40" BEFU Scale Scarab for sport build thread

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  • befu
    Senior Member
    • Aug 2009
    • 980

    #1

    40" BEFU Scale Scarab for sport build thread

    Years ago when I was a student in Kalamazoo MI, my boss had a 38' 377 scarab. That was a beautiful boat and fun to ride on and got me started on offshore vee hulls. the mystics are fantastic, but it is like that first kiss and love, you keep remembering it and going back to it. I love the large offshore Vee hulls! For years I ran the Dumas 55" 38kv Scarab hull with gas power. Ended up making several of them, still have a couple. fun big boat, but always wanted the simplicity of electric.

    Fast foward about 1-2 decades...... Alright, first picture shows my inspiration for this build. I got this in trade years ago from a friend in Kalamazoo and always wanted to build it. A bit small for gas as a scale, so it sat around and collected dust. Finally, I dusted it off and debated for several months then bit the bullet and pulled a mold. Dumas does not make these any more, so I figured if they won't make me one, I will! Following picture is the hull being molded.
    Note: I have never seen a vee hull molded this way, or any other boat for that matter. I did not know why, so I decided to try something different. Let me know if you have seen this before.

    Well, after pulling the mold, I hastily prepped it and pulled out a sample hull. Not sure how it would turn out or wanting to waste time, I did it quick. No vacuum forming or anything fancy, just good ole kevlar, carbon and epoxy. Popped the two halves out and started gluing them together.

    Not sure if it just looks mean and ready, or the fact that it looks like a phalic symbol that turns me on to it so much!!!

    OK, so now I have this 40" offshore hull. time to prime it and install stuff for a sport boat.
    Attached Files
  • befu
    Senior Member
    • Aug 2009
    • 980

    #2
    priming and hardware

    OK, so I prime it up, add a simple swim platform to the stern and set the original hatch cover in place just for ambiance! (scaring anyone yet!)

    Boat looks nice primed, so lets see if I can stuff things into it and get it running. Then if I am happy, I will paint it.

    Just for comparison, here are some pics of it. First is my DF mini hydro and the 18.5" BEFU mystic hull sitting on it. Another one of the 18.5" mystic hull being glassed sitting next to the hull, then a couple with the 32" twin drive apparition. Yeah, it is a cavernous hull after working on a few small boats like the HK bolt, DF hydro and mystic. Makes the apparition seem tiny on space.

    Hatch cover I am going to try vacuum forming from plastic. Not sure how it will work, but that is my plan for right now. It will eventually have hand railings and other details as well.

    For power, I originally planned on twins running through scale outdrives. Not real Z drives, but more like the old scale funcraft drive that I used to have on my gas boat. (see last picture) Replace the U-joint with flex cable and away I would go. Well, I am not the best with patience, so I am just putting a single drive in it. Still want something scale, so will go over that in the next thread.

    Brian
    Attached Files

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    • befu
      Senior Member
      • Aug 2009
      • 980

      #3
      interior and drivetrain

      Well, being inpatient, I started planning and studying. I read up on the traxas titan. It seems like a 36" boat that is going to be really fast on a motor that is rather small. I do not want 50mph out of this thing, but it got me thinking. Being a standard Vee hull for rough water and 40" long, got me wondering. I really wanted a scale looking drive, but didn't want to go to the trouble of making and building a steerable drive. So I started researching. Thier is something called a levi drive. It uses a fixed drive shaft operating as a surface drive, but the prop is wrapped with a U-shaped rudder. Interesting.

      One, it is a scale drive. Not a Z drive, but scale. Two, wrapping the prop will cut down on the large rooster tail a surface drive gives. That is impressive, but not very scale looking. But the U shaped rudder sticking 4" out behind the boat wouldn't look good either. So start again, looked at fountain boats. He has been running a pad and notched transom for years so he can mount the drives higher and run them in more of a surface mode.

      What the heck, I can make another hull if need be. Out came the dremel and I put a 3" step in the back of the boat. Now the surface drive exits the boat and the prop is right at the back of the transom. Works perfect for the levi drive, not sure how it will work for actually running! Another problem is you will need multiple rudders for trying different props. Trim tabs will be another interesting one, haven't solved all of this yet. Right now it has a 42mm prop on it, but it hits the rudder so I have to make a larger one before I can try it.

      Drive: I ended up selling my mean machine cat without hardware, so I took the 3648-1450 turnigy outrunner (36mm dia x 48mm long can) and mounted it in there. Going to try 42mm to 47mm three blade on it. Put in the HK SS 90/100 amp ESC. yeah, big bucks here, think I spent $45 combined on this combo. Now all I have to do is find room for some batteries! I have some 2s-4800's I can series up, or 3s-2200's I can parrel/series up. Will plan on running it on 2s, 3s, 4s, 5s and maybe 6s. I will start on 2s and progress from there with different props and measuring amps/speed. The drive isn't done, I am going to make a cover to hide the angle and rudder mount so it looks cleaner. After that, it will be hidden under the swim platform.

      Cost: Well, I had the original scarab. Mold cost me around $10 as I had some old polyester resin left over at work that I needed to use up. To old and thick to use in hulls, so a mold was perfect. The hull cost me the epoxy, maybe another $15 worth? $45 in the ESC and motor which I pulled from a used cat. I think everything else I had in the used box or made from scratch. So I think my cost on this so far is well south of $100.

      So, any predictions on what happens?

      Brian
      Attached Files
      Last edited by befu; 08-14-2010, 11:06 PM.

      Comment

      • Rumdog
        Fast Electric Addict!
        • Mar 2009
        • 6453

        #4
        You shouldn't have primed it! Looked awesome before? Can you take a pic of the keel? Looks different. I'm thinkin.... that bent double rudder may cause a lot of lift. Who knows though.

        Comment

        • befu
          Senior Member
          • Aug 2009
          • 980

          #5
          Keel and rudder

          Well, I went out tonight to run the crackerboxes and my twin apparition tonight. While out, I test floated the scarab. Not sure what to put in battery wise, I started with a few I brought for the apparition. So she is floating in the picture with 3s-8800Mahr of battery in it. That would be for slow scale speed I guess. i am thinking it needs more batteries to weigh it down.

          Rudder. I went large to try to limit the spray roostertail. I was going to try that and work my way up from there. that is only a 42mm prop on it, not sure if it will push it up on plane or not. The rudder I am making now will take up to a 47mm 3 blade hopefully.

          No comments or help on this one huh? Trying a larger boat for the first time. I really liked that scale princess build, so want to duplicate it in a scale scarab.

          does anyone think it will not work? or think it will work? For scale running, would like to get 20ish out of it. for faster fun running, would like to get "30ish" out of it.

          Brian
          Attached Files

          Comment

          • marko500
            Senior Member
            • Aug 2008
            • 861

            #6
            I'm watching this build. I have one of these hulls complete with hatch and a radar arch under a 1/2 inch of dust under my work bench. We've been trying to decide gas or electric but it seems that now the electric technology is catching up with these big hulls and big electric motor prices are dropping, or at least we have cheaper options. Is the hull you built any lighter than the original? If yours works out this may be my project for next winter. Please keep us updated.

            Mark

            Comment

            • befu
              Senior Member
              • Aug 2009
              • 980

              #7
              Originally posted by marko500
              I'm watching this build. I have one of these hulls complete with hatch and a radar arch under a 1/2 inch of dust under my work bench. We've been trying to decide gas or electric but it seems that now the electric technology is catching up with these big hulls and big electric motor prices are dropping, or at least we have cheaper options. Is the hull you built any lighter than the original? If yours works out this may be my project for next winter. Please keep us updated.

              Mark
              My original hull and hatch weigh in at 4lbs, 12 oz.

              This boat weighs in at 4 lbs, 14 oz. without hatch. Of course, all this one needs is batteries, so yeah the hull is a bit lighter. Lots of batteries will give a nice play time with it.

              Comment

              • marko500
                Senior Member
                • Aug 2008
                • 861

                #8
                Can't wait to see this hull run. My son has wanted to get this boat going for awhile now. Your build just may be the inspiration we need. I agree with you Mystic cats and the others are beautiful boats , but there is just something about the old Scarabs and Cigarettes.

                Mark

                Comment

                • treystoys
                  Senior Member
                  • Oct 2007
                  • 163

                  #9
                  I think your motor choice needs to be quite a bit bigger, slow speeds or fast, its not going to last long. I'm not up enough in recent years to make a motor recomendation for a boat this size, back when I was still competitively racing 30" electric boat was considered huge. I'm going to wager a guess that you'll need a minimum of 45mm worth of prop to get the boat up on plane, and you'll need something bigger motor wise to turn it.

                  Ask around a bit about motor recomendations from someone running large hulls already. I would like to see you get this running, but minus unwanted problems.

                  I personally love the older style offshore hulls, the aeromarine 50" apache is my all time favorite hull. I only wish they or someone else offered that very hull scaled down to about 35" to be more feasable to set up as electric and I'd be all over it.

                  Good luck

                  Trey

                  Comment

                  • Jesse J
                    scale FE racer
                    • Aug 2008
                    • 7116

                    #10
                    I gotta side with Trey, more motor. Beautiful work and very nice looking hull. I had that MRP Fountain (more like 39" w/o overhang) with not very dissimilar shaped hull. When I suited her up with 4S4P she ended up weighing in at over 12 lbs. Her problem was getting up on plane, I am sure you remember that video I posted, that was with a 46mm prather prop! That was with a 1300ish KV Neu 1524 1Y (I know a lot of $$) but I would go with something similar - just low KV and XL can with big prop should get you your scale speeds and not frustrating out of the hole woes. As for outdrive... I am interested in what your innovative rudder will deliver. Nice work and definitely outside the hull!
                    "Look good doin' it"
                    See the fleet

                    Comment

                    • marko500
                      Senior Member
                      • Aug 2008
                      • 861

                      #11
                      I was thinking about and looking at the Little Screamers outrunner that Steven sells here on OSE. Seems like it would have the power to push these big heavy hulls and the price is nice also.

                      Comment

                      • befu
                        Senior Member
                        • Aug 2009
                        • 980

                        #12
                        Trey, I agre with the 42mm prop. That is alot for it to push. If it does get up on plane, I think it will have a lot of prop slippage and be slow, like 15mph slow! I think the next rudder will fit a 47mm 3 blade, at least I hope. Until I fit it over a prop, I will not know. OK, it will fit when going straight, it is the turns I am concerned about.

                        With the step in the hull, I am hoping it has the wetted area of a 37" hull when up on plane. the titan does not have much motor in it either. Please keep in mind, I want a scale running boat, not a competitive racing hull. Remember Fastvee's princess build? Lower power, but had a submerged drive. So the motor should be fine, longevity should be more related to the motor lasting, not me abusing it. I will be pulling well under 70 amps.

                        Jesse, I remember your build, but do not want a boat with that much battery (Because I do not have that many batteries!) so my weight will be much lower. My speed will also be lower, yours was rather fast.

                        My motor is a 36mm outrunner, those will put out some good torque. It is also a low kv motor at 1450kv. I have used this motor on my Mean machine and it would push that no problem.

                        Mark, that little runner is way to much motor for what I want, that thing is a monster.

                        Think of it this way. Lets say I wanted to put a small cheap weedeater in this hull. Stock, it would put out about 1hp. it would also be rather heavy. But I do not think anybody would really question if it would get up on plane. It wouldn't be a race boat, but it would be a good sport boat. 70 amps on 3s would get me to 1HP.

                        We will have to see how it runs.

                        Brian

                        Comment

                        • treystoys
                          Senior Member
                          • Oct 2007
                          • 163

                          #13
                          Brian even comparing that motor to a cheepo weedeater is way off, think of the moving mass inside that weedeater motor, then compare it to the small brushless motor you have. A stock weedeater motor will still swing a 50mm+ prop which would get the boat going say a solid 25-30 mph, think of it this way, you say the motor worked in the mean machine...what was the prop you used on the mean machine? You'll need to step down quite a few sizes just going from a hydro to a mono of the same dimensions...now consider the fact that its 8-10 inches bigger, and has more wetted surface...see what I'm getting at? I just think the surface area of that big mono is going to overwelm the motor unless you plan to go with a 30-35mm prop and be content w/o planing the hull. Same basic principle applies about the motor in the mean machine working...think about the planing surface or each boat, with no measurements I'd guess the tunnel has less than a 1/4 wetted surface of the V...takes way less power to move a tunnel than a large V-hull. Just trying to save you some headaches...I may be out of the loop on the current set ups, but I was building fast electric boats when to make an electric boat fast, it had to be feather weight, smaller than 20", have a high dollar car motor you were willing to destroy, and were happy running about 90 seconds max at hopefully 25mph and that with a highly efficient set up. I just can't help but think about the time I tried to use a mabuchi 380 in a parma ski-tiger with a prather 215 prop hoping it would run...lets just say it planed out then the motor cooked itself. Trust me, I'm not trying to insult you in anyway, and maybe you'll prove me wrong but I think a motor swap would be a better idea. 1450kv means nothing unless the motor has enough torque to swing a large enough prop fast enough to move the hull.

                          Trey

                          Comment

                          • Jesse J
                            scale FE racer
                            • Aug 2008
                            • 7116

                            #14
                            another motor option keeping cost down would be one of those Turnigy motors, you could get an XL for $30-40 - I agree that the OR you are gonna use sounds a little light. I will be watching to see how it performs the way you have it planned out.
                            "Look good doin' it"
                            See the fleet

                            Comment

                            • befu
                              Senior Member
                              • Aug 2009
                              • 980

                              #15
                              Well, all valid points and I did ask for input, so I appreciate it. I do have a eagle tree with GPS and rpm sensor. So I think I will try it but put it out there, do a lap and bring it in. Go home, look at data and post it, go from there. I will definately be cautious about it, you guys have some good points.

                              I am starting to wonder about the larger boats again, I really like the 15" to 24" range and how easy they run. Even my twin apparition seems like a current hog. Stock it ran 32mph and was pulling 32 to 33 amps once up to speed on each motor - 3s. Acceleration spikes peaked in the 45 to 50 amp range.

                              Those dang crackerboxes are a hoot. My one son put a 2s-4800 in his. We ran it a long time and the battery never did go dead. They were just playing around and having fun, so not all out running. but a $8 2s-2200 battery will last at least 15 minutes running hard.

                              Thanks for the input, will be interesting.

                              Brian

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