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.



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[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

[RC boat addict]

Hey Mic, what is divinicell 3/4? and G10 ?

[NativePaul]

I will try to remember to take some photos tomorrow when it is light. My sponsons are a glass top bottom and outside molding with a carbon sheet inside face, they are empty.

I cant recall if it has one in there now or a cheap Suppo, but when I had the cash I was a big fan of ESCs with datalogging, like the Castle Creations Ice range, no bigger than any other and give you a lot of info to help with setup.

If it is perfect in all ways but the GPS, just stop running the GPS and be happy!

Divinicell is a closed cell extruded PVC foam available in several densities but is generally much heavier and stronger than expanded or extruded polystyrene foams, 3/4" is just the width of the foam he used for his sponsons. G10 is an epoxyglass with a USA certification for PCBs, it's very consistent, fairly strong and fairly easy to get hold of.

[HTVboats]

Divinnycell is a dense somewhat structural foam that makes sponsons a bit more ridged and better to fasten boom tube supports.
https://www.aircraftspruce.com/catal...iABEgIya_D_BwE

G-10 is an epoxy glass composite I skin sponsons and use for running surfaces that is much cheaper than carbon fiber.
https://www.mcmaster.com/grade-g-10-...eets-and-bars/

[RC boat addict]

Mic, I just noticed your point about rudder angle, I missed it back when I read your reply. Could you please expand on your comment it might explain a problem I have.
I fitted bigger sponsons, the set up weighs 7.6 pounds so I thought looking at the ML380build of SammyHal (my first wood build)as he got great speed out of a heavy set up with bigger sponsons, he also is running quite a lot of tub clearance to the water.
so when I made the bigger sponsons I also raised the tub,I also made a turn fin like the ML 380 has and looked at his CG and copied his battery and esc and motor and turn fin placement so now I have mire speed.but it turns way to sharp.
so I tried no turn fin as the sponsons dip in on a turn and I blamed my home made turn fin but this only helped slightly,the rigger still turns way to hard both ways.ss then tried higher AOT on the sponsons,thinking they are to low at the front at 3.5 degrees.so it?s now 5 degrees and its still no good ,I now realised I raised the tub height at the sponsons but not the rear shoes thus I think it has added forward angle at the bottom of the rudder.
Could this cause the sponsons to dip in ?
It will even bury the inside sponson under the water and then turn in its own length.

[Fluid]

Angling the bottom of the rudder towards the bow will cause the stern to squat, that?s not the problem although the rudder hinge should usually be set perpendicular to the water surface.

- Where is the CG relative to the center of the turn fin?
- Is the tub offset to one side?
- On which side of the transom is the rudder mounted?
- How much movement is there at the back of the rudder, full left to full right?
- At what speeds does it turn too sharply, full or part throttle?
- Why is the OP trying to turn hard left?
- Exactly what rudder servo is being used?
- What is “mire speed”?

Actually, without some photos it will be tough to diagnose the OP?s issue.
- side view of entire rigger sitting on a table with CG position marked
- transom rear view showing rudder and strut
- top view of entire boat
- rear view of right sponson showing fin



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[HTVboats]

Fluid (Jay T) has summed it up pretty well. In general I try to keep the tub and strut parallel to the water surface and rudder perpendicular. AS stated photos and detailed info on motor esc and batts help the diagnosis.
Mic

[RC boat addict]

Thank you both Fluid and Mic for your reply and insight,
I don't know yet how to post photos to this forum but I try to sort it out.
This rigger was very twitchy in its handling until I moved the turn fin forward a few inches and limited the servo travel to about 1/8 inch either way off center.
Prior to doing these two things, It would be going along at full speed and it would literally spin out at full speed at the slightest movement of the steering, seamingly on its own.
Once I done these 2 things it at least was able to get up to full speed and go straight but I am too scared now to give it a turn at full speed to see what it does so I have been slowing down to turn at this lower speed lets say 35 mph The sponson seams to dip in if turning to the right it can dip in that hard it spins out in its own length and the sponson can go completely under the water.
I tried it with the fin off completely and it is the same.Since my reply to mick I looked at the rudder angle and it is at 90 degrees to the water surface.
The photos will show the 5000 mah 50 c HRB 6S lipo at the front of the tub then the 200 amp ZTW Seal esc behind the lipo this ESC touches the front of the TP 4060 6D 1650KV motor right at this point is the COG, the COG is at the rear tip of the sponson. the steering servo and the radio receiver are nearer to the back of the rigger.
The rigger weighs 7.6 pounds ready to run.
I'm running a sharpened and balanced ABC 1717. I could not buy a 1816 in Australia at the moment but at least its better than the Octura M447 and the X452
The part of the sponson that touches the water at full speed is about 11/4 inches forward of the rear end of the lipo and about 6 inches forward of the COG.or 6 inches forward from the very back of the sponson.
I have tried the turn fin in 2 places firstly,wrapped around the rear sponson boom tube, this is puts the rear tip of the fin 11/4 inches forward of the COG this spot I thought would perfect compared to Riggers I have had in the past but it was not.
The second position was forward of this position so the leading edge of the fin was exactly at the trailing edge of the rear riding surface of the sponson so basically there was no air gap from the rear of the sponson step up, to the turn fin.
This position I copied from the ML RSX 380 on this forum(Sam Hallstom, my first wood build)Also this is where I got the size of the sponson running surface from and the layout of the LIPO ESC and Motor because its a similar size to my rigger with not to different motor and he is actually even heavier than my rigger.
I checked the ML RSX 380 on ML's web site and there is a side on shot showing like a see thru image of the battery and esc and motor in relation to the sponson tips etc.
This is not where I started of course, I started trying to build a bit bigger carbon fibre version of the KEPS rigger to suit the high powered very long TP motor I accidently purchased not knowing that 40 60 meant something different than 40 mm diameter and 60 mm long for some reason it means 40 mm X 92 mm after building it this way and it did not have any speed I went looking for possible reasons why, looking at the ML RX 380 and it having such big sponson and still handling and going fast I thought my sponsons were just to small for the weight.
So now I have more speed, not (MIRE) SPEED sorry Fluid it was just a typo. but the cornering is weird I am no expert and love playing with things even if I give up on this home made rigger and bought the ML RX 380 I would still build it and mould it so I could save the weight and have carbon fibre.
I would never do this as a business, its all to hard,and I am not good enough at making things look pretty but making these things go fast and not leak is well. an addiction now I am hooked.
Plus I live on the water on Lake Macquarie her in Australia so running them is easy but it comes with the salt water associated damage and cost when things go wrong.
Its says I can post attachments BELOW but I hover the mouse over where it says this and nothing happens, could someone instruct me on how to attach the photos.

[Fluid]

Yes, we really need photos. Basically you need to go to Go Advanced in the reply, then under Additional Options choose Manage Attachments. You can add photos from your computer, choose the ones you want in your post, then when done post. More instructions are here:

https://forums.offshoreelectrics.com...highlight=Post



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[RC boat addict]

Hello fluid, unfortunately there was no (manage attachments) in my advanced within reply. I read the link you sent as well but without the manage attachments I couldn?t even get started. I can?t even upload a screen shot but there was something about parse and email but nothing about manage attachments

[RC boat addict]

There is only a ticked check box saying automatically parse links in texts. And then another check box ticked saying subscribe to this thread and notify me of changes and also a drop down box saying instantly using email and other choices within the drop box none of which are manage attachments also another choice rate this thread excellent and choices and that is the total under advanced.
I am replying from advanced so I could read and write what I see below exactly.

[NativePaul]

No need to go advanced, there is a button at the top of the reply box 3rd from the right it looks like a painting of a tree in a picture frame and is called "insert image", click that and it brings up a pop up box, click "from computer" browse the file explorer to find your image, select your image, click "open" in the file explorer, click "upload file(s)" and it pastes into the reply a text link to the image it uploded from your computer.

[RC boat addict]

IMG_2608.jpgIMG_2611.jpgIMG_2617.jpgIMG_2614.jpgIMG_2615.jpg

[RC boat addict]

IMG_2618.jpg IMG_2619.jpgThis first photo shows the rudder and prop location.this second photo shows the strut is just below the rear skis and level.The above previous 5 photos are the first photo shows the placement of the lipo esc motor etc the second shows the AOT s adjustable on the outer edge of the front boom tubes the third photo shows the COG The 4th photo shows the fin bend the 5th shows the more forward fin mounting in this photo you can see the U in the fin where it originally mounted around the boom

[fweasel]

Alright, James you figured it out. Photos can be tricky the first go around.

[Fluid]

From the photos posted I don’t see anything grossly wrong with the setup. Most riggers are more sensitive to rudder inputs if the CG is well behind the center of the fin and they prefer the CG and fin to be nearly the same for neutral steering in a turn. I know the OP believes his boat behaves the opposite from this, which seems odd to me. My JAE rigger has the CG at about that location and the fin is about 1” ahead of the CG. It drives like an F1 car.

If the sponsons are digging in then they are either too narrow for the boat’s weight or their AOA is too shallow. The easiest fix is to increase the AOA by a couple degrees.

It isn’t possible from the photo to tell if the strut is parallel to the tub bottom. The OP may want to try lowering the strut to see if this helps or hurts his steering sensitivity. Are the rear sponsons out of the water when the rigger is at full speed?

Because his rudder hinge angle is adjustable, he can try moving the bottom of the rudder forward slightly - with the tub at the ride angle. This will take some weight off the sponsons in a turn and might reduce the risk of the sponson digging in.