Not so Ultimate BiPlane

It has been over 40 years since I last scratch built a plane and then it was balsa and tissue, and it crashed… So this time not wanting to make life easy, I printed a A4 version of a foam plane, scaled the general proportions and used a flight test method of construction. The general specification:

Wing span: 840mm
Target weight: 1400gm
Wing area circa: 35dm2
Motor: 3536/1100/7 – 470watts
ESC: 60A

To give you an idea of the current build state, I have (I think) attached a couple of photos. During the ongoing build, I will provide updates, but do not intend to maiden it until the weather is better and I have mastered the RIOT!!!

Wing construction
Wing construction

Main components

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Partial painted components

Hi all, now for a quick update; as can be seen from the pictures, the BiPlane is basically finished, however I do want to replace the wheels as I’m not happy with the current foam board version. I am trying a bit of an experiment with the sprung under carriage to help with landings on rougher ground (not that I would miss the landing strip).

At the start of this project, I had some target design figures with the key target being weight which has come in at 1.29kg fully loaded with battery. The result of this shows in its ability to not only lift itself vertically, but also pulls my arm up… All we need now is better weather so I can practice with the Riot before risking this plane.

BiPlane front quarter view
BiPlane front quarter view

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OK… The first maiden flight lasted a couple of seconds… the last maiden flight was a few seconds longer as shown in this clip

All is not lost, the parts have evolved into the FlighTest Spitfire, a little over powered, but still within the FT design weight at 830 grams including battery

The evolution of the not so Ultimate Bi-Plane - Reborn
The evolution of the not so Ultimate Bi-Plane – Reborn

Great little fun jet

When Mel sent me the video for this plane, I thought I gotta give it a go, there is no plan to build off you just have to follow the video here…

The first (of many) problems was the weight of the foam board, the stuff they can get in America is much lighter, so I decided to have a go at building mine from mainly depron with balsa wood for extra support.

I started with a balsa base and built up from there…

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Had to make the fuz a little bigger as I wasn’t doing the side folds in the build video…

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I still tried the EDF unit in for size, once happy I stuck it in with double sided tape

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For the wing I took two pieces of depron, stuck together with cross weave tape, then carried on the same as the video…

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I folded it over, and also added a carbon rod for support. The ailerons I made out of balsa…

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I added some more cross weave tape  when I stuck the wing on…

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The tail section I added some thin carbon rod for support and again used balsa for the control surface…

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And for the finished plane…

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Flew great…

Just a shame I forgot EDF’s need air speed to stay up… Ooops

No Plan — No Clue — My FW-42

Recently Scott pointed me at ‘Printed Warbirds’ in that list was the Focke-Wulf FW-42.

Focke-Wulf FW-42A fantastic looking plane that looks like it is something out of the wacky races and I was a little surprised that  Scott hadn’t noticed and already started building it. So with a bit of persuasion I decided to have a go.

 

 

I couldn’t find any plans for the plane, but I did manage to find a sheet with the 3 views, front, top and side already blown up to a 48″ wing span. So I downloaded, printed and tiled it up on the dinning room table.

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I thought the lovely square body lent itself perfectly to foamboard and flitetest’s method of folding fuselages rather than depron, and the main wing with the engines attached would need quite a lot of carbon reenforcing if made out of depron, but made into an aerofoil shape with foamboard could probably quite nicely support the weight and stress. Also the 2 motors should be able to give the model enough muscle to lift the heavier foamboard into the sky. And I’ve still got a few boards of foamboard left, so foamboard it is.

Unfortunately my tiled image is rather low resolution, so I put a piece of board under the plan and started by using a pencil to go round the outline of 1 wing, this produced a light dent in the foamboard which I then made into a better shaped wing, added the extra underside so it could  be folded into a aerofoil shape and cut it out. Because the plan was so low resolution if I did the same for the other wing they would never match so I flipped this wing over and made a new trace of it for the other wing. The spars were next. On the plan the wing is very tapered almost to a point, although I dont think I can quite get this, I did make a tapered spar to try to mirror this, but still leaving just enough room for the aileron servo in the wing void.

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I didn’t want to glue this up yet because I am still not sure how this will go onto the fuselage, or how the engines will connect to it.

So the next step is the canard. Initially I was going to make this a KF step but thought that was a bit of a cop out after making the main wing as an aerofoil. So I decided to make this an aerofoil shape also. I also wanted to make this out of 1 piece so used a piece of paper to trace round the front canard on the plan with the intention of folding it and cutting it out to produce the full wing template.

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Then after I added the underside of the wing I realised that because of the shape of the wing, and the direction of the folds (not perpendicular to the body centre line) the base of the wing would need to be in 1 piece and the top would need to be separated and come together when folded, so I cut this 1 sided paper template out and traced round it twice to create my front canard wing.

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I also initially wanted to put the elevators on this canard but the placement of the servo and the connecting of the pushrods eluded me. I did want to put it out of the bottom of the plane since the base of the plane was such a nice square shape, putting a servo inside the body with a connecting rod to each side of the canard would be almost impossible to thread and connected. Putting 1 servo on 1 side with a bit of bent wire to make each elevator work together was an option but would create a rather lob sided look. The best option I could come up with is 2 servos, 1 either side each connected to each elevator, but this would mean there a 2 servos right at the front putting extra weight and extra complexity. So although the elevators are marked they are not cut and the plane for the moment is going to be going forwards with Elevons and the hope that I can get the plane balanced enough for these to give enough control. But that might change yet…

Next I turned to the engine mountings, These will need to fit over the wing and key into the wing for strength. So to try to make sure I get the right shapes, and location for keys to avoid the spar I made a little paper mock up

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A bit of shaping and fitting and it fits to the wing nicely, perhaps needs shortening a bit so it fits just the flat underside of the wing and doesn’t trail onto the tailing angled edge of the top side

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Marked up where the keys should go on the paper and then a quick check with the motor placed in front of it to see if they are somewhere about the right size pointing forwards from the wing. The sheet was traced from the main plans because it is easier to move a single A4 sheet than the whole big sheet.

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It looks about the right length, maybe even a little bit short to the scale but not too bad.  I think that will do, I am still wary of putting too much weight too far forwards on this model. Once I transfer to foamboard I will try to bend up the underside to a nice curve by removing the inside paper and put a top on the box which will hopefully taper into the wing. Although this of course needs to happen after the wing has been pushed through the main body.

The main body is a nice simple shape, effectivly 2 boxes, a larger to the back and smaller to the front, although the plans do show that the body behind the main wing is narrower than the main body in front of the main wing. Since I dont have the plans of how this reduces I have discounted this and created a standard box for this section.

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So now with all the pieces are cut we are ready to start assembly. The plans show the bottom of the canard wing is level with the baseline of the body, I am going to bring this up slightly so as to put a 5 degree inclination on it and add strength. The main wing also appears to come through the top of the main body, again this I think I will need to put so the main body remains in tact above it for strength.

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More updates to follow…

Next update:

I’ve created the torque bar by bending up a single piece of wire with a loop in the middle to put a z bent piece to the servo, as suggested by Mr Mel. Here is the piece sat on the plane:

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I did initially think of putting the wire in a hearing aid tube were it come through the bodywork so that it can be glued and not impede the movement of the elevators, but this didn’t work very well so I removed these tubes. Here is the canard, servo and mechanism all in place and working with the torque bar stuck to the elevators with epoxy glue.

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I wanted to now fold up the engine nacelles and do a quick check of the receiver, speed controller and both motors to ensure that they reacted the way I expected. With the 2 speed controllers, 1 BEC had to be disabled by cutting the red wire from one of them. Everything checked out, both motors work fine, so I’m happy with that setup.

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The next step was to put the wires through the main wing for the motors and the elevon servos, then join the 2 sides of the wing. To get a good fit I sanded these then hot glued them together. Passed it through the body, I used the plans to line up the wing and glued it into place

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So the nacelles go onto the wing and the servos connected to the control surfaces

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Now with the engines in place and held I could do a power test of the engines. The first prop I tried was a 6×4.5 triple blade prop (as shown above) this would be an ideal size since it clears the ground so the plane could belly land. On test these drew 11 amps each on a 3 cell battery, about 125watts each. This would give total power of 250watts. The weight of the model now was about 900grams, still with some work to do, so the estimated dry weight of the plane would be about 1kg (2 pounds) with an extra 500grams (1 pound) of batteries so 3 pounds all up weight, 250 watts would be a little under power. So I also had 2 triple blade 7×3.5 props. Surprisingly under test this developed even less power about 8 amps or 90 watts each definitely no good. So my triple blade 8×4.5 was next. This drew around 17amps, 180watts per motor this is still within the motors rating, but with a total power of 360watts this should give a reasonable power level for a 3 pound model, its not going to be acrobatic, but should lift it into the air nicely. So the 8×4.5 props it was. This did give another problem that the plane now could not be a belly lander, the prop does stick out rather too much and would be likely to do some damage to either the props or even the plane on landing. So I had to make some landing gear. The rear wheels where quite simple, making them in the same way as flitetest created the landing gear for the FT Cruiser attaching them to the engine nacelles. The front wheel was a little more of a problem, this was what I came up with

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Hot gluing a piece of plywood on the bottom of the plane and bending a loop of wire through the wheel, retaining it with an elastic band to give it a little play. This now nicely lifts the whole plane up above the level of the propeller touching the ground. Although I haven’t yet put the vertical tail fin on, the COG is currently towards the front of the main wing, using this calculator online: http://adamone.rchomepage.com/cg_canard.htm it should be about half an inch in front of the main wing. So placing the batteries in the main body ahead of the wing should move this to the correct place. So I created a hatch in the top of the main body for this, put a bit of velcro in to stop the battery moving around and a magnetic catch to keep it closed.

The final step is to put the vertical tail fin and hook it up to the servo and receiver

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All looking good and ready for its test flight, final dry weight is exactly 1Kg, with 2 1400mah batteries the all up weight is just under 1300 grams. This maiden may not be this week, although the ground is nice and soft it is supposed to be a little windy tomorrow. So I will need to upload details of the maiden when I pluck up courage to do it. You never know I might even decorate it….

Build log of Versa Wing

Time to start a new project, I have built a Versa Wing before, it was made from foam board and was configured as a pusher.

Although it flew, it wasn`t nice to fly, because it was to heavy, foam board itself is not the lightest material and with the motor at the back a lot of nose weight was needed to balance the model.

So I am going to try again, this time using depron for the wing and foam board to house the motor, esc, battery etc. It will now be in tractor mode with the motor and prop at the front.

I like to make templates for the parts using tracing paper to copy the parts from the plan, the tracing paper is then stuck to the 6mm depron sheet using tape, the parts are the cut with a knife following the lines marked on the paper.

I first made the wing spars, each spar has two halves which are stuck together to form a single spar 12mm thick.

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Here are the four pieces that will make the spars.

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Spars made from depron alone are of no use, just to weak, so I have found a couple of pieces of wood strip, I think it`s spruce, and have used epoxy to stick these to the depron and make the spars stronger.

Updates will follow as I make progress.

First update, I have cut the wings out but left off the elevons. The elevons are cut out with the upper wing surface when using foam board the paper covering acts as a hinge, but no paper covering on depron so I will have to think about hinges later.

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Tracing paper copy from plan, stuck to depron with masking tape before cutting out.

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With both top and bottom wing halves cut out, they have been joined together along the leading edge using tape.

Depron will not bend very far before breaking, so I have covered the whole wing with lightweight fibre glass weave using a water based resin to stick it down. This was very easy to do and once the resin had dried the excess fibre glass was cut off. This process seems to be quite successful and the wing can be bent without any problem.

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The spar was fitted and lines scored into the underside of the upper wing half using a ice lolly stick, these so that when folded over it will bend in the right place.

The wing servo has to be fitted at this time, it just glued into place.

Watch for next update.

UPDATE.

The top and bottom wing halves were folded over and glued along the spar and the trailing edge. I didn`t realise at the time but I made a mistake here as I later found out the two sides were not correctly aligned.

This was repeated for the second wing, and the same mistake was made again, which was just as well as it turned out.

Now joining the two wings together was a bit of a pain, this because of the misalignment mentioned above, a lot of cutting and sanding of the wing root was needed to get a decent and straight fit, but after much moaning and groaning I managed it. I was helped here by having made the same mistake twice, by this I mean that both wing halves were the same so need identical work to make them fit to each other.

Once happy that the two wings would fit each other I used epoxy to glue them together, and reinforced the joint with tape and fibre glass on both the top and bottom sides.

The elevons were next, I cut these from depron and covered them in the same way as the wing. I used a couple of pieces of carbon fibre strip to add some strength and stiffness then fitted them to the wing using tape.

 

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This picture shows the two wings joined and the elevons fitted.

The “pod” which carries the motor, esc, etc has a square front to it, and it sits at the pointy end of the wing, so as not to leave a gap here I cut the wing nose off and glued a piece of balsa in it`s place.

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This made the front of the wing square and so making a better fit for the “pod”.

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This shows the underside of the wing, I made two servo horns from plywood and glued them into place on the elevons, then fitted the push rods btween the servos and the horns. You can see the two servo cables emerging from the wing.

The two small dowels are for the location of the motor “pod”, which can been seen at the top of the picture.

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Now I have fitted the “pod” to the underside of the wing. The motor, esc and receiver have to be fitted at this point.

I managed to find a folding prop that fitted the motor I brought, which was a bonus.

I have glued the “pod” in place so I have cut a hole in the top (or is it the bottom) of it to allow the flight battery to be fitted.

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Here is the Versa Wing completed.

I have come across a problem with using a folding prop, that is once folded during flight it cannot be started again because the prop blades catch on the underside of the wing.

So after removing splinters from my fingers after scratching my head, I have found a solution, I have used a small rubber band wrapped around the two prop blades, this pulls the blades forward when the motor is stopped but does not prevent them from opening while the motor is running.

 

 

 

 

 

Dusters maiden and Prop Selection

I recently finished the FT Duster, I’ll not go into the build since the video on Flite Test goes through the build so much better.

http://flitetest.com/articles/ft-duster-build

The maiden flight could have gone much better:

I reduced the throws slightly and increased the expo a little more, reduced the size of the battery I used from a 2200mah to a 1400mah 3 cell. At Mels suggestion I also removed the cab. All this moved the COG slightly back so it is on the back side of the spar in the wing.

I don’t have a video of this, but this made it a much easier plane to fly, still a little twitchy and under powered but much better.

So I then decided to pick a better prop I had a few to choose from:

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from left to right an 8×4.5 triple blade, a 6×4, and 8×4 which was on duster for its maiden, an 8×6 orange, and 8×6 black and a 9×5 orange prop. I then setup Duster with an amp meter and anchored it through a set of scales to give some idea of the thrust generated:

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Although the measurement of the trust is by no means perfect it should give some idea of how good each prop is. The motor that is in duster is a 1580kv motor with a 20amp 14.8volt maximum power rating, so I have installed a 30amp hobbyking speed controller. I will be running it on a 3 cell (11.1 volt). The results of the current draw and trust measured is shown in the table below:

Prop Max Current (amps) Max Thrust (grams)
6×4 10 Did not register
8×4 16.5 220
8x6Orange 23 250
8x6Black 25 320
8×4.5 Triple 27 520
9×5 27 320

Apparently a plane flying through the air will take approximately 10% less current than the same plane static on the ground (due to the air movement over the prop, so I have found on the internet). Based on these numbers, although I think that the 8×6 black and orange trust figures are skewed by the setup, but I would say that the best prop would either be an 8×5 of the black type or the 8×6 orange prop, giving the maximum thrust with closest to the maximum power of the motor, and running it on a 3 cell should give the extra allowance to mean that it will take the current tested without burning out. The triple or the 9×5 prop would give more trust, but are both too far above the motors maximum working load current.