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building "light"

Daver

Well Known Member
My wing kit just arrived.

Its all there & I'm excited to get started.

I've read here and other places to "build light".

I agree its a good idea.

So what can I do at this stage of construction to build light.

I'm going light on primer (nothing corrodes here in the desert - my 28 yo pickup has NO rust).

Anything else I can do?

Any recommendations to keep the weight down will be greatly appreciated!

Thanks!

Dave
 
Not much to be done on the wings, in terms of light. Installing the recommended motor is probably your best option at controlling weight. Composite prop would help too. Van is big on no interior, but I am just going to have to have grey leather!
 
Daver said:
......Any recommendations to keep the weight down will be greatly appreciated! Thanks! Dave
There is no one thing you can do to keep the weight down. Significant and overall weight savings are best accomplished by paying attention to all the little things during the course of construction. If you have a choice between using a #6 screw or a #8 screw...use the #6! Little things like using the shortest acceptable grip length fastener with a thin washer instead of a thick washer. Even smaller details like using dacron cord instead of common tie wraps to secure wire bundles. Awhile back, I added lightening holes to the interior ribs of the flaps...against the recommendation of more than a few people. However, I have a highly seasoned aerospace engineering friend with a DER credential who reviewed my plan, looked at the assembly, and convinced me that such a change would not alter flap strength in any appreciable way.

I routinely do something else to help keep weight down that is sure to raise a few eyebrows among a few but hey.......it's always worked for me with absolutely no problems. It is after all, my airplane and I sleep very well at night, thank you. Okay, here is my personally developed tip. You know those fiber/nylon insert AN365-1032 nuts that are called out to be used almost everywhere with AN bolts? I almost never use em. I use what we routinely used on the combat jet production line and go with MS210473 self locking nuts instead. For our purposes, these nuts are normally used firewall forward where fiber or nylon inserts are a no-no. In a side by side comparison, they weigh exactly half as much but......cost twice as much per nut. Admittedly, the newer kits contain far fewer bolts than the older kits do but nevertheless, just count up the total number of AN bolts that will eventually be installed throughout the airframe.

Van has refined the kits to such a degree that there are few things you can do to enhance the weight savings already built into the kits. Because of Van's foresight, genius and product quality, your contribution towards weight savings will be a dogged effort to save a gram here and a gram there.
 
Rick6a said:
I use what we routinely used on the combat jet production line and go with MS210473 self locking nuts instead.

Just for clarification, I think Rick may be referring to MS21043 nuts here; the slang term is "jap nuts". These are the stainless steel version; MS21042 is the alloy steel type, and he's right that they're used all over in military and commercial aircraft.
 
Thanks for the quick replys. This forum is a great resource!

I guess I'll stay on my diet & loose a few lbs that way :D

Dave
 
Keep it light

There are a couple of good articles in the "24 years of the RVator" on weight reduction techniques. Also exercise and diet...
 
Battery weight

Use an Odessey battery and save pounds, not just grams. Stay away from CS props. Find someone who knows how to paint. REALLY knows how to paint. Lots of weigh difference between just enough to get a good finish and almost enough to run. I couldn't do it so I hired someone. I'll bet it saved 6-10 pounds.

Bob Kelly, complete painted RV-9A at 1054 lb
 
Some sound advice and good tips there on weight saving. However, the easiest weight saving of all is not what you take out, but what you don't put in. Extra do-dads, sound deadening, leather seats, nav lights, landing lights, anything other than the basics....
It is hard to resist adding things - 'improvements' - as you go, but ask yourself one question ...do you need it ? or 'will this improve performance ?
If you can answer this then it will be easy to keep the weight off....

Martin in Oz
 
Glass vs. steam?

Mornin' all,
While we're on the subject, has any of you converted from a full six-pack panel to glass and measured the weight savings, if any?

Dave, you will have to have night lights if you plan on much night flight, otherwise leave all the lights off. Same goes for VFR only. Don't add IFR stuff if you're not gonna fly IFR. As was pointed out already, a plush, padded side panel and baggage area adds weight. Balance that with just how spartan the interior can be to suit you. Paint adds a good bit of weight but do you want to always spend half a day or more polishing?

A composite prop saves a bunch of weight and a pile of money as well but you have to either give up some takeoff and climb performance if you pitch it for max speed (as we did) or give up a few mph cruise if you opt for less pitch and better takeoff and climb. Bear in mind though, even with a max speed prop you can still climb near 2000 FPM :D and take off in around 600'

Regards,
 
What I am trying

I have decided the plane doesnt fly without a pilot so I am working on loosing about 30 pounds. It might sound dumb and simple but just think about it if you are a little over weight. It makes lots of difference on performance when the plane is light.

Jim
RV6
Burlington Iowa
 
Pierre, I haven't done this (as I went straight to glass) but I know that GRT Sport weighs 2.8lbs..... let's call it 3 lbs with wires and magnetometer.... that should be less than the six-pack combined.. right?


pierre smith said:
Mornin' all,
While we're on the subject, has any of you converted from a full six-pack panel to glass and measured the weight savings, if any?


Regards,
 
Glass - no contest on weight

Radomir said:
Pierre, I haven't done this (as I went straight to glass) but I know that GRT Sport weighs 2.8lbs..... let's call it 3 lbs with wires and magnetometer.... that should be less than the six-pack combined.. right?

RC Allen lists their vacuum gyros (AH - DG) at 3 lbs. each

Altimeters/Airspeed/VSI are all about 1/2 lb each

TC somewhere in between, say 2 lbs...

This gives the 6 pack at 9.5 lbs.

Then you have to add the vacuum pump (3 lbs - RAPCO), hoses and regulator....

The Dynon D-100 is similar to the above one at 3 lbs. with the internal back-up battery.

It's absolutely No Contest on the weight..... :D

gil in Tucson

was detailing this last night but my IE7 hung up.... :rolleyes:
 
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Every little bit helps

There are a few choices with the wing, mostly lighting and pitot, as well as priming internal parts.

Every little bit helps, but the big weight items are the prop, engine and than accessories (panel, light, interior and exterior)

From tip to tail:

Prop: wood (RV-7's suffer from tail heaviness so metal props not such a liability CG wise, RV-9? I don't know?)

Engine: (I)O320, with RV-9, heavier 360's are not really an approved option.

Engine instrumentation: CHT, EGT on all cylinders and Fuel Flow is optional. I think its probably weight worth spending, but many planes have flown for many decades (cessna, piper, etc) with out these items monitored. Leaving it off saves, weight, cost and build time. How about just one or two CHT/EGT channels. Flying GA planes in the 80's I can't remember many that had more than one CHT or EGT if any. We seemed to get along fine with out engine monitors. With that said with a well balanced Fuel Injection (FI) and careful leaning, you can run Lean of Peak (LOP), saving some gas. A 4x4 channel engine monitor is key to getting safe LOP operations. If you are carburated than LOP is pretty hard to impossible to get regardless of engine instruments, so standard roughness or 75-150F ROP ops works as well as it always has, therefore a single CHT/EGT may be good enough. Again I love the 4x4 engine monitor and its a great tool.

Cowl: Finishings and filling pin holes, read about it, search these archives for threads. The idea is to fill with min weight. You can add lots of weight with excessive filler.

Lighting: Nav lights, strobes, landing light...... LED Nav lights could save some weight. For night two all in one (nav/strobe/nav) wing tip units mounted externally is probably best. If you go with lots of lights, landing light and tail light/strobe, you may need a larger alternator than a smaller (lighter) one. Each light adds wiring, fuse/CB and switch for each light cuircuit. Also running wire out to wing tips and tail is not totally trivial. Landing lights are not needed even at night. How much night are you going to do if any? Do you need two landing lights or one or none?

Heated Pitot: My "Pet Peeve" on VFR planes with VFR pilots. This one item adds big cost and yes weight. Heavy current demand adds heavy wires run out the wings and demands a bigger alternator. If you can hold back from this popular "must have" you can save some weight. Do your really need it, even if you plan on occasional IFR?

Panel & Electrical: Some obvious weight to be saved with autopilots, dual EFIS and panel mounted entertainment systems. I am a circuit breaker (CB) man, but the popular use of an automotive plastic fuse block and blade fuses looks lighter than a bank of CB's. On the other hand you don't NEED a fuse or CB for each item.

Builders today tend to put in 20-30 separate fuse's or CB's in. You can gang several items on one fuse or CB if the total load does not exceed the capacity of the fuse or CB and the wire is protected. The key is the wire gage, which is what you are protecting, not the individual device. For example 10 amp protection for sevral devices, all with 18 awg feed wire, is fine, for example, five 2-amp items or three 3 amp items. Look at Vans planes, they have a hand full of CB's for the whole plane and that is it. The last few Van prototypes I saw actually had a few CB's or a few fuses mounted visibly in the panel. Van's factory planes tend to be very light weight when compared to average builder weights and this is one reason, simple, minimal, functional. Bottom line, the popular electrical design books like Aeroelectic (by Bob Nuckolls) tend to be very involved and promote dual battery, dual alternators, multiple buses, diodes and more switches. There is good stuff here but KISS - Keep It Simple Stupid, saves weight. If you have an all electric aircraft for IFR flight or an electrically depended engine, than redundancy of the electrical system is needed, so the weight of two batteries or alternators may be justified. If you are a day / occasional night VFR pilot with a magneto fired, mechanical fuel pump Lyc with basic instruments, than you don't need that Boeing 747 electrical system. Is it ok to put 30 fuses in that VFR plane? Yes, but it adds weight.​
Vacuum system: Pretty much gone the way of the DoDo bird. Leaving it out will save lots of weight. Of course that puts the emphasis on the electrical system with electrically dependant flight and engine instruments.

Interior: Bare, painted upholstered, except covered seat cushions. It does not have to be horrible or crude, just spartan.

Paint and Priming: If you prime all parts inside and out, it will add weight. That is a fact. How how much weight is debatable, but it does add weight. If you do prime use "wash primer" which is translucent. In fact its reported widely that Van does not PRIME his factory planes, at least in the past. Van just etched, alodine and painted the exterior. Why? Weight. If you leave it un-primed and unpainted you can save $4000-$8000 and up to 30 lbs. How long will it last? Depends on many factors but probably will out live you.

Everything: Every little nylon tie wrap, nut, bolt, washer, clamp, bracket adds weight. Consider using electrical lace tape verses nylon ties.


Now some weight is good for your comfort, safety (fire extinguisher) or type of operation (big dual landing lights for night ops off of dark private fields). One basic thing is build it per plans. Anything you add or change will usually add one or more of the following: time, money and almost always weight.
 
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Harvey said:
However, the easiest weight saving of all is not what you take out, but what you don't put in. Extra do-dads, sound deadening, leather seats, nav lights, landing lights, anything other than the basics....
Martin in Oz

But Martin, the do-dads are the fun parts. I luuuurv do-dads. Stuff the weight. :)
 
gmcjetpilot said:
Builders today tend to put in 20-30 separate fuse's or CB's in. You can gang several items on one fuse or CB if the total load does not exceed the capacity of the fuse or CB and the wire is protected. The key is the wire gage, which is what you are protecting, not the individual device. For example 10 amp protection for sevral devices, all with 18 awg feed wire, is fine, for example, five 2-amp items or three 3 amp items. Look at Vans planes, they have a hand full of CB's for the whole plane and that is it. The last few Van prototypes I saw actually had a few CB's or a few fuses mounted visibly in the panel...​
Very good point George.

I elected to put in "20-30 separate" CB's, one for each item in the plane and I was surprised at how much $400 worth of CB's and switches weighed.

The quickest way to build a light plane is to start with a light kit. Van's will be very happy to tell you the lightest combination is a tip-up tail dragger. Add to that a small engine and a composite prop and you can get down to (and below) 1,000 lbs empty. At least in a -9 you can. I know of one O-290-D2 powered -9 that came in at 998 lbs and a -9A w/ vacuum and the same engine that tipped the scales at 1020 lbs.

Just more food for thought.
 
building light

Just because your plane is going together in a dry acid reduced climate, does not mean you should not prime. I'm going to be using MFP varish, enamel, enamel hardener, et throughout the process. For all interior surfaces and between sheets, I'll use thin varnish with the hardener applied wet with a brush on the spot. most of the objects that we own, were not built for us individually. They're legacies from something else. Leaving out corrosion protection is overdesigning.
 
My -6 is primed entirely and weighs in at 1028 lbs with paint. Dual coms, dual GPS, O-320, Catto 3-blade.
Oh yea, Tip-up taildragger.
 
Just because your plane is going together in a dry acid reduced climate, does not mean you should not prime. I'm going to be using MFP varish, enamel, enamel hardener, et throughout the process. For all interior surfaces and between sheets, I'll use thin varnish with the hardener applied wet with a brush on the spot. most of the objects that we own, were not built for us individually. They're legacies from something else. Leaving out corrosion protection is overdesigning.
Empennage paint weight

Hi I need some guidance. I'm building a 9 and trying to keep the weight down, have read all the posts and really appreciate the valuable info.

I have a question on how much my paint weights, I am using single stage with a primer under and have finished the all the empennage components.

Is there any numbers available on the unpainted weight of the empennage pieces either assembled or free standing. I wanted to match the unpainted weight to my painted pieces and see how my paint coverage is working out and how much weight I have added.

I will use a FP light prop with the O-320 engine. So I figure because I will be light way up front I don't any extra empennage weight that would need to be offset. I plan on buying the lightest good quality tailwheel to help.

Thanks for any numbers, looking forward to seeing how I'm doing with trying to keep the painting light.

Steve in NH
 
When I first flew, my EW was 990 pounds. That was with no paint, interior by Rustolum (sp?), and an O-290.

It is now up to 1068 pounds, with two stage paint, fully primed, different panel, leather interior, auto pilot, and an O-360 w/ a Catto two bladed prop.

The baggage compartment is not carpeted, which is fine with me.

Just don't add all the options you see on this forum and you will be fine. For example, flap position sensors (you can see the flaps), etc. If an option requires solenoids, leave it off. They just add weight and complexity for little gain.
 
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And don't forget Mr. Rutan's old adage about aircraft add-ons; "Take the item in question and throw it up into the air. If it comes back down, it's too heavy."
 
There are a couple of good articles in the "24 years of the RVator" on weight reduction techniques. Also exercise and diet...

not you, but the "exercise and diet comment" reminds me of the 250# guy that spent an extra $3000 for a carbon frame bicycle to save two pounds.
 
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Daver,

My recipe for building light , use a stock Vans RV9A kit, no paint, no primer, light engine, no avionics redundancy , no cabin upholstery and everything installed as far forward as possible.

The biggest issue to worry about is the CG.
Most of the significant weight you can save is forward of the empty CG. ( Engine, Prop, starter, alt, mags as well as the Avionics, seats, seat belts, strobes, landing lights, antennas and so on annd so on...)

There is little you can remove aft of the empty CG. I have only Vans kit, an ELT and AP servo.

Paint is between 20 - 30 lbs for a RV9.

I finished at 980 lbs Fairings and seats included. However, I got bit by the aft CG devil. I had to add weight to the nose to improve to a useful empty CG. My final empty weight was 1005 lbs complete.

My CG battle is long and difficult, too long for here.

If you are serious about weight, start at the beginning and eliminate every part of an ounce from day one. I started with a project and many opportunities were already behind me. I did not know then the significance, at that time, of the missed opportunities.

If you are going to pursue this concept let me know, I can show you my scars and help you avoid some potholes.
 
As a point of interest, my -9A weighed in at 935Lbs sans gear fairings and oil. I'm expecting a ready-to-fly weight of 950Lbs give or take a couple.

This is with a Sensenich G/A prop, OX-340S, single Skyview and Xcom VHF, and polished with a couple of vinyl graphic stripes. A PlanePower FS-14B on the vacuum pad provides all the power I need, there's no lights, no landing light, no autopilot servos yet, but I do have 2-axis trim. The wires are run for the servos and lights as I figured I could afford that 1Lb to save heartache later! I made my own seat cushions and they probably weigh 3Lbs per side, but they're very comfy.

If you want a light RV, build it to plans and only to plans. Van did not design in any unnecessary weight. Trust me, you are not smarter than Van!
 
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