HPR C5008 185cm prop size dilemma... Any suggestion???

[ManuelW]

Hello 6Boost,

interesting that you seem to have the knowledge. But then the big question is "WHY"?

Why is it necessary to use 2x 18-21S and 3080's in this hull, beside being very dangerous? For SAW purpose I'd say its no problem to get this boat with 2x LMT 3040 and 10S1P 5000mAh Lipos per motor to 100mph, with 2x 3060's on 12S1P each you could aim to reach 125mph IF the hull alows it. So whats the point of using this big engines and so much lipo cells?

Best regards,
Manuel

[6BOOST]

Hi Manual, are you friends with Hanspeter? I have a mono on order with him now.

How do you justify running the same speed in a 20% larger boat with the same motor? The record is held by a 53" boat with twin 3060 LMT, so I don't see why it would seem unreasonable to think that the twin 3080's are a perfect match for the larger hull for similar speeds.

As far as running 18-21s vs running 10-12s goes, we could debate all day, but you learn very quickly in drag racing that just because it's the way everybody/most others do something, doesn't mean it's the best way of doing it. You may want to keep in mind tho that I am not running the same kv motors or close to, and my total rpm will be very similar.

As far as knowing what I'm doing goes, with 9 boats, 14 motors and as many batteries and esc's, I can assure you that my path of destruction will be done with on the cheaper boats before stepping the 3080's up to their ultimate potential in the CT03. I don't want to claim speeds and list goals, I am just here to learn and have fun like everyone else, I look forward to sharing my triumphs and failures with everyone and hopefully we can all learn something together=) Work can't start in earnest until I finish building a race car for a customer, so a few months yet but all in good time.

6BOOST

[ManuelW]

Hi 6Boost,

yes I'm quite a good friend of Hanspeter and also help him out from time to time.

And for the record: Well I'm not sure which one you mean, except one HPR06 from Florian Schönböck all >125mph cats are in the 53" size and run motors like LMT 3040. I've never seen one using 3060's. These were just a few recommendations I could give you, what you try or not is your decision.

And nice hint with the idea of different thinking, but maybe there's a reason that up to the Fighter Cat ESC every available ESC or charger had its limit at 14S (one exception: Kontronik PowerJazz could be used up to 15S). Even all the electric powered 233's used 12S setups.

Best regards,
Manuel

[6BOOST]

That is correct Manual, all the cats are 53", NOT 67" like mine. That is nearly a 30% bigger boat, and it takes exponentially more power to move a bigger boat, so I think the engine choice is perfect AND logical, however time will tell. I will be back to back testing with NEU 2230's which some claim are better than the LMT3080, most say not quite as good, time will tell=)

You should have a paypal notice for payment for my HPR mono, please let Hanspeter know when you get it so that he can get my order ready=)

Regards, Kyle.

[graill]

Manuel gives sage advice. Pay attention to it. :)

I have flat out refused to help folks with builds when they show they know nothing about electricity and speed or are out just to have something because they can. Sounds mean, but it removes onesself from responsibility as Manuel alluded to and hopefully makes the folks with zero FE experience think twice about building monsters that will cost them or someone else.

[NativePaul]

I have gone with 3s batteries for my LMT3080/7's (similar kv) so that I can step up in 7500rpm steps from 15-18 and 18-21 for saw purposes. This will bring your heat down and your speed up and put less strain on the esc's

That is 7x 3s packs in series for 21s, assuming 4" on the ESC and if a typical pack comes with 4" of wire that is 64" of wire in your system, if you can cut them and your ESC down to 2" average and manage to connect them up you would still have 32" of wire and 8 pairs of bullets, many ESC manufacturers recommend having less than 8" of wire between the battery and ESC. I would ask your father about inductance before you run it and either rethink your strategy and use bigger packs or ask him to design you an ESC that will cope, because I don't think anything off the shelf will for very long.

[6BOOST]

That is 7x 3s packs in series for 21s, assuming 4" on the ESC and if a typical pack comes with 4" of wire that is 64" of wire in your system, if you can cut them and your ESC down to 2" average and manage to connect them up you would still have 32" of wire and 8 pairs of bullets, many ESC manufacturers recommend having less than 8" of wire between the battery and ESC. I would ask your father about inductance before you run it and either rethink your strategy and use bigger packs or ask him to design you an ESC that will cope, because I don't think anything off the shelf will for very long.

Thanks for the advise mate. Some things to take under consideration, let's say you stack the packs 3 and 4 high, and mount the wired ends towards each other, all connections can be at a maximum 1" long and still reach the next pack in series. Secondly, if the esc is mounted level with the centre of these packs, it would be more than feasible to consider that it would take less than 4" of wire from the positive and negative to reach the ESC. How will the bullets transfer the current? Don't know, with castle 8mm bullets I'd say they should pass 120-160a ok? Maybe not who knows, having 9 other boats with packs from 6s, 8s, 10, 12, 15 and up, I will find out long before I burn a pair of LMT's or esc's. If it means buying more packs later so be it, with so much money invested the cost of a battery pack is hardly something I'm going to skimp on for the best result, 3s packs at this point in time allow for the most experimentation across a range of projects.

I realize that there are noobs to this hobby that regularly waste people's time and dream like a 12 yo school boy, lacking the general common sense, dedication and problem solving ability to support their aspirations. Let me be clear I am not one of those people, I am fine with people questioning my goals and generally rolling their eyes, I do hope tho that when the time comes you look back and admit you underestimated me I will crawl before I walk, walk before I run, and run before I sprint, but rest assured I will sprint

Now, back on topic, with the money invested in your boat Peterpan, there will be a number of people able to help you with your props, however to get started get it built, buy some X450's and 457's in each rotation and do some testing and have some fun, worry about outright speed when you have a handle on it. Or do what I did and buy 1/a few other boats with some cheaper hardware and cut your teeth on that while doing a thorough build of this one, then by te time you put her in the water you already have a fair idea of whats going on:)

6BOOST

[graill]

Since your spending the cash 6boost, go with ultra lam connectors, 6 or 6.5 will do nicely for even the most demanding saw setup, though pricey (15 a pair), you get what you pay for. 8 mm are huge, hard to pull apart in the field or in an emergency and the solder job will need to be specific, plus you need to think about if your math is wrong, that big 8mm beast Will act as a heatsink in regards to your wiring, of course you know what i am referencing so i wont bore you with details. To date i have not found the point of manufacture for the ones floating around on the market.

If your investing so much into your artwork i suggest you use the best parts available, not ones that simply have no white papers or simply look good enough. :)

Good luck on your build.

[6BOOST]

Thanks for the heads up Graill, I will look into those today=)

[alhaddad]

[alhaddad]

Very nice to read all the rave information from you guys