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Greyhead · 28-12-2004

That’s a neat DIY fuselage jig you’ve got there Dave, it could even utilise the underside of a building board. When something like this crops up I always think “why didn’t I think of that?”!!!

As to your question “what to do when the pins don’t line up?” the answer is simple; to produce a straight fuselage the pins have to line up , you can’t alter the laws of mathematics, so adjust the rear post until they do and then worry about tidying things up later. In practice I can’t remember building a model where everything lined up perfectly, no matter how good a modeller you are discrepancies will occur, I suppose there is a possibility that the sum of the discrepancies will cancel each other out but then again I might win the lottery tonight!

If the error at the rear of the fuselage is too great then it’s worth checking it out, the chances are that it’ll be too late to do anything constructive about it but it will be a lesson learnt.

So what can go wrong?

Firstly the fuselage sides can be different lengths but we can reduce the chances of this happening. If the sides are “built up” make one side on the plan, cover it with cling film and then build the next side on top using the first side as a template, any discrepancies will be duplicated. If the sides are from sheet balsa (don’t assume they are equal just because it’s kit) pin them together at a known “square” point, for example the wing trailing edge, then check the front and rear edges and adjust as necessary.

The formers may not be at 90º to the sides. Before fitting the formers ensure that the fuselage side is flat on the building board. On my present model I started the process with a balsa “shaving” trapped under the side, luckily I noticed that something was amiss before it was too late! Having applied the glue, set the former at 90º using a setsquare not your eye, arrange some “scaffolding” to hold it in place then re-check the angle. Leave time for the glue to thoroughly set before continuing.

The above assumes that you have a “standard” fuselage with a parallel sided front section, if it’s a more complex shape or one with the “firewall” at an angle for built in side thrust then things are a bit more difficult, but that’s a different story.

The most awkward problem to deal with is fuselage sides from differing wood qualities. Really the only way to deal with this one is to dampen the outside of the stiffest side to induce the correct amount of bend to match the other side, a very hit or miss process. The moral being to ensure the sides are as near equal as possible before building starts, even if this means making new sides for a kit.

28-12-2004	#15 (permalink)
Greyhead Scale Model Member Join Date: Oct 2004 Location: County Durham Real Name: Grahame My Models: Preference for biplanes Visit Greyhead's Gallery Posts: 590 Images: 653	That’s a neat DIY fuselage jig you’ve got there Dave, it could even utilise the underside of a building board. When something like this crops up I always think “why didn’t I think of that?”!!! As to your question “what to do when the pins don’t line up?” the answer is simple; to produce a straight fuselage the pins have to line up , you can’t alter the laws of mathematics, so adjust the rear post until they do and then worry about tidying things up later. In practice I can’t remember building a model where everything lined up perfectly, no matter how good a modeller you are discrepancies will occur, I suppose there is a possibility that the sum of the discrepancies will cancel each other out but then again I might win the lottery tonight! If the error at the rear of the fuselage is too great then it’s worth checking it out, the chances are that it’ll be too late to do anything constructive about it but it will be a lesson learnt. So what can go wrong? Firstly the fuselage sides can be different lengths but we can reduce the chances of this happening. If the sides are “built up” make one side on the plan, cover it with cling film and then build the next side on top using the first side as a template, any discrepancies will be duplicated. If the sides are from sheet balsa (don’t assume they are equal just because it’s kit) pin them together at a known “square” point, for example the wing trailing edge, then check the front and rear edges and adjust as necessary. The formers may not be at 90º to the sides. Before fitting the formers ensure that the fuselage side is flat on the building board. On my present model I started the process with a balsa “shaving” trapped under the side, luckily I noticed that something was amiss before it was too late! Having applied the glue, set the former at 90º using a setsquare not your eye, arrange some “scaffolding” to hold it in place then re-check the angle. Leave time for the glue to thoroughly set before continuing. The above assumes that you have a “standard” fuselage with a parallel sided front section, if it’s a more complex shape or one with the “firewall” at an angle for built in side thrust then things are a bit more difficult, but that’s a different story. The most awkward problem to deal with is fuselage sides from differing wood qualities. Really the only way to deal with this one is to dampen the outside of the stiffest side to induce the correct amount of bend to match the other side, a very hit or miss process. The moral being to ensure the sides are as near equal as possible before building starts, even if this means making new sides for a kit. Last edited by Greyhead; 28-12-2004 at 04:00..