SCRAP variant

Summary¶

SCRAP — Simple Configurable Repeatable Aerial Platform — is the entry-level printable 3-inch 4S FPV build in the libdrone family. It is not an official platform variant with a payload interface or a mission role. It is the build that teaches you to build. SCRAP uses a freely downloadable printable frame, a standard 20×20 FC/ESC stack, and the same ELRS and HDZero ecosystem as Core and Pro. A pilot who builds and tunes SCRAP has directly transferable skills when stepping up to Core. A builder who crashes and reprints SCRAP has learned what breaks and why — which is the Core design input it was designed to provide.

Concept¶

What SCRAP is not¶

SCRAP is not a libdrone platform variant in the mission sense. It has no GX12-7 payload interface. It has no defined sensor suite. Its sub-250 g design target has regulatory implications for where it may be flown — see legal-and-regulatory and decide for yourself. It will crash. It will crash again. That is its purpose.

What SCRAP is¶

SCRAP is the learning environment that precedes Core. It answers the question every builder asks before committing to a full Core or Pro build: can I actually do this? The answer is yes — and SCRAP is the proof. The frame prints in an evening on a Prusa CoreOne+ in PETG-CF. The electronics cost roughly CZK 9,500 total. The build takes one afternoon. The first flight can happen within 30 days of the decision to build.

The printable frame¶

The Whifflepick 3" toothpick frame (Printables model 1207344) is the reference SCRAP frame. 3 perimeter walls, 3 top/bottom layers, 0% infill, no supports. PETG-CF is the correct material — carbon-fibre-reinforced PETG is abrasion- resistant, available on a standard 0.4 mm hardened nozzle, and stiff enough for 4S loads on 3-inch props. The arms are integral to the frame. When an arm breaks — and it will — the print time for a replacement is under two hours.

The 20×20 mm FC stack mounting pattern is the only dimensional constraint that matters. It is universal across every micro FC stack sold.

Ecosystem alignment¶

SCRAP uses the same radio ecosystem as Core and Pro: - Radio: ExpressLRS 2.4 GHz UART (EP1 Dual or EP2) — same as Core and Pro - FC firmware: Betaflight — same as Core - Video: HDZero ECO Bundle — same ecosystem as Pro, lower weight than full HDZero stack - Transmitter: EdgeTX on TX16S — same as Core and Pro

Every hour of SCRAP flight time is directly applicable to Core and Pro operation. Betaflight rate profiles learned on SCRAP transfer directly. ELRS binding procedures are identical. The only difference is the absence of a payload interface and the smaller prop disc.

Core design input¶

SCRAP is a Core prototype with a lower budget and a printable frame. Every crash produces information: what breaks first, what survives, what is fiddly to reassemble under field conditions. This information feeds directly into Core frame design decisions. The educational intent of Core — building and repairing a drone as a workshop curriculum — requires a builder who has built and repaired a drone. SCRAP is how that builder is made.

Reference¶

Procedure¶

Rationale¶

The decision to build SCRAP rather than buy a BNF tinywhoop (e.g. Happymodel M8 HDZero) was reached by analysing the actual use case: outdoor pilot practice in a 2,700 m² space with obstacle poles in variable wind conditions. A tinywhoop at 80 mm wheelbase and 33 g is dominated by wind above 15 km/h and provides no crash resistance in grass. SCRAP at 130 mm wheelbase with 3-inch props and 4S power handles outdoor conditions while remaining buildable, repairable, and cheap enough to crash without concern.

The choice of HDZero ECO over analog video was made on ecosystem coherence: the operator already owns HDZero Goggles 2. Buying an analog VTX plus an analog receiver module for the goggles would have cost approximately the same as the ECO Bundle while creating a separate ecosystem with no skill transfer value. HDZero ECO keeps the video pipeline identical to Pro.

The Whifflepick 3" was chosen over the PecaJosef 3" because it is actively maintained (updated April 2025), requires no supports (fast reprints), and uses PETG-CF natively. The PecaJosef has more community build reports but is a heavier design and the Whifflepick community has confirmed 4S flight.

Connections¶

requires: - platform-overview - print-profiles - betaflight-setup - lipo-batteries related: - core-variant - digital-fpv - elrs-protocol - wire-gauge-selection - electronic-speed-controllers - brushless-motors - petg - pccf leads_to: - sk-scrap-build-guide - core-variant - betaflight-setup