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Author Topic: what sise prop for a 28 engine  (Read 1635 times)

edible_engine

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what sise prop for a 28 engine
« on: February 24, 2007, 06:27:29 PM »

i just used my finished boat and put a 40mm prop on it but i think its to big and the engine wont rev up like it shuld smaler prop maby ?
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BJ

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Re: what sise prop for a 28 engine
« Reply #1 on: February 24, 2007, 08:23:06 PM »

Check out the link http://www.funrcboats.com/prop_chart1.htm#Chart BUT do remember that PRATHER ceased trading as of January 31st.

Are you running a submerged or surface piercing drive? What engine have you fitted? The chart in the link SHOULD point you in the correct direction but without more information more advice is impossible.

You can order Octura from the link below
http://modelmarinesupplies.co.uk/shop/conditions.php?osCsid=5f36a2fcb7228184c00e90834c688bdc
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edible_engine

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Re: what sise prop for a 28 engine
« Reply #2 on: February 24, 2007, 09:11:29 PM »

sory i forgot to mention its a 28 mds submerged drive
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BJ

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Re: what sise prop for a 28 engine
« Reply #3 on: February 24, 2007, 09:52:37 PM »

MDS  - may be not the best of engine choices but may be better than SC. Let us know how it runs after you get it sorted.

Why don't you go and see Paul Firmin (Nimrif) on the Ridgeway ay Plympton. He can offer you advice. Think he may be closed on Monday mornings, (well he was last time I was down that way).
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edible_engine

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Re: what sise prop for a 28 engine
« Reply #4 on: February 24, 2007, 10:15:07 PM »

i was waiting for somebody to say that the sises on that prop chart are for raceing engines by the looks of it i might just by a selection of props ans see how it goes.
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martno1fan

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Re: what sise prop for a 28 engine
« Reply #5 on: February 25, 2007, 01:32:49 PM »

Hi try a 35 mm prop for it that should be a good size for that engine,i run a 54 mm on a.60 size sc engine submerged drive i use the jp props from here they deliver fast if i were you id order a few diff sizes in sports and race types.the sports ones have a bigger blade than the race ones .try them and see which one works best.at less than a quid each you cant go wrong!!http://www.pandanmodelboats.co.uk/acatalog/JP_Plastic_2_Blade_S_Series_Props.html
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omra85

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Re: what sise prop for a 28 engine
« Reply #6 on: February 25, 2007, 02:35:37 PM »

If the JP props are the same rating as other makes, the 'S' is a 1.2 to 1 diameter/pitch ratio whereas the 'X' is a 1.4 to 1.
This means that, for the same blade diam, the 'S' gives a LOT less thrust (and consequently less loading) than the 'X' series.
If the 40mm you tried was a 40X, then a lighter loading one is the 35X. - OR - you could try a 40S and work upwards until you find the most thrust without overloading the engine.  They are available in 40, 45 or 50mm so, as has been said, its worth getting a few plastic ones to try.  Graupner have very big front ends (don't know the technical term - I know its not leading edge) which tend to "grab" and need a size smaller than the old "Radioactive" ones. I don't know if Radioactive are still available but they may be the "JP" ones.
Plastic (strickly speaking - carbon reinforced plastic) will "give" ie straighten out under load, so if you need a bit more speed, find the plastic size and then get one size down in aluminium.  Speed will increase but they cost more, though the range of sizes is far greater.
Danny

 
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retro boats

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Re: what sise prop for a 28 engine
« Reply #7 on: February 27, 2007, 11:52:30 AM »

hello
 we run alli 1815 or 1816 mocom props on our direct drive  21 club boats.
 have a look on ebay as PMC has sone on there at a cheaper price now & then
             good luck steve
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martno1fan

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Re: what sise prop for a 28 engine
« Reply #8 on: February 27, 2007, 02:05:09 PM »

i think they are 39 mm and 40 mm props? i think with his engine he needs a smaller one 35 mm should be ok.
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