First thing is to get your wood. I like to do things in easy steps so have the little woman make you a drink (it's important to include them) and make your shopping list. For the younger reader who may not have a little woman to hand volunteer to make your parents a drink, you may need to be in their good books by the end of this. Wood selection is very important and there is alot of good information on different wood grades on the inter web. I like to see the wood I'm buying so having a local shop is a bonus, give them a thought in these difficult times, you'll miss them if there're not there. Lets start making the ribs. The best way to do this is to transfer the plan image on to the wood. There are many ways to do this and I use the photocopy iron on method. |
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| This entails getting a photocopy of the ribs, cutting them out and laying them on to the wood in the most efficient way. Note: the black ink (toner) side faces down. Once happy with the layout I dampen the ink surface with white spirit and press the image down using a hot covering iron. |
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| There are other liquids that can be used to 'activate' the ink and I only used white spirit as I had it to hand and using any flammable liquid with a hot iron would be plain stupid!!!! I have used water and got a similar result on sanded wood but not so good on grainy surfaces like lite ply. Chance for others to contribute here. |
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| Remember the photocopy distortion I mentioned earlier. I always cut the wood outside the line and sand back to shape using the original plan for reference. Here I've placed a number of sheets of balsa together and using a bench saw, rough cut a few ribs at the same time. There's no need to go to the expense of this type of saw, a craft knife or small frame saw is good enough. |
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For the Bulldog tailplane the elevator is initially built all as one piece but as you can see here the elevator has a counter-balance stepped leading edge. Ribs T2a and 3 are cut and shaped just like a normal T1 rib. Later we will be cutting them but for now leaving them as one piece will make it easier to align when we assemble the unit over the plan. |
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| You will need a building board. Mine is a piece of MDF cut to the size of my workbench. This will need to be covered with cork so that you have something to stick pins in (this is not some strange voo doo ritual but simply the best way to keep everything in place while the glue dry's). Place this on your bench, or table for those lucky enough to be allowed to work indoors, and check that it's level using a known straight edge. Pack up as necessary. |
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You can see here the darker paper copy of the plan. This needs to be pinned or tapped down so that it can't move. It is advisable to cover the plan so that you don't stick the wood to the plan during assembly. I use candle wax, rubbing it over all the lines on the plan. You can use cling film, acetate or anything that PVA or epoxy won't stick too. Cut and pin out the spar. In this instance this is the trailing edge of the main section and the leading edge and mid spar of the outer elevator section. |
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| The tailplain is a scale aero foil section rather than the flat sheet type many of the simpler models have so I had to pack up the leading and trailing edge so that the ribs are kept aligned. There are no instructions on the plan but it is easy to work out by just drawing a horizontal line along the bottom of the rib and measuring the distance between this and the lower edge of the rib, front and back. |
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Dry trial fit ribs T1 & 2 and when happy glue and pin them down. Make sure the ribs are upright before pinning. This can be done with a square of some sort but even a playing card will do the job. I like to use PVA for balsa wood joints. Don't be shy with it, just have a damp cloth handy to wipe the excess away. |
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| Next ribs T2a & T3 are cut and a section removed to accommodate the leading edge of the elevator outer section. I've used scrap pieces of wood to maintain a gap between T2 and T2a as we will be cutting between these later when we remove the elevator. |
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| Once the glue is dry add the top spar and place some weight on it to keep it all straight. The leading edge doubler simply butts up against the front of the ribs. I cut this extra wide so that it would rest on the surface of the building board and extend above the top of the ribs. |
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| When everything is set, the leading edge doubler is plained and sanded to the extended profile of the ribs. Leaving the packers in place the top sheeting is applied. The photo shows the tailplain after the sheeting has dried. You need to make sure the sheeting is held down evenly at the leading and trailing edges as well as the middle. I use a combination of masking tape, lengths of wood and a variety of weighty objects. Turning the assembly over we can position the additional elevator end ribs, have a close look at the angled ribs in the center. As I mentioned the elevator is built as one but there was no end rib on the inner edge like there is for the outer. This was the first error I found on the plan. |
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| Before removing the elevator, the trailing edge of the elevator needs to be sanded to a taper, this provides about an 1/8th gluing surface when the top sheet goes on. The elevator can now be removed by running a knife along the trailing edges of the tailplain. I left about a 1/8th of an inch behind the trailing edge to form a shroud, more on this later. You can see better now the extra end ribs on the inboard of the elevator halves. |
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Plain and sand the leading edge doublers and rear spar then add the top sheeting. Tape and weight the sheeting down as before and leave to dry.
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| The elevator halves are joined with a 3mm U shaped wire, this needs to be in position before the aft fairing section is sheeted. I made mine from a push rod and soldered on a brass control horn made to the same dimensions as a standard horn for a model this size. When the tailplain is fitted to the fuselage the horn is housed neatly inside. |
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A slot needs to be cut into the lower edge of the tailplain so that the joiner has some range of movement. The elevator halves can now be sheeted and the leading edge and end caps fitted. When dry, these are sanded to the shape as shown on the plan. Trial fit regularly during sanding and when happy dry fit the hinges. I'll cover hinges in more detail when I get to the fin. |
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