Watch the Roll

Nope—not talking about flying here—I’m talking about building—specifically, I am talking about cutting and fitting baffle seal material. No matter if you choose the old standard black fabric-reinforced rubber or one of the fancier silicone materials, baffle seal fabric generally comes in a roll. And once you unwrap the roll, it shows a distinct tendency to want to curve in the direction that it has been rolled. Take advantage of this when cutting out your seals!

Baffle seals generally attach to baffles that meet your cowling at a right angle, and the seal material curves in toward the pressurized area above the engine. On an airplane that has flown for several hundred hours, you can see how the material curves after having taken a “set” from repeated heating. But when it is fresh, it is not uncommon to see it curved the wrong way—spilling all of the cooling air—when a cowl is put on for the first few times. You can enhance your chances of getting a good set (and avoiding the “wrong-way curve”) by thinking about this when you cut your seals.

Cutting baffle seals is an art form if you don’t have templates from your kit company. You start by making “paper dolls” from card stock, guessing how the material will curve and then transferring those templates to your roll of fabric for cutting. And of course you want to minimize waste, because any aircraft material is expensive! You will try and nest the various pieces onto the roll of fabric to minimize waste, and it is easy to forget which way the fabric has to curve—so add this to your consideration when laying out your material. Once you have installed the baffle seals with Clecos, check how you did before permanently attaching them—and if something curves the wrong way, make a new piece. It’s far easier to admit a mistake and rectify it at this stage than to fight the natural curve for many flight hours to come.