Today's Message Index:
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1. 08:40 AM - Re: Plumbing in some extra fuel capacity (David Jones)
2. 01:22 PM - Re: Plumbing in some extra fuel capacity (Kelly McMullen)
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| Subject: | Re: Plumbing in some extra fuel capacity |
How about having your injectors matched flowed to save around 2 gallons per hour.
Your temp will go down and your range will go up. You will not change your
load capacity.
Sent from my iPad
> On Mar 4, 2019, at 9:27 PM, Kelly McMullen <kellym@aviating.com> wrote:
>
>
> A few thoughts as to extra tankage. Traditional methods have been to either add
to the wing capacity, or put an additional tank in the baggage compartment.
One advantage of the baggage compartment is that the weight can be determined
with great accuracy, and it is a safer, easier place to add the fuel. I know
that for most loading up to 150 lbs works for c.g. Apparently Vans later clarified
that the limit was supposed to be 100 lbs. Easy enough to do a tank for 100
lbs...allow 5-10 lbs for the tankage, with 90 lbs or 15 gal fuel. 20 gal baggage
compartment tanks are very common in other aircraft and allow adjusting
fuel for rearmost allowable cg for max speed. Much more than 20 gal is going to
suggest need for baffling and puncture resistance, as well as cg issues. It
may be possible to do a 15 gal in baggage and 15 gal in rear seat area, if you
want to be assured 6 hr plus minimal reserves.
>
> Lets put a little reality into the range needs. You can do 170-175 kts on 13
gph at any altitude that you can achieve that fuel flow while LOP..generally it
will be below 8500 and higher than normal cruise rpm.
> You can do 160-165 on about 11 gph LOP, and 150-155 on 10 gph.
> Take the later, which will get you 5 hours with one hour reserve, while going
750 nm, on stock fuel. Go fast mode gets you 4 hrs with 8 gal reserve..bare minimum
in my book. That gets you 680 nm. An extra 15 gal would get you 850 nm
with 10 gal reserve, in 5 hours.
> Now if you want to go a bit faster, you can operate ROP with about 1.5 gph more
fuel flow, and may close to 180 kts. You would need the extra 15 gal tank to
go 4 hours with 15 gal reserve, giving you a 720 nm range.
> Oh, I would suggest you need relief tube or equivalent to consistently go 4-5
hours non-stop without having issues with dehydration.
> In summary, you can easily get 750 nm range with stock tanks by slowing down
a little. Sticking to LOP and adding 15 gal tank will get you up to about 850
nm range without slowing noticeably, or over 950 by slowing to 150kts. That would
require sitting for 6.5 hours without relief.
> You can do two comfortable legs of 3 to 3.5 hours at 160 for reasonable speed
and economy to cover 1000nm. With 30 min for refuel, relief, snacks, that is
7 hours, vs 6.5 to do it non-stop with additional tank.
> Not arguing that one answer is better for one method over the other, just trying
to quantify the alternatives. I think going beyond 6.5 hours at one sitting
is moving into the territory of long range ferry flights that use special gear
and techniques, where water leaves no options.
>
> What ever you do, you want to consider failure analysis for your plumbing. If
the plan is to pump all the aux fuel into one tank, your fuel selector becomes
critical, with 60% or more of your fuel being dependent on being able to switch
to that tank. Which side of the plane do you want that extra 100-200 lbs of
fuel, for lateral trim?
> What if transfer pump fails? You probably recall the Cirrus that had to ditch
about 100nm from Hawaii, because something in the transfer process failed and
wasn't detected until beyond turn back distance.
> Going above a wide spread fog layer might as well be the same as over ocean.
> Sure, I would like an extra 15 to 20 gal capacity, but I haven't found not having
it to be particularly limiting.
>
>> On 3/4/2019 3:48 PM, Carl Froehlich wrote:
>> Interesting timing, I just discussed this with another RV-10 builder earlier
today. Some thoughts:
>
>> My thinking is that 99+% of the time having more than the five hours of gas
will not be needed, so the ferry tank will spend most of its life on the shelf
in the hangar. Make it easy to get in and out of the plane.
>>
>> For the RV-10 you lose one or both back seats depending on ferry tank size,
but the added weight of the fuel translates to not carrying four people.
>> Carl
>> On Mar 4, 2019, at 4:03 PM, Kent Ogden <ogdenk@upstate.edu <mailto:ogdenk@upstate.edu>> wrote:
>
>
>
Message 2
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| Subject: | Re: Plumbing in some extra fuel capacity |
You don't want to flow match the injectors per se. You want the
cylinders to all peak at nearly the same mixture. Similar but not the
same. You still won't save any fuel unless you operate LOP, which above
altitude where you can achieve desired power, will cost you a little
speed. It is also the lean of peak operation that lets the cylinders run
cooler. Matching mixture is what lets you run LOP.
On 3/5/2019 9:38 AM, David Jones wrote:
>
> How about having your injectors matched flowed to save around 2 gallons per hour.
Your temp will go down and your range will go up. You will not change your
load capacity.
>
> Sent from my iPad
>
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