First hydro help needed on old boat......please !

[69zandar]

Hello all , I just bought a dumas pay n pak off ebay because I need a hydro, Ha . I currently just finished a make over of a Great planes wildcat catamaran and dig the way a hydro looks especially the older ones so it seemed like the logical next step even though I am pretty green when it comes to F.E. boats. The boat has nothing other than just a assembled hull ( and I think it was a while ago ) and I would like to know where to start. I want to make it as badass as possible If you think it can. There is some dents and nicks in the wood I would like to repair ( epoxy ? ) as well as paint it to look like the original ( decals ?) I am not sure about the flexshaft, etc. I see it has a large stuffing tube installed already that point pretty low , I am not sure if that angle would be correct. As for power I have a few 3s lipo's already so I would like to use those unless you think I need something else .Wow Lots of questions but I will start there for now Thanks in advance and please let me know if there is anymore questions? pak 2.jpgpak 3.jpgpak 4.jpgpak 6.jpg

[rcboatmanwithkids2880]

Hi Mate ,

It's good that the hull you bought requires some work , as it allows you to come up with a colour scheme & power Set-up your of own choosing , at this stage . Looks like the hull is around 36inches long , so therefore you are going to need at least 4s battery power ( IMHO ) to keep amps relatively low . With so many good budget BL Motors available such as Leopard , the ball is in your court as far as brands go , though read threads on similar lengths of hulls & what is required to power them efficiently .....

Brad
Oz

[Boaterguy]

i have outrunner fever but upon reading his post I thought one of the 3736 FC outrunners on 4S would be a good start.
any idea what the diameter of the tubing is?

[siberianhusky]

It's an old Dumas kit so you have to keep in mind it was designed to run a pretty low powered nitro motors from back in the 70's. It can still be a fun boat but it will not handle the speeds and power people are getting with new motors.
The sponson design and air trap sections of the hull are just not the same as modern boats.
I'd remove the existing straight stuffing tube and replace it with an appropriate sized one for a flex so you can get the prop angle adjusted properly.
Try to remove as much wood as possible to lighten it up, paint it up nice and scale looking. Be happy with moderate speeds and have a nice running scale boat.
If you over power it it will spend most of its time on it's back.
Some people have put hours into re-cutting and changing the kit around, replacing the stock wood etc. trying to get them to run with the new designs.
I did own one of these years and years ago when nitro was it as far as power, was my very first hydro and 2nd of 3 Dumas kits I've built. First boat was a deep v 20, then this, than the original square nose 3.5 tunnel hull.
Cheers and have fun with it. They are a fun boat and can look really nice on the water.

[69zandar]

Thanks for the input , I would like to put a normal flex shaft in it , the current tube is huge , ha , I didnt measure it but I bet its about 5/16 to 3/8 or so. As far as cutting the old stuff out how do I go about repairing the wood , patching the holes , etc. Is there some where to find info on prop angle as well

[siberianhusky]

Can you post a pic looking down on it so you can see the entire "engine compartment"?
Kind of need to see where you can put the batteries. Some surgery could be required so you can balance the boat. The CG of the boat should be slightly behind the ends of the sponsons.
I have a 34" shovelnose hydro, either a 1500 or 1800kv motor from a SV 27 or the Mystic/Stiletto Proboat motor is what powers it on 4s as per the 1/10 scale hydro racing rules. SHould be ok, they race them so it must work!
There is also a group out west that runs under their own rules, their motor is a scorpion outrunner on 4s, not sure of the KV or size.
Not sure how it runs yet! LOL 2 year scratch build, went a bit overboard on the scale details, not sure I want to run it, well not sure I want to race it! It will make it's debut this spring, It's a 1957 Miss Wahoo.
Not expecting nor do I really want it to be a speed demon. Want it to look as good on the water as the beach.
Your strut angle should be pretty close to flat. With the boat on a table, sitting on the strut and back edges of the sponsons, the hull should be sitting level. This should put you in the ballpark for strut depth, being a hydro it will need some tuning to get it dialed in.
No idea what you could use for power with the 3s packs, all I've ever run is 4s boats, find them to be a great compromise between price and performance. Although I am trying a 2s powered cat this year, in the process of mounting everything in the hull. Saving up for the 300 amp esc!

[69zandar]

Thanks Siberian , That sounds like a nice boat , I have always thought the shovelnoses were cool looking ! I bet it would be hard to race it , Ha ! I currently have a 3060kv seaking and a 180a seaking in my 26" catamaran that I run on 3s and it seems to work pretty good . I also have a spare 180a esc that I was hoping to use on the hydro but all of that is to be determined . Would there be a benefit to the 4s and a 15-1800 kv motor ? Sorry still new to this FE stuff . Here are some pics I took with my phone so I hope the quality is ok


pak top 01.jpg.pak top 2.jpgpac side.jpg

The overall length of it is 30 3/4" . I also took a side pic to kind of give you an idea of how it sits currently , it sounds like its kinda close as is but I do intend to remove the prop bulb and goto a strut , flex shaft

[rcboatmanwithkids2880]

Yes it is an old kit , though fitted with a 7.5 - 11cc K&B units originally ( 60mph give or take ) , I don't think it has lost that much to modern design ( IMHO ) . Most F/E Boaters would be happy their boats achieving that kind of performance - just a thought. ...

Following this one .....

Brad
Oz

[siberianhusky]

OK sport 20 kit, I'll post pics of the inside of my 80-82 pay n pak it's 1/12 scale, just shy of 30". This one is a scratch build as well.
I need to get the graphics for it still, but i have run it a couple times at the end of last year, didn't have the right prop for it at the time.
Once again I'm using 4s and a "spec motor" the 2030kv Aquacraft motor from the UL-1 hydro in this one along with the 60 amp esc that goes with it.
LOL basically the same stuff but yet a different class of racing.

[siberianhusky]

IMG_0515.jpg

Here is the inside of mine, 2 2s packs in front of the motor, esc between the batteries. Thats the UL-1 motor and esc. Nothing is really connected in that pic, just stuck everything in there to show where it was mounted, the rudder servo is tucked under the deck in the back port corner.
LOL a bit of wood shavings in there, just added that block at the back to brace the transom. Need to brush on some epoxy to seal the wood and she's ready for spring.
A single pack may be the way to go in yours, mine is open under the decks so I can jam the 2 packs under there and wire them in series.

[69zandar]

Very cool ! That thing is really clean !! I have some work to do on mine to get there, Ha ! I did some test fitting in mine and I think I can get a 3c in front of everything maybe a 4c if I try and move the motor back a little . Am I right that I want to center the weight right around the rear of the sponson ? I have read that you want to be able to grab the skid fin and have the boat balanced at that point ? Is there a benefit to a 4s and a 15-1800 kv motor vs. a 3c and a 3000kv motor ( I am still trying to figure all of this out ) Another question I have is there is no way to access the rear of the right sponson from the inside for mounting the skid fin , do you just run some wood screws in from the outside and hope it holds or is there some way to do it right ? Thanks for all the help Siberian I appreciate it !!

[siberianhusky]

The benefit of higher cell count in lower amp draw for the same amount of power.
Say you have 2 motors each making 800 watts. One about 2700 kv on 3s one about 2100 on 4s
800/11.1 = 72 amps
800/14.4 = 55 amps
Both will turn he same rpm and produce about the same power but the 4s set up draws fewer amps to do the work, this means things will run cooler for the same work load. And run longer for the same mah pack capacity.
When you remove the stuffing tube you can move the motor just about anywhere you need it, then replace the tube in the new location as required. Use it and the batteries to set the CG, leave some room so you can move the batteries back and forth a bit for tuning.
The CG on mine is about and inch to inch and a half behind the sponson, depends a bit on speed and water conditions.
You can add a doubler to the back of the sponson on the outside, some 1/8-1/4" ply would work fine, use a syringe to shoot some epoxy inside the sponson through the turn fin mounting holes, I think I'd use sheet metal screws, then stand the boat on it's tail so the epoxy flows around the screws.

http://www.hobbyking.com/hobbyking/s...FInrunner.html

been thinking about trying one of these, people have been having great luck with the bigger versions of these motors. Should be good for 4s with a 120 amp esc. First runs would be with a 42mm prop then work up and monitor the temps and amp draw.
I'm using a turn fin from a JAE 12 rigger, happened to have it on hand, the turn fin from a Aquacraft UL-1 hydro would be a perfect fit, think they come with all the mounting hardware required. The cg should be somewhere in about the turn fin, not something I'm scientific about, I set it about right and run the boat make changes.
I've seen two identicle boats run completely different with the exact same setup and cg. Who knows, they could have come from different moulds, different day of the week? Chinese mass produced for one of the two big manufacturers of ready to run boats.

[69zandar]

Wow, Thanks again ! I am slowly learning more and more about the motors and that was a great help ! I did order one of the ul-1 turn fins , my dad bought one for his boat and it looked like a quality piece . The transom is pretty flimsy and well used so I think it needs a doubler of some sort. should I put it on the outside or inside ? I am going to basically gut the inside including the prop shaft so I will be sure and dial in the CG . Thanks for the turn fin tip , I was also considering some two part foam for the sponson I may try and drill a hole to pour it in,has anyone tried that? Thanks again and it is time to do some shopping on O.S.E. !

[Boaterguy]

if you do use two part foam, do multiple small pours, do not fill it completely either.
that stuff cracks hulls if used too generously.

[Rumdog]

no it wont. If you use the correct foam, and it has somewhere to go, it won't crack anything.