Carbon Spars

This page gives the carbon tubes to order and the lengths to cut. The cut list in the manual is the primary reference. We measured the bores below in the v1.0.0 STL pack. We sliced each part and fitted circles to the through-bores. The script is in the git history, in the docs/spars.md commit.

What to order (manual, step 1)

Order	Cuts into	Left over	Est. cost
2m x 8mm pultruded	Rear fuselage spar (690) + two wing spars (630 each)	50mm	$30
2m x 14mm woven (roll-wrapped)	Front fuselage spar (400) + two VTOL spars (420 each; 416 on our mounts, see below)	760mm	$45
1m x 6mm pultruded	Two elevon spars (350 each, see below)	300mm	$20

The 8mm carbon tube has the smallest margin. The three spars are 690 + 630 + 630 = 1950mm from a 2000mm tube. This is three cuts, with a total margin of 50mm.

CAUTION: Mark all three cuts on the 8mm carbon tube before you cut it. The total margin is only 50mm.

If a supplier sells only 1m or 48in (1219mm) lengths, one tube holds only one spar. Two spars need at least 690 + 630 = 1320mm or 630 + 630 = 1260mm, and both are longer than 1219mm. Thus each of the three spars needs its own tube.

If the supplier sells only 1m or 48in tube, buy three tubes. Cut one spar from each tube.
If the supplier sells 1.5m (60in) tube or longer, one tube can hold the 690 spar and one 630 spar. Buy one more tube for the second 630 spar.
Cut all spars approximately 5mm shorter than the manual length, except the VTOL spars. This lets the segments touch each other. For example, a 400 spar becomes approximately 395.

CAUTION: On our keel B and front stilt B motor mounts (the first build), cut the two VTOL spars to 416mm, not the manual’s 420mm (th-main, 2026-10-15). The mounts’ spar end stops are at Y 68 and Y 484, so a 416mm spar seats in both. That puts the lift rotors at Y 40 and Y 512, centred on Y 276, as the CG and SITL models use. A 420mm spar pushes the rear mount 4mm aft. Drill the spars on the VTOL spar jig, which locates from the same stops.

CAUTION: Use the two elevon spars at their full 350mm on the own-section wing (th-blender W73, 851d43db). Its Wing Tip seats the spar’s end: the spar fills X 331 to 658.2. Put the spar in before the tip. Do not cut the spars to 329.9mm. That length was for the earlier flat tip, which had no pocket for the spar’s end.

Ordered for airframe A (2026-09-30)

Tube	Qty	Price	Gives
CFT3K14121, 3K carbon tube 14 x 12 x 1000mm, matte	2	$43.98	Tube 1: two VTOL spars (416 each on our mounts). Tube 2: the front fuselage spar (400), about 600mm left
CFT861, carbon tube 8 x 6 x 1000mm	2	$17.98	Two of the three 8mm spars
CFT641, carbon tube 6 x 4 x 1000mm	1	$7.84	Two elevon spars (350 each) and the two 125mm keel B front stilt cores, about 45mm left

CAUTION: One more 8mm tube is necessary. Each 1m tube holds only one of the 8mm spars (690, 630, 630), so the rear fuselage spar and the two wing spars need three tubes. Two are on order.

One airframe (Ryan, 2026-10-04), so no second set.

Bore diameters measured in the STLs

Spar	Nominal OD	Part	Measured bore	Clearance
14mm woven	14.0	VTOL Spar Mount (PETG)	14.3	0.3
14mm woven	14.0	VTOL Motor Mount (PETG)	14.3	0.3
14mm woven	14.0	Fuselage Front (LW)	14.3	0.3
14mm woven	14.0	VTOL Section (LW)	14.3	0.3
14mm woven	14.0	VTOL Cutting Tool (PETG)	14.4	0.4
8mm pultruded	8.0	Fuselage Mid, rear spar (LW)	8.3	0.3
8mm pultruded	8.0	VTOL Section, rear spar (LW)	8.3	0.3
8mm pultruded	8.0	VTOL Section Plate (PETG)	8.3	0.3
8mm pultruded	8.0	Wing Inner, Wing Outer, Winglet (LW)	8.8 to 8.9	0.8
8mm pultruded	8.0	Wing Inner Plate (PETG)	8.9	0.9
6mm pultruded	6.0	Elevon Inner, Elevon Outer (LW)	6.6	0.6
6mm pultruded	6.0	Wing hinge holes, Winglet (LW)	6.9	0.9

The measurements have these effects on the order:

The 14mm bores have only 0.3mm of clearance in all parts. You drill and bolt this spar. Thus, buy a tube that has a true OD of 14.0mm. A “14mm” woven tube with a sanded finish usually has an OD of 14.0 plus or minus 0.1. This tube is satisfactory. Do not use 14.5mm or 15mm stock as a replacement. It does not go through the PETG mounts.
The 8mm rear fuselage spar goes through 8.3mm bores in the fuselage and section plates. Thus, the same rule applies: buy a tube with a true OD of 8.0mm. Pultruded 8mm carbon tube usually has an OD of 7.9 to 8.1.
The wing bores are larger on purpose (8.8 to 8.9mm). This clearance is for the ooze of the LW-PLA. It is not for a larger tube. Thus, the manual warns that “avoid crossing walls” must be on.
On our Elevon (one piece) the bore measures 6.39mm (area-equivalent), 0.39mm of clearance (th-blender W46). The flat wing tip has no elevon hole.
The 6mm elevon spar is also the hinge pin. It has 0.6mm of clearance in the elevon and 0.9mm in the wing hinge. Thus, the elevon turns freely without reaming.

The kit does not specify the wall thickness. For the parts, only the OD is important. The 14mm spar carries the lift motors, and you drill through it. For this spar, a 1mm wall (14 x 12) is the usual woven size and is the safe choice. A 14 x 10 tube (2mm wall) is heavier and stiffer, and is also satisfactory. For the 8mm and 6mm pultruded spars, 8 x 6 and 6 x 4 are the standard sizes.

Where to buy (US, researched 2026-09-24)

Nomadium does not sell a spar kit. The Digital Hangar listing says that the kit does not include spars, tools and electronics. The electronics list has no shop links. Thus, these suppliers are our own selection. The prices are the prices that the sites showed on the day of the research. Do a check of the prices before you order.

8mm pultruded (needs one piece of at least 1950mm, or a split plan)

Option	Product	OD x ID	Length	Price
Best match	Rock West T-RND-314 pultruded tube	7.98 x 5.99	78in (1981mm)	$38.99
Cheapest	ReadyMadeRC 8x6 1m, three of them	8 x 6	1m	$8.40 ea
Same, AZ	Superstition Hobbies CFT861, three	8 x 6	1m	$8.99 ea
Alt	Goodwinds PCT .315 x 60in plus a 36in	8.0 x 6.0	1524mm	$32.59

The Rock West 78in tube is the only US stock that is sufficiently long for the single-tube cut plan in the manual. The 1981mm tube gives 31mm of remainder. Cut the 690 spar first. With 1m tubes, cut each of the three spars from a different tube. Do not use the CST 2m 8mm tube. It is 8 x 7mm, with a 0.5mm wall.

14mm woven roll-wrapped (400 + 420 + 420)

Option	Product	OD x ID	Length	Price
Best	Superstition Hobbies 3K 14x12x1000 matte, two	14 x 12	1m	$21.99 ea
Same, MI	Wind Catcher RC 3K 14x12x1000 matte, two	14 x 12	1m	$20.83 ea
Only true 2m	Easy Composites US 14/12 woven	14 x 12, OD +/-0.15	2m	~$56.90
Pre-cut 420 (cut 4mm off each for our mounts)	Amazon 14x12x420 twill matte, two, plus any 1m for the 400	14 x 12	420mm	$8.99 ea

With two 1m tubes, cut the two 420 spars from one tube. Cut the 400 spar from the other tube. A matte (sanded) finish is closer to the nominal OD than a glossy cello-wrapped finish. This is important because the clearance is only 0.3mm.

6mm pultruded (2 x 350)

Option	Product	OD x ID	Price
Best	Superstition Hobbies CFT641 6x4x1000	6 x 4	$7.84
Cheapest	ReadyMadeRC 6x4.5 1m	6 x 4.5	$4.40

Carts

Option A, one 8mm tube as the manual shows: Rock West 8mm 78in $38.99 (+ approximately $15 to $30 UPS from Utah) + Superstition 2 x 14x12 $43.98 + Superstition 6x4 $7.84. The total is approximately $115 to $130 with shipping, in two shipments.
Option B, the lowest cost, in one shipment from Superstition Hobbies (Queen Creek, AZ): 3 x 8x6 $26.97 + 2 x 14x12 $43.98 + 6x4 $7.84 = $78.79 plus shipping.

Carriers add an oversize handling fee for items longer than 48in. Thus, hobby shops usually sell 1m tubes, and 2m tubes are rare in the US.

Source: docs/spars.md in the repo. Edit it there; this page is generated.