pinky_d_brain

I am working on an airboat project and wandering what props to use. I’m going with two props run from a .12 buggy motor was thinking two 4” in diameter 4 bladed I’m new to this but not worried about having lots of problems setting it up I just don’t know anything about props. I also don’t know what the numbers mean if you can explain that would be grate. I no the .12 is small I was thinking maybe some of the electric motor props would work. I plan on putting them on a shaft any ideas how I would do that? Thanks in advance for any info

TERBObob

My Feedback: (21)

It really depends on WHICH .12 buggy engine you are gonna use . Since some have WAY more BHP and RPM's than others do . There really would not be a general rule of thumb for buggy engines .
let us know which engine and we can from there .
The numbers ? The numbers for the engine size ? Or the numbers for the prop size ?
Again , which engine ?
If its threaded , ( which it more than likely is ) , then simply get yourself a nut that fits the threads on the shaft . If the shaft is short ( which , again , most are ) , then you will need to either make , or buy , an shaft extension . You can make them , if you have a tap and die set with the proper teeth per inch tap . Reason for the extension ( if you haven't already found this out ) is because the prop will hit the carb .

let us know which engine .

pinky_d_brain

I’m going to run 2 props form one motor. The props will be mounted on two different shafts with a belt system from each prop to the motor in the boat was wondering how to attach the props to shafts hope that clears things up for you. Form what you say sounds like I can just bolt the props on the shafts with couple nuts. I will have to wheat tell I get home to check the motor but its a TRX .12 nitro motor don’t know the RPM or BHP need to check, I have a tuned pipe for it. How do the numbers for prop size work?

RS 38-40

My Feedback: (3)

Prop size lets say is 8x6 . First number is the lenght and the second number is the pitch .

TERBObob

My Feedback: (21)

you say that your gonna run a pair of 4 bladed props , correct ( 2 props , each with 4 blades on them )
belted .... ? Is it a cogged belt ? If not , be prepared for LOTS of slippage . To mount the props to a shaft , you would need HIGH speed bearings that have their pressure being applied to the sides , rather than front to back . Then , you would need to form fit them into your metal mount - which , your engine should also be mounted to , BUT , with some form of slack adjustment . ( belts WILL stretch )
Do you know what pitch they are ? And about the EP props ... NO ! ! ! They will NOT hold up .
you need NITRO ( sometimes called gas ) props . They are thicker and thougher .
Not sure about the props that you plan on using ...
Theoretically , that would equal out to a 10 inch prop , but , we still need to know the pitch .
( reason - the is a kinda formula that you use which is take the diameter and multiply it by the pitch and this is the number you should basically use when changing different prop lengths and pitch's .

IE - say that you are using a 10X7 prop ... that would equal 70 ... well , theoretically , a 5X12 prop should range aprox the same . Same with like a 8X6 which is 48 , and so is a 6X8 ( remember the first number is the distance from tip to tip of the prop and the second number is the pitch - pitch meaning that in theory - the distance the vehicle should move within one revolution of the prop )

Tim Wiltse-RCU

pinky,

To really get this to work you have a bit of work to do! Geared or belt driven drives for airplanes have been around for a long time. Being that you want to run two props you will need to run a belt drive if you want the props side by side. You could run a gear drive if you wanted to run the prop in line of each other. I am guessing you want a cool side by side set up. There is a number of places to score cogged belts, SmallParts.com is one. I have around here someplace a bunch of small belts that I got from some old lazer copiers. I would think you could get away with nylon gears without a problem as your running a rubber type belt. The engine, shafts, gears, props, tensioner etc would need to be mounted on a custom made motor mount to ensure to keep everything solid. As for props well a .10 sized plane engine only swings a 7x3 or 7x4 at the most sized prop. Most model car engines are made to run at a higher rpm but have a lower torgue number. Even with a tuned pipe a set of props like the APC 4.2x4 might be to much for it.

Later,
Tim

pinky_d_brain

Thanks guys mounting the props and motor is not a problem I was planning to doing exactly what you are saying vary good at that stuff its finding parts I need thanks for the site Tim. As for prop size I need help looking for a recommendation for 2 props 4 bladed trying to keep them small but want to keep the boat fast. I can get a .47 plain motor think I will go with that have to scale up my boat but not a big deal, I may need a heat sink the motor is farley open but not in the prop wind what you think.

Tim Wiltse-RCU

pinky,

It's most likely going to be hard to find a 4 blade prop in the size that you need. A .47 turns what a 10x6 or 11x6 prop. So you would be looking for something like a 7x3 4 blade prop. You can find 3 blade props pretty easy but 4 blade may be hard to come by. What is your reason for running dual props?

LAter,
Tim

biteme

According to the Zingali (zinger props) website, the 4 blade (based on a 10x6, 2 blade), would be 9x5(you'd have to make your own - the closest they sell is 10x5). Their formula: from 2 blade to 3 blade, decrease the pitch by 1, for 2 blade to 4 blade, decrease both pitch and diam by 1. http://www.zingerpropeller.com/_2_blade_.htm
Sean

Tim Wiltse-RCU

dog,

Just note that he is wanting to run twin props off one engine. So a 9x5 is to big.

LAter,Tim

biteme

Sorry Tim,
I thought you meant 10x6 went to 7x3...um...yea, two7x3 would be just short, but I'll assume you were compensating for loss of efficiency (belt drive). A good place to start in any case. My misunderstanding. Sean

pinky_d_brain

I here two bladed are faster is this true and if so why? And if I was to go with 2-bladed props I would need two 5x6 correct, to get the 60 form the 10x6. I would like to keep the 5” diameter if I can do they make a 5x6 two bladed. The reason I’m using 2 props is to rebus the torque on the hull in relation to the surface friction I’m running on.

Tim Wiltse-RCU

pinky,

I think you will find it very hard to find over square props i.e. props with more pitch than diameter. If you know of a source for a 5x6 please let me know I would love to try one on my pylon plane. Not to throw another wrench into the mix but be aware that larger props are more efficant air movers than small props. A slower turning larger dia. lower pitch prop is used where you need thrust and pulling power to haul around a heavy draggy plane/boat.. A small prop with high pitch is used for high rpms on a small light craft for speed. IMO if I was building a airboat with the intention going fast I would use that .12 buggy engine you first talked about and I would prop it to keep it in it's power band and run it on a light weight out-rigger type hull, keeping the boat wide enough to be able to make safe turns. Mount the engine as low as you can to keep the CG as low as you can. With balsa covered foam sponsons with carbon booms and a light ply/balsa tub the thing you FLY! the trick for us guys wanting a fast airboat is to build a hull with a minimum amount of hull in contact with the water, snow, road etc. I have a couple ideas and a couple spare engines laying around. Maybe I need to put pencil to paper and work up a little airboat racer myself. My last airboat was many years ago.

Later,
Tim

pinky_d_brain

Well I’m glad to hear I inspired you as for what you are saying about the speed boat that is what I was planning to do you caught me think I’m still going to us the bigger motor I no bigger does not mean faster but I need new motor I want to put the buggy motor in other projects

pinky_d_brain

well the best i found so far is 5x5 i going to try them
http://www2.towerhobbies.com/cgi-bin...?&I=LXFJY8&P=0

Tim Wiltse-RCU

pinky,

Do not run those props on a nitro powered engine. They will sling their blades in quick order.


Later,
Tim

pinky_d_brain

k i was wondering about that thanks

pinky_d_brain

Well I can’t find small props but I found a 7x9 which I think is small enough I will go with one and save on loss of power form the extra belt. Pain in the butt they don’t say there for nitro but it is under the nitro area hop they are let me no what you think theirs a 7x10 there as well. 7 looks like a good number, lots of variety
http://www.sheldonshobbies.com/listing/apc04.html