alan007bandit

hi all i have recently built a vern cobra 45 gt she run great and gets up on the plane instantly, the problem i am having is at full throttle it is pulling hard to the right and i have full left rudder on to compensate, then she will run straight can any one help.......cheers...alan

whizzy

do u have turn fins and trim tabs on it

alan007bandit

hi no turn fin and no trim tabs.........alan

whizzy

well on my brothers he only has turn fins and no trim tabs but he has a small length rudder and his runs straight as a die but reading other post id wait and see what other replies u get as we may just have been lucky with the build

alan007bandit

cheers whizzy mine has a short rudder also from bonzi sports i like the boat it must be curable i have a set of turn fins ill give them a try........alan

mopartybob

lucky indeed whizzy...,the problem with prop walk starts right there ..at the prop.. be sure it is SHARP AND BALANCED,I've heard of other's thinning the prop also to help,reducing pitch also helps, alan, you need to let us know all the specs your runnin there buddy,engine size,current prop size, also does the hull run straight and true at lower speeds?? is your rudder servo strong enough to go for the ride.....spin fins and tabs are great to have for fine tuning the trim also when installed correctly so's not to add drag unless of course where needed....[:-]

glennb2006

Also, how much prop is in the water?

Glenn

alan007bandit

hi the boat runs true at lower speeds,the engine is a stock zenoah 260pum the hard ware is bonzis rudder and strut ass. and the prop is a 275

whizzy

cheers mopartybob oh and i run sharpened and balanced props too just never thought about it as to me it would be the first thing i would do before i put it in the water

mopartybob

is the prop,sharpened,balanced,polished....??[:-] ok then whizzy,moving right along.....if the hull runs straight n true at lower speeds,I would suggest trim tabs installed closer to the keel rather than to the chine,be sure to mount them at least 1\16" above the bottom of the boat to insure no unwanted drag,if using 1 piece stainless tabs,bend the "inside" starboard tab down 1\8" to offset this torque\steering role,(you may only need to bend the corner down)and NOT the whole tab.....the only reason I would suggest this is that I have been there before and this has proven effective for me, through MUCH trial and error I might add....[:@], good luck.....

alan007bandit

my prop is shapened and balanced..........alan

mopartybob

refer to my edited post....

alan007bandit

cheers mopartybob got that will try and thanks for your valued input....alan

wayneuk01

whizzy u may have one of the only straight boats in the uk or your bloody lucky with the set up

is it anything like in the videos alan ?
http://www.youtube.com/profile_videos?user=wayneuk

alan007bandit

hi wayne we meet again, cheers for the previous info on drilling intake manafold for water pump, no mine cobra isnt as bad as that..........alan

whizzy

lol i was catching up on the threads i have never came across those problems on my brothers hull so his must be straight and the set up must have been lucky

wayneuk01

oh yeah i remember u i posted the bonzi carb pluse fitting for u a while back hows things going apart from the probs posted

alan007bandit

yeh the boats spot on very happy with it,it just this problem, i can live with it now i now what its going to do, i am thinking of gutting it, and buying a marles panther, i dont know if to spend the extra 90 quid on the kevlar whats yours...........alan

mopartybob

Straight AND Lucky.... sounds like a winner to me, put a fin on her in the fifth for me at the downs will ya........please post vid of results.....

Believe It

if you have an offset rudder, shim the right side of your strut bracket out so when you are looking at the rear of the boat, the entire strut is angled to the left instead of straight. You only want about 2-3 degrees offset.

alan007bandit

cheers the the rudder and strut are inline.......alan

wayneuk01

mines epoxy and glass cloth i also considered the kevlar but for the diffrence could also purchase the exhaust & a few other parts that i havent got round to getting as yet ..If u have the dosh go for it but bare in mind u wont be cutting any large holes in the kevlar hull with ease due to the construction materials . The epoxy and cloth is still 10 times stronger apparently than a fiberglass gel coat layup & no gel coat cracks ever also dont forget your cowl locks and make a list of items u will require like the low radio box he sells for this boat .Then u will only pay one delivery cost

patriktegelberg

Could you post a couple of pics on the transom and rudder from diff angles.

martno1fan

hi alan im having the same problem on my scratch built mono and after input from guys here rather than use trim tabs im angling my prop to the left a cpl of degrees this was done by loosening the bolts holding the strut to the transome and shimming the right side with some 1 mm ali sheet thus making the prop angle to the left .this is suposed to overcome the prop walking .also make sure the props very sharp,ive been told if it doesnt cut your finger its not sharp enough ill be testing my boat again either tomorrow or tuesday ill let you know how i get on.check out my thread and ill post on there the results.
[link]http://www.rcuniverse.com/forum/m_5452887/tm.htm[/link]

mopartybob

hey alan, the only reason I did'nt suggest shimming the strut was that you mentioned it ran straight and true at lower speeds, so don't you think that if you shim the strut a coupla degree's,that it would'nt affect your lower speed tracking...? correct me if i'm wrong here guy's,I'm still on a learning curve.....[:-] I would think that by increasing the amount of trim tab area thats bent down to offset the torque roll will allow for the variation of throttle given per amount of offsetting force needed to continue straight n true tracking,whereas by shimming the strut a coupla degree's might not be enough to overcome the effect,without affecting low-speed tracking....[:-] duhhhh, i hope dat made sense........