I like the concept of less seams for both ease of sewing and waterproofness on the roll top bag.
Roll top frame bag.
For most full suspension bikes a zippered frame bag is your only option.
Then this combined unit fits nicely in the water bottle cage.
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Many frame bags are being built this way and it will make stitching and construction easier and cheaper.
In addition moveable straps make using it with other bags such as a gas tank easier.
This can be a good compromise that still gives a useful amount of storage space.
Instead of using sewn in fixed straps on the back top front and downtube panels consider using a daisy chain and velcro onewrap.
Most of the seat bag systems have a roll top closure.
Some frame bags only use some of the space under the top tube to get around the issues of fitting the whole frame.
I like the form the zipper bag has due to the pattern and how it has the thin piece stitched all the way around the frame contact.
The zip pod provide the bag with the proper size and shape to fit the water bottle cage.
A rolltop bag requires a mostly straight top seam and a fair bit of height to make the straps work.
The exception is if you have a large frame in the style of the giant anthem trek fuel ex kona hei hei etc.
The zip pod with zipper cut off fits perfectly inside the b rad roll top bag.
And although the dry bag design keeps your equipment from getting soaked it also packs air.
Since a frame bag is a relatively simple shape some bikepackers make their own so it completely fills the available space.
Here is where small b rad roll top bag comes into the picture.
That depends on what bike you have.
Ortlieb tells us the new roll top frame bags will be available from the 1st of january 2021 while the fork packs are available effectively now early september 2020.
Newer bags have an air release valve that allows.
I will say that i was surprised not to find any other diy or myog folks who ve done a roll top frame bag yet maybe i didn t look hard enough.
Higher in price than the other two on our list so far is this thule covert roll top backpack which has been designed and manufactured specifically with urban explorers in mind this is ideal therefore for owners of drones and other photography equipment.
Great job on both those frame bags.