How to fish the FAB or foam arsed blob fly

The foam arsed blob or FAB is one of the most versatile stillwater fly patterns for rainbow trout and works on fly lines of all types - whether sinking, intermediate or even floating. It's also dead easy to tie.

How to fish the FAB or foam arsed blob fly
© Davie McPhail
How to fish the FAB or foam arsed blob fly
Picture copyright © Davie McPhail
How to fish the FAB or foam arsed blob fly
Fly fishing tips Estimated reading time 5 - 8 minutes

What is a FAB fly?

The FAB, or foam arsed blob, is a small colourful variant of the popular blob fly with a buoyant tail end. It is a versatile fly pattern that can be used on floating, intermediate and sinking lines and works all year round.

Why fish a buoyant fly on a floating line?

The FAB can be used as the point fly (that's the one tied to the very end of your tippet) when fishing a method known as the washing line.

Here, you'd fish two or three buzzers or nymphs on droppers and tie the FAB to the point. As it floats on or in the surface, it helps hold the buzzers up near the top better than you could if you were fishing just buzzers on their own.

Just as when conventional blobs are fished subsurface, the brightly coloured FAB also serves as an attractor pattern and can bring fish in to investigate. They'll usually take one of the nymphs, but they'll sometimes take the FAB too.

The FAB is a great fly pattern for rainbow trout on UK stillwaters.

How is the FAB normally fished, then?

The usual method is to fish the foam arsed blob subsurface, a bit like a booby. Here, you'd use either an intermediate fly line to help it sink slowly through the depths, or go for a full sinking line like a Di3, to get the flies down deeper.

You can also pull the FAB so it creates a wake in the water and attracts fish, twiddle it back with a slow figure of eight retrieve, strip it quickly, or even use a roly-poly retrieve. Effectively, it's even more versatile than the original blob.

Why do people fish FABs with buzzers?

If you're fishing heavy epoxy coated buzzers, then you can use a FAB to help slow the descent of the flies. I use a leader of about fifteen feet with a FAB on the point, and a buzzer four feet from the point and another four feet up from that.

On a floating line or midge tip, the FAB will slow down the descent of the buzzers to a much slower speed. If you want them to drop a bit quicker you can tie FABs with a shorter tail, while if you want them to be much more buoyant you can use a longer one.

How do you fish FABs on a sinking line?

On a sinking line, a FAB behaves a bit like a booby. Once you've cast out your sinking line you let it go down to the bottom and it will slowly pull the FABs down from the surface and submerge them.

Each time you pull during the retrieve, the FABs will dive down to the bottom and each time you pause, they'll bob back up. This up and down motion can really get trout going.

FABs are normally fished on sinking lines.

Can you fish FABs static?

Yes, you can fish foam arsed blobs static, as some people do with boobies. However, you should check the rules of the fishery before trying this.

The use of buoyant flies on sinking lines is often banned on catch and release waters, as it's harder to detect bites and fish often swallow the static flies more deeply. Boobies are banned at many waters as a result, and the FAB probably originated because someone was trying to work around the rules!

If you're fishing your FABs static, you can either let the natural undertow and water currents of the lake waft them around. Or, add in the odd pull to attract fish. We've seen this method used to devastating effect in competitions and it's amazing how many fish fall for it.

How do you tie a foam arsed blob fly pattern?

The FAB fly pattern is very easy to tie. It's well within the grasp of the total beginner to fly tying. You really only need a hook and three materials - some thread, some blob fritz and a 10-15mm length of booby cord.

After first laying down a base layer of thread to provide grip, I cut a slit in one end of the booby cord and place it horizontally at the back end of the hook. I then tie over the top of the booby cord to reduce the size and hold it in place.

Then, take a small 15cm length of blob fritz (I love the FNF Jelly Fritz as it's really easy to use) and dip it in some water, then dry it off in a towel. Strip off a few strands of the fritz and tie in the central core at the tail end. Then, wrap the fritz around the hook shank taking care to stroke the fibres back between each turn.

Tidy up the head with some thread, whip finish and either varnish the thread or seal it with some UV resin. It's dead easy and you can tie one in just a few minutes. Here are some great foam arsed blob patterns to inspire you to tie your own.

FAB fly pattern by Davie McPhail / YouTube.

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