Is homebuilding right for me?

[SportyPilot]

This will be my first time home building an aircraft, and looking through the many kit aircrafts, I've settled oin the Vans RV-12. I've settled on the RV-12 because I like it's easy to assemble design and the fact that Vans now offer a Skyview panel.

However, I have no prior experience in building an aircraft, and I don't really plan on building the RV-12 as an E-LSA. Mainly because 1.) Vans has no plan to make a FWF kit for the 912iS, and I'd like to have a fuel injected engine in my airplane & 2.) I'd like to build and put in this (https://picasaweb.google.com/117081108891056780334/SEATBACKFUELTANK?authuser=0&authkey=Gv1sRgCLnX4YDy0PuVaQ&feat=directlink) fuel tank instead of the one that comes with the RV-12. Mainly because I think it's a better design.

However, I don't have any real experience in building an aircraft, or any kind of metal work TBH. I've helped my dad build his Factory Five Cobra, but that's about it. So I'm doubting my actual ability when it comes to building a fully functional aircraft. *laughs*.

Any advice or help would be appreciated.

[Todd copeland]

Go for it, but think carefully through any changes from the design. You don't have to have the building experience, just the ability to read, the determination to see it through, and the foresight to take the project one page at a time. Too many builders get stopped before they start because they look at all the boxes and trays and manuals and are overwhelmed before they even start. You build it one page at a time.

[Neil]

If you are going to build one of Van's designs the best advice is to build it as Van's designed it. While I am not familiar with all the Vans designs I think they all carry the fuel in the wings. That way the fuel is not in the cockpit with you in the event of an accident. I'm baffled (pun intended) as to how you think sitting on the tank is a better design.

[steveinindy]

I'd like to build and put in this (https://picasaweb.google.com/117081108891056780334/SEATBACKFUELTANK?authuser=0&authkey=Gv1sRgCLnX4YDy0PuVaQ&feat=directlink) fuel tank instead of the one that comes with the RV-12. Mainly because I think it's a better design.

What makes you think that is a better design? The only advice I can offer is that a fuel tank in the cockpit is not the best idea unless you want to run the distinct possibility of being bathed in fuel in a crash scenario. When it comes to fuel tanks and fuel lines, you want to keep them as far as possible/practical from the cockpit (routing them through the wing box and under the floor of the cockpit is slightly better than running a thin plastic line through the cockpit itself) and protect them from damage. Generally, the fewer sharp (non rounded) corners a tank has and the fewer welds or seams it involves the better. Rounded corners spread out the hydraulic force involved in a crash and minimizing the number of seams or welds gives fewer weak spots for the tank to be burst by the fuel slamming around inside of it as the aircraft comes to an more abrupt stop than normal.


So I'm doubting my actual ability when it comes to building a fully functional aircraft. *laughs*.

At least you're honest. Most folks given support and assistance can build an aircraft of some sort.

Folks who doubt their abilities scare me a lot less than those among us who think they have it all figured out. Usually those folks wind up like this: http://rvnewsletter.blogspot.com/2009/06/dan-lloyd-crash.html http://rvnewsletter.blogspot.com/2007/11/what-killed-dan-lloyd.html (BTW, before anyone gets up my butt about using Dan as an example, he was someone I considered a friend)

The first rule of homebuilding should be don't assume that "Eh, it works" is a good approach. Other good rules:
1. If someone doesn't look right, ask someone with knowledge and experience. Having one or the other is good, having both is best.
2. If you have a question, ask.
3. If something breaks, replace it completely. Some of the folks in this hobby want to push their build as far as possible to prove something to themselves and/or others and a few of us (Dan included) pay with their lives.
4. A build is not something to rush. Never set a deadline for completion of anything. It's better to be sitting in the shop than to be sitting in the morgue or in the file cabinet in which I keep the autopsy reports and crash investigation records that form a large part of the basis for my research.
5. The more people you get to look at your work before it is sealed up the better. Bribe the local EAA chapter(s) members with food if necessary.
6. Don't take a criticism of your build personally if the person can give you an engineering, practical or mechanical reason for the criticism.

[steveinindy]

That way the fuel is not in the cockpit with you in the event of an accident.

Honestly, an integral fuel tank ("wet wings") is only a very modest improvement in terms of safety given how frequently the wings are damaged in the course of a crash.

[Flyfalcons]

If you are going to build one of Van's designs the best advice is to build it as Van's designed it. While I am not familiar with all the Vans designs I think they all carry the fuel in the wings. That way the fuel is not in the cockpit with you in the event of an accident. I'm baffled (pun intended) as to how you think sitting on the tank is a better design.

The -12 is designed with a fuel tank that sits in the baggage area.

[SportyPilot]

The fuel tank in the baggage area is a RV12 design. My problem with it is that it takes up half of the baggage area. Also, as for the fuel injected engine, so far the 912iS seems to be the perfect candidate. The RV12 already takes a Rotax 912 engine, so I'm hoping that only minor adjustment in the Foward Fire Wall will be needed.

[steveinindy]

My problem with it is that it takes up half of the baggage area

Then the solution is to find something equivalent that doesn't increase the risk to the pilot and passenger. Honestly, in something designed to be a light sport aircraft, you probably don't need to be carrying that much baggage to begin with. Opening up the baggage compartment further just seems (at first glance) to increase the possibility that a pilot might chance putting more weight back there than the aircraft can tolerate. If the design does not work for you as is, then you might be better off looking for another aircraft to build rather than trying to push the fuel tank into the cockpit unless you have the ability to design a very, very resilient fuel tank (along the lines of what the US Army used to drop its burn mortality rate in helicopter crashes to effectively zero from something like 40-50%). We have a design that hopefully will be able to do do that in an LSA and other GA aircraft but it's still at least couple of years away from being ready to market as we are still trying to test out it against the various standards that are established by the military and by our own investigations into real world tests.

[Auburntsts]

The fuel tank in the baggage area is a RV12 design. My problem with it is that it takes up half of the baggage area. Also, as for the fuel injected engine, so far the 912iS seems to be the perfect candidate. The RV12 already takes a Rotax 912 engine, so I'm hoping that only minor adjustment in the Foward Fire Wall will be needed.

Looks like you're in for some major cowl work. Here's what Van's posted on FaceBook when the 912iS was announced:

"We´d been aware of this project for some time, and the concept is exciting; but there are several reasons that, in its present form, the engine is not suitable for the RV-12.

Weight: The Rotax press release says the f.i. version weighs 6 kilograms more than the carbureted version. For the metrically-challenged, that´s 13.2 lbs - a significant increase and difficult to absorb, given the RV-12´s forward-cabin configuration and legally limited gross weight.

Size: The photos accompanying the Rotax press release make it quite clear that the engine will not fit in the RV-12 cowl. Re-designing the cowl and making new molds would be an expensive and time-consuming project, increasing the cost of the kits.

Cost: We haven´t seen final numbers, but the new engine is likely to be priced significantly more than the one we use."

Since you're new to building, I'd hold off on commiting to the engine right now. Get some build time under your belt first. You might find your appetite for making major mods diminished once you get your hands dirty. I can tell you that even simple mods can sometimes add major time to the build. The quickest way to flight is to build per the plans so you need to think long and hard about what your main goal is here. There's absolutely nothing wrong with experimenting and making the design your own, just understand the consequences of those decisions.

[Auburntsts]

While I am not familiar with all the Vans designs I think they all carry the fuel in the wings. That way the fuel is not in the cockpit with you in the event of an accident.

The RV-12's wings are removeable in just a few minutes without the use of tools, hence the fuselage tank. Van took some heat for the design but it doesn't appear to have hurt sales any.

[Neil]

I've worked on or counseled builders with RV 4, 6, 7, 8, and 9s. Guess I shouldn't have assumed a design standard. Still, first time builder with no building background and modified design is seldom a good mix.

[Eric Witherspoon]

The quickest way to flight is to build per the plans so you need to think long and hard about what your main goal is here.

The quickest way to flight is to find a flying one already on Barnstormers and write a big check...:thumbsup:

You have to build because you want to build. Though I agree with Auburn - if the goal is eventually to fly DO NOT VARY FROM THE PLANS. If you're still keen on the idea of the modified tank - I agree with you, the packaging looks to make better use of space, and the cg change with fuel burn may be reduced (though it may be more forward in the range to start with - not good if you are attempting to pair that with a 13+ pound heavier engine) - but keep an eye on that guy as you go through the years of building. See if that tank cracks. See if it leaks. See if other people build it. Best yet, see if the factory takes it on as an option - sometimes they see stuff like this and make their own version (with a good bit more engineering behind it).

Though I also agree with Steve - in a payload-limited airplane, there's not much point to more "baggage space" if there's no weight capacity to go with it. (Depending on what you really want to do, this might not be the right airplane...)

The whole discussion of fuselage tank vs. not is not relevant to this thread. The RV-12 is what it is. They made a LOT of compromises for quick-remove wings. To that end, you may not want to pay for all those compromises - pitot through the gearbox, surface contacts for the wing lights, handles in the wing tips, fancy fittings where other aircraft simply use bolts for wing attach - and probably others involving the position of the seats/spar (and obviously the fuel tank) - there's other designs out there that haven't done so much in the direction of quick-remove wings - though no doubt Van's has a very complete, thought-out, well made kit with a lot of experience behind it.

[steveinindy]

The quickest way to flight is to find a flying one already on Barnstormers and write a big check..

It also seems to be the quickest way to pick up someone else's modified design that they don't tell you about. No offense to my fellow builders out there but if I'm going to buy an already completed airplane, it sure as heck isn't going to be an experimental built by someone I don't know. If I just want to fly, I'll go get a used Cessna, Piper or Aeronca. If I want an experimental- which I do- I will build it. :)

[Auburntsts]

It also seems to be the quickest way to pick up someone else's modified design that they don't tell you about. No offense to my fellow builders out there but if I'm going to buy an already completed airplane, it sure as heck isn't going to be an experimental built by someone I don't know. If I just want to fly, I'll go get a used Cessna, Piper or Aeronca. If I want an experimental- which I do- I will build it. :)

Personal preference--some folks just aren't inclinded to build but they don't want a 40 year old airplane either. My original quote assumed that the OP wanted to build. The age old addage is if you want to build, build, if you want to fly, buy. Looking to build as a cheap way to get into ownership is fraut with fautly logic IMO. Sure, when comparing a new E-AB to a new factory built of similar capability and performance, the E-AB can be significantly cheaper, but only if you discount the opportunity costs associated with building. Folks buy used E-AB because they want something that the Piper's, Cessna's, Mooney's, etc of the world can't provide. For a used aircraft like an RV, determining the quality of the build and it's airworthiness is no different than a Cessna. A rivets a rivet regardless of who set it. Any A&P can look at an RV and provide an assessement. Now move into the glass world and I'm more inclined to agree with you, yet Lancairs and Glasairs change hands all the time. I think in the case of glass, it's more importrant to get the aircraft inspected by an expert on the model and conrtruction techniques used rather than just any old A&P.

[Frank Giger]

However, I don't have any real experience in building an aircraft, or any kind of metal work TBH. I've helped my dad build his Factory Five Cobra, but that's about it. So I'm doubting my actual ability when it comes to building a fully functional aircraft. *laughs*.

Don't be concerned about this in the least bit - the skills required can be learned by anyone with the motivation and the patience to learn them.

I didn't know nothin' about building no airplanes when I started mine - never put in a rivet, bent a piece of metal, etc. - but there are loads of people waiting to help you. It starts with the right local EAA chapter, has a couple of the EAA training sessions in it, and includes the huge sky armada of RV builders and their groups all over the country.

I'd add another call not to modify the plans very far without A LOT of research and review by others with the know. Not to say that the plans are perfect, but the compromises and decisions were made for good reasons.

I'll also add a few items to Steve's homebuilder list:

1) Budget the build and have the money up front, or a solid way of obtaining it on the way. Then add ten percent.
2) If you don't have a tool set, take twenty percent of the kit price as a starting guide.
3) I'll put a modification on Steve's notion of not having timeline requirements. Set them as motivation to keep working on the project, but use them as guides, not deadlines. Somethings will take longer than you think, but then again some things will take less.
4) If you have a "significant other" make sure they have buy-in, or at least agreement. Having to break the news that you just discovered your drill's RPMs were set too high and you just ruined a forty-five dollar bit and have to buy another should be met with a sigh rather than a tirade.
5) Perfection is the enemy of performance. A solid part that meets spec but has a minor flaw that doesn't impact its reliability or usefullness is just that - don't needlessly reproduce parts over and over again.

[prasmussen]

Hey, experiment! It's what we do. You are going to learn a lot, build and rebuild until you own that airplane. That is why first flights are such a trip. I would recommend a Sport Aviation Workshop if they come close to where you live. And don't forget to include your family in the workshop maybe. Best of luck!

[steveinindy]

For a used aircraft like an RV, determining the quality of the build and it's airworthiness is no different than a Cessna. A rivets a rivet regardless of who set it. Any A&P can look at an RV and provide an assessement.

I'll agree, although I've seen LOTS of experimental aircraft where there are gross deviations from the original design. If this is done in a way that isn't obvious the person doing them didn't know what they were doing (as an example, one crashed aircraft that I was given the chance to examine the wreckage of that had multiple mis-drilled holes and other signs that the builder just plain had little in the way of mechanical skill and even less in the common sense that would make you replace such parts that are damaged), an A&P who isn't intimately familiar with a particular design may not pick up on something important.

[Bob H]

The original question was whether someone with no aircraft experience should build an RV-12 and make mods. My answer is that you can build that particular plane with little experience because all holes are predrilled and the fastening is easy and the wiring is already done with connectors; all the thought processes are done for you. But I would not recommend doing any aircraft mods if you admittedly don't have the judgement to know what you are doing. As far as an injected 912 is concerned, the cost and weight is more than carbed engine and the carbed engine works fine so unless there is some reason currently undisclosed, the 912S is the engine of choice. Remember that the RV-12 is certificated to be built exactly as the factory specified without changes or mods. It is not like a standard experimental which requires 40 hrs of flyoff; it only requires 5 hrs flyoff because no changes allowed to original design.
If you want to get into aircraft construction, get smart and start taking builder courses thru EAA workshops and work with experienced builders to understand the basic technology. Flying in a plane you built is not like building a car where you pull over if something stops functioning.

[Tony_Fletcher]

Folks who doubt their abilities scare me a lot less than those among us who think they have it all figured out. Usually those folks wind up like this: http://rvnewsletter.blogspot.com/2009/06/dan-lloyd-crash.htmlWhat a tragic story. Rushing to get to Oshkosh. Unbelievable.

[Auburntsts]

.... Remember that the RV-12 is certificated to be built exactly as the factory specified without changes or mods. It is not like a standard experimental which requires 40 hrs of flyoff; it only requires 5 hrs flyoff because no changes allowed to original design.
If you want to get into aircraft construction, get smart and start taking builder courses thru EAA workshops and work with experienced builders to understand the basic technology. Flying in a plane you built is not like building a car where you pull over if something stops functioning.

Bob, that's only true if you go the E-LSA certification route. However, the RV-12 can also be built and certified as E-AB with its associated 25 or 40 hour Phase I and no requirement to match exactly the S-LSA the design is based on. IOW the builder is free to mod from the get go if they opt to build E-AB.

[steveinindy]

some folks just aren't inclinded to build but they don't want a 40 year old airplane either

As opposed to what?
RV-3 1972
RV-4 1979
RV-6 1986
Questair Venture 1987
Long EZ 1979
Vari EZ 1975
Europa XS 1992
Pietenpol 1928

In other words, let's not try to use that argument when most of the designs people build at just as old as the "40 year old spam cans" we like to pick at.


What a tragic story. Rushing to get to Oshkosh. Unbelievable.

What makes it even more tragic is the number of people who tried to get him to stop being in such a dead set hurry (myself included). Dan's a perfect example of how self-confidence is a double-edged sword in this hobby that we must at all costs know when to put back into the scabbard.


Bob, that's only true if you go the E-LSA certification route. However, the RV-12 can also be built and certified as E-AB with its associated 25 or 40 hour Phase I and no requirement to match exactly the S-LSA the design is based on. IOW the builder is free to mod from the get go if they opt to build E-AB.

The only change I would recommend with good conscience is to improve the roll cage around the pilots (that is to say, actually put one in the aircraft), seats with taller backs or headrests and get away from a front-hinged canopy.

[Auburntsts]

As opposed to what?
RV-3 1972
RV-4 1979
RV-6 1986
Questair Venture 1987
Long EZ 1979
Vari EZ 1975
Europa XS 1992
Pietenpol 1928

In other words, let's not try to use that argument when most of the designs people build at just as old as the "40 year old spam cans" we like to pick at.

I'm not talking design age. I'm talking actual age of airframes on the used market and comparing apples to apples (ie new standard certified vs. new E-AB airframes) vice apples to oranges (ie 1978 Sky Borer with 3500TT vs a 2012 I Built-it with 0TT). The point I was trying to get across is some, like myself, prefer new to used. Sure I could get a used BO for a lot cheaper than what I'm sinking into my RV-10, but I don't want a plane that's as old as I am. Absolutety nothing wrong with BOs that old, but it's just not me, and for a lot less than a new BO I'm getting a brand new airframe that I assembled to exactly my wants which has intangible value to me outside of the raw value of the kit and compontents.

[steveinindy]

The point I was trying to get across is some, like myself, prefer new to used.

Outside of the hardcore vintage junkies, I'd say you'd be hard pressed to find someone who doesn't look at it that way. That said, I apologize. I run into a lot of people who seem to think that the experimental designs themselves are newer and therefore necessarily better. Pardon me, I'm going to go finish removing my foot from my mouth. LOL


lot less than a new BO I'm getting a brand new airframe that I assembled to exactly my wants which has intangible value to me outside of the raw value of the kit and compontents.

Likewise. There is simply nothing on the market- either as plans, a kit or a commercially completed aircraft- that meets my requirements so I decided to design and build something that meets those desires.

[Auburntsts]

Steve, it's all good!

[CarlOrton]

Sorry for the thread creep. I'm just finishing my Sonex; will be taking it to the airport RSN. In the back of my head, along with some "help" from friends, is that I should be able to do first flight, make adjustments, and get my 40 hrs flown off in plenty of time for AirVenture 2012. The Dan Lloyd link (yes, I read it all) will forever be lodged in my brain as how NOT to rush things.

Maybe I'll be ready for AirVenture 2012, but I really don't want to finish the 40 hrs on July 20th then set out on a long x-c. Thanks for posting the link. It resonated with me.

[SportyPilot]

The reason for the desire to have an Alternate engine in the RV12 beside the 912ULS, is that honestly, I want a fuel injected engine in the aircraft. I'd get a simpler engine (with dual carbs, they have to be timed right in order for it to work) and better GPH. Plus, no more carb icing. So really, my RV12 is going to have a EFI engine in it. It's just a matter of which one.

[BushCaddy]

Sporty, have you considered the UL Power engine? An RV 12 builder has paved the way...here:http://www.vansairforce.com/community/showthread.php?t=82678

and here:http://www.vansairforce.com/community/showthread.php?t=84495

I would not change the location of the fuel tank. Evryone who builds a plane (including me) thinks they need this, that or the other thing...then it turns out you rarely use that thing. I can almost guarantee you will rarely, if ever, need a larger baggage area.

Also, another complicating factor with a fuel injected engine is you will have to engineer in a fuel return line.

Lastly, you can build an airplane as long as you have common sense and know your way around basic household tools. There is no great level of skill needed. You can do it. What is needed is the will to finish, you need to be persistent. You also need the support of family, more than one divorce has ocurred and more than one plane never got built because family obligations take precedense. Customizing adds time and complications. I would build the plane with the carbed engine and leave the fuel tank in its current location.

[steveinindy]

You also need the support of family, more than one divorce has ocurred and more than one plane never got built because family obligations take precedense

Burt Rutan is fond of answering the question "How long does it take to build an airplane?" with "About one and a half marriages."

[Mike M]

I've settled on the RV-12 because I like it's easy to assemble design and the fact that Vans now offer a Skyview panel...I don't really plan on building the RV-12 as an E-LSA....like to have a fuel injected engine in my airplane...like to build and put in this (https://picasaweb.google.com/117081108891056780334/SEATBACKFUELTANK?authuser=0&authkey=Gv1sRgCLnX4YDy0PuVaQ&feat=directlink) fuel tank...

so - what difference does it make that van's offers a skyview, a simple change, if you don't plan to build it as E-LSA? you plan to put in a different engine and different fuel tank, but you selected the design based on the PANEL configuration? wow.

you did look at the RANS S-19, right? historically RANS has been very supportive of alternative engine installations. ok, so you looked at that and decided against it.

you're committed to going experimental/amateur built to gain freedom. does the fuel tank mod increase or decrease the empty weight? does the engine swap increase or decrease the empty weight? do you intend to keep the max gross below 1320lbs for LSA operations? if the answers are "increase" "increase" and "yes" then good luck to you on having a satisfactory LEGAL and SAFE useful load. because you'll be breaking new ground on engineering otherwise!

as to doing it, hey, why not, have fun. all it will cost is extra time and money. amounts unknown. your mileage may vary. but it CAN be done and you (or your checkbook) CAN do it.

[Bill Greenwood]

What is your want to have fuel injection, so much so that you want to use a different engine than the design? Is it just from a techno geek standpoint that is seems more modern? I doubt it you could tell the difference in flight between one and the other. The fuel injected engine may put out a little more power, but it is also likely to be harder to start when hot.

It is good that you are asking and seeking advice before plunging in. I am no homebuilding expert,but we did build a Starlite, with a Rotax carbureted 2 stroke engine. It didn't sound too good but ran just fine.

There were were 2 fatal accidents not long after the Starlite came out. This really hurt the designer and its following. Investigation of the wreckage showed that IN BOTH CASES THE BUILDER HAD ALTERED THE DESIGN, AND LEFT OUT A MAJOR STEP IN CONSTRUCTION, WHICH LED TO THE FAILURE IN THE AIR.
IT IS HARD TO BELIEVE, but the normal plane had a really nice piece of fir or spruce as the main spar. It was strong in the veritical plane, especially for aircraft that only weighed 254 lbs complete. But there was one hole in the middle of the inboard end of the spar, where a metal cap was inserted to hold the pin which held the wing on. So to prevent the force from spliting the spar from this hole, the entire inboard end of the spar was to be wrapped in about 6 or 8 layer of fiberglass and resin. That was no big deal, only took a couple of days.
But BELIVE IT OR NOT, ONE BUILDER TOTALLY IGNORED THIS AND OMITTED ALL THE GLASS WRAP. Of course the spar eventually split and flailed in flight. The designer could not believe that a builder would willingly do this, but it was very plain in the wreckage. It was like the builder wanted to play Russian roulette.
Where the tail spar slid into the fuselage, there was also some reinforcement in the design; can't remember if it was some glass wrap or not. This was more difficult as it was a tight fit. Anyway another builder first tried to do it the right way,but then when he had trouble getting the tail on, he did it is such a way that eliminated all the reinforcement. The designer himself, Marc Brown ?, was test flying this plane for the owner, at SUN N FUN when the tail came off. Marc successfully parachuted to safety. So much for those who think wearing a chute in a homebulit or experimental is foolish. Marc is perhaps 5'8", and slim so he could get a chute in ok. I am about 5'!0', not so slim,and it was a tight fit, but I sure wore a chute everytime in ours.

The lesson is don't change a design, especially a kit, without discussing it with the builder. This would be especialy true in Van's case, I think, since he isn't just s theory guy, he has had a lot of success over the years in a number of designs.
Now the builder, may not approve a change, maybe just from a liability standpoint, but at least give him a chance to consider the changes.

Good luck in whatever you build, go do it and get to flying.

By the way, the new SPORT AVIATION, issue has a story and a program where you go to the Glassair factory in Wash or Oregon, and at the end of 2 weeks you have an almost complete airplane. No pipe dream, folks have and are doing it. Only thing the model is not one of the sleek low wing ones, it is sort of a Cessna look alike, but still may be a good plane,and sure worth 2 weeks.

[Bill Greenwood]

Yeah, I'd be embarassed to be seen in one of those 40 year old (or 70 year old) designs. I sure hope no one gives me something so old fashioned like a Porsche 911 to drive or any of those WWII clunkers like a T-6, P-51, Spitfire, or B-25 to fly. They probably don't have a glass cockpit, fuel injection or even Bluetooth.

It would be worse than having a house that did not have granite counter tops, oh the shame of it.

Wouldn't it be great if some hot new genius designer, like Rutan came along with a new race design for Reno Unlimited? Maybe twin engines, twin fuselage, carbon fibre/glass and use modern auto engines which are so far advanced beyond those old, Pratt or Wright or Rolls clunkers.

It ought to be so easy to show those old guys in the 70 year old designs how it is done.

[steveinindy]

Plus, no more carb icing.

Three words: "Fuel induction icing"

A fuel injection system is not a magic bullet to the engine icing issue although it does reduce it significantly.

[steveinindy]

with a Rotax carbureted 2 stroke engine. It didn't sound too good but ran just fine

That's one of the big reasons I got away from ultralights. I dislike having an engine that sounds like it's dying. The other big reason was that I got tired of hitting bugs while in flight. After two cicadas to the face (on separate occasions), a bumblebee and a sparrow in the space of one summer, I came to dislike open cockpit flying. LOL


So much for those who think wearing a chute in a homebulit or experimental is foolish.

It's not foolish, but in a lot of designs, getting out of the aircraft is next to impossible, especially the canopy equipped varieties where it hinges to the front. Also, it has limited utility since most events leading to crashes happen at altitudes where you won't have time to get out of the aircraft let alone get the chute deployed. That said, I'll never knock someone for wanting to wear one. If I were just flying a single or two seater, personally I'd be talking to Martin-Baker.

[Mike M]

The fuel injected engine may put out a little more power, but it is also likely to be harder to start when hot.

the Rotax fuel injection is not the old reliable mechanical Bendix-style fuel injection that is admittedly sometimes problematic on some engines in some installations when the PIC tries to use the cold-start procedure on a hot engine. how many fuel-injected 2012 factory-made automobiles are harder to start when hot? i'm betting exactly that many Rotax 912iS engines will be harder to start when hot. old wives' tales probably don't apply to new technology. your mileage may vary.

[Bill Greenwood]

I am not sure what "old wives" or their "tales", you may be associated with. I am the PIC in my Bonaza and when hot I use the hot start procedure, that is boost pump on low, throttle closed and crank as you advance the throttle, no pre priming like on cold starts. In hot weather, the engine may start, but easily tend to die like vapor lock. I don't know the brand of injection system. I can read a start list and have been a pilot for about 30 years.

[Mike M]

I am not sure what "old wives" or their "tales", you may be associated with. I am the PIC in my Bonaza and when hot I use the hot start procedure, that is boost pump on low, throttle closed and crank as you advance the throttle, no pre priming like on cold starts. In hot weather, the engine may start, but easily tend to die like vapor lock. I don't know the brand of injection system. I can read a start list and have been a pilot for about 30 years. well, that explains it! i'm a lycoming kind of guy. you're a continental gentleman. my limited time in bonanzas and barons and t34b's and t41d's using continentals with bendix injectors (only a few hundred hours over the last 44 years) has been positive when using the published checklist procedures. sounds like your experience in Bonazas hasn't. guess our mileage did vary. maybe Bonazas don't use bendix systems? oh well. maybe when i have your experience, i'll know better.

[Bill Greenwood]

I owned and flew 2 Mooneys for over 10 years, with Lycoming, one carb, one injected. I don't recall much trouble with hot starts, but then it has been a long time.

I owned a T-34A for 10 years, and it had a non injected continental engine, O-470 with a sort of pressure carb, I think.
I have only a flight or two in the T-34 B, but I thought it was mostly the same engine as the A, carb instead of injected.

My Bonanza will start but easily die in hot weather if you turn off the boost pump right after a hot start.

[Mike M]

Bill, i apologize for being a smarty-pants but i couldn't resist. and you took the bait. nobody cares how much experience ANY individual has with aircraft mechanical fuel-injection systems because NONE of it applies here. NONE of the ENTIRE aviation community's experience with Bendix fuel injection applies to SportyPilot's questions. NONE. because the rotax in question has electronic fuel injection. totally different. we all have thousands of hours' experience with EFI in automobiles, and i'm betting not a single problem with hot starting. and that's what the 912iS has. EFI. so back on track. does the engine swap increase or decrease the empty weight? will that adversely affect the payload? it will cost extra time and money. amounts unknown. your mileage may vary. again, Bill, sorry for being impish.

[Dana]

...we all have thousands of hours' experience with EFI in automobiles, and i'm betting not a single problem with hot starting. and that's what the 912iS has. EFI...

The engine in my 280Z was EFI (Bosch L-Jetronic), and it often had problems hot starting. Granted, that was 1978 technology, but still...

I don't know, but I wouldn't be surprised if the hot starting problems I experienced (and which were common on that model car) were related to the implementation in that particular car. Other cars with L-Jetronic EFI might have no problems with hot starting, and that's my point... the variances in installation in different model aircraft (or even different builder's installations) could be an issue.

Then again, the good old carbureted A-65 in my T-Craft always had problems hot starting... on a hot summer day I could give myself heat exhaustion swinging the prop if I didn't let it cool for long enough before restarting.

[Mike M]

The engine in my 280Z was EFI (Bosch L-Jetronic), and it often had problems hot starting


i stand corrected.

[Joe LaMantia]

This is a Great Thread!

I'm not a builder, but I'll add my 2 cents worth of advice. Having taken the "Introductory to Homebuilding" course with Sportair at Oshkosh can you answer this question? "What is the mission of this project?".
Based on your opening statement, quoted below, I get the impression you've decided you want to be a builder first and foremost and want to start with something easy.

"This will be my first time home building an aircraft, and looking through the many kit aircrafts, I've settled oin the Vans RV-12. I've settled on the RV-12 because I like it's easy to assemble design and the fact that Vans now offer a Skyview panel".


Well, I have spent many hours looking at RV's and following Van's design and build philosophy. The RV-12 was designed for first time builders who wanted an LSA. People who have enough $ to buy a kit and want to fly this aircraft ASAP. It is designed to be easily built and meets the manufacturing standards for this segment. If you don't have a need for the LSA, (third-class medical) then your money is better spent on an RV-9/9A. The dollar difference when the whole project is completed will be minor and the aircraft performance will be "different" then the RV-12. You can have the fuel in the wings (where it is safer), without any modification or changes in the CG or structural integrity. As for engines you can mess with that up to 160HP and I think you'll find some fuel injected models with long flight records available. Yes this will burn more fuel, but if you don't need the LSA, is the lower fuel cost that big a deal?

If your really interested in building for the sake of building, then by all means take some Sportair workshops b/4 you start writing checks. Bill and Steve have given you some super advice, if you want to experiment get some hands-on experience b/4 you go out and screw around with an aircraft with a narrow CG range and a very light structure. One more thing, do you intend to sell this aircraft some day? If so, do you think you will be able to get more or less for "Experimental" version vs the factory E-LSA? Having said all this please answer the question, "What is my mission?", when I did that I found that for me flying a 40 year old "span can" is just fine.

Best of Luck on whatever you decide!

Joe
:cool:

[FlyingRon]

Looks to me your proposal is going to have definite CG problems. Adding 13 pounds to the FWF and moving the fuel weight forward are going to move the CG substantially forward.