36 inch rigger slow

[RC boat addict]

I finally have sorted out the leaks and the drive system in my home build 36 inch rigger I styled it on the KEPS plans I downloaded for free on this forum and I just changed the construction from plywood to carbon fibre and the sponsons are solid balsa with 1mm fibreglass ride plates.It is lighter and stronger and has less flex than the KEPS but it is a bit bigger, I wanted more room so I made it a bit bigger in some places and a bit pointier at the nose to cut the air nicely. It has a TP40 60 6D 1650 KV running a 50 /100 C HRB 5000 mah and a 200 amp ZTW Seal esc and a Andy Brown sharpened and detonated balanced 47 mm Octura with 1.4 pitch with a .78 piano wire drive Shaft.
I am only getting 54 mph The strut is level when I put a straight edge from the rear shoes to the sponson ride plate tips. I tried a 31/6 flex at first and it was noisy and slower.
The run time is hard to tell from such few trouble free runs but I?m guessing 4 mins I tried the amp meter on a run and it said max 2100 watts and 85 amps nothing gets over 105 degrees except the battery it vet around 120 after a 4 minute run. The run this morning was 2.5 kilometres and went down to 22.5 volts about 4 mins run time the balance is even on the batteries but I had to delete the low voltage cut out.
Any thoughts ?

[NativePaul]

I normally see maximum peaks of about double the average current, so I would say 54mph is pretty good speed for a boat running on about 45A.

I've never run rear sponsons on a rigger so I could be wrong, but from what I have read the strut is usually set up slightly lower than the rear sponson shoes, not level.

[HTVboats]

Your propeller is the issue limiting speed, assuming radio & esc are giving you full throttle. That motor should pull 3 to 4 1/2 watts easily or more (3000-4500mw) 50-52mm and even more pitch will go faster but cut run time. Watch you temps with short runs and work up to longer runs.
Mic

[NativePaul]

assuming radio & esc are giving you full throttle.

That is a good point, as I would be expecting 1650kv on 6s with a 447 to be pulling maximum amps of much higher than 85A. I was assuming 4s at first for those numbers, but

2100 watts and 85 amps

indicates 6s.

[RC boat addict]

You must have misunderstood it was 85 amps 22.2 volt 2100 watts in fact I was rounding up it was 2060 watts by memory so you comment about double those 45 amps is pretty accurate thanks for your reply.

[Moonie]

He’s right. The strut should be slightly under the rear sponsons/shoes. You will gain more speed and more amps with the strut lower.

[RC boat addict]

Hi Mic, I read somewhere riggers like pitch but it blows the back of the boat up.
I also read the ABC props have multiple rake choices and 17 or 18 degree rake is best I guess I?ll start with 52 14 Octura I have as it is no cost for now and check amps and temp and then finally work up to run time testing, then if that Size and pitch Gives decent results I can drop down the diameter in an ABC prop with more pitch and maybe 17 degree rake to maintain similar amp draw and hopefully gain speed.
I tried this 52 mm 1.4 Octura when I had the 31/6 flex shaft and it pulled 67 mph but it burned the 150 amp Flycolor out in 2 straight line runs but it was over 12 months old running in salt water in my smaller rigger it might not have been that good. No amp or watt readings and temp as it burnt out so fast . It now has the very smooth wire drive now and the 200 amp ZTW seal esc .
Thank you for any critique of my thoughts here.

[RC boat addict]

I wonder how much lower and I guess Start straight and if it hops tilt up at the back 10 thou or so

[RC boat addict]

Hey Paul I tried no rear sponsons on a previous rigger and it was super twitchy and did not corner well but I?ve seen them on YouTube really fly so I probably had something wrong.
I have a small TFL arrow running the normal KEPS type ski in the middle at the rear(actually slightly off center)and it corners like on rails but the strut angle hardly effects it?s ride. it is a weird little boat it weights 1.4 kg in running trim,using 2600 mah 70c graphene dinogy 4 s a 3300 KV SSS 29 mm diameter motor 58 long it pulls a 38 16 CNC magnalium 2 blade prop has a wire drive and a 150 Flycolor ESC it does 3-5 min run time and it only does 85 klph 51 or 52 mph on the OSE speed calculator it should do 105 to 110 k or 65 to 68 mph I don?t get it .
I had to put solid balsa sponsons with 1 mm thick fibreglass ride plates on it to get it to handle in bumps without flipping.
it revs very high 49000 rpm minus any losses it rides on the lash millimeter of the sponson plate tips.
I was thinking the SSS motor might not be very efficient at those revs but it has good run time no heat issues. I don?t understand at all,some you tubers get this speed on this rigger using 3s

[HTVboats]

I would keep the strut at parallel (0*) with the running ride. I have Keps & Jae with similar power. I use a JAE 33 tub and made Keps dimention sponsons with divinicell 3/4" and G-10. With a 1600kv 4074 I see high 60's with an X447. (FC150) Actually an M545 and 645 work better. An 1819 17* ABC and 1815/3 19* work best on my hull. low 70's. Your 1452 is too much diameter and killed the 150.
52mm X 1.4 =72.8mm pitch An X447 X 1.4 = 65.8mm, An M545 is 45mm X 1.5 and 67.5mm pitch An ABC 1817 is 45.72mm X 1.7 =77.7mm pitch. If you ran the 1817 I bet you would have run faster and not stressed the esc as much as the 1452. Bottom line know you prop pitch and diameters and how they relate to speed, run time, and heat. On a rigger I like more pitch less diameter. Bear in mind you need X amount of actual blade area to push any hull efficiently. The magic is figuring it out and that's where the winners come in.
Makes it a challenge and fun to test.
Mic

Pitch doesn't blow the boat up alone. Angles of attach, rudder angles contribute. High rakes lift the bow and flat rakes lift the tail. Try 3 blades as one is always in the water pushing rather than a 2 bladed paddle.

[Fluid]

...That motor should pull 3 to 4 1/2 watts easily or more (3000-4500mw)....

Wow. Just....wow.



.

[NativePaul]

RC Boat Addict,
I don't have any experience of the Shark, but have raced several hydro1 class boats (same class the Shark was made for).

I suspect that your cells are collapsing under the load and not delivering near the voltage they should, it could also be the motor bogging down under load, or a combination of the 2.

The best cells available are only about 55C, so I know the 70C on your packs is BS, but I don't know how much BS it is, the best cells are also labeled 70C but put out 55C and there is a brand that labels 150C but can't put out 20C, when almost everyone in the LiPo game is BSing about C ratings, it becomes hard to tell what is real and what is not without having the pack yourself and datalogging it.

I have not used a SSS motor and know nothing about them other than they are cheap and Chinese, I know there are very good cheap Chinese motors out there and very bad cheap Chinese motors out there.

My Hydro1 is a chunk lighter at 1150g, it uses a similar size and KV Leopard 2860 3400kv motor, on 3s zippy compacts from 25C 4500mAh to 40C 6200mAh spinning a detongued and backcut x435, and attaining about the same speeds as yours for 6.5 minutes. Most of my fellow racers are using similar electrics to me with a Graupner style CNC alloy 1.4 36mm prop, or a bit more KV and a 1.2 36mm DrProps Naviga prop. Having a bigger prop with more pitch and an extra cell should be putting out a LOT more current, which would put the 2958 motor well out of its efficiency peak and generate a hell of a lot more heat, and you say your motor temp is fine which is why I suspect your battery as being the worst offender.

[RC boat addict]

Thanks Paul, so much info in your reply, I can look into this is a bit more now with consideration given to your points. This TFL Arrow is too small to fit a data logger into unfortunately. I have made a slightly bigger tub out of carbon fibre it weighs 200 grams so I could swap to that an achieve your lower weight it?s hard given this thing just seams so perfect in all ways but the GPS.
The company that is the agent for the battery I am using have done their own testing and rate this battery at 55 c having said that all batteries are not the same the run time and equal balance voltages and temps are so good and the revs sound so high it?s like my GPS is wrong but I?ve tried my phone in a zip lock bag as well as an IGP Sport and both give the same speed. Some how I need accurate logging, this should be my mission I think.
There is a guy on YouTube that put a similar size TP motor in his and his GPS shows 64 mph and only 3 s by memory and 4100 or 4300 KV though and an ABC prop.
So fast.
I know it?s hard to compare just looking at YouTube but my thing looks as fast and with the KEPS type sponsons is much more stable it?s is still capable of lift off and blow over but much better than the stock sponsons.
I?m not understanding what your sponson material is maybe some sort of high density foam I?m guessing There could be more weight savings there.
I appreciate all the time it took to compile your reply it?s awesome.
Do you have photos of your rigger i?de love to see it .
Regards James

[RC boat addict]

Sorry Paul I had the other post about my 36 inch rigger confused with your on the sponson material. Disregard that part mate .
James

[RC boat addict]

Thanks Mic,
It looks like I should get the ABC prop you suggested and check the amp load and GPS and go from there. So much info to go through and try. The time you guys put into these reply?s is so awesome.
This thing has so much power I had to put the battery right up the front then the quite large ESC then the motor otherwise it just kept flapping around on its tail like a Marlin fish and I had to be so fast to react to stop blow overs.So you are right about the strut angle for this one level seams best.
Do you have any photos of your set up ?
Kind regards James