Higher Pitch props on a twin.

[Ken Culbertson]

I am curious if using a higher pitch on a twin would have the same effect that it does on a single.  I am thinking about replacing the  BadAss 10-5's I am using with 9-7 or 10-6 three blade props.  The BadAss chip the tips and split just sitting in the pits.  In the past I have always run a 6 pitch.

Ken

[John Miller]

I'd at least see how things ran with 8x4-7, or 9x4-7. On the Pathfinder Twin using OS.15's, an APC 9x4 trimmed to 8.5-8.75 seemed to work best. YMMV since you're running Electric.

John M.

[M Spencer]

Withim Twins , the ' hole ' in the engine - run , With 8x6s it sags , with 9 x 4s it stops. but less often . 

The ' Locked In ' bit , of course , with the 8x6's is higher , speed . So - with revy motors , the 4 inch is good . The 6 is more the 4-2 set up .
SO , try 5 inch . 

With lectric , Id think the 4 would be the go . Heavier props can create exitement. Tourque Roll . and so on , so a ' locked in' run on 4 inch pitch , is safer.

BUT Yr dont say wot your air & altitude ( density ) is LIKE . If its all dry & thin , youll need pitch . Whereas if its good cool dense air , less .
Blade AREA comes into it too , with that . Cutting a bit off the iameter , with I C , frees things up ,
Theres old Top Flight 3 1/2 inch pitch Free Flight Power , props , and the old grey Cox / Rossi .15 type, too . If you really got Revs .

Matter of the WEIGHT , too . Thats related to the BLADE AREA . Having flown a twin or two . The Old Nylon Top Flight work better vertical ( up ward )
so give a more controlled run , than the Tornado . Wich are dead rigers for their wood props . So Those - Treated with timber oil to reflexify , are o.k.

Generally the modern Zinger your better reworing , thinning & polishing . Prop Drag ( rotational ) is a big factor too ( in the tourque roll under load factor .

Logitudeinal stabilty damps it . swing / yaw- roll ( dutch Roll ) . But you ( With i.c. ) can get good results with say a .19 & a . 25 on similar props . Maybe one trimmed in Dia.
And Not Neccesarilly the bigger inboard . So E Lec Tronic programmeing ? if you had one steady & strong with minimal pick up ( 4-2 ! ) doing most of the work , and the other yapping along
and chiming in substantially when theres work to be done , can get a very good steady pattern. Ands entertaining . But this all sounds / gets , a bit awkward. No Doubt . So as to the QUESTION .

Try a few . Not Neccesarilly the same either side either ! Trim or thin or narrow a few unhappy props , if its no loss . But old Top Flights hook in good , going uphill . Keep on keeping on.

Study up furnature oil , or timber oil . Best for that type of timber . As it FEEDS the stuff so it has better elasticity / flexability . So its less brittle / more durable . Amourall on Plastic Props , likewise .
Was an art reworking wood props for flex , in the dim dark ? ages . Increase or decrease pitch under load . Speed & aerobatics had disimilar requirements . You wanted it to ' fine off ' going uphill ,
whereas speed wanted to pull in pitch with rpm & speed .

Theres a thing . 

[M Spencer]

I prefer the 4s or 5s on I. C. , maybe tornado 8x6s if its hot & high . On FPs in the 60 ounce things . On Veco's 5 20 % got 90 from the Mosquito , in a speed comp . All about that weight.

If you trip ovr any of these , lube em up , and have a go . Theyre a good prop for our r.p.m.s , seem to have a bit of load response , not slippage . and ease off otherwise . Like a ' V ' ee engine .

That might be a higher pitch one , in the middle , there .    ( can help to visualise extreemes , to get a hold . As it were .)