” .063” bars to sell/test.

How many bars do you think you will get done with that? Can't wait to see these in action