This picture shows modifications to second cylinder head to ensure better cooling of rear cylinder in the free air cooled version. Dick Rake, I will keep your suggestions in mind if I find the free-air-cooled engine they are suggesting, has any issues with cooling.
Why not just go with a rotax 277 and eliminate all the headache of engine redesign. I know the 277 vibrates quite a bit more compared to a two cylinder engine but I guess that is the price to pay for saving weight and fuel burn. using lord engine mounts that has been suggested by george may cure that issue. If I wanted the smoothest engine possible and fuel burn wasn't a priority I would go with the rotax 447. This is assuming money isn't a issue, I don't think a used rotax 447 would cost that much more than a kawasaki but I could be wrong.
Why not just go with a rotax 277 and eliminate all the headache of engine redesign. I know the 277 vibrates quite a bit more compared to a two cylinder engine but I guess that is the price to pay for saving weight and fuel burn. using lord engine mounts that has been suggested by george may cure that issue. If I wanted the smoothest engine possible and fuel burn wasn't a priority I would go with the rotax 447. This is assuming money isn't a issue, I don't think a used rotax 447 would cost that much more than a kawasaki but I could be wrong.
Jeff, Thanks for sharing your thoughts on engine choice. I appreciate it.
Unfortunately I already bought a Kawasaki 340 along with a 3 blade composite prop, from JBird recently. Presently it is just sitting in the garage. I will come to engine installation after about 6 weeks.
I too was initially leaning towards a Rotax 277 or Hirth F33. The elevation here is around 5400 ft, so I thought the 4 or 5 extra ponies that a Kawasaki 340 delivers when compared to these 2 engines, may help to offset the power loss from the thinner air. Even though the k340 weighs 10-12 lbs more than Rotax 277, overall performance will still be better than a R277. Also fuel burn is not that big an issue for me.
I discussed with JBird whether I should go for the k440, and they said the 340 is smoother than the K440, mainly because the displacement is less, so unless I really need the additional power, K340 is an adequate motor for an ultralight. Frankly I have no idea how it is going to turn out. I am just hoping it works out OK.
I used ceconite to cover the flat deck behind the pilot (under the curved deck) to store small assorted stuff like my jacket or my back pack, a first-aid box and a small tool kit. Total weight probably 1.5 to 2 oz. Planning to use a stretch cargo net in front edge of compartment to keep things from sliding forward.
I made a similar layout for my panel, cut the holes, and only now I realized that it had stated somewhere in the instructions for CHT / EGT gauge that " Do not mount this instrument closer than 12 inches from a compass."
On my cut panel, the compass would come about 7 inches from the CHT/EGT gauge.
Now what ? 12 inches separation on a Max panel is doable, but does it make such a big difference ?
This happened partly because initially compass was not part of my panel layout, and I had made some rough mental layout on what will go where. Later when I added a compass my attention was focused on where to place it and in the bargain I forgot about this 12 inch limitation.
The problem is gauges which operate on magnetic mechanisms... this is why you have to calibrate the compass and have an error chart for correction. You can always check how much it swings the compass with power on and off.
Thanks Steve. Got it. I was concerned about the compass affecting the CHT/EGT readings. I think this gauge is more important to me as an ultralight operator than the compass. I will be mostly flying in the local area, so compass is of limited utility.
Keith, if you need to get your compass a bit further away, you could make a mount & position it on top of the instrument coaming. This is quite often done - I'm thinking of doing this myself. Then you have space in the panel to fit a ROC indicator or maybe a fuel gauge.
Bruce, thanks for the idea. I ran into some other issues on the panel, so had to remake the panel anyway.
In the new layout, I moved the CHT gauge and compass to opposite ends thus eliminating the interference issue. In attached pic, some work is still to be done like routing the tach wiring towards the back. But generally this third attempt at panel cutting came out OK. My hole cutting also got progressively neater with each panel.
But yes, I have also seen some other builders mounting the compass outside of panel.
Looks good, Keith. Just one more quick point that I learned the hard way on my panel. If you are mounting any electrical power switches (e.g. master switch, 'mag' switches) on the panel, do not tie the power leads into the same bundle as the CHT & EGT leads. I did this so I'd only have one penetration through the firewall, & my EGT's stopped working.
Turns out they are influenced by the current flowing in the switches on my panel, & the problem disappeared when I routed the power & instrument leads through firewall holes 12" apart.
Maybe this is common knowledge, but I didn't know it, & it took a while to suss the problem.
Bruce
Bruce, thanks for the info. I did not know the EGT readings will get affected when the probe cables are bundled with power cables. But now that you have confirmed it, I will avoid doing that. These sort of small tips / alerts do help.
Mine is a very inexpensive CHT/ EGT gauge. I do hope it gives reasonably accurate readings.
Since I have not updated this thread in quite a while, here is a short 2 minute video, that shows where the build is right now. ( The 2 blanks on the panel are for the kill switch, the smaller hole, and the key/starter switch, goes in the larger opening to the right.)
very nice build Keith. my 103 initially had a primer bulb like yours and luckily the valve in it locked up while I was taxing instead of on takeoff. the bulbs are not very reliable for an aircraft IMHO. I went back to a plunger primer like yours and that as all I needed to get my 277 started. fuel systems need to be as simple as possible. your tank and engine are close to the same level so the fuel will always be close to the carb. I did have a pulse pump installed. good luck on your build.
very nice build Keith. my 103 initially had a primer bulb like yours and luckily the valve in it locked up while I was taxing instead of on takeoff. the bulbs are not very reliable for an aircraft IMHO. I went back to a plunger primer like yours and that as all I needed to get my 277 started. fuel systems need to be as simple as possible. your tank and engine are close to the same level so the fuel will always be close to the carb. I did have a pulse pump installed. good luck on your build.
monte
Monte, Thanks for your feedback.
Since this is my first build, and I had no clue about how to rig up a fuel system, my installation is per schematic provided by engine vendor.
The only optional component is the quick start primer which comes at additional charge; all else comes standard with the engine. There is also a choke assembly, the control for which I plan to install on the left side wall along with the throttle.
The fuel lines are all packed on the forward right wall.
I asked them about installing a Facet pump in parallel and they said it is really not necessary.
Keith the filter should be installed between the tank and shutoff valve because any trash out of the tank can plug the valve. the probability of that happening is low but I believe in murphy's law when flying.
very nice build Keith. my 103 initially had a primer bulb like yours and luckily the valve in it locked up while I was taxing instead of on takeoff. the bulbs are not very reliable for an aircraft IMHO. I went back to a plunger primer like yours and that as all I needed to get my 277 started. fuel systems need to be as simple as possible. your tank and engine are close to the same level so the fuel will always be close to the carb. I did have a pulse pump installed. good luck on your build.
monte
Very wise advise, this isn't a boat! The primer system is all you really need, the fuel bulb only fills up the carb float bowl. Your build looks good keith, I have been around flying my whole life and assume this is common knowledge. I may come off as a dick at times but its because I want you to succeed!
Maybe I missed it, but do you have a low spot sump (water and debris drain) (low spot collector with poppet valve or gascolator)? Very important in my opinion during preflight, plus makes periodic fuel drains quite easy (removing old gas or inspections etc). Agree also with the primer bulb removal.
Fabulous workmanship. Cant wait to see the final product.
Will it have electric start? If it has electric start, then you shouldn't need a primer system, just a choke or enrichment circuit. I have no problem starting my 503 in the winter, the enrichment circuit / choke does the trick.
Maybe I missed it, but do you have a low spot sump (water and debris drain) (low spot collector with poppet valve or gascolator)? Very important in my opinion during preflight, plus makes periodic fuel drains quite easy (removing old gas or inspections etc). Agree also with the primer bulb removal.
Thanks. I may add a gascolator at a later date, if the need comes up. There is space just under the engine compartment to install the gascolator. That location is going to be the lowest point in my fuel lines, the other fuel lines are at a higher level. But many builders are flying Maxes without a gascolator with no major issues, so I will not install it unless I really have to. ( Weight is also an issue, mine is Pt 103 )
ULBuilder had earlier posted a link to a nice article on fuel system management. I read through that before designing this system.
The plunger system weighs only 1 oz. The additional 1/8 hose weighs another oz. Total is 2 oz. The plunger squirts fuel to the outlet pipe of the carburetor directly into the space near the inlet manifold. It totally bypasses the carb. It is a standby arrangement to be used when normal cranking is failing to fire up the engine. I do not have to use it for each start. The weight penalty is so negligible, I decided to keep it as a tool in my bag for a rainy day.
Also I would like to get this project into the air before long.Though all safety and structural aspects have to be mandatorily completed before first flight, I will continue to work on many cosmetic aspects / and other enhancements even after I start flying. I want it to be a "fly while you continue to build" process.
you are on the right mindset, keith keep the weight down for now until were flying and then we can turn our little birdie into a porsche. vs lets pour money into something that will never fly as good or be as fun to fly while dumping all your money to airport and faa fees while that makes you feel good when you could have been out flying
Keith the filter should be installed between the tank and shutoff valve because any trash out of the tank can plug the valve. the probability of that happening is low but I believe in murphy's law when flying.
monte
Hmm. So you are saying the only way to change the filter is to drain the tank first?
You are golden, keith, god has created a plan! No need to over complicate the plan.
The engine vendor gave me drawings for wiring each independent circuit - one circuit for kill switch, one for starter motor and key switch etc.
I put all together and made this spaghetti maze.
There are many experienced builders here, so I am hoping they can take a look, and if something totally does not look right, they can give me a heads up.
It might be wise to put a couple of fuses into the system. I've got an electric start on one of my microlights, so I fitted fuses between the voltage regulator and battery (though it probably doesn't need it), and between the ignition switch and the starter switch. I've also got a strobe on the aircraft and fitted a fuse in the circuit for that as well. If I remember correctly I fitted a 15 amp fuse between the vr and battery, either a 15 amp or a 10 amp between the ignition and starter switches (can't remember which), and a 5 amp in the strobe circuit. So far all are working well.
Thanks, Bob. Yes I plan to to include a couple fuses, though I have not figured out which is the most suitable / accessible place for them.
I also plan to not mount a key switch, instead use a simple push switch to start the engine. As most of the current flows through the solenoid, a simple 5Amp push switch should work for starting the motor. I am separately mounting a master switch for all power, which will be close to the battery. The kill switch is on the left of the panel and start button on the right. I also need to put a safety cover for the kill switch.
Your basic circuit is reasonable but electrical systems are interesting...
Really need multiple diagrams to really tell the story. What you have is fine for a circuit diagram but I suspect any geographical information is misleading. For example is the battery really behind the cockpit as suggested by the diagram? With this in mind I would not even show the firewall on this diagram, that would be a different diagram.
That said the geography of the electrical system is fairly important. Location of components will drive length of wires and that can impact wire sizing, voltage loss, and weight. Copper may be a good conductor but it is a heavier metal too. An interesting example here is your 16G wires from battery to VR and also to starter switch... is this really run as two wires or one wire with a daisy chain of connections?
As already noted circuit protection is important: A) Circuit protection needs to be as close to the current source as possible. This minimizes the amount of unprotected circuit. B) Protection devices need to consider the failure mode. Fuses are very simple but once blown they are faulted until replacement. Circuit breakers are the next step up since they can be reset. And finally at the top of the food chain here are self-reset circuit breakers. Use these where a fault is a very bad thing and you might want some partial operation instead of total failure. C) The powerless wire is inherently safe. In particular since your solenoid appears to be separate and a complete break in the high power cable you want this to be right next to the battery. This removes power from the high power battery lead which may carry currents above what common protection devices can handle and thus be unprotected.
There are charts online for wire sizes and current carrying capacity. Your 16G is reasonable and the 8G *may* be reasonable for the starter, but I would double check that size for the starter. Note that wire capacity is usually derated for bundled wires because most capacity charts are based on temperature of the wire rather than voltage drop. And a single wire can radiate thermal energy faster than a wire in a bundle (which is also picking up thermal energy from adjacent wires). Recommended wire sizes increase as the run gets longer to minimize voltage drop, so that 8G might be ok if it is one foot long but insufficient for 4 feet. And don't forget to add the ground path in the total wire path for voltage drop
And lastly power wires between battery and "alternator" are quite interesting. Which way does current flow there? They should be circuit protected too but where? One approach is to protect on the end with the highest current source (battery) and then use wire large enough to handle the maximum current provided by the other end. This way if they short the battery will disconnect and the wire will survive the full current provided from alternator.
Some of this may not be *quite* as critical in a wooden non-conductive airframe than it is in a metal conductor airframe
Steve, Thanks for taking the time to review my wiring schematic and offer your comments, which are deeply appreciated.
I totally agree that the starter solenoid should move closer to the battery, to avoid a long wire of about 5 feet ( coming from the battery) staying energized all through the flight.
Yes, as of now I have planned to keep the 12V battery just behind the seat to the right corner just ahead of Station 4. Some people keep the fuel pump / gascolator etc at this location, but my fuel lines are all plumbed ahead of the cockpit.
The diagram does actually indicate the location of various components. This way, I actually know what length of wire is involved for each circuit. Since it closely corresponds to the physical layout, it helps me keep track of various wires. However, all my wiring is going under the seat from the battery to the left wall, and then going forward to the firewall along the bottom of the left wall of the cockpit.
I have a standby location for the battery in the tail, in case I experience W & B issues. ( I have glued a 1/8 ply cross piece at the bottom, just under the horizontal stabilizer). But at 2.4 lbs, my battery cannot offset serious discrepancies in W & B. That location will also add weight, as the harness travels a longer distance. So I am hoping the cockpit location for battery works out ok for W & B.
I have not decided whether to install the VR/rectifier. Reason being, I am planning to use 12 V supply only for starting the motor. I have no other frills like strobe etc - all for the sake of keeping weight down. The only optional item is the electric starter, which has added about 6 lbs ( 3.2 lbs for starter motor and 2.4 lbs for lithium battery, and a few ounces for extra wiring that was needed). To allow for this slight extravagance in weight addition, I may have saved about 8 to 10 lbs in my paint job. So the build will still hopefully comply with FAR. Pt 103. A fully charged lithium battery should be able to provide at least 3 to 4 starts without re-charging, so why not just charge it on the ground in between flights and totally do away with the VR / rectifier.
I found all the other information in your post really useful. Thanks again for your suggestions and help.
Most of your weight comes from the engine and your instruments. If you want to make part 103 weight you need a light two stroke engine. A wood tennessee prop, Little to no instruments, and plastic wheels. being 103 legal will also make your airplane fly sporty, which always fun.
My engine weighs 44 lbs and delivers 32 HP. Just 5 lbs more than a Rotax 277 that is fan cooled. The instruments with panel and bracket / mount are 3.03 lbs. ( The CHT / EGT probes and pitot and static lines are extra. )
More than the engine, the re-drive and exhaust pipe are the major weight generating components. My redrive is 14 lbs and exhaust/muffler is 13 lbs. These two, together with the prop, are nearly as heavy as the engine itself.
Please see attached weight / HP chart for commonly used engines:
I was just virtue signalling to future 103 pilots. I thought your engine choice was good, just be aware if your kill switch wire becomes ungrounded your engine will die
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