Some Consideration

[saleens7]

on the third run of the OM21, i had the propshaft vibrate itself off of the flex shaft and now my prop, drive dog, prop nut, and propshaft are all resting at the bottom of my lake......

Luckily thats all the happened, but before when it did run, it still had a lot of problems. It porpoised like a b!tch and could never get past 3/4 throttle without spinning out (and at 3/4 it was hopping around pretty wildly)....I can tell i overpowered it (i figured it would be earlier, but i didnt know it would be THIS overpowered).....

now im thinking...should i fix it up and keep running it as is? Or move on to a bigger hull, like the OM26, or even the 29? both hulls can be aquired relatively cheaply, but if i upgrade i would need to buy new hardware, as well as a new flex shaft.....if i do stick with this hull, i think i might move down to a 380XL size motor...but what im worried about is the shaft vibrating again if i stay with the surrent setup....i think what caused it do to this was a combination of a raw, unblanced prop, and the small amount of play that the propshaft had in the octura strut.....i would have gotten a carbon prop since their pre-balanced and sharpened, but i cant find any available in the size and type i need...The smallest they come here without being meant for a 4mm threaded shaft is 40mm, and i need a 35mm one..

so what should i do?

[ozboater]

what motor do you have in the om21 ?? my bud runs one with an 8s... 2 2s lipos together for 7.4 V but doubled up the mAh for 7400... he uses the rhino lipos 7.4 V 3700... runs sick... pretty much hangs with my sv27... 35 or so mph.... maybe a touch more... seems a shame to build a new boat before you get the om21 dialled...

good luck with it..

cheers

oz

[saleens7]

i also running an 8S, with twin 2s packs wired in parallel o_O.....it will hit about 25-30 before it just gets wayy to squirly to handle....

but it seems that its too much motor for the boat....needless to say i will need new hardware anyway....a struck a sprinkler drain float thing (holds it above the muck at the bottom of the lake) and i bent my rudder slightly as well as the fin below the stuffing tube....i bent it back, but cant get it 100% straight again...

i tried trimming out the strut some too (for some reason i cant get much angle out of it) but that didnt help....

EDIT: what prop does your friend run?

[ozboater]

i m not sure what prop he uses.... i ll check for ya... in real flat water his boat screams... gets a little squirelly in the chop and boat wakes here... you really need to drive the thing... in flat water it s just WOT and go...

[saleens7]

yeah the water was a bit choppy when i used it, but that didnt explain it spinning out every time i took it past..oh say 3/4 throttle?

i would ease it up to that speed too and the second i pushed it a little past 3/4 it was doing it still.....

[saleens7]

and what hardware does he run too? im thinking a strut thats a little more adjustable....i could also get a rudder with a pickup that way i can cool my esc as well....

i also think im going to replace the coupler as well....the twist tightening one is a hassle to use since the motor mount blocks 1/2 of it....the one with the little set screws would be better....

[Fluid]

That hull was designed for less power and more weight. Add 8-12 ounces at the CG and see what that does for your handling. You have to balance speed with lift, and you do that will hull design (which you can't change), setup and weight.


.

[saleens7]

well i guess i could go to the hobby shop to get some lead weights...i think they sell them for planes so they can get the CoG right on them....not to mention i need some CA...epoxy doesent want to hold on ABS very well, even if it is roughed up....

and to think i wanted to keep it light >_> yet here i go adding nearly a pound to it

[saleens7]

does anyone know where ic an find carbon props under 40mm that arent just meant for 4mm threaded shafts? or atleast where i can get an adaptor for a 1/8" shaft to threaded 4mm?

if theirs a way to do this, i already have 2 4mm threaded props ones 36mm, the other 34.5....so those are already around the right size i would need....