spanky6263

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Looking for advice on replacing a super tiger 90 engine with a Gas replacement engine for my float plane?

dryverman

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DLE 20 or 20RA, VVRC 20 might do it...what's the float plane?

spanky6263

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It was a plane i picked up at a fire sale.. I dont know the model type. It has a 9’ wing span and is about 6’ long

dryverman

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May be someone knows what it is...guys?

Truckracer

My Feedback: (19)

I have no idea what that airframe is but if you could give some dimensions (wing span, area, estimated flying weight, etc) would be helpful in determining engine size. Keep in mind if you plan to fly off water it will take more power than a similar sized land plane ... at least if you expect it to get out of the water in a reasonable distance. Firewall size and cowl dimensions would be critical requirements too. Prop clearance between firewall center and fuselage? Has the plane ever been flown?

ahicks

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Pretty sure we're talking about an Anderson Kingfisher. They're home built/experimentals. I THINK the full scale used Cub wings, or Cub parts to build that wing, but not 100% on that.

Where did the idea of .90 power come from?

Weight?

Small gas twin might work out well here.....

CG might be an issue here as well. -Al

spanky6263

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Ok I’m going off memory here as I am out of town and I can get more specifics when I get back home.

it has a 9’ wingspan. Will have to get the wing area. The 90 idea came from the mounting brackets and several of the other ac I picked up in the fire sale all had the same engines so it was just a guess. It weighs in at 15.8lbs and I have room for at least a 15” prop and may have more room will have to measure. I will get more specifics on Sunday when I get home. Thanks for the help.

spanky6263

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And yes it has been flown before.

ahicks

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15.8 lbs with no radio or power, or are you calculating that as a finished weight?

15" prop limit, if that's what you end up with, means you are likely looking for a 3 bladed prop when going gas. Thinking 20cc here. Pretty sure a 30-35cc is going to need more room for a prop.

spanky6263

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Ok. Made it home from the Toledo show.
looks like it could swing a bigger prop 17!or 18 inch. I will post some pics with a ruler so you can see. Also the wing looks like a cub wing. Flat bottom curved top. 16”x49”. So I’m assuming to find wingsurface you multiply length times width times two or is it 4 for top and bottom ? If that’s accurate it would be 3126.

spanky6263

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Truckracer

My Feedback: (19)

What is the length of the cowl from firewall to the back of the prop? A DLE20 requires about 6" depending on the motor mount used and the most common sized prop used on that engine is a 17-6. I would think a 30 would fit in there also and as Ahicks said, a 3 blade prop would solve clearance issues ..... but a 19" 2 blade is pretty much standard for a 30. A 30 will need 6 5/8" + or - a bit from the firewall to the back of the prop. I might be concerned whether the firewall is strong enough for these engines. I see the ply slotted into the firewall and would want to know it well supported on the back as well as being torsional resistant.

Wing area is just the flat plane measurements of chord x span (including any center section or areas where the wing projects through the fuselage) and reduce that number to allow for curved wing tips if any. Going back to the original ST 90 idea, I can tell you that a ST90 in a 1/4 CUB has less than sparkling performance and that's being kind. A gas converted one would be even more anemic. I'm thinking this plane will be even more draggy than a CUB and will eat power to fly well. This is common for anything designed to fly off water. I see wheels on this model but the airframe will still probably be draggy. Not saying it is a bad plane at all as it will probably be a blast to fly, just will need some power to make it fun.

spanky6263

My Feedback: (5)

I can measure the current cowl but it’s kind of a mute point as I can remake a cowl. I was just looking for some suggestions on a gas conversion. I think I have what I need to make an educated guess on what engine to install. Once I make that happen, I will post the pics of the flight or the crash. Thanks for all the help.

Truckracer

My Feedback: (19)

Enjoy the project and please let us know what you decide and how it all works out. Part of the enjoyment of RC flying for all of us.

ahicks

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With the weight we have here (this thing is going to be heavy), I'm thinking the more the merrier when it comes to power. The upper limit there might be determined by how big a prop can be used.

Agree too regarding the strength requirements of that firewall, as well as the pylon mounting within the wing structure.

Awesome project. One of the better looking amphibians built - to my eyes anyway, but focus will be required to keep it as light as possible. -Al

spanky6263

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Thanks all. I will double check engine mount and see if I can squeeze the Dle 30 on it. I think I can rework the mounting area and if I can raise the mount a little I may squeeze a 19” prop in.

Truckracer

My Feedback: (19)

The footprint of the DLE30 stand off mounts is 54mm high and 70 mm wide. That would probably be my first choice. Should fit that firewall if it is strong enough. I would resist raising the engine unless absolutely necessary. A high pylon mount like that can cause major pitch changes with throttle change so you want to keep the thrust line as low as possible. Even on full scale planes like that it was necessary to avoid rapid throttle changes. There are several interesting videos on You Tube to substantiate that.

ahicks

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Thinking lower is better too. 3 blade prop may be the better plan.

spanky6263

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Ok, will look and see how it all lines up once I get the Dle 30 in that I ordered.

If I go with a 3 bladed prop anybody have any suggestions on size and pitch? Thanks

Truckracer

My Feedback: (19)

Looking at your ruler, you might clear a 19" prop OK. I wouldn't use a 3 blade unless you absolutely have to.

ahicks

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So, a 19x8 for a 30cc powered what is likely going to be a 20lb plane?

Thinking a 6p prop to get best possible acceleration/low speed control would be what I was looking for. It's too bad there's no APC 19x6w. That would work good.

I don't remember what happened with an 18x6w on a 30cc. If that didn't over rev, that might be a good choice?

Truckracer

My Feedback: (19)

My favorite prop on a 30 in a heavy / draggy airframe is a 19-6. On a 35 I use a 20-6.

ahicks

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My only concern over a 19x6 would be over reving. No concern over revving a 19x6?

Truckracer

My Feedback: (19)

No concern at all because it is a non issue and a very happy combination. I’ve run a Xoar 19-6 laminated on a DLE 30 for probably 10 years in a CUB and it is a great combination. On my little YAK, I use a Xoar 19-8. If we were talking APC props then yes, a 19-6 would probably over rev. I never cared for anything about or for APC props in these size ranges. If flying from water I’d probably try one of the carbon props but would have to test several to find best size. For a starting point, I’m thinking something like a Falcon 19-7 carbon if they make that size.

ahicks

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It being a seaplane, I was thinking APC.

Carbon fibre is OK for use on seaplanes? No clue as they're generally considered too rich for my blood. Anything I've flown of water way smaller than this....