c_nut

This will be a build log for the Seagull Models - Piper Twin Comanche. - Manufacturers Website and Specifications

Ideally, I would like to keep this thread relevant to nitro power, if you are interested in going electric, Nick is documenting an electric build over at RC Groups

I live in Queensland Australia so I am also going to address an issue that affects Aussie builders (ie, the Australian Distributor does not stock the optional wheel well and gear door set)

I'm in the planning and shopping stage at the moment, I will be on holiday in 3 weeks and this build is my holiday project so feel free to open discussions but the actual build documentation wont start for another 3 weeks. However, I expect to update the thread daily once I start. I'll be taking photo's along the way and hopefully some video of the Maiden flight. If you have any special requests for photos (detail, close-up's etc) feel free to ask.

OK Then......... Here we go........

There aren’t too many twin engine ARF’s about and I just don't have the time to scratch build these days so I was very excited to see the Twin Comanche on the shelf at my local hobby shop and eagerly watched as the box was opened for inspection.................... and there she was, a beautifully finished airframe with quality accessories and those fibreglass engine nacelles are two of the best I’ve seen. Oleo struts fastened to fixed 5mm undercarriage wires leave the door wide open for the optional retract conversion and whilst not “strictly” scale, the airframe is a pretty fair reproduction of the full scale Piper PA-30-160 Twin Comanche registered ZS-EMR which is based in South Africa.

This Comanche really had my imagination going, I could strip a lot of what I needed from what was left of the Dual Ace and tip in a little extra money to make this project “something special”.

It was about that time that I decided to share this build with you. I see a lot of modellers that assemble their ARF kits according to the instructions and never contemplate the little customisations that can be made along the way to produce a model that is even better and perhaps just a little more unique.

So here’s the plan.
I’m taking the Seagull Twin Comanche and powering it with a pair of Thunder Tiger 46 PRO’s (extracted from the old dual ace). I’ll add a couple of nice alloy spinners to help it match the real thing and I’m going to dismantle the included Fixed Oleo undercarriage and fit them to a set of Electric Retracts. I think it would be nice to fit it with Navigation lights and perhaps some anti-collision strobes and a tail beacon. Yeah, I know, it’s not really necessary, but it is an awesome looking airframe and I think it deserves the extra attention :-)

Along the way, I'll document any modifications that may be necessary to improve strength or structure (although I have found Seagull Models to be fairly well built)

Now one thing about twin engine aircraft, if you lose an engine, things can get really ugly really quick. So I’m going to minimise the risk on this project by installing an engine management system called Twinsync. Unfortunately, Twinsync is not currently available in Australia but can be purchased from www.troybuiltmodels.com or direct from Bill Wike (the creator). This is a great piece of electronics that monitors the RPM of both engines and synchronises their speed throughout the throttle range. Add to that a safety feature that automatically brings the running engine back to idle if one engine fails, and you've got yourself some peace of mind.


Nothing quite like the sound of perfectly synchronised engines and knowledge that if one engine stops pulling, the twinsync will know about it before you do and close the throttle long before your pride and joy rolls onto it's back and heads for the crash site. If you want more information on the Twinsync, head over to this thread

The only other challenge I'm facing is the optional retracts. Firstly, Seagull have provided for optional mechanical retracts, which in my mind, just doesn't make sense because the main retract servo is mounted in the fuse and the wings are two piece removable. I don't know about you, but I certainly don't want to be connecting and adjusting retract linkages every time I go flying. Second problem is that the Australian Distributor does not import the optional “gear door and wheel well set” for the retract conversion.

Solution to the first issue is easy, I'm going for electric retracts, probably the E-Flite 60-120 Tricycle set (EFLG430) but happy to hear any recommendations on other options (RC Lander and Turnigy come to mind)

The second problem was a bit of a challenge, the obvious solution was to order the gear door and wheel well set from Horizon for $13.99 so off I went, added to cart, proceed to checkout only to find that postage to Australia was going to be $79.10.......... Hmmmmm $93.09 all up........ As we say here in Australia "that's **** mate..... "

So an email to Horizon reveals that unfortunately, Horizon does not have another shipping option at this point in time. Don't get me wrong, Horizon was very helpful and I believe that they are looking for alternative shipping solutions to address the issue so don't rule them out without checking to see if things have changed. Anyway, after a little searching, I was able to order the set from Hobby Zone for the same price plus $3.78 postage (US$17.77 total) Now here in Australia, that's a "You Beauty Mate........." - UPDATE - The Gear Door and Wheel well set arrived today from Hobby Zone - very well packed, fast efficient service and very reasonable postage cost - big thumbs up from me for Hobby Zone.

I'm still looking for a good lighting set - something bright but not too expensive - I'm thinking red and green wingtip Nav + red tail beacon + wingtip strobes + tail strobe and maybe landing lights. Although I'm not sure if I will hack the leading edge to put landing lights in the "correct location" or if I'll just put a single white light in the end of the nose cone????Feel free to offer suggestions.

Thats it for now, looking forward to bringing you an informative build tread

Craig

c_nut

Time for an update,

sj3cub

My Feedback: (9)

Subscribed. Comanche is on my to do list. Thanks for sharing.

c_nut

Hey SJ, welcome to the build.

Paul from Victoria (a couple of thousand Km's south of me) is also lurking in the wings, I'm sure we'll be hearing from him as he is also putting the Comanche together and we will be sharing ideas along the way.

The next two weeks will not pass quick enough for my liking, but I have a good feeling that it will be worth the wait.

Craig

sj3cub

My Feedback: (9)

Thanks CNut. I'm lurking on Paul's thread to. Thanks again for posting.

Quigleywins

Hi Craig see your having a look around on line.Just been out in the shed making some space for the project for when the rush starts on the builds. I will need to remove a 55 out of one bird that can have a Merco 61 in it for a while. I did run out of the old OS 55 AXs I have 5 but all in work some where holding the engine mounts in place on somthing that I intend flying soon.I did look at the mechanical retracts ,its a bit sad that this model and the last one have such a poor landing system. thing should be getting better not going the other way. Yours Paul T

Carlos Murphy

My Feedback: (72)

A friend of mine has a Twin Comanche, he keeps it in pristine condition with upgrades and immaculate paint. I flew with him one night from Hayward airport to Napa and back.

We flew up the coast past San Francisco part way in the fog, kinda eerie, the bay area is a beautiful place in which to fly.

c_nut

Hey Paul, 55's will be heaps but if you've got them, might as well use what you've got aye. I agree with you on the landing gear, but I also understand that the ARF manufacturers are stuck somewhere between producing a product that has a good enough quality but at a price that people will buy.

Chicken and egg problem, they skimp on quality and us modellers bag them out on public forums then they don't sell any kits. OR they produce a top quality fully featured kit and we all complain that it's too expensive............ (there are topflight kits and ARF's for those that are happy to pay for the total solution)

I actually think that what most of them are doing now is actually a good solution. Produce a good quality airframe that modellers of any level can appreciate but leave some options for those of us with the time or interest or skill to "trick out" with accessories and finish the way we want. Good for everyone????

That's one of the reasons I decided to document this build. I read a few other threads on the Comanche where guys were not happy with wheel wells and gear doors not being included or couldn't figure out where to put things etc etc but when you look at this kit as supplied, it is actually very complete (when was the last time you got oleo struts with a fixed gear ARF?)

So if you buy the Comanche and build it as supplied, you are still going to have a nice model, what I hope to share and show is that anyone can take an ARF and with a little bit of time and a few extras, take that ARF to the next level of personalisation.

It's that "next step" for modellers, a little effort for a nice result but without the time, effort and skills that would be required for a kit or scratch build.

Trust me...... if I had the time I would be scratch building something because I love working with my hands, but the fact is that these ARF's give me a good foundation to build upon since I don't have the time to scratch build. Not to mention that I doubt I could scratch build an airframe any cheaper than I can buy the ARF.

So this is not a dig at you, simply an expression of my view, I think the kit is great as supplied, but if I want to add a few things, then I should be prepared to solve a few problems along the way.

What do you think?
Craig

sj3cub

My Feedback: (9)

I actually think that what most of them are doing now is actually a good solution. Produce a good quality airframe that modellers of any level can appreciate but leave some options for those of us with the time or interest or skill to ''trick out'' with accessories and finish the way we want. Good for everyone????

That's one of the reasons I decided to document this build. I read a few other threads on the Comanche where guys were not happy with wheel wells and gear doors not being included or couldn't figure out where to put things etc etc but when you look at this kit as supplied, it is actually very complete (when was the last time you got oleo struts with a fixed gear ARF?)




I couldn't agree with you more. These kit (arf's) are for the more experienced modelers who want to do things their way and actually like assembling and working. I think what's happening is as the new generation of foamie "flyers" that is used to not even having to adjust a clevis, or anything for that matter, buys these arf's, they expect not to have to do anything that would require the use of their brain. Then they get on line bashing and complaining away, making themselves look totally stupid. Having to plan, think, use the brain that God gave them, no way!!!!!! I WANT IT NOW, AND I SHOULDN'T HAVE TO DO ANYTHING TO GET IT!
Now back to the beautiful Piper Comanche!

Quigleywins

Well Lets look at the Commanche. First if you want the gear up then there are better systems than the Mechanical that are on the market. I actuly have them and the only reason was to get the wheel wells that I think I will need even if I use the fixed gear,This was a very expensive set of wheel wells and should have been in the Kit. If the gear goes up on mine it will be a different system.
I saw one the other day and the chap had put a plate on the bottom to cover up the insilation of the fixed gear,something that I had not thought of. The plate over the attachement point was no bigger than a wing sevo cover made of ply, did the job.
AS for the BH aero commander. the gear is a shocker. I'm about to remove them again and rebuild the actuating sustem for the rasing of the wheels till that is completed it stays in the shed The century jet set is an expensive option but that maybe the way I might need to go and that so we can have the first flight. It looks great but the wheels move around like nothing on earth.
I have no problem with the Lancaster system whiich you have the option of getting with the aircraft. If you dont want them then they stay in the hobby shop.
Same with the TF B25 and the (ARF) TF Mustang there are Mechanical supplied but the Air set realy go straigh in ,very small amount of work required to fit..
I have all the above in my collection and I know which systems I like .

c_nut

Nice collection Paul, I think I can hear that Comanche begging to be finished hahahahaha.

Thanks for the info on your retracts, I agree that mechanical is definitely not the right option for the Comanche, I had considered Air but it seams like a lot of extra plumbing and weight and multiple points of (possible) failure with hose joiners etc etc.

I have decide to go electric retracts based on the following;
- less points of possible failure
- simplicity (mount and plug in)
- more realistic speed of retraction and extension.

I had a look at what was available and after reading reviews on some of the cheaper ones, I have decided to spend a bit extra and go for the E-Flight 60-120 Tricycle set (EFLG430). By no means the cheapest nor the most expensive, however it would appear that they are reliable and strong so I'm going to give them a go.

I know you already solved your gear door and wheel well issue. So any advice from me is too late now, but for anyone else looking to do retracts,I was able to order the door and well set fromHobby Zonefor under $20 including postage. I had considered lining the wheel cavities with balsa and making my own doors (would be pretty easy) but for under $20...... why bother :-)

c_nut

WOW, my lighting system arrived, prompt service, well packed and excellent price. did an eyeball test for brightness (big mistake) these things are BRIGHT. Pretty sure these lights will be visible even during daylight flights in the bright Aussie sun [8D]

c_nut

Ok well the Comanche is here, box unpacked and assembly begun. I Have started with the wings and needed to focus first on the installation of the wingtip navigation lights, anti Collision strobes and Landing lights since these were going to be impossible after attaching the wingtip tanks.

Since the wiring for the lights was going to run through the front section of the wing, the next task was to install and epoxy the nacelles prior to completing the cabling since it passes through the nacelle.

Finally, attaching the wig-tip tanks and hinging the flaps and Ailerons.

They say a picture paints a thousand words, so here they are. Feel free to ask me if you want more detail on my methods. You will notice that I don't use pins to hold my hinges centred. Instead, I fold the hinges in half then insert into the wing before sliding the flight surface gently into place (from an angle). This way, the crease holds the hinge centred and I can get a nice close fit prior to applying CA to the hinges.

c_nut

Here are the hinging photos

c_nut

today I installed the flap and aileron servos. Fairly straight forward and no surprises although I have a preference for "Z Bends" rather than the little plastic pushrod clips that seagull use in their kits. You can see from the photos that I use a Z Band on the servo end and clevis on the control surface end.

All the hardware is as supplied in the kit and is of good quality. The only thing I changed was the Z Bend instead of the supplied plastic retainer and the short piece of fuel tube on the clevis which guarantees that the clevis wont spread under load.

c_nut

Here's the twinsync, a nice compact circuit board. It will occupy two channels on the receiver. The Throttle channel will provide the master throttle input signal and an auxiliary channel which can be used for a number of programmable options. I will be using the independent run up mode on a three position switch. first position will allow throttle control of engine one while engine two is held at idle, mid position will be throttle control and sync of both engines and third position will be throttle control of engine two while engine one is held at idle.

This configuration will make independent tuning of each engine as simple as flicking a switch to isolate the other engine.

You can see from the photos that I have drilled a diametric magnet into the prop hub rather than using the standard magnet in a spinner backplate. I preferred this approach simply because it allowed me to keep the whole RPM sensor system mounted to the engine.

The sensor itself was more of a challenge. I based my idea off the typical sensor on a gas engine. I cut a few strips of balsa and built a box around the sensor which I then hardened with CA. Once the CA had set, I shaped the balsa to form the pickup shape, hardened again with CA and cable tied to the crankcase.

I know from others experience that engine temp will not be high enough to melt the cable tie and the beauty of this solution is that it can easily be removed and does not rewire any drilling or modification of the engine itself.

Acetronics

Hi, C_Nut

I've a little question about engines choice ...

Here I have ( brand new):

- 2 OS 46 SF
- 2 OS 56 FS Alpha
- 2 Saito 62
- 2 Saito 72

From what I have read about the Comanche and my own experience ... even the OS46 are a bit Overkill for 11/12 lbs ...

BUT the Seagull manual states 45 to 55 2 Strokes or 72 to 82 4 strokes. that looks enormous to me ...

The videos available on the web show more a " fighter " speed flight than a " looking scale " quiet flight ...

So I'm really tempted to use the smallest available, the OS 56 Alpha. The Saitos 62 being quite the same in terms of output ( but not sound ... )

Could you give me your thoughts about that ??? ( looks you choosed the OS 46 ...)

Alain

c_nut

Hi Alain,

I'm expecting the 46's to be more than enough, I had them in a dual ace before and mostly flew around at half throttle or less.

The Comanche will be a bit heavier than the dual ace but I still think the suggested power is more than enough. Perhaps the higher power is suggested to be able to maintain flight on a single engine? Although given the risks, I would prefer to treat one engine out as a dead stick rather than playing with the devil hahahahahaha.

Why not try it with the 52's, you can always maiden it without the cowls, then if you do need to change the engines, you haven't cut into the fibreglass so it wont matter

I'm sticking with my 46's simply because I already have them and I am adding a bit of extra weight with the retracts and lighting. I also prefer to be a bit overpowered, you can always pull the stick back for scale flight but it's nice to have something there if it's needed

Would love some more details on your DIY lighting, I love the system I bought but I would be keen on building my own system next time.

Craig

PS - mine are Thunder Tiger 46 Pro's not OS

Acetronics

Thanks for the reply, Craig

I'll keep on using the 56's ... as I do not have 52s ...
With Bill's twinsync, there won't be any BIG dissimetry problems ... so over powering could bring more problems than solve any ...

I'll be happy to send you the lighting system files ( PCB + Program + Proteus sim file ) ... if you give me a mail address ( Not enough room here ... [&o] )

I got the leds from http://www.befr.ebay.be/itm/5-PCs-10...item564560a6c3 and http://stores.befr.ebay.be/TopBright...4.l1513&_pgn=1

the tail beacon led being a Luxeon 5W Side Emitting LXHL-DW03 ( Halas out of production now ... but equivalents available )

Alain

c_nut

Hey Alain,

hmmmm, typo on the 52's best you stick with the 56's hahahahaha

PM'd my email address to you

Craig

Acetronics

Craig,

I received your mail address, but ...
My mail comes back with " undelivered message returned back to sender " ...

Alain

Acetronics

Should be fine with a "point" ...

c_nut

yeah, those underscores will get in the way of a good point hahahahaha...... (I mixed up two email addresses)

c_nut

Today started with engine mounting, the manual calls for 118mm from the firewall to the prop hub face but with a test fit and measure, I felt that the clearance between the cowling and the spinner backplate was going to be a bit more than I wanted so I decide that I would mount mine at 117mm.

Measuring, holding, clamping, drilling engine mounts can often be a juggle. Over the years I have changed the way I do this and now it's a simple exercise performed directly on the workbench rather than in the airframe.

As you can see in the pictures, I clamp the engine to the engine mount and use a spinner backplate to give me a larger platform to measure to. Set your vernier to the desired measurement and simply measure from the work surface to the spinner backplate. Adjust the engine as necessary and if you check the measurement on both sides, you are also ensuring that your engine is mounted square to the firewall. Since most models have the required thrust angles set in the firewall, a square mount here is exactly what you want.

My clamps are a bit clumsy and I have to put them over two of the mounting holes, so I just drill the two I can see, then fasten the engine with those two screws or bolts before drilling the other two.

The result is good squarely mounted engine at exactly the right distance from the firewall

c_nut

The rest of my day was spent on the age old dilemma of cowlings....... To cut or not to cut.......

I could get the cowlings over the engines (muffler and carburettor removed) and could also get them centred on the prop shaft but this resulted in the trailing edge of the cowling being off centred.

It was close.......... sooooo close......... I desperately wanted to avoid cutting an opening for the engine head, soooooo, first task was to draw a centre line from the prop shaft to the trailing edge of the wing (easily done with a string line). This marks the point that the trailing edge of the cowling needs to centre while the prop shaft and a spinner backplate is all that is needed to centre the front.

I found that the two uppermost cooling fins on the engine head were the only thing that was stopping me from lining up the way i wanted. Now know a few people will cringe at this, but I decided to remove the two cooling fins to achieve the clean finish I wanted. With the engine fully closed in, there will be plenty of air coming in through the openings up front and there is a good sized outlet on the underside of the cowl so I expect that a couple of missing fins wont cause any problems and I can always buy a couple of new heads if the engines find their way into another airframe.

You will notice from the photos that I have also decided to use all four of the ply boxes for mounting the cowls. The manual calls for one on the cylinder side of the nacelle but fails to point out if this is the same for both left and right wing. After some test fitting, I found that neither position was perfect so I grabbed the two extra boxes from the electric conversion nacelles and found that there is room for both. Now with a little extra cladding and sanding, I will be able to shape them to perfectly match the cowl width. I will then use a single screw on each side to secure, rather than two screws on one side. This will give me far better control over the precise positioning and centring on the spinner backplate

Next......... Hmmmmmm, now I know I need to cut a hole to get the glow driver on, I wonder if I should use the onboard glow driver option on the twinsync ??????? I debated this thought for almost an hour before deciding that YES, it would be kind of cool and convenient as a simple rocking of the magnet past the sensor (ie rotate the prop) automatically fires up the glow driver. So that will mean prime engines before switching on the transmitter and receiver, then just flip the prop to start......... yep, lets do it

This introduces yet another set of wires. There will now be 9 plugs to connect on each wing!!!!!!
Yep, NINE!!!!! (Nav Light, Strobe Light, 2 x Landing Lights, flap, aileron, throttle, RPM sensor, Glow driver) Perhaps I'll find some nice multi connectors to minimise this but I'm not overly worried about it right now.

In the photo, you can see the glow driver board mounted on the right side of the nacelle, it has a small red LED to show it's functioning and by mounting in this position, I will still be able to observe the LED through the front of the cowl

Tomorrow I will visit the electronics shop to pick up a couple of batteries for the glow drivers. I will mount the battery behind throttle servo, one in each nacelle and will wire in a charging socket so that the battery can be recharged in place.

Th Last picture is a nice little silicon glow plug boot I found at my local hobby store, this will protrude about 5mm through the cowl but its a nice neat boot so It should look OK and certainly no worse than a hole for a plug driver.