Common Deviations / Modifications from Plans

skyfrog · #1 11-26-2007, 02:37 PM

I was wondering if anyone has compiled a list of modifications or deviations from the plans that are popular for the RV-9A or other models.

I would like to anticipate these modifications and perhaps make notations in the plans as I get to those sections. I don't mean engine or prop choices, but instead modifications from the plans that make life easier for the builder, or provide for future enhancements.

For example, adding the quick release pins to the canopy sounds like a modification I would want. I also understand there are: air intake choices; running wire considerations (XM antenna); built in ER tanks; detachable instrument panel; etc.

Eventually I'd like to have a list modifications to consider by section. For example:

Canopy:
- Quick Release pins for emergency.
- Tip-Up/Slider combination mod

Wings:
- Extend tank by 3 ribs for more fuel capacity
- Leading edge extened tank

Thanks

Jeff R · #2 11-26-2007, 03:27 PM

Some things I can think of off the top of my head:

1. Drill 3/4" holes in the wing ribs for conduit.

2. Enlarge the tooling holes next to the 7/16" holes in the left wing ribs that are used for the pitot line, so you can use it to run an AOA line with snap bushings. I didn't think of that until I had the top skins on, and it took a really long drill bit to enlarge the existing tooling hole. If you are sure you won't use a combined pitot/AOA probe (i.e. Dynon), you can skip this.

3. Drill a hole in each fuel tank end plate for a possible fuel return, needed for some fuel injection systems. You can always plug it if you don't use it.

That is all I can think of right now for the tail and wing kits.

Of course, the other list we need is a list of those extra things we should order with each kit. There are some good responses to my post on what to get with the fuselage kit, but it would be nice to compile such lists for every kit.

pierre smith · #3 11-27-2007, 07:10 AM

John,
The slider/tip up is my next move. Luggage is a bear to get in and out.
Why the extended range tanks? Does your back/butt not hurt after three hours?

If you're considering really long cross-countries, OK. My buddy, Robby Knox, has the ER tanks in his -8 and one of the reasons was to be able to go to Bermuda and have nearly an hour reserve. What's yours?

Regards,

Bob Axsom · #4 11-27-2007, 08:03 AM

If you plan to travel Extended range tanks are a extremely beneficial addition. The stock tanks are way too small for IFR travel where missed approach at the planned destination plus flight to the alternate airport plus 45 minutes of fuel reserve are required. Even with 17 gallons of additional fuel any real trip (to California, Florida or New York from Arkansas) requires one or two refueling stops. Fueling stops require time far in excess of that required to pump gas in the tanks. Fly around weather capability is greatly enhanced. I recently made some 3" span racing wingtips for races of 300 miles or less but for normal operations I remount the tip tanks and stock tips with all the required lighting.

Bob Axsom

skyfrog · #5 11-27-2007, 08:06 AM

Quote:

Originally Posted by pierre smith

If you're considering really long cross-countries, OK.

Yes, that's my reason also. I probably would make 2-3 hour, biologically necessitated stops, on a long trip anyway, but it?s nice to have a large reserve in case of unforeseen circumstances. Also, a trip to the Bahamas would be nice, stopping at various islands that have no fuel.

However, I just got to see the insides of a partially completed wing yesterday (Thanks Jeff). Now I?m not so inclined to go with ER tanks in the wings at this point. Perhaps a removable tank in the baggage area would be better.

Anyway, I am just looking for various options so that I can plan ahead and do some additional research. I realized that I hadn?t looked ahead in the plans to see where I might need to deviate from the plans for some feature, like the slider/tip-up. If I just blindly follow the plan, I might not be able to retrofit a feature later.

Thanks,

John Edwards

Kahuna · #6 11-27-2007, 08:30 AM

Here is a good reason to build bigger tanks & stick in some port. oxygen.
http://flightaware.com/live/flight/N687MS
That trip aint happening on 42gal.
My grandma lives in Hobbs. I go there often.
KHOB - KLZU the other day. 17k'. Fun!
Best,

rfinch · #7 11-27-2007, 09:18 AM

Quote:

Originally Posted by skyfrog

However, I just got to see the insides of a partially completed wing yesterday (Thanks Jeff). Now I?m not so inclined to go with ER tanks in the wings at this point. Perhaps a removable tank in the baggage area would be better.

John, could you explain this? I too think the stock tanks are smallish.

skyfrog · #8 11-27-2007, 09:35 AM

Quote:

Originally Posted by rfinch

John, could you explain this? I too think the stock tanks are smallish.

The current tanks are inboard, where the main spar in strongest. Extending the tank by three ribs looks like an acceptable plan, however extending them the full length of the leading edge may require structural consideration.

Instead, I read that someone placed fiberglass tanks in the baggage area. I assume this is similar to other baggage tanks I have seen where the tank has a small pump feeding fuel into one of the main tanks (at 8gph). With some design effort, I think one could make them removable in case you need the room.

airguy · #9 11-27-2007, 10:40 AM

Total weight distribution of the tank should be considered, as should total wing bending moment. Fuselage tanks will increase the bending moment at the wing root while pulling G's (or in turbulence), thus decreasing your available margin - not to mention playing with your CG while depleting the fuselage tank. Wing tanks eliminate the fuel-induced bending moment entirely, since the weight is common with the lift. Weight is weight - you still have to carry it - but there are advantages (and disadvantages) to WHERE you carry it.

kentb · #10 11-27-2007, 10:51 AM

Quote:

Originally Posted by skyfrog

The current tanks are inboard, where the main spar in strongest. Extending the tank by three ribs looks like an acceptable plan, however extending them the full length of the leading edge may require structural consideration.

Instead, I read that someone placed fiberglass tanks in the baggage area. I assume this is similar to other baggage tanks I have seen where the tank has a small pump feeding fuel into one of the main tanks (at 8gph). With some design effort, I think one could make them removable in case you need the room.

I would put the fuel anywhere to make a ferry flight. But if it is to be a permanent part of the plane, I would put it in the wing.

Number one reason is in an accident (tip-over or anything else) I would not want to be sharing the cabin with a lot of fuel.

The second reason to go with the wing placement of the fuel is that it would be closer to the CG. Using up the fuel would not cause much shift in the CG.

The third reason that I would go with the wing is 'the wing carries the plane not the plane carrying the wing'. You would be placing the extra weight of the fuel in the structure that is doing the lifting. This would reduce the required strength of the wing to fuse attachment. Not that I would recommend leaving out some of the bolts.

The down side on the extra fuel in the wing (besides a little weight gain for the plane) would be increased turning moment. I don't think that in a 9 or 10 this should effect the enjoyment of the airplane.

I didn't add ER to my 9A, but have seen others have done this. I think that adding two extra bays on the leading edge is probably the easiest way to go.

Kent