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What is Flat-hop in airsoft?


If my airsoft career were a kid, it would already be in school and I would probably do math lessons with it. However, it is difficult for me to clearly indicate one breakthrough that would impress me as much as the recently fashionable modifications of the hop-up system, including the flat-hop system. When I first saw this modification, I could not believe that at such a low cost you can significantly improve the most important performance of the replica without absurd power tunings.

Briefly about why a traditional hop-up is imperfect

At the outset, I would like to point out that I am neither a physicist nor an airsoft technician, so I may not use professional jargon to describe the BB's flight path. However, I hope that the perspective of an ordinary user will be even more interesting for the audience, who probably have a similar understanding of how airsoft replicas work. So, to the point. I have heard once that the hop-up system plays a similar role in airsoft replicas to the threaded barrel in a firearm. Probably from a technical point of view this is nonsense, but it is easy for me to associate that in fact both are aimed at introducing the projectile (in our case, the BB) into a rotational motion, which in turn has a positive effect on flight stability by extending the range and improving accuracy. You know - there are differences. In firearms, the projectile rotates around its axis and the airsoft ball is perpendicular to the barrel, using the so-called Magnus effect. Anyway, talking about the fact that the rubber "curls" the BB should not surprise anyone why we need it.

And here we come to the chase - how is the BB curved? Well, without going into too much detail, at the initial stage of its path through the barrel of the replica to the target, the ball physically touches a special thickening of the rubber located on the barrel of the replica inside the so-called hop-up chamber. This chamber has an interesting function, allowing us to regulate the pressure of the rubber, so we can influence the ball by curling it more or less. And if the downforce is too low, either the impact on the ball's flight will be none or it will be too low to improve our range. On the other hand, if we "turn" the hop-up too much, the BB will spin too much and it will fly up after it leaves the barrel, which is also undesirable because it leads to a limited range. It is optimal for us to spin the BB in such a way that it flies straight and stable after leaving the barrel. The adjustment allows us to choose the strength of the spinning depending on the weight of the BBs and other conditions such as the type of the hop-up rubber or its material.

standard hop-up unit

Source: https://airsoftranch.com/ultimate-guide-to-airsoft-hop-ups/

Traditionally, hop-up rubbers come into contact with the BB through the aforementioned slight thickening, a kind of hump with a semicircle cross-section. Usually, this part of the rubber is pressed by the hop-up chamber thanks to a spacer, which has a form of a small roller. So, what physically presses the rubber and what contacts the BB, giving it a spin, is oval or somewhat rounded shape. That's the problem. Such a shape of the pressing elements causes that the ball has a small contact point with the material, and therefore its rotation is imperfect. Flat-hop solves this problem by changing the shape of the element pressing the ball down and making it rotate. As the name suggests, we change this element to be flat and additionally elongated compared to the original one. Thanks to this, the ball is curled stronger and more stable. It is not only touched by a hump on the inside of the rubber band, but has the opportunity to roll over a flattened and elongated curling element.

How is Flat-Hop made?

Beware, thereis a controversial sentence ahead. In my opinion, making a flat-hop in a replica is simple. Seriously. If even I did it, it can't be hard. But to the point. The first and probably the most difficult step to describe in this article will be to disassemble the replica to get to the barrel and hop-up chamber. It would be hard to describe all possible constructions here, so let me skip it. After all, we don't want to make this text a "I fix it myself" guide. Depending on what replica you have, this step will be more or less complicated, but there is one general rule. Check the Web if someone does not provide a step-by-step guide on how to disassemble the replica and follow it until the inner barrel assembly is removed. Then, carefully remove the Hop-up chamber from the barrel so as to expose the rubber itself.

Now, after removing the hop-up rubber, you will have to fold it inside out. Literally. I used a pinching tool, which has no sharp edges so as not to damage the material. I grabbed the rubber from the inside, holding it, and pulled. It took a few tries, but there is work to be done. The point is that the inside of the rubber, what usually comes into contact with the barrel, should be outside. Then we will see what we need to get rid of the eraser. On the one side, it will have such a hump. This is the previously described element that curls the ball. Exactly on the opposite side, there is usually such a narrow strip that corresponds to the groove in the barrel and is intended to stabilize the rubber on the barrel. We get rid of both elements from the barrel thoroughly and carefully. Both the hump and this spine-like element on the other side. I used a mini grinder for this and sanded them. You can also cut them with a razor blade or wallpaper knife and then clean with sandpaper.Below pictures show the elements we need to get rid of the rubber.

flat-hop modification

flat-hop modification, inner barrel

After that, install the rubber on the barrel turning it 90 degrees from the original setting. Thanks to this, we are sure that the place that will be in contact with the ball is smooth (where we sanded, there may be surface imperfections that may adversely affect the curling of the ball). At this point it is worth mentioning that it is worth making Teflon-fix during such a modification. In the next step, we assemble the Hop-Up chamber, but with one small difference. Instead of a standard spacer, we use one that is dedicated to the flat-hop system. It will have a flat profile where it touches the ball, and that's what we mean. From my experience, it is best to use one of the ready-made spacers available on the market (e.g. Flat Knob Spacer). Finally, we assemble the replica and enjoy the improved performance. Simple isn't it?

Other similar systems

If you have read the above paragraphs carefully, you can come to a sensible conclusion that if we remove the element that originally curled the ball and only replace the spacer with a flat one, in such a system we lose some material in the hop-up rubber, which would spin the BB. It makes sense and is absolutely rational. If we use relatively light BBs that are easy to spin without interfering with great force, this should not be a problem. For me, this simplest modification works with BBsweighting 0.25 to 0.30g. I have heard of cases where flat-hop also shot heavier BBs with no problem. Much depends on the material our rubber is made of and the shape and hardness of the spacer so your mileage may wary. 

R-hop and S-hop are basically similar designs. Similar to each other and to flat-hop. The main step is still to change the shape of the BB curling element. The difference is that with the use of special materials, the hole for the spacer in the barrel of the replica is also filled. Thanks to this, you can spin the BBs with greater force, which may be useful for people who have more power in the replica and who use heavier BBs. In my opinion, however, these are more complex systems. You have to make sure that the hole in the barrel is properly sealed so that there are no imperfections on its inner surface, which may then adversely affect the quality of spinning the BB. It is also often difficult to achieve a significant improvement in the performance of a replica compared to a regular flat-hop. 

Another issue is what I would call indirect systems. It seems that some manufacturers of airsoft parts have noticed the potential of flat-hop systems and have incorporated some of their assumptions into their designs. A good example here are Maple Leaf hop-up buckings. Instead of the traditional hump, on the inside of the hop-up rubber, they use flatter structures. In combination with the spacer dedicated to the system in question, it gives good results without the need to interfere with the rubber itself. Staying on the subject of ready-made solutions, it is also good to mention the "H" type spacers, popular a few years ago. It seems to me that they are not as well received in Poland as in other European countries, but they are also an attempt to introduce innovations to our hop-up systems. I am aware that probably each of the systems discussed in this part of the articles deserves a more in-depth discussion. If you are interested in this topic, let me know in the comments if you want separate articles about any of them.

Final word 

Fast, easy and fun. This is how I can sum up my experience with flat-hop so far. At the beginning, when I was looking for information about this system, I had the impression that it was some kind of magical way to improve the performance of the replica using non-existent forces. I had the impression that people writing about it on the Web were exaggerating and probably succumbed to collective self-suggestion. However, after talking with friends who successfully use this system, I found out and tried it myself. Above all, such a modification is quite easy and does not interfere with the replica too much. It is easily reversible and requires relatively little cash to start with. If something goes wrong, we simply put on a new hop-up rubber and an old spacer. We lose a maximum of few euros and maybe two afternoons. Additionally, it is a good opportunity to learn how to disassemble our airsoft replica. Basically, we don't have to move the gearbox, where it's easy to break something. Getting into the hop-up chamber on its own in most popular replicas is not too complicated. In my case, it required unscrewing three screws and removing two pins. 

Flat-hop gives us a clear improvement in important performance if done correctly. In my case, it definitely improved the focus of the shots and slightly improved the range of the replica. Assuming that my replica generates about 1 J and I usually play short distances, focus was the decisive factor for me. However, we must not cheat ourselves. It's not like we'll use a flat-hop sniper rifle from a 30-meter spitting replica. This system will not replace good power tuning or replacement of the inner barrel. This is just one piece of the puzzle. It's worth starting with this, especially in the CQB replica, where we can't go crazy with power anyway. But that's not all. Let me know what you think about flat-hop and similar systems. Do you use them in your replicas? What are your experiences with them?



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