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Thread: Dumas Scarab


  1. #1

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    Dumas Scarab

    Hey Guys! I'm Lil Dave. Can you help me Identify? I know Dumas, I think scarab. I've been looking at ur forums all day and you guys are more experienced than I and would like your help to do A quality build. I got hull, 25cc homelite, and outdrive for CHEAP! I got my birch ply today and hope to get to making parts tonight. Thanks for looking!
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  2. #2

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    RE: Dumas Scarab

    Ok, So what Are the thoughts on mounting my outdrive? I like the idea of surface mount. Pros? cons? any mods That can be done to the little homelite internally? and finally cooling? I'm not going to run a clutch. wet liner?

  3. #3

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    RE: Dumas Scarab

    Mount your set up about 1/2 inch up and 1/8 -1/4 inch to right. Use 10/32 stainless blind nuts and 10/32 by 3/4 inch stainless allen bolts and you should be running straight turn like you want it to.

  4. #4

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    RE: Dumas Scarab

    Up and over huh? is that due to a flaw in the mold? I'm looking at mounting the engine, whats the best method at figuring position for best performance and handling?

  5. #5

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    RE: Dumas Scarab

    I started out with a setup much like what you have there. Set the outdrive up for surface drive. That is when the boat is on plane, ~1/2 the prop is in the water. This means that the prop shaft exits the hull right at the bottom of the "V" in the transom, not under the hull. Since you are using an air cooled engine, keep it that way. The trouble of converting it to water cooling is not worth the effort. It can be done but no gains are realized on a Homelite conversion.
    BTW keep the flex shaft from the trimmer if tyou still have it. The prop shaft looks to be 1/4" so adapters are readily available form parts houses to make the connection from the flex to the prop shaft. The bonus is that the square end of the flex shaft is the way it originally connected to the engine in the trimmer. Just create the stuffing tube to contain the flex from K&S brass tubing stock and your there! Check out radio boxes for your electronics from the same parts houses. I like the ones at http://www.eellspdx.com/ they work wellin deep Vee hulls, are quality and inexpensive.
    Check out Marine Specialties http://www.marinespecialties-rc.com/hullprice.htm for other goodies like the adapters..
    Good Luck...
    I never met an airplane I couldn't crash.

  6. #6
    martno1fan's Avatar
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    RE: Dumas Scarab

    Dave before you fix the motor in position place things in the boat where they will be going such as tank radio gear etc and hang the hardware on the back even if you just tape it in place for now then balance the boat on a broom 28- 30% from the transom,use the motor to find the balance point then mark for mounting that way your boat should be well balanced for best performance.As was said for surface drive exit transom 3/8" up from the vee to centre of hole for tube and 1/4" to right of centre to overcome prop walk which monos suffer from.Leave it air cooled and run as is,it will get plenty of air to cool the motor but leave the shroud on to help direct the air where its needed.You can mod the motor,a bit of simple porting will wake it up if needed but id run it as is first.Also a tuned pipe will add to its performance.
    Mart
    Waveridermouldings,Manufacturer of quality race proven Hulls.

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    RE: Dumas Scarab

    So Here is some progress pics. I measured the stringers at 5" apart, I made a reinforcement for the transom, and a second to make a compartment for the electronics. the reason for the crossmembers is i have to do things above required cuz I'm like that. I'm building the stringers and a web for the front out of the plywood i have left, I couldn't decide on stringer length so I'm doing the whole thing. I doubled them up because I have no idea what engine this may end up with once I get over the homelite. Once the construction on the support structure is complete I will glass into place and decide on a floatation material.

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    RE: Dumas Scarab

    I like it
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  9. #9

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    RE: Dumas Scarab

    So I'm finishing up my stringers now. I am having a hard time with mounting my outdrive up and over and not dead center. I understand why but I think it will look funny, can someone show a pic or two of how theirs have come out? Keep the tips coming boys, I appreciate them

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    RE: Dumas Scarab

    I never had an issue with propwalk with the prop centered on the transom. The V is sufficient to hold position and the Homlite is not going to develop enough power to lift the boat and allow prop walk. K.I.S.S. and put it in the middle of the hull and close to the bottom to keep 1/2 the shaft in the water. Save your money and effort on engine mods until you move up to a Zenoah. Then add a pipe and porting mods to wake it up.
    You can add some performance to the Homelite by opening up the stock muffler and gutting the baffels, stuffing the crankcase by adding to the thickness to the rear crankcase cover with 1/8" aluminum plate or using a very thin gasket between the cylinder and the crankcase to increase compression. The latter is sometimes a wash because lowering the cylinder also retards the intake port timing. These are old tricks but they are still valid today.
    I never met an airplane I couldn't crash.

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    RE: Dumas Scarab

    Cool. I finished my engine mount, since I am doing this on a really tight budget I made everything myself. as of now I'm into this whole project 130 bucks.. heh! So i'm saving for a nicer engine. In the process of glassing now and will post pics soon. My other boat is nitro and kinda finicky so I just want the homelite to be reliable and fun to play with until I get my hands on a zen. Is there any minimum distance from prop to transom?? My outdrive gives me an 1.250 distance. I was thinking of building a extension? Whatcha think?

  12. #12

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    RE: Dumas Scarab

    Heres a few new pics. I thing I got the center of gravity good. Nice and low and About 30%. Waiting on some parts now. and have to finish glassing.
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  13. #13

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    RE: Dumas Scarab

    Nice build!!! But I don't believe that's a Dumas Scarab 38kv. That boat has a center spine running right down the top of the boat. Also, the cockpit area is squared off, not rounded like yours.

    Beautiful job!!

    Darin
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    Duratrax Vendetta (Quark 33a Pro Car/Permax 400/4D) Losi Mini-T (Mamba 25/8000 kV)

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    RE: Dumas Scarab

    Its a Dumas 38 Scarab

    http://www.udisco.com/hobbies/pics/016032.jpg

    Dumas made a few type of Scarabs. The Scarab 38 KV is the squared off version.

  15. #15

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    RE: Dumas Scarab

    Gotcha! I have the Dumas 48 inch, and didn't realize they made another besides the 55. Thanks! I did note the "A Dumas Boat" badge in the interior..
    _________________________________________
    Duratrax Vendetta (Quark 33a Pro Car/Permax 400/4D) Losi Mini-T (Mamba 25/8000 kV)

  16. #16

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    RE: Dumas Scarab

    I have an original color catalog from Dumas with those boats, always wanted both of them.

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    RE: Dumas Scarab

    YEs! Thats exactly what I wanted. That is the first pic I have seen of a hull the same as mine! Any Chance of posting a few pics from the catalog? I'll be posting more pics soon. Thanks for looking! Keep the comments and suggestions coming!

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    RE: Dumas Scarab

    Well theres this picture

    http://www.udisco.com/hobbies/pics/016032.jpg


    http://www.happyhobby.com/hobb_html/.../dumas1440.JPG


    I'll look for the catalog, it may take a while to find it.


  19. #19
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    RE: Dumas Scarab

    Hey Dave it was good talking to you today! Didn't realize I got someone that's soo close to me with the same addiction We will deff have to get together to run some time. Build is looking great by the way! -Edmond
    WARNING: Socratic Method is in progress.
    SIDE EFFECTS: It will always make the β€œfake smart” look dumb.

  20. #20

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    RE: Dumas Scarab

    No worries Nd. Thanks for the pics. Darin, Have some pics of ur scarab? And Ed, I have ur number in my phone and I will be in touch. Feel free to call me and we'll go out for some hot laps! Tempe town lake!! lol

  21. #21

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    RE: Dumas Scarab

    Dave- I have some pics in my other thread, regarding a new motor in a Scarab 60- have a look!!

    Thanks

    Darin
    _________________________________________
    Duratrax Vendetta (Quark 33a Pro Car/Permax 400/4D) Losi Mini-T (Mamba 25/8000 kV)

  22. #22
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    RE: Dumas Scarab

    Expresscraft also makes a Scarab with the rounded hatch area http://www.expresscraft.com/scarab.htm

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    RE: Dumas Scarab

    Hey, ND.

    If you can dig up that old Dumas catalogue I would love to have a digital copy of it! If it is too much of a PITA another Scarab owner mailed me a copy of the original 38KV build plans, I scanned them and shot them back with a thumb drive hiding a set of digital copies of the plans. If you do not have the time to scan and don't mind lending the literature...I will do the same?

    Pop me line at tprice@villagemarina.com if you are interested...

  24. #24

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    RE: Dumas Scarab

    I have to find it first! Its in with about 30 years of rc boat,car,airplane magazines, plans, catalogs etc. Its good thing this rc hobby is only a passing interest...

  25. #25

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    RE: Dumas Scarab

    Heres a few new pics. I took My nitro Sk Daddle too out for it's first voyage today. It was ok, I lost a rudder due to a poor solder. I like muh gassers best. I may convert it to electric and use it to pull a floating line out for retrieval purposes. My stuffing tube on the scarab is stainless, so Is the hardware, I made all the braces from aluminum since I have more mechanical aptitude than money. Oh well I like being creative. I'm waiting on my radio box and outdrive standoff still before I can finish my glassing. The black is a 2 part epoxy which will be glassed over and likely painted. I'm still gonna put in the bulkhead behind the front tube mount I just need to make sure my rad box fits. Thanks for looking!!
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