Routing boat parts in plywood - tab / bridge / punch out

[Sam A]

I am new to both cad cam software and cnc routing.

When I bought a boat kit in the past it had tabs/bridges in the cuts that were used to hold the part in the plywood. These tabs were 1" every 20" of cutting.

I am looking at cutting kits and was wondering if you left .5mm of material uncut as a carrier it would be easy to punch out or cut out with a utility knife? To little, to much?

What are others doing?

I will put complete sheets of ply board on each side of stack of plywood for shipping and strap with steel straps.

I use Bobcad and Bobnest to create the cuts and don't want to manually put the tabs in if I can keep from it.

Thanks in advance for your ideas.

Sam

[dshowalt]

Sam
You're probably going to have trouble with the final (utility knife) cutting of the parts. Unless your customer is very careful they run the risk of tearing the veneer of the plywood as they "punch" out the parts
Additionally what a pain to have to cut out the entire perimiter of the parts by hand with a knife. With tabs just use a Jig saw to cut the final tab and then only have to sand the 1" area where the tab was.
Just my thoughts.

[layertone]

I highly recommend an down-spiral bit with a bearing mounted on a table top router to trim those tabs off; just bought another one of these yesterday

http://www.woodcraft.com/family.aspx...s=8004&pcs=fam

the down-spiral bit will actually save tearing of the veneer / plywood skin. Even a straight spiral bit will not work as well as the downspiral

Tried all those methods to trim off tabs: knife, sanding, dremel.... this is the absolute BEST & fastest way to do it, trust me

[High Seas]

Dremel with the drywall cutting bit?
I imagine the bulkheads could be large and awkward to move to table top router.
At least the 1/4 shank on the down-spirals would fit into a trim router.
Neat find!
Jim

[Syil_Australia]

Hello Sam.

Welcome to the world of Boat kits... What designs are you looking at cutting?..

In our other business http://www.capeboatworks.com.au we cut marine plywood from 4mm to 18mm.

If you don't have vacuumn hold down then you need to use Tabs/Bridges in your toolpaths. Bridges can be 2D or 3D.. Start with 2d. Depending on the size of your part, say a Bulkhead you would need around 6 Tabs to secure the piece.

If your material was say 9mm thick use a Tab of around 10mm length by 6mm thickness. They generally don't need to be larger.

These tabs are then easily removed by either a Jigsaw or a very sharp chisel without damaging any edges.

To make successful tabs you need the right CAM software. As far as I know there are not many programs that produce tabs. CAM programs such as Artcam, Mastercam and Alphacam do allow tabs.

Bobcad doesn't have Tabs for toolpathing and according to Bobcad it won't be included for some time.

If you are going to cut boat kits with any commercial success you will need to either fit a Vacuumn table or purchase software that create Tabs.

Manually putting tabs in is crazy in a commercial operation. If you want to do it right you will need to invest. It will pay off in the long run.

Good luck. If you have any other questions I would be only to pleased to help.

cheers

Frans
Capeboatworks

[Sam A]

Syil,

I am cutting kits for Dudley Dix for the North American Market. I am manually adding the tabs because the software I have does not do it automatically.


My volume now is very low and I am not doing that many kits yet to get in the way of production.

I am going to cut kits for John Welsford, Paul Fisher at Fisher-Selway and am looking for other designers to rep in the NA market.

As the kits will always ship via truck, I will be leaving tabs in them to keep the parts together for inventory control......

I will check out your website to see what you are doing. Mine is www.thirdcoastcomposites.com .

Sam

[ger21]

To make successful tabs you need the right CAM software. As far as I know there are not many programs that produce tabs. CAM programs such as Artcam, Mastercam and Alphacam do allow tabs.

Bobcad doesn't have Tabs for toolpathing and according to Bobcad it won't be included for some time.

V Carve Pro will do tabs, and it's a fraction of the price of the packages mentioned above. www.vectric.com

[Oldmanandhistoy]

http://www.sheetcam.com/ will do tabs.