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Every control surface on an RC plane lives or dies by the hinge it swings on. A sloppy hinge shows up in two ways: binding (glue in the pivot, a misaligned axis) or slop (loose hinges, worn linkage). Both feed the same high-speed problem, which is flutter. The good news is that choosing a hinge is less about brands and more about one question: what is the airplane made of?
A quick note on method. This page is a researched guide based on manufacturer documentation and published modeling articles, not on our own bench or flying time. Where a maker or a magazine says something, the page says who. Where we could not confirm a popular rule of thumb, it is left out or marked as a guideline.
Hinge types at a glance
| Hinge type | Typically used on | Key point to remember |
|---|---|---|
| CA hinge (fiber strip, thin CA) | Balsa and ply; also foam, per FMS | Needs thin CA that wicks; BSI says never use accelerator on it |
| Tape hinge | Foam, foamboard, small electrics | Needs a bevel; Model Aviation cites micro and indoor aircraft under 8 ounces for Blenderm |
| Silicone hinge | EPP and Depron, per FMS | A bead of silicone caulk makes a gapless hinge |
| Nylon pinned hinge | Sport to large balsa | Six glue holes per side on Du-Bro's; keep glue out of the pivot |
| Pin-point hinge (Robart) | Larger and high-performance balsa | Drilled into the edges, aligned with a jig |
| Molded "living" hinge | Many ready-to-fly EPO foam models | FMS: can fatigue, tear or go floppy over time |
How hinges work, and why the gap matters
A hinge does two jobs at once. It lets the surface rotate freely through full throw, and it passes every control load through without play. Friction in the pivot strains the servo; slop lets the surface move on its own.
Some hinges, such as CA and pinned types, leave a small deliberate gap between the surface and the airframe. Tape and silicone hinges are gapless. Either approach works, and the choice is driven mostly by the material.
The gap is not a cosmetic detail. Model Aviation's article on hinging IMAC and 3D airplanes warns that the space between the control surface and the fixed surface carries "a high risk of flutter," which it describes as a violent oscillation that can cause a surface to depart the airplane. It says sealing the gap also improves control response. Its method on covered models is to fold strips of covering into the bevel between the hinge points and iron them down with the surface fully deflected. If you are re-covering a wing while you are in there, our covering guide walks through the film side of that job.
BSI makes the same point from the glue side: large hinge gaps can cause "nightmares with control linkages, surface effectiveness and even flutter."
How many hinges?
There is no single official number, but two sources give a consistent starting point. FMS Hobby's hinge guide suggests one hinge an inch from each end, then more hinges every 3 to 4 inches in between. For 35 percent scale airplanes, Model Aviation's rule of thumb is a hinge every 4 inches on the ailerons and every 3 inches on the rudder and elevators. Treat both as guidelines: bigger, faster or heavier models, and surfaces with high loads, deserve more hinges rather than fewer. Leaving the ends unsupported is how a surface bows away at speed.
CA hinges: thin CA is the whole trick
A CA hinge is a strip of porous material that fits into matching slots in the surface and the airframe. Thin cyanoacrylate wicks into the strip and the surrounding material, and the cured glue is the joint. Du-Bro's installation guide is blunt: "CA hinges require thin CA."
Bob Smith Industries (BSI) has the most detailed published installation advice. In its tips article, a CA-hinge walkthrough stresses a handful of points:
- Fresh glue matters. As CA ages it thickens and takes longer to soak in.
- Use a small capillary tip and add one drop at a time to the fiber of the hinge, one hinge at a time, until the drops stop soaking in. Then flip the surface and repeat.
- Drill a small hole in the middle of each hinge slot so glue reaches deep into the hinge. BSI's product page gives the size as 1/16 inch.
- A small straight pin in the middle of the hinge keeps it from being pushed too deep while you align things. Remove the pins before gluing.
- "Never use Accelerator, this will make the hinges brittle."
- After 10 to 15 minutes the surface will feel stiff. Flex it and the glue breaks free in the middle with a crackling noise that BSI says is normal.
Which CA for which material
On wood, BSI's Insta-Flex is a flexible thin CA it describes as ideal for CA hinges, but BSI is clear that Insta-Flex "can not be used on white foam." For foam, look for a foam-safe thin CA. BSI's Super-Gold thin is odorless, "does not attack white foam," and is listed by BSI for CA hinges among its recommended uses.
BSI Super-Gold foam-safe thin CA
Be careful when shopping, because the Super-Gold name covers a thin and a gap-filling version, and hinge work needs the thin one.
Where CA hinges struggle
CA hinges are only as good as the glue that reaches the fiber. Per BSI, old, thickened glue and accelerator both work against you (see the list above), and FMS adds that a loose hinge can be re-glued. FMS also calls CA hinges "the standard and most effective option" for EPO foam, especially for repairs, and says they also work well on EPP and Depron. If a CA hinge lets go, FMS describes cleaning out the old glue, poking small holes in the slot material and reapplying thin CA.
A fair summary: both the "CA is always stronger" and the "tape always beats CA on foam" slogans are oversimplifications. Material, load and installation quality decide.
Tape hinges: bevel, apply, check
Tape hinges use a flexible transparent tape to make a gapless hinge line. FMS describes the method as beveling the control surface and applying the tape on both the top and bottom, and recommends it for EPP and Depron.
Model Aviation's hinge-tape Q&A gives the practical conditions. Blenderm, a 3M medical tape, is soft and flexible and "works well on micro/indoor aircraft under 8 ounces." The same column says hinge tape "works best on hinge areas prepared with appropriate bevels for top hinging," that spacing between the surface and the main surface is critical (too little binds, too much causes flapping or vibration), and that "very few tapes are fuelproof," which is why tape hinges are mostly an electric-model and sailplane method. The columnist used 1/16-inch balsa scraps as spacers and painter's tape to hold both surfaces while applying the tape.
Two product notes. Du-Bro's Electric Flyer Hinge Tape (item 916) is sold as a 15-foot roll for electric models, sticks to foam, balsa and other common building materials and peels away without residue. Model Aviation reports that this item was Blenderm sold under Du-Bro's label, though Du-Bro's own page does not say so. 3M's catalog describes Blenderm only as a hypoallergenic medical tape, so its hinge use is a hobby practice rather than a 3M recommendation.
Du-Bro Electric Flyer Hinge Tape
3M Blenderm tape, 1 inch x 5 yards
Tape is also not a "fit and forget" part on a heavier model. Check it periodically and replace it when edges lift. For models above the weight range Model Aviation mentions, treat tape as a temporary or repair solution and move to a mechanical hinge.
Silicone and glued foam hinges
FMS also describes a silicone hinge: a bead of 100 percent silicone caulk smoothed into the gap, which cures into "a tough, flexible, and completely gapless hinge" suited to EPP and Depron. Beacon says its Foam-Tac "dries clear, remains flexible" and "can glue control surfaces directly onto the RC airframe without hinge tape or any other kind of fastener." Its directions: clean, dry surfaces; spread glue on both sides; let it air dry for a few seconds; press together and immediately pull apart; wait a few seconds more; then press firmly together. Beacon says the maximum bond comes within 24 hours or less.
Pinned and pin-point hinges
Mechanical hinges come in two families. Nylon pinned hinges slot into both surfaces. Pin-point hinges go into drilled holes and are glued with epoxy.
Du-Bro nylon hinges
Du-Bro makes its nylon hinges with a locked-in hinge pin, and each has six holes per side so glue flows through for a reinforced joint. Per Du-Bro, they install with CA, epoxy or other standard model adhesives. Du-Bro's installation guide adds that nylon hinges "may need epoxy or wood glue depending on the model design" and advises test-fitting each hinge, confirming the hinge line is straight and the surface moves freely, then wiping away excess glue before it cures.
| Du-Bro hinge | Size per Du-Bro | Weight per Du-Bro | Intended use per Du-Bro |
|---|---|---|---|
| Micro E/Z hinge (937) | 1-9/32 in long | 0.18 g | Micro indoor and park-flyer models |
| Mini nylon hinge (118, 119) | 7/16 in wide, 1-1/8 in long | 0.2 g | Smaller, lightweight aircraft |
| Standard nylon hinge (116, 117) | 5/8 in wide, 1-1/8 in long | 0.5 g | Medium to large aircraft |
| Heavy-duty nylon hinge (257) | 3/4 in wide, 1-3/8 in long, .040 in thick | about 1 g | Giant-scale, warbirds, 3D and aerobatic, high-stress surfaces |
The heavy-duty hinge uses a removable 3/64-inch cotter pin, which Du-Bro says can be pulled for maintenance or replacement "without cutting into the control surface." That is a real advantage on a big airplane where re-hinging otherwise means surgery.
Du-Bro standard nylon hinges, 15-pack
To cut straight, centered slots, Du-Bro's Kwik-Hinge Slotter comes in a no-handle version (216) and a with-handle version (660). Its guide recommends a rocking motion with the fork tool and, in harder woods, marking the slot, drilling a few pilot holes and opening it with the hook tool. The tools are sharp, so mind your fingers.
Robart hinge points
Robart pin-point hinges are installed by drilling a hole in each surface edge. Model Aviation's IMAC-and-3D hinging article prefers them to flat-style hinges, which it says often break, and gives a size ladder: the 3/32-inch hinge point (item 305) for .10 to .40 size models, the 1/8-inch point (item 307) for 1.20 size models, and the 3/16-inch Super Hinge Point (item 309) for 30 to 40 percent models. Airfield Models notes a point can be "rotated into perfect alignment," which it presents as an advantage over slotted flat hinges.
Horizon lists the 15-pack of 1/8-inch steel-pin hinge points (ROB308) and Robart's hinge-point drill jig (ROB319). Per Horizon, the jig is made of hardened steel, adjustable for all control surfaces, and has removable bushings for 1/8 and 3/16 inch drills. Robart's larger kit pairs 3/16-inch Super Point hinges with a jig and bushing and calls for a 3/16-inch bit and either epoxy or aliphatic resin glue, per a retailer's listing of the product.
Robart steel pin hinge points, 1/8 inch, 15-pack
Two installation habits come up repeatedly in modeler write-ups. First, keep glue out of the pivot, and many builders put petroleum jelly on the hinge before epoxy for that reason; this is common practice rather than a maker instruction, so follow the sheet that comes with your hinges. Second, align before the glue cures. Model Aviation says to push hinge joints tightly together to remove any gap and to watch them while the epoxy cures, because they can slip.
Molded living hinges: replace, don't nurse
Many ready-to-fly EPO foam models have molded "living" hinges, which are foam folded thin enough to flex. Per FMS, "over time and with repeated flexing, these hinges can fatigue, tear, or become overly flexible," and "if a living hinge fails, it must be cut away and replaced with one of the other hinge types." If you are not sure whether your model is built that way, our ARF, RTF and PNP guide explains how these kits differ.
Replacement options for a small foam model include a CA hinge with foam-safe thin CA, tape or silicone, or Beacon's Foam-Tac. For the glue side of that decision, see our adhesives guide, and if you are still choosing between materials, foam vs balsa usually settles the hinge question before anything else does.
Choosing by airframe
| Airframe | Common hinge options named by makers and magazines |
|---|---|
| Foam or foamboard park flyer | Tape (FMS: EPP, Depron), CA with foam-safe thin CA (FMS: EPO standard), silicone |
| Foam ARF with failed living hinge | Cut away and replace with CA, tape or silicone (FMS) |
| Small to medium balsa | CA hinges with thin CA; Du-Bro nylon hinges |
| Large, heavy or gas balsa | Du-Bro heavy-duty nylon hinges, Robart hinge points |
| Giant-scale and aerobatic | Robart Super Hinge Points with the drill jig; Du-Bro heavy-duty hinges. For aircraft in this class, our giant-scale guide shows what the airframes look like |
FMS says pinned hinges are best for larger, heavier or gas-powered balsa planes and that their "rigid, precise pivot point makes them ideal for preventing 'flutter' on high-speed aircraft." That is a maker's opinion, but it fits the general pattern: the faster and heavier the model, the more the hinge line should be mechanical and slop-free.
Failure modes worth knowing
- CA hinge pull-out. Poor wicking, old glue and accelerator use can all leave a CA hinge holding less than it should. BSI's three fixes are fresh glue, a small hole in the slot, and no accelerator.
- Glue lock. Glue creeping into a mechanical hinge freezes the pivot. If one hinge in a row binds, the whole surface fights the servo. Prevent it rather than trying to cure it.
- Tape lift. Tape edges lift with age and flexing. Check them.
- Slop and unsealed gaps. Loose hinges, worn clevises and a wide gap all invite flutter. This is why the servo guide tells you to look at the whole control chain, not only the servo.
- Fatigue. It is not only a model problem. Per the UK Air Accidents Investigation Branch, a full-size Edge 540 (G-EDGY) lost its right aileron on 1 May 2021 when the centre hinge attachment failed from fatigue cracks with multiple origins, and the manufacturer issued a Service Letter recommending regular inspection of similar hinge attachments. The scale is different, but the lesson about cracks at the hinge line is the same.
A simple free-movement check from Model Aviation's "Perfect Hinges" article, written about a piano-style hinge: release the surface and it should easily fall under its own weight. If it does not, look for burrs, kinks or glue lumps.
Frequently asked questions
Q: What is the difference between a CA hinge and a tape hinge?
A CA hinge is a porous strip glued into slots with thin CA, leaving a small deliberate gap. A tape hinge is a flexible transparent tape on a beveled joint, which makes a gapless line. FMS describes CA hinges as standard for EPO foam and tape as suitable for EPP and Depron.
Q: Can I use regular CA on foam hinges?
Not safely if you are unsure of the foam. BSI says its Insta-Flex cannot be used on white foam, and its foam-safe Super-Gold thin is the product it lists for CA hinges where foam is involved. When in doubt, test on a hidden scrap first.
Q: How many hinges does a control surface need?
There is no universal number. FMS suggests one hinge an inch from each end and more every 3 to 4 inches between them. Model Aviation suggests a hinge every 4 inches on ailerons and every 3 inches on rudders and elevators for 35 percent scale airplanes. Use more on big or fast models.
Q: Why does my control surface feel stiff after I glued in the hinges?
The most common cause is glue in the pivot of a mechanical hinge, or a CA hinge that has not been flexed free after curing. BSI notes that a freshly glued CA surface feels stiff and then breaks free with a cracking noise when flexed after 10 to 15 minutes. If a pinned hinge is truly glue-locked, replace it and follow the hinge maker's instruction sheet next time.
