Effects of carrying weight in float compartment?

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Skylark60
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Effects of carrying weight in float compartment?

Post by Skylark60 » Sun Jun 02, 2019 10:46 am

I am about to cross the country in a Cessna 175 /w O-470 and Aqua 2400's

I do not have much range so I have to carry access fuel. Rather than carry jerry cans in the cabin ( what I am use to) I decided to carry 40L in each float compartment

What effect will this have on handling, carrying weight below the centre-line of the air-frame?

I have installed a plywood floor in the compartments that rest on the rivets / ribs.

I could really use advice from experienced pilots on this
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TeePeeCreeper
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Re: Effects of carrying weight in float compartment?

Post by TeePeeCreeper » Sun Jun 02, 2019 11:47 am

Hi Skylark60,

I used to do this routinely with my C180.

Same set up with reinforced plywood bottoms. No differences on handling although I did find it harder to get up on the step at max take-off weight when the outside temperature was over 20 degrees.

Have fun and shoot me a PM with your planned route!

Regards,
TPC
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North Shore
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Re: Effects of carrying weight in float compartment?

Post by North Shore » Sun Jun 02, 2019 11:55 am

Well, I've never carried fuel in the floats on a 172/180/185, but I have carried it in an Otter, and seen it done on the Beav, and I've carried a variety of boats and canoes on 185s and Otters...Balance the load out laterally, and place it in the centre compartments, and you'll be good. Assuming that your float rig weighs ~1200lbs, the extra ~120lbs of gas is only 10%..
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Heliian
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Re: Effects of carrying weight in float compartment?

Post by Heliian » Sun Jun 02, 2019 2:25 pm

All depends what the floats are rated for. There would be structural limitations for the added weight and also buoyancy safety factors. It's a popular practice and floats used to get filled with jerries, those loads are now reduced to comply with weight and balance and other limitations.
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Skylark60
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Re: Effects of carrying weight in float compartment?

Post by Skylark60 » Sun Jun 02, 2019 3:57 pm

I believe the floats are rated for 2600+ however the air-frame engine combo is limited to 2450, I done a weight and balance and can keep it inside the parameters of the design.

I don't know how the weight in the floats (below the center line of the airframe) will behave. I also reached out to the manufacturer of the float for input as well.

Thanks for your input
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PilotDAR
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Re: Effects of carrying weight in float compartment?

Post by PilotDAR » Mon Jun 03, 2019 5:32 pm

As long as you conform to the W&B limits for the plane, you'll be fine. Don't overload it. The greater portion of the approved weight below the fuselage is not a problem, consider how much weight is down there with a set of amphibs. Or, those pilots who forget to pump out their floats!
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Heliian
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Re: Effects of carrying weight in float compartment?

Post by Heliian » Tue Jun 04, 2019 9:43 am

PilotDAR wrote:
Mon Jun 03, 2019 5:32 pm
As long as you conform to the W&B limits for the plane, you'll be fine. Don't overload it. The greater portion of the approved weight below the fuselage is not a problem, consider how much weight is down there with a set of amphibs. Or, those pilots who forget to pump out their floats!
There are also structural limitations for each compartment.
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PilotDAR
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Re: Effects of carrying weight in float compartment?

Post by PilotDAR » Wed Jun 05, 2019 4:34 am

There are also structural limitations for each compartment.
Yes, there may be, and they must be followed.

There maybe a placard near the compartment, and a reference in the limitations section of the flight manual supplement for the float installation on the plane. Many float installations lack both.

Of course, a pilot must abide by all limitations, and is responsible for determining them (you can't ignore just because the placard was worn off). But commonly, floats and skis get installed on airplanes without such data being conveyed with a placard or FMS. It's a gap in our system that sometimes floats and skis don't have much documentation accompanying them to the next plane.

I did check back that the Aerocet 3400 amphibs I had installed on my friend's 182 do have an FMS, and a 100 pound limitation per compartment.

I opine that for many light floatplanes, particularly amphibs, that this is a self solving problem, as the airplane does not have enough excess payload to allow the plane to carry enough to overload the float compartments!
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J31
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Re: Effects of carrying weight in float compartment?

Post by J31 » Wed Jun 12, 2019 7:37 pm

Good advice given above.

I did several seasons hauling fuel and other items all over the Arctic in the float compartments of a Cessna 185 amphibian.

My experience is that it WILL take longer to get on the step and WILL take a longer water run than if you put the same weight in the cabin. Up to 20% longer takeoff runs depending on weights and density altitude.

Carry only items that do not mater if they get wet. There is always a bit of water in the floats and everything will be wet.

I would reinforce...DO NOT OVERLOAD the float compartments. DO NOT put fish in the float compartments unless you know EXACTLY how much they weight!

80 liters of fuel in the floats (176 lbs) might make it very doggy at gross weight getting off the water. Be very careful of short takeoff areas.
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Heliian
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Re: Effects of carrying weight in float compartment?

Post by Heliian » Thu Jun 13, 2019 4:01 am

J31 wrote:
Wed Jun 12, 2019 7:37 pm
DO NOT put fish in the float compartments unless you know EXACTLY how much they weight!
Lol. There must be a story behind this.
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shimmydampner
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Re: Effects of carrying weight in float compartment?

Post by shimmydampner » Tue Jun 18, 2019 11:47 am

I don't have any experience with a 175, but spent years flying other Cessnas and de Havillands with all manner of junk in the floats and in my opinion, you're over thinking it. I never noticed a discernable difference. If you're within your max takeoff weight for wherever you're operating, you shouldn't have a problem related to stuff in the floats.
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chicken hawk
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Re: Effects of carrying weight in float compartment?

Post by chicken hawk » Thu Jun 27, 2019 7:00 am

I agree, you are overthinking it. When you put weight into the aircraft, the floats will displace water and it will sit lower. It doesn’t matter where the weight is located, 200lbs is 200lbs. The more of the float that is in the water, the longer it will take to get up on step. You will find that loading the float compartments will keep your c of g forward, as opposed to having it aft in the cargo area. This is where you will notice the difference in handling characteristics.

Keep the load in the compartments within the limitations for the floats and don’t load anything pointy or sharp. Most importantly don’t put anything corrosive in there, a battery, case of pop, etc.
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