Engineering A Top-Strap Shoulder Bag

[doe]

I want to make a flap-style shoulder bag, but unlike the bags where the strap attaches to the gusset, I want a single loop strap attached to the top of the bag. It would be modeled (in style, not in craftsmanship!) on the Hermes Constance (pictured), where the simple strap can either be doubled up to wear on the shoulder or worn at a single thickness messenger-style.

I've never owned any bag like this, much less a Constance, and I was wondering if there are any particular aspects of the construction I need to keep in mind to be sure the bag does not tip over when it is opened while being carried, for example. It also seems like the clasp would have to be fairly strong to handle the stress of the way the bag would be carried--but maybe I'm overthinking this?

I know that messenger bags with a top handle usually have a reinforcing strip on the inside of the bag under the handle, so I would definitely do that, but was just wondering if there's anything else I'm overlooking.

I'll prototype first, but still want to try to think it through as much as I can before getting started on the pattern/design.

[JamesR]

What will this bag be used for?

Do you plan on hauling books and other heavy items?

Also how big will it be?

You are not overthinking it when you bring up valid concerns.

[doe]

This would be an everyday purse. Medium in size--around 12" wide by 9" high by 3" deep or so. No books, just everyday carry type stuff (wallet, phone, keys, sunglasses, small odds-and-ends pouch) plus a 12-ounce bottle of water.

[JamesR]

The strap dee rings need to be attached to the flap somehow.

I like to use a billet that is attached under the flap and comes through oblong holes in the flap. See photo.

I have found that the stress on the billet is not perpendicular to the stitch line but more parallel to it this way.

Yes the latch is also under stress when the weight of the bag is transferred to the strap and flap.

Most of the bags I have made were for carrying heavy loads (text books,tools,instruments) and the latch I have used mostly were DOT common sense connectors. The connectors don't fail but the connection between the bag and the connector can be overly stressed.

This is one of the reasons I started using horse collar latches.See photo.

I imagine this kind of a latch would not suit your design though.

Anyway one way to reduce the stress on the latch is to move the dee rings to the rear of the bag so the force is shifted to the back of the bag and not the front of the flap so much.See photo.

I also realize that all of these suggestions can compromise your design and vision for this bag.

Your post caught my attention when you used the term "engineering a Top-Strap Bag".I have always approached my work this way.

I wish you luck and success.

[doe]

This is incredibly helpful and the photo examples are beautiful. Thanks for sharing your work and experience!

I like the idea of attaching the dee rings to the back, but in that case I would have to use a chain strap, which I wouldn't want to do. For the closure, I was thinking a simple turnlock.

I found an example of a bag similar to your second example in a way, but where the dee rings pierce the front and back at the top of the bag. This is a little more complicated visually, but I like the idea.

Thanks again for your advice--I'm going to keep mulling this over.

[JamesR]

You are very welcome.

That bag thumbnail you attached is very interesting. It looks like the top of the bag has a dowel or tube stitched under the leather to reinforce the top.

If this were done where it was off center toward the back of the bag it would probably would reduce stress on the turnlock. It would also provide a very solid connection point for the strap.

I have seen this done with exposed copper tubing at the top of the bag. Your example seems like a more elegant idea.

[doe]

That bag is a vintage Coach Willis. Here is a side view.