【Kyudo】Hard case for Takeyumi(bamboo bow)

I’m not good at English. I’m sorry if there is a wrong expression or it is difficult to understand.

I made a flight case for a bamboo bow

I wrote an article about how to travel by plane with a bow.

Ingenuity of traveling by airplane or Shinkansen with a bow
ingenuity of traveling on an airplane with a bow, part 2
Ingenuity of traveling on the Shinkansen with a bow Part 3

In 2018, I had many opportunities to travel by plane with a bow, and while writing an article, I wanted a flight case that could carry an important bamboo bow with peace of mind.

This time, I made my own flight case for bamboo bow.

I’m a do-it-yourself, and the concept takes about two years, and the actual production takes about a year, including prototypes.
It was completed through a number of prototypes and processes. I will write a detailed production article in the future, but if you want to make it, I think that it will be helpful, and this time, I will introduce the whole version.

Flight case for bamboo bow

Carbon fiber is hardened with polyester resin , and it is made by the so-called CFRP method.
For 2 pieces (maximum 4 pieces ), it supports warpage of 10 cm to 25 cm .
Length: 230 cm, Thickness: 6 cm, Width: 20 to 30 cm (approx. 40 cm considering curvature)
Weight: 4.1 kg without a bow, 5.5 kg with 2 bamboo bows.
Also, when not in use, it can be divided into pieces with a length of about 120 cm 。

The main body is divided into two on one side and three on the other.

The structure is such that the divided parts are connected using joints. The joint is fastened with a snap lock.

I will lock other places as well.

After splicing, insert the bow. The standard is for 2 pieces.

Cover and lock with a snap lock.

it will stand on its own even in this direction.

Corresponds to changes in warpage.

It won’t break even if a person sits down (it doesn’t have a bow)

Can be stored small.

You can lean against the wall.

Conception of flight case for bamboo bow

When I thought about what kind of case to use, I referred to the case of musical instruments such as violins, the rod case for fishing rods, and so on. Looking at them, I was wondering if I could make it for a bow.

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As a condition that you want to meet,
(1) Not too big
(2) Can respond to changes in the backing
(3) If possible, 2 can be put in
(4) Can be stored shortly
(5) Strong enough

I was thinking about that.
(1) Not too big
For example, if you make something like a duralumin case, it is nice to be able to carry it, but it will be too big.
So I want to make it so that it doesn’t get too big as possible. If possible, the size of a taxi is good.

(2) Can respond to changes in the backing
The most difficult part is here, where the back warping is different with individual bows, and the back warp changes immediately after removing even one bow and after a few hours.
If it does not change with a constant warp, you can make a case that is about the same width as the bow, and you can make it considerably smaller, but you need a size that can absorb the change.

(3) If possible, 2 can be put in
Because it is for traveling by airplane, it will be an expedition, so in the case of a bamboo bow, if it is a stretch, a sardine etc. will occur, and if there is a thing, the bow that can be pulled will be lost, so I want to take two tensiles. So, I want to make it a case where two can be put in by default. If it is used for 3 tension, it will become too big as expected.

(4) Can be stored small
(1) overlaps, but this is also an important point. In some rod cases of fishing rods, the length can be adjusted. When it comes to bow cases, it becomes about 2 m30 cm. If you keep it, you will carry a fairly large thing, so it is quite convenient to be able to fold and store it. It is easy to get on taxis. It is a point that this small storing can be stored and strength can be secured.

(5) Strong enough
Because it is a protective case, it needs sufficient strength so that the bamboo bow does not break. It doesn’t make sense to be as strong as it is with bamboo. Ideally, it is possible to protect well.

Introduction of the actual made case

Cfrp body　

The main body is made of CFRP, which is made of carbon fiber hardened with polyester resin . It will be a light and durable finish. I am making a prototype with Styrofoam, which
is shaped to handle both the deep bow of my bow and the shallow state immediately after removing it .。

Five carbon fibers are stacked and molded with polyester resin .

It takes more than a week for the resin to harden firmly , so I did a fairly large-scale work on each side.
The last is painted with urethane paint .

As for strength, it does not break even if a person rides on it.

I bought carbon fiber here.

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The rubber rail of the violin case is used for the joint.

As a result of considering a suitable material for closing the carbon body, I used the rubber rail used for musical instrument cases such as violins . There is no rail-only product on the market, so I asked a domestic musical instrument case maker if I could sell only the rail, but it was impossible. I searched for a cheap violin case (I needed 3) and diverted it. In the end, the violin case was also diverted from other metal fittings.

I didn’t find any snap locks that fit, so I made some of them myself.

The biggest problem with making this is that there is no snap lock that fits it. The thickness of the case is 6 cm, but most types of strong snap locks stick out. This was a lot of trial and error, and in the end, I cut some of the existing products with a grinder and remade the steel wire part by myself. Overall, CFRP processing took the longest time, but it took a considerable amount of time to find this metal fitting and get here. I am using stainless steel.

The model number is Takigen’s “C-1021-2”, and I bought it from the manufacturer because even Mr. Monotaro didn’t handle it and changed it directly from the manufacturer.

C-1021 / C-21: Stainless wire snap lock | TAKIGEN | TAKIGEN Manufacturing Co., Ltd.

 https://www.takigen.co.jp/products/detail/C-1021

Blind rivets are used for fixing.

It still has load-bearing performance so that it can be made compact by making three joints.

I wanted to ( 1) if it wasn’t too big , ( 4) it could be stored small , but I thought about how to shorten the body of the long CFRP I made. In the end, I put a joint between them like a woodworking biscuit joint (though it is a dried bonito rather than a biscuit) so that it can be joined. The CFRP processing of this is the biggest difficulty of this case, “joint molding” → “joint molding” → “fix the carbon fiber again with the joint inserted” → “cut the surroundings leaving only the joint” There was processing, and after going through a prototype on the way, I managed to complete it. It took a week to cure each resin, so it took more time than molding the main body .
Since the final strength cannot be maintained without the strength of the joint, we increased the thickness of the carbon fiber.

I am making a joint with CFRP.

It was difficult to cut leaving the joint.

Even if it is divided, it maintains the strength that people can ride (it does not have a bow).

However, if you apply too much force, it will break, but it seems to be much stronger than just adding the bamboo that I used to use.

Furthermore, the joint was finished with silicon for caulking.

(Later I noticed that the silicones would stick together, so I taped them to get rid of the difficulty. There may have been a better material.)

One is divided into two and the other is divided into three so that the joints do not overlap.

For the interior, create a velor fabric cover that can hold urethane sponge.

The warp of the bow may change while it is in the case, so I thought of a material that could cushion it. Also, I would like to make a beautiful interior like a musical instrument case. Finally, I made a cover of velor fabric and made a structure to put urethane sponge in it. It is a fastener type so that the thickness of the urethane sponge inside can be changed in the future. This is actually a premise that you can put 2 pieces vertically, but if you put them alternately, you can put up to 4 pieces. At that time, if the thickness of the sponge for 2 tensions is too thick, it will not fit, so I thought of a structure that could be changed to a thinner sponge. Creating a sponge cover using a concealed fastener was quite difficult.

↓ Only the sponge before putting it in the cover

I used this fabric, blue gray, which was a very nice color. The back is dark blue.

Supports independence and leaning with legs

I have attached my legs so I can stand up.
I also put my feet where I hit when leaning against the wall.。

After completion

Safely responds to changes in back-end warpage

It is a correspondence to the back warp that I was most worried about, but it is one hour after storing it in→ the case in a state where there is no warping.
I can respond to the change of the back warp properly.。

Actually, it will be stored by winding a bow.

Create a storage bag for when not in use

Previously, when I made a successful bid for Gore-Tex cloth at an auction, the store gave me a waterproof cloth as a bonus, so I used it this time.
Now, after arriving at the site, you can carry it in this storage bag. It’s a little bigger than the quiver. It will be a baggage, but considering that there is a flight in between, this is not an acceptable range.

I attached an inner bag for joint parts

I try to fasten the bag with a string.

It’s like this.

Points and drawbacks to be worried about

service life

CFRP seems to last for quite a long time, but I’m worried about the useful life of rubber rails and silicon. I’m also a little worried about urethane sponge. Is it about 10 years? How many times do you have the opportunity to use it until then …

How waterproof is it?

　It’s not completely waterproof. Being a split type is also a little disadvantageous for waterproofing.

Can you actually get on the plane or will there be an additional charge?

　So far, I haven’t been charged an additional fee for domestic flights before this case, but I’m worried because it will be a little bigger than when I only have a bow. Is there an addition on international flights? For this area, the blog of the person who carries such a case with fishing gear will be helpful.

Can’t you handle other bows? Supports up to 2 inch growth

Actually, I made it based on the bow I have. A bow with a warp of 10 cm or less cannot actually be inserted. Therefore, it is exclusively for bamboo bows and for bows with some warpage.
Since it is for my bow, it is for 2 sun extension,
so a bow longer than that cannot be inserted.
It cannot be rented or put together. It’s done …, the teacher who wants to go on an expedition together was using 4 sun stretch …

How much does it cost?

By the way, regarding the production cost of this, since making it is a hobby, I make it without profitability , but for reference.

Considering only the actual cost
・ Carbon fiber 1m × 7m 30,000 yen
・ Polyester resin 15,000 yen
・ Three violin cases 20,000 yen (actually higher)
・ Metal fittings 10,000 yen
(patch lock, (Stainless snap lock)
・ Painting 5,000 yen
・ Velor fabric 5,000 yen
・ Sponge 5,000 yen (actually more expensive)

Is not it. In that case , the material cost would be about 100,000 yen (did you do that …).
If you can buy a violin case with only rubber rails, it may be a little cheaper …

However, I bought a disc grinder for this, because I consumed more resin and fiber to make a prototype (carbon fiber is high, I also tried glass fiber FRP once before carbon FRP in the first place) , Riveter I bought also, I bought a heat gun , I made my own tent for painting, I bought a vest with a fan for summer work, I bought a lot of snap locks for trial production, I also bought tools that I did not use after all In reality, it will take more than 1.5 times. Furthermore, considering the wages in the production period of one year, it is not possible to put a price on it.

The production process that took a year will be introduced in each item in the future. Each was created by repeating trial and error.

This time, it was completed for the time being, so I introduced it in the summary version first.

It was completed, but I enjoyed it the most when I was working on ideas and making them.

How about such a flight case for bamboo bows?

I hope the time will come when the corona will converge and you will be able to fly more freely.

Please see the video if you like.

https://youtu.be/tdtQqo5WDDg