Engine or avionics, first?

Is there an advantage to either? Would love to hear arguments from those who have reached this stage in their build.

Engine

I did the engine first. The avionics continue to evolve rapidly, engines, not so much...

My vote is engine first—hold off on avionics as long as you can because the avionics industry evolves at a near light speed pace compared to engines which are static for all intents and purposes,

I did avionics first and wish I had held off. I’m happy with my panel but had I waited it would have been even better.

Definitely engine! The engine has been sitting here for my -8 project for years and Rhonda gives me **** about it every OSH. Life happens when you least expect it. I'm not at all concerned with it getting "out of date" or being "old tech"... Avionics is a whole different thing.

Buy the engine and prop at the last ?Van?s Show Special? that you can wait. Engine is required for cowl fit up.

Decide on the brand of avionics you want, then buy the mounting kits for the autopilot servos, pitot, ADHARS modules and such as these are much easier to do when fitting out the airframe. Buy all the rest of the avionics as the last step.

Carl

Carl Froehlich said:

Buy the engine and prop at the last ?Van?s Show Special? that you can wait. Engine is required for cowl fit up.

Decide on the brand of avionics you want, then buy the mounting kits for the autopilot servos, pitot, ADHARS modules and such as these are much easier to do when fitting out the airframe. Buy all the rest of the avionics as the last step.

Carl

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scard said:

Definitely engine! The engine has been sitting here for my -8 project for years and Rhonda gives me **** about it every OSH. Life happens when you least expect it. I'm not at all concerned with it getting "out of date" or being "old tech"... Avionics is a whole different thing.

Click to expand...

Auburntsts said:

My vote is engine first?hold off on avionics as long as you can because the avionics industry evolves at a near light speed pace compared to engines which are static for all intents and purposes,

I did avionics first and wish I had held off. I?m happy with my panel but had I waited it would have been even better.

Click to expand...

rocketman1988 said:

I did the engine first. The avionics continue to evolve rapidly, engines, not so much...

Click to expand...

Engine it is. Thanks to all!!!

I did both at the same time, but engine for sure would be first as mentioned.

A lot of the avionic wiring you can do without the high dollar items also. (lights, antenna's, etc.)

Decisions

You will be amazed (overwhelmed?) at the number interdependent decisions required FWF. Example fuel, exhaust, cables, low power vs heavy power conductors, cowl, baffle etc. Avionics positioning and wiring much more forgiving in my opinion.

I did it the other way around. And I would still do it this way. I am still happy with my avionics as there is Nothing really new since I bought them 2 years ago?

But I agree to the others that firewall forward is nearly endless with decisions etc..

Hi All,
Just a quick note on engines, please be careful of internal corrosion if it is going to be sitting around for a long time.
Rob.

Quick note on ordering a new engine. I ordered mine July 2018 and it will finally be delivered today. Planning plays a big role with the entire build.

For sure, engine first. So much to do once you get the engine that the avionics can wait a really long time. Your avionics decisions could change quite a bit depending on money, availability, tech etc (glass, no glass, combination, who knows?), but the general engine choices are pretty well defined and what you need to do once you get it (cowl, prop, controls, exhaust etc) are also pretty clear. I always seem to gravitate to doing the knowns first......

I'm building an RV-3B, the single-seater, and will be installing much of the avionics and wiring first. Here's why.

The fuselage is just so much easier to rotate now that the engine mount and landing gear is off. Pretty simple, I'm taking advantage of access while I have it.

I've chosen the brand and configuration and don't expect those to change much in the next two to four years. They might, though, and that's a risk. The big thing, though, is access - small fuselage and hard to squirm around inside.

I do have an engine but not the prop. I expect to order that when I've started the canopy, so it might be on hand when I need it to fit the cowl.

Dave

maintenance

David, don't forget that you will need to get into that stuff sometime down the road.

Oh, there's access - it's simply that access isn't all that fun.

Small airplane and all that.

Here's me on the work platforms, feet towards the firewall. Good view of my belly and elbows. The plywood piece later went away.



Dave

Dave,

With a little research & planning, you can do just about all the 'extremity' wiring without ever purchasing or even selecting any of the avionics. Label wires, pull a few extra to each location, and wait to install connectors until the avionics du jour are purchased. If the -3 fuselage is anything like the -4, the 'boot cowl' (forward top skin) can be attached with screws. I have better access to my 1990-era -4's avionics wiring than my still-under-construction tipup -7, even though the -7's the boot cowl is not yet installed.

If you're going bare bones on electronics, buying now is probably not a big deal, but if you're doing glass, autopilot, etc, you could waste hundred$, if not thousand$ buying now. ex: Several years ago, I bought a really nice used Trutrak 2 axis autopilot for less than half its new price at the time. Today, Trutrak will sell me a much improved version with more features for less than I paid for mine (purchased for 1/2 price) a few years ago. We're talking what looked like >$2k savings when I bought it, but I would have spent even less money, for more features, and gotten new instead of used, if I'd waited. That's just one piece of gear.

Charlie

Another vote for the engine first, but more importantly make sure you get everything down you possibly can before you hang the engine. If you build a regular setup this means that you can have many of your passthoughts drilled, firewall insulation in place etc. I even had my entire aircraft painted before I hung the engine. You can also precut and reinforce your panel/sub-panel early so you spend less time on your back later in the build. I purchased trays early from Stein, but left the avionics until later. You can also run conduit in the wings, center section, beneath the seats, down the aft fuselage etc. This will make running the wires far quicker in the future when you get onto the avionics. I wouldn't run the wires early, just put the conduit in place, as you may change your mind on the wiring requirements for the avionics during the engine install.
Once the engine is out of the sealed bag/desiccant, they say don't move the crank, however for things like fitting the cowl/propeller/spinner etc you can't help it. That's why I'm a big believer in keeping the humidity down inside the engine, using a dehumidifier circulating the crankcase air and desiccant plugs in the cylinders, as well as taping over every inlet/outlet possible. Details can be seen in the link below. I still run the dehumidifier whenever I am not flying the aircraft.
http://www.vansairforce.com/community/showthread.php?t=157922
Good luck.
Tom.
RV-7