doodh

I am about to commence build of Shorts Sunderland.
Plans I have are Jan Hermkins 1/10 scale using 4 x .46 os 2 sstrokes.
I already have the plans and also the engines.
Was hoping to buy a kit from kit cutters but they are not taking orders till next year. I can get hold of a 1/12 kit from precision cut kits but the recommended engines are .25 or os wankels.
My question is, would it be feasable to use the .46 s on the smaller model.
two issues as i see it.
1. Is the weight difference going to be an issue. Note there is only ~2 ounces difference between the wankels and the .46, but a bigger difference with the .25s. I seem to recall reading that most of these models tend to be tail heavy so am thinking more power available is better than dead lead.
2. Is being overpowered that big a deal. I was thinking i could adjust throttle end points in the radio to ~ 75% or so, possibly even program dual rates for full power in the event of loss of a motor. I have bought quadsync so loss off 1 motor will also take out its opposite engine. Could this be a good thing to have the power available if it becomes a big twin?
The .46s will fit the 1/12 model albeit with cutouts for top of head.
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Ram-bro

My Feedback: (101)

what is the wingspan and weight? one problem you might have to worry about iis ground clearance for the props. The Jack Stafford B24 has a 90" ws and uses 4x25s. The 46 would have been to big and 2 much in my opinion but its your world[8D]

doodh

Ram Bro.
The 1/10 model is 135 inch wingspan. Weight circa 42 lbs
The 1/12 model is 112 inch wingspan Weight circa 14 lbs

Ram-bro

My Feedback: (101)

have you checked the ground clearance ?

doodh

Ram Bro
No I havent.
What is the significance with that?

doodh

Ram Bro,
Went and checked the 1/10 plans.
Ground Clearance will not be an issue.( I dont think)
Is ~ 20 inches + with wheels and somewhere between 14 - 18 (worst case) on water. Depends on how far down in the water she sits.
Centre to centre between inboard and outboard engines ~ 17 inches.
Attached is a picture of a 1/10 scale model in Australia. Courtesy of Geoff Reichelt
[img][/img]

Ram-bro

My Feedback: (101)

boy was I off and don't know as much a I thought I did. I knew the Short was a amphibian but it just did nt register. I was thinking for some reason this would be flown ROG and not ROW. You shouldn have any real issues...especially with ground clearance. Thanks for waking me up

doodh

Ram Bro.
Thanks for the input.
Im pretty new to all this so is a steep learning curve.
What about the weight and overpower issues.
Do you think it will be allright.

Boomerang1

I don't think you will have any problems at all. I have a B-29 at 100 inch, 15 pounds with a pair of 40's & a pair of 20's & it is by no means overpowered.

The B-29 is long & thin with a high aspect ratio wing, the Sunderland rather portly with a broad wing so overall it will be a much bigger model. The extra power will come in handy one day, until that day there's always the throttle! - John.

doodh

Thanks for the reply John.
Hope you are right

alanc

PLEASE NOTE, the sunderland (aka flying porcupine ) was a dedicated seaplane, the wheeled undercart was only used for beaching operations, it did in fact, weigh several tons, and the aircraft would not have been able to lift it, now, go get the plan, and get a good band saw, and get cutting!!!! i saw the thing fly at the woodvale rally, over here, it was superb--but--he flew it withy the wheeled affair on, Hmm, sad thing is, on his way back to holland, he suffered a major traffic accident, was injured, and the trailer, and model, was flattened!!

doodh

Alan,
I have spoken (email actually) with Jan, he helped me track down his plans in the first place. Ideally that is the model i would like to build.
Thing is I dont really have the time to cut it out from scratch, nor would it be cost effective. At the time i thought i could buy the kit from Kit Cutters.
Whatever the size i opt for it will be flown primarily from water, because of geographic constraints. I will build the wheel setup as a secondary option only.

In any case a compromise appears to be required. Either buy 4 more engines, or see if i can get away with using the bigger engines combined with judicious throttle application and or throttle channel setup. What i am trying to ascertain is whether this second (preffered) option is viable.

Boomerang1

A friend in Sydney built a Sunderland years ago. His was all fibreglass, also with 46 size engines. I do not know what happened to the model, I will be seeing him at a flying display weekend after next so I will ask him. - John.

doodh

Let us know what you find out
Cheers

ram3500-RCU

My Feedback: (221)

When clearance is an issue, you can go to 3 or 4 blade props and shorten the disk by 2 or 3 inches.

dutch Jan Hermkens

Hi Guys,

I flew my Sunderland (from my own plan) from land as well from water. Prop clearance is no issue!
the 4x 0.45 Osmax (2-stroke) had a 2-blade 12x6 prop.

have a look on my homepage; www.home.versatel.nl/jan.hermkens/

by the way the australian guys Geoff Reichelt and another one, used my plans too, to build his sunderland.

kind regards,
Jan (by the way Hermkens, not Hermkins)

doodh

Hi Jan,
Sorry about misspelling your name.
I am well aware of your website. It was the original inspiration to build in the first place.
What are your thoughts regarding the original query regarding weight and power if i try to put the .46s in the 1/12model.
I would have preffered to build your model and have already bought your plans, but the kit availability sort of leaves with no other option.

dutch Jan Hermkens

Hi ...... (do not know your first name)

Yes the 0.46 two strokes are realy too much and very, very oversized for the 1/12th Sunderland.(14lbs)
As I wrote before I flew my 1/10th sunderland (42lbs) with 4x 0.45 two strokes and had more as sufficient power.

P.S
I can hardly believe the 1/12th should weight only 14 lbs! not 14 kg? (=31 lbs).
If so (14kg=31lbs), that will be a complete different story and you will need 4x 0.35 two strokes.

kind regards,
Jan

Catalinaflyer

Another issue to consider with oversized engines is being able to get the plane slowed down. Swinging bigger props creates more thrust at an idle. I ran into this many years ago when I overpowered a Cub, I had to side slip it to land it or kill the motor for a dead stick otherwise it would float a half mile in ground effect. I don't know much about the model your looking at but it looks like it might be a dirty enough airframe to slow down with the larger power.

Boomerang1

Not a problem with multi engined models, they tend to glide like an anvil at idle, most have to be flown onto the deck with a surprising amount of power.

Spoke to the friend who built the Sunderland a few years ago. He said it was overweight & had a poor choice of airfoil section on the wings. It was fully molded. It now has a new life as a static model somewhere. - John.

cyclops2

Here is a similar plane.
Martin China Clipper 72" ..... blue fom scratch... soild wing.... solid then hollowed out fuselage... it has 4 brushed 400 motors....1 ESC... 3-- 2300 mahr cells from a Dewalt drill pack.. weighs 3 lbs....

I tested the COG with a hand toss. Perfect flat glide of 30' to 40'

Seaplanes back then, put the engines as close as possible. I cheated the props to a standard size of 6".

My hull settles 1.25" into the water

Rich

GeoffReichelt

Hi
I'm new to this site.

My Sunderland was pretty heavy at 52 pounds, but the ASP .46 engines were more than enough power, when they were all running at once. If one stopped the model would just slow down and if I didn't realize it had stopped,and push the nose down, the model would stall, and take about 150 ft to recover. That accounted for a few prangs.

The ASP engines were just hopeless until I put very fine pitch propellers on them, (Bolly 3 blade 11 x 4.5's, cut down from 12 x 4.5's) at which point they were suddenly more than adequate.

I think the airfoil Jan Hermkens used on the Sunderland Model, which is the NACA 4415/2415, works ok, but I wonder if the modified Gottingen 436 of the original might not have been perfectly ok, even better, as it is very thick with the thickest point well forward, and I think it would be better at recovering from a stall. Also I think that it would be less inclined to porpoise on landing.
I have made a mould for the wing with the Go. 436 airfoil and I look forward to flying it soon.

The funny thing about my Sunderland was that if I cut all the engines so the props stopped at say 500 feet up, and set it up in a stable glide, it would glide very well, and eventually do a big circuit and land easily. It was a case of timing the landing so that it came off the plane a few meters from the shore and drifted in, otherwise it would be a case of rowing the dinghy after the disappearing model.

cheers
Geoff

cyclops2

I use a flat bottomed Clark Y for the wing and tail surfaces. The verticle section is 2 Clark Y's glued together. Stall speed is a fast walk.
I think a lot of the slow stall speed is due to all surfaces being Clark Y's.

A 80" foam A-10 is almost the same glide ability. Clark's on the tail and scale undercambered main wing.
Harder toss and the glide distance is less. Very draggy plane.

All my planes that are scratch built, blue foam, come out to 1 lb. / sq. ft. wing loading.

Rich

cyclops2

Hi Geoff.

You mention porposing on the landing. I have found that it is usually caused by 1 or 2 things.
Wing and tail not parallel.
Just a slight bit tail heavy. (COG is a tiny bit too far back.)
Or a slight combination of both.

I know flying boats are supposed to have the wing tilted up a few degrees. But I just build speed and it takes off like the Howard Hughes "Spruce Goose".

Rich

Rich

GeoffReichelt

Hi Rich
I think the Hermkens model, and hence mine, has the correct incidence for the wing and the tailplane, the same as the original which should be pretty right.

I tried cg very forward and cg aft and everything in between, but unless the model was landed with virtually no rate of sink, the second it touched down it wanted to bounce back up again.

In contrast, the real aircraft could be flown onto the water with a 200ft/min rate of descent, without porpoising, I believe.

My theory is that because the NACA 4415/2415 airfoil of the model has its point of maximum thickness well back, and the Go. foil has its point of max thickness well forward, the centre of lift point wanders back and forward with slight changes in angle of attack much more with the NACA foil than it does with the Go. foil, causing the porpoising.

I'm the first to admit I could be wrong here. I need to make another model with the new foil and test it, otherwise I'll never know.

cheers

Geoff

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