Gangster 75 Build Blog

[Peter Jenkins]

Thanks Ron, so am I!

[Jimbo565]

Cracker job Peter, well done.

I have the 63 lite and it flies a dream.

Jim

[Peter Jenkins]

Thanks Jim. The 75 I flew really impressed me and I hope this one lives up to it.

[Jimbo565]

It will Peter, Mick reeves should have a medal for this one.

JIm

[Peter Jenkins]

Didn’t get much done today but did manage to fit the canopy. I hate this job as it’s so nerve wracking! I just couldn’t get the canopy to stick down in places until I tried using my covering iron to heat the canopy and the glue underneath. Not much heat and finger pressure on the bits that didn’t want to stick worked a treat!

I fitted the throttle servo next and then the engine with the throttle pushrod fitted in place (it’s a z bend onto the throttle arm) and fed into the screw fitting on the servo arm making sure the grub screw had a dollop of thread lock. I could then offer up the top cowling to make sure that the throttle could move without any hindrance and connected up the pressure nipple and carb feed pipes.

I made up the extension leads from the Rx position to the elevator and rudder servos and fitted the servos. I fitted the Dubro heavy duty horns and assembled the turnbuckle pushrods. After zeroing the sub trims and then fitting the control horns at the closest position to 90 degs to the servo, I fine tuned this position using the sub-trims and bolted the pushrod in place. Final adjustment of the control surface was simply a matter of twisting the turnbuckle to suit. Still need to trim the rudder horn fixing bolts but ran out of time!

[Braddock, VC]

A bit late with this info but may be worth looking here - https://www.nrshealthcare.co.uk/eating-drinking-aids/cutlery-aids/plastazote-tubing-1metre?fee=19&fep=48442&gclid=EAIaIQobChMI9-Dx75GQ4AIVWeh3Ch27xQKUEAQYAyABEgLyZ_D_BwE#228=407742

[Peter Jenkins]

Hi Braddock, thanks for that. I looked it up and it seems to say that there are 3 sizes namely 12 mm internal bore, 9 mm and 6 mm. I need a 20 mm bore so doesn't seem to fit the bill. Do you use it for connecting exhaust components and does it stand up to the heat? Looks quite soft for such use but it may work OK for those with the right bore requirements.

[Nigel R]

Looking good Peter

re: the above, are you looking for a header/pipe joiner? If so, 19mm ID silicon tube is available on ebay, £3.60 for 1/2 metre here:

https://www.ebay.co.uk/itm/Silicone-Vacuum-Vac-Hose-Pipe-Tube-3mm-4mm-5mm-6mm-7mm-8mm-9mm-10mm-Available/290742298928?hash=item43b1976930:m:mukwgwKXqWPSCPCt7EqavOw:rk:6f:0

[Braddock, VC]

I thought it may prove a substitute for the pipe insulation you used to stop your leads rattling, not everyone has that amount of space for large diameter tube.

[Nigel R]

ah, oops, ignore my post

[Peter Jenkins]

Posted by Braddock, VC on 28/01/2019 11:52:21:

I thought it may prove a substitute for the pipe insulation you used to stop your leads rattling, not everyone has that amount of space for large diameter tube.

Oh! Got hold of the wrong stick there! Thanks for that.

[Peter Jenkins]

Posted by Nigel R on 28/01/2019 10:45:50:

Looking good Peter

re: the above, are you looking for a header/pipe joiner? If so, 19mm ID silicon tube is available on ebay, £3.60 for 1/2 metre here:

https://www.ebay.co.uk/itm/Silicone-Vacuum-Vac-Hose-Pipe-Tube-3mm-4mm-5mm-6mm-7mm-8mm-9mm-10mm-Available/290742298928?hash=item43b1976930:m:mukwgwKXqWPSCPCt7EqavOw:rk:6f:0

Thank you Nigel, that's very useful. Might just get some of that.

[Peter Jenkins]

Today, was a rather frustrating day. I had a number of extension leads to make up which went fine - unusual for me! It was then time to fix the Rx in position and connect up all the servo leads and the switch harness. A quick check on the elevator and rudder movement had them in around the right area for low, medium and high rates. That left the balancing.

Having bolted on the top cowl, I then bolted the wing on and attached the manifold and tuned pipe. The good news was that there was minimal bending of the exhaust joiner to get the tuned pipe correctly seated on its support bracket. The first problem was that there was insufficient clearance between the bottom cowl piece and the manifold. Manifold off and cowling piece adjusted to clear it, and then manifold on again. Fit the spinner backplate, prop and spinner. No need to carve the spinner to accept the prop as there was a large enough cut out to clear the prop - hooray!

Carefully sighting from one mainwheel to the tailwheel showed that there would be very little space for the beautifully made exhaust efflux pipe. Careful adjustment of the position of the pipe support bracket gave a bit more clearance. This won't mean much to you as I forgot to take a photo of it, but it looks like I shall have to rotate the end pipe so that it doesn;t curve down but rather curves to the side. Will only make a final decision once all is in place and I can put it onto its wheels and measure the clearance between the pipe and the ground.

One thing you can see in the picture below is the problem with the bottom cowl piece. How I came to make such an error in shaping the cowling to match the spinner I really don't know. Suffice to say, that I will have to decide how best to achieve the desired shaping as most of the underlying structure is going to be sanded away to get the cowling to blend smoothly onto the spinner!

Despite these annoying problems, all the items to enable flight were now installed except for the battery and switch harness. I did a trial balance at the rearmost quoted CG figure of 5 inch back from the wing leading edge at the root. The aircraft was slightly tail heavy.

Placing the battery pack, a 2S Life of 2500 mah capacity, as near to its most forward position with the switch just behind it gave a balance. Looks like I'll need to make a battery box before installing the Rx in the original, but now empty tank bay.

Placing the battery pack, a 2S Life of 2500 mah capacity, as near to its most forward position with the switch just behind it gave a balance. Looks like I'll need to make a battery box before installing the Rx in the original, but now empty tank bay. The alternative battery, a 2 cell NiMh of 2500 mah, as well, is a good deal heavier than the LiFe cell but I could see no good reason for fitting it until I’d flown and checked how the Gangster actually flies.

Back to balsa bashing tomorrow..

[Ron Gray]

Lower cowl piece, don’t bother re-shaping as you won’t see it when the right way up. If you must do something with it, cur a slot in it, aka chin intake. For more pipe clearance, fit bigger wheels, they’ll be too small for excursions off our runway anyway! 😉

Edited By Ron Gray on 29/01/2019 07:49:54

[Peter Jenkins]

Hi Ron - too late! The balsa bashing was initiated as soon as I found the problem! The pipe clearance issue is linked to the final curved pipe exhaust which can be rotated to any angle and locked by a grub screw. Until I have the Gangster sitting on its wheels I won't know exactly how much space there is. I like the idea of bigger wheels though but they are much bigger than on my F3A birds!

[Charles Smitheman]

Hello Peter,

This is looking good. I am glad to see the model getting built.

One point I may have missed, I hope you took the engine backplate off to drill it for the pressure nipple, to be certain that no swarf got inside.

Your colour scheme is most impressive, very intricate.

Good luck with the maiden.

Charles

[Peter Jenkins]

Hi Charles - thank you.

Yes, I removed the backplate before drilling and cleaned it of swarf before bolting it back on.

I pinched the colour scheme from the Vanquish although the underside was pinched some some of the current F3A designs. Of course, against a blue sky when at the top of the box, they all look black anyway!

Peter

[Peter Jenkins]

Not much done today. I've adopted a revised cowl design. The front of the cowl from the carb forward is now part of the main cowl piece while the lower cowl now just abuts this. I'll put a picture up tomorrow as I forgot to take one and it's a bit wet and windy to head out the the shed at the moment!

Once I've covered the re-worked part of the cowling, I'll need to finish making a battery box, install the switch and fix the tuned pipe retaining bracket to the wing. Then it will be engine running time!

[Peter Jenkins]

I've now covered the revised cowl and it looks much better than the first attempt!

The other benefit is that the carb is now flush with the cowling so it will be easier to choke. In this photo the carb is covered with tape to avoid sawdust getting in.

The photo also shows the new arrangement for the cowl that I mentioned in the last post. The rear part of the cowl is held down by the bold in the plastic washer you can see behind the engine. The front part of the cowl is attached to the main part. The top cowl is held in place with a 3 mm bolt through some square strip spruce into a T nut through the engine bulkhead. The bottom of the cowl is retained with two long servo screws again through some spruce strip into the bulkhead. This seems to give a very firm fixing and makes it easy to check the tightness of engine mounting bolts although to do that I have to remove the tuned pipe and manifold and then the bottom cowl.

The photo below shows the tuned pipe in place. It took several hours of annealing the manifold and bending it to provide both an increase in height of the manifold at the point it joins the tuned pipe and also to align the manifold direction at the point of joining.

The manifold is yet to be cleaned up! The rear pipe support I bought from the US and consists of an anti-vibration mount supporting a semi circular plastic channel with the ends turned through 180 deg to provide a channel for a large rubber ring to be pulled tight over the pipe.

The front end of the pipe is retained in the Teflon joiner by a spring clip so installing and removing the pipe will be fairly painless. I hope the AV mount will further reduce any exhaust noise being transmitted to the wing structure.

I also made up a balsa battery box but when I came to fit it in the old tank compartment I decided that I preferred to have a completely removable battery retaining system. As I had some blue foam available, I used that to provide a means to locate the battery which is now wrapped in a thick black neoprene pad. The whole lot is retained in place by the hatch you can see right behind the cowling. The is currently retained by 2 long servo screws through the engine and wing mount bulkheads into spruce strips glued to the balsa hatch. I'm toying with the idea of using the same fixing method as the cowling in front of the hatch. The only drawback is that with a centre bolt it will be under the manifold so the manifold will have to be removed first. Could mount the bolt off centre I suppose. Will make a decision tomorrow.

The last thing needed to be done is to cut a hole in the fuselage side and mount the Rx switch. That's tomorrow's project.

[Peter Jenkins]

So, today, I cut the hole in the fuselage side for the switch and fitted it and connected up the battery, switch and Rx. Quick check and all was working. I like the Al's Hobbies switch that has a green LED when on.

The equipment bay under the wing, without the middle former, is huge! This now contains the tank, on the CG and the Rx so there is bags of room. This photo shows the Rx and to its left the two snakes that I use to hold the aerials at 90 degs to each other. The secondary Rx is mounted in the original tank bay immediately behind the engine. The tank is retained by velcro straps with non-slip material under the tank, a foam pad the then the tank and between the tank the the velcro strap at the top. The tank is pretty solid with this arrangement. Bearing in mind that there will be 18 oz fuel in the tank when full, I might put in a former immediately behind the tank but I'll see how it goes in practice.

The aircraft is now ready for engine runs which will include the running in process. I'll leave the cowling off for this so that I can reach the fuel pump if that needs adjusting. The manual says run 2 tanks through the engine (its a ringed piston) so needs a lot off richish full power runs with cooling off periods. Sounds like ear defenders will be needed even though I'm getting a bit deaf! After that, it says it's OK to run in in the air using the same technique for another 45-60 mins gradually leaning out the mixture. I have just sent off for 2 props as the one I thought I'd use is not man enough for the job when there is a tuned pipe in the equation. Talking of the pipe, the annoying thing is that I'll need to have the wing on a) as the u/c is mounted on it and b) as the rear pipe support is on it. I'll see how I get on with starting the engine inverted but I may need to start it upright and then turn it over. We shall see!

[Peter Jenkins]

Finally got round to weighing the Gangster today. I have to say that it had felt heavy when I was building it compared to today's 2 mtr electrics that I normally fly. However, its wing span is almost identical to my petrol powered CPLR designed Majestic although the Majestic fuselage is 2 mtrs long. The Gangster fusleage is about 2/3 that length.#

Fuselage - 5 lb 15 oz

Wing - 3 lb 5 oz

Total - 9 lb 4 oz or 4.2 Kg

On the other hand, the Gangster is a good deal tougher than a 5 Kg 2 mtr electric bird. Will have to see how the ST90 on a Hanno pipe copes with this weight. The Majestic, with a DLE 35 RA, tips the scales at 5 1/4 lb dry although the fuselage is fibreglass up the cockpit and carbon fibre forward of that. You cannot lift up the Majestic by its fuselage as it's very thin material and flexes inwards easily.

[SR 71]

Hi Peter a lovely model
I have always thought or been led to believe one should always have the wings on when running the engine in the model
Looking forward to the flying report
Tony

[Peter Jenkins]

Hi Tony, thank you. In this case, as the wheels are on the wing, there is no option than to run in the engine with the wings attached. Where the wheels are mounted on the fuselage, I've left the wings off when running in the engine. I can see little to be gained by having the wings on when running in an engine - perhaps I'm missing something?

I suppose that I could mount the fuselage upside down in a cradle and run the engine in that way but I'd prefer to have the aircraft tethered on the ground in the normal way.

Edited By Peter Jenkins on 01/02/2019 18:58:02

[SR 71]

I think it is something to do with the vibrations, the wing helps to disperse them

[Peter Jenkins]

In truth, that could go either way. The change in fundamental frequency of the structure could help or hinder. I think that most fuselages are stiff enough to resist the forcing frequency of the engine. I've never had a problem but I suppose there is a chance that could occur.