View Full Version : Amphib Performance

03-10-2011, 07:11 PM
Looking at a couple different Amphib choices.

1) Super Bushmaster (extended Pacer) - 210hr Continental IO-360 - Clamar 2500 Amphibs - Gross Weight 2800lbs - Useful Load 865lbs

2) 185 Cyclone - Experimental 185 - 285hp Continental IO-520 - Clamar 3500 amphibs - Gross Weight 3400lbs - Useful Load 860lbs

3) Certified Cessna 180 - Edo 2790amphibs - 230hr (260hp??) - Gross weight ?? - usefull load 750lbs ????

My biggest concern is the aircraft will have to be operated off a grass, slightly rolling runway that is 2300' usable ...... and of course there is trees at one end and a transmission line 1000' from the other end. Which aircraft is gonna do the best job getting in and out "close to gross". Any comments out there for running amphibs off grass??

Anything is good info if it makes me think!!!
Thanks guys

bob turner
03-11-2011, 02:34 AM
I have very little experience with amphibs, but by measurement, a 150 Cub on wheels takes a shade over 200' to get airborne, and a 180 amphib Cub takes over 600'. That's on pavement with normal 8 knot winds down the runway.

03-11-2011, 07:42 AM

I have very little experience with the Clamar floats. I do have some experience with 2790's. ANY amphibious floats REALLY prefer pavement or at least a solid, smooth runway. Those nose gears are pretty tough, but they are also small and much more frail than the mains.

The thing I'd worry about on a grass strip would be things that are hard to see, like a gopher hole or other potential gotcha that could prang a nose wheel. The heavier the airplane, the more trouble you're apt to have with that sort of thing, because you'll have more weight on the gear.

A lot of the key to amphib performance on wheels is where the main gear is located. Don't know where that is with the Clamars, but it's fairly far aft with the 2790s, so it takes a bit of airflow to get the nose gear light.

Also, how solid is that runway after a rain? Any soft spot will cause problems. Depending on where you are, that may or may not be an issue.

Biggest issue is how smooth and consistent that runway is. And, frankly, I think 2300 feet with obstacles could be a problem for any of those airplanes if they were heavy on amphibs. And, you'll ALWAYS be heavy on amphibs.


03-11-2011, 04:00 PM
Thanks guys, the runway has a very hard base and no holes. It is a personal runway that is kept in great shape.
Does anyone out there have experience with amphibs on grass with some of the higher power higher weight aircraft??

Ron B.
03-11-2011, 04:47 PM
I have a Smith cub on amph., 180 hp , fixed pitch. I have 500 hrs now and most of that is on my grass strip. My strip is 2000' and very smooth. Other than spring ( I won't try as I don't us amph. winter and early spring) I'll easily get off at gross 2400lbs. I have a 20' power line on one end and a great approach on the other. The strip has a 20 plus foot slope . The power line end is the low end which is good.
Last summer I landed on another grass strip which I don't call smooth and I was observed landing by a Super Cub guru. As soon as I came to a stop he said did you see/feel that. I had no idea what he was talking about other than it was not a good landing in my opinion. He said my landing was not the problem it was the nose wheels castering. They were swinging 180 degrees rapidly. Because of his observations we inspected both nosewheels and both forks were bent.
With new forks we also installed anti shimmy kits. Now these made a very noticable difference landing on asphalt and I'm sure they will help prevent this problem from occuring again. I will still probably not land on that strip with amph.
Moral of the story depends on the strip conditions.

03-12-2011, 08:54 AM
I have a fair amount of amphib experience over the past nearly 50 years in both boats and floats. This has included operation on pavement, gravel and grass. I know nothing about Clamar floats other than what I see on their web site. A very important feature to have is a large nose wheel tire. Large in diameter and width. You need tire floatation on soft ground, grass and sandy beeches. When you apply full power to take off or to taxi on soft terrain the force is directed to the nose wheels driving them into the ground thus generating a lot of drag or preventing any movement at all. Another consideration is the suspension of the landing gear, both nose and main. It needs to be fluid not stiff legged. The Wipline, Montana and it appears the Aeroset amphibs are stiff legged. The EDOs and it appears the Clamar and Baumann have a fluid suspension which works very well on uneven surfaces making the airplane easier to handle during takeoff and landing. Look at pictures of the different nose gears. The soft riding ones are articulated from the front bulkhead with a vertically mounted shock strut. The hard stiff legged ones have a nearly vertical flat spring strut that has no vertical motion shock absorption only spring back. These cause the airplane to rock forward and back while following rough terrain surfaces. Not only is it uncomfortable but it retards performance and creates a lot of extra wear and tear on the structure.

The above having been said, grass generates more drag than pavement so runway length requirements will be greater. The EDO 2790 floats are a good float for grass. They are fast (low drag) in the air and have the good suspension, actually probably the best that I have used. They are a little small in the floatation department particularly if you want to load up to go into the water in the boonies. The normal engine on a 180 is 230hp so if it is a 260 that will help. I would question the 750 lb useful load, it sounds high to me. I have found that a 180 on 2790s should be considered to be a 2 place airplane only.

The 185 Cyclone- does it have longer wings than a "real" Cessna 185? I thought that I heard that somewhere. If so that should be a good prospect. The 860 lbs useful load indicates that there likely is not much in the way of "extra" equipment in it. No interior or radios?

I can't say much about the Bushmaster other than to say that I owned a 172XP on straight floats for a while with the same engine and it did a great job. The Bushmaster is likely slower in cruise than the other two because of the wing airfoil being higher lift and drag.

Good nose wheel shimmy dampeners also are important. I have not had any problems on grass. But on pavement that is another story. It can be bad enough to render the plane uncontrollable. They MUST be in good working order.

I hope that this helps you during your investigations.

03-12-2011, 01:36 PM
A local is flying the clamar's on his 180 exp cub and I've seen the shimmy of the nose wheel when he landed on pavement, not sure if it happens on every landing. I'm flying the Baumann 1500's on my PA-11 and noticed a longer T/O roll vs wheels when heavy, 200' +/- to 450'-500'. (I know that's light for everyone else) I fly off my 1800' grass strip and have landed on quite a few grass strips and feel they do a very good job, I have had a lot of comments about the tires being so small but with the weight of the plane I don't feel it's a big issue (yet). A few years ago at sun and fun myself and another guy asked the clamar rep about making a smaller set of floats for the light planes 1500# and after his reaction and comments I would be hard pressed to buy anything from them.

bob turner
03-12-2011, 02:17 PM
Yeah - while I have little amphib experience, I have a lot of shimmy experience. I am one of the guys who suggested to Wip that they needed a dampener up there. They said no way, but about eight months later I got a kit that solved our problems! If your Wips do not have this kit, stay off of pavement or buy new tires weekly.
Also watched a set of PKs practically destroy themselves with shimmy issues, and PK does have a shimmy damper. Cost over three grand to fix just one side, and that was just the damage to the strut itself. The struts require heat treating after welding.
Don't let these things shimmy.

03-12-2011, 04:21 PM
The old shimmy problem again. Sounds like they need to get the caster angle right instead of all these dampers.

03-12-2011, 09:13 PM
Hi Cooker, I currently fly a turbo 206 on Edo 3500s and a cub on Wip 2100s out of our backyard strip which is 1900 ft long. We have 45 ft trees at one end and the other is clear. I have in the past have flown a 180 on Aerocet 3400s and 185 0n Wip 3730s and a 160 cub on Clamars all from the same runway, all at gross. Fourtunatly the wind favors the no abstruction departure 85% of the time.If I have to depart over the trees I cut back on fuel load and stop on my way at the airport to fuel. As stated by others the runway condition is very important. We roll the runway continuously and keep the grass well manacured. The key like Mike said is to get the front as light as possible, soon as possible and on the stiff leg models keep the controls aft on roll out to minimise the stress on the airframe and float structure. I agree with Skywagon8 that the models with fluid oleos are the best suited for grass runways and are easier to get the front light. All things considered, pick the machine that will serve your mission the best, possibly have these machines fly in and out at the runway for evaluation and keep in mind that you can always go out light and stop at the nearest airport and load up for your adventure. Be safe and think every departure through before you advance the throttle.

03-12-2011, 11:03 PM
No issue with Clamar's on grass. Customer flies his Elite on 2250's out of here day in day out.. uses about 600 feet to leave and about the same to land and stop. None issue, even when it's soft... other than his brakes rip the sh it out of my lawn when he tries to get those darn nose wheels to turn. This was the very first Elite mounted to Clamars in the world, by myself. The Clamar 3500's bottom was pulled from a plug taken off a set of EDO 3500's I own.



03-12-2011, 11:46 PM
The EDO 2790's use a scott 3400 series tail fork. The Gar Aero or ABW wide fork may be installed on the float. You may have to mix and match the dust caps it does wonders for the handling on soft surfaces. There is no tendency to increase any shimmy that I found.