Independent dojangs
One sabeom, an assistant or two, and a steady group of students. C3NTR puts your kicks, locks and breakfalls in one place.
For martial arts schools
A knowledge home for your hapkido dojang.
Joint locks, throws, kicks and the three principles.
→ See a quick tour
Free for up to 30 students
No credit card
UK GDPR · EU (London)
Works offline
Your school's curriculum deserves a home
Joint locks get demonstrated but not explained in writing. Korean terminology gets re-introduced each module. The three principles sit on a poster nobody reads. C3NTR is a quiet place to write it all down once.
Who this is for
Schools with multiple instructors
Several sabeoms teaching across the week. C3NTR holds the shared standard so every class draws from the same library.
Lineage schools
You're carrying Sin Moo, traditional, Combat or another lineage forward. Content locked by grade keeps each gup progressing at the right pace.
Built for teachers, not for IT
Your sabeom opens the app, taps Edit, and writes the next joint lock breakdown in plain prose. The next class, the students read it before stepping onto the mat.
Write directly in the app
Like a notepad. New articles are drafts until you publish, so nothing goes live by mistake.
Mobile-first authoring
Edit on the phone between classes or on the way home. The same library, the same edit screen.
A working library in under an hour
Import the starter template in a few taps. Edit anything that doesn't fit. Publish when ready.
Gup and dan grades
Content locked by grade, in your dojang's gup and dan
Tag any article with a minimum gup or dan. New students see breakfalls and the basic kicks. Higher grades see joint locks and throws. Sabeoms see everything.
A glossary in Korean and English
Every hapkido dojang carries Korean terminology. C3NTR's glossary holds the terms in one place: the Korean, your dojang's translation, and the article each term appears in.
- Hapkido
- Hapkido (합기도), "the way of coordinated energy." A comprehensive Korean self-defence art combining joint locks..
- Dojang
- The training hall (도장), the place where Hapkido is practised..
- Sabeomnim
- A respectful term for a master instructor (사범님) in the Korean martial arts..
- Hwa
- Harmony..
- Won
- The circle (원), the second principle of Hapkido..
- Yu
- Flow..
Gradings, seminars, demonstrations
C3NTR isn't only the library. Schedule the gradings students are working toward, post when a visiting master is teaching, and let students see what's coming up at the dojang this month. Announcements land on their Today tab and events sit on the calendar.
Start from our Hapkido template
A working starter with 15 articles, 2 short videos, a 9-terms glossary across 5 tags (Getting Started, Foundations, Practice, Progression, Resources). Import in a few taps, then edit anything that doesn't fit your school. Every article, term and tag is yours from the moment you import.
See the Hapkido template Template source:assets/templates/martial_arts/hapkido.c3t.md
Inside the app
A look at how the library, articles and grade controls feel in your students' hands.
Plays well with what you already have
Bring your existing technique lists and Korean terminology in with smart Word document import or paste Markdown directly from your dojang's archive.
Word documents
Smart import reads headings and turns them into draft articles. You review before anything publishes.
Markdown from any editor
Notion exports, Obsidian notes, Bear, plain .md files. Paste or import.
C3NTR templates
Open .c3t.md format. Schools can share templates with each other without us in the middle.
UK GDPR · DPA 2018
UK GDPR compliant. Hosted in the EU (London).
C3NTR is built around UK data protection law from the ground up. Your school's data sits in the EU on Google Cloud London, the same region we manage from.
UK GDPR + Data Protection Act 2018
Built around UK GDPR Article 6 lawful bases. Subject access requests answered within one calendar month.
Hosted in the EU (London)
Your school's data sits on Google Cloud in the europe-west2 (London) region. No transfer outside the UK or EEA for core operation.
Encrypted in transit
All data is TLS encrypted. Access restricted to personnel with a clear business need.
Account deletion on request
Permanent deletion of personal data and content via in-app or written request.
What C3NTR is, and what it isn't
A library your school owns
Another booking or billing system
Built for how schools actually teach
A generic course builder
Calm, focused reading for students
A feed competing for attention
Start free. Move up when you outgrow it.
Seed
Free forever
Up to 30 students
All core features. No credit card.
Start freeSchool
£39/mo
£32/mo billed annually
Up to 150 students
Push notifications. 1 GB media storage.
Choose SchoolAcademy
£69/mo
£57/mo billed annually
Unlimited students
Multi-instructor publishing. Engagement analytics. 5 GB media storage.
Choose AcademyStudent? Show this to your sabeom.
If you train hapkido and you'd love a quiet library between sessions, share this page with your sabeom. Most schools start on the free Seed plan in under five minutes.
Common questions
Can students only see their grade's material?
Yes. Tag any article with a minimum gup or dan. New students see only breakfalls and basic kicks. Senior instructors always see everything.
Does it cover Sin Moo, traditional and Combat lineages?
C3NTR is lineage neutral. Joint locks, throws and kicks are written so any major hapkido tradition can adapt the curriculum without rewriting.
Can my school customise the hapkido template?
Yes. Every article, technique and tag is editable. Add your style's curriculum, your grading syllabus and your house standards.
How long does it take to set up?
Most schools have a working library in under an hour. Import the starter template in a few taps, then edit anything that doesn't fit. Starting blank takes a little longer. Allow an hour or two to write your first ten articles. Students can use the app the day you publish.
Do I have to stop using my booking system?
No. C3NTR is a knowledge library for your curriculum, terminology and progressions. Booking, billing and scheduling stay with the tools you already use.
Is there a free plan?
Yes. Seed is free forever for up to 30 students, with no credit card required. Move up to School (£39/mo) or Academy (£69/mo) when you outgrow it.
Teach a different style? Tell us.
Whether it's a specific hapkido lineage we don't list, or another discipline entirely, drop us a line and we'll add a starter template. In the meantime, the app already works for any structured curriculum, your library starts blank in a few minutes.
Ready to give your hapkido students a knowledge home?
Free for the first 30 students. No credit card. A working library in under an hour.
Start free for your school