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Dumas Drag 'N Fly 20?

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Old 06-20-2004, 11:28 AM
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Default Dumas Drag 'N Fly 20?

Hello all,

Has anyone heard or even built a Dumas Drag 'N Fly 20? I was just given one from a friend, and wondering if anyone has any building tips, or even running hardware selection tips? This will be my first boat that my Fiancee and I will be putting together (ok she's building and I'm supervising!!) I know this is quite an old kit just not sure how old....anyone have a clue? It has a few missing pieces (1 former and the engine plate) but that will not be a problem to fix.

Thanks for the help!!
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Old 06-21-2004, 08:23 AM
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Default RE: Dumas Drag 'N Fly 20?

The Dragon Fly has been around since the late 1960"s. It was my first heat racing boat. We didn't have a source for good marine racing engines at the time. Mine started life with an OS Max .19. I upgraded to modified Super Tiger .19's with a cool clamp, a Taipan .21, and finally a K&B .21. The boat was originally built stock (as show on the plans), but as we progressed, I pickle forked the boat, added small rear sponsons, put tunnel air dumps through the hull on either side of the engine and added an air dam across the forward part of the tunnel just forward of the air dumps. In it's day, it was the boat to beat in NAMBA District I. The boat still hangs in my work shop. No, it will never leave my shop. That boat and I have a lot of great memories racing with good friends in District I.

My guess is that the plans you have, show the solid drive shaft with universal joints at either end. Replace that with a flex drive system. Also get the prop out behind the boat. About 1 1/2 to 2 inches behind the transom is what I recall in my setup. Consider adding sponsons at the transom, just outside the tunnel walls and faired into the non trips ("wings"). No need to extend them past the transom. As I recall, they were about 1/2" high with 1/2" of width at the running surface. Don't go for a hot engine. In the stock form, you will not be able to keep the boat on the water. Blow overs will be a common event. A K&B .21 engine is the most power I'd put in the boat and that may be a hand full.

The boat will require an on plane launch. Don't expect it to get on plane by just dropping it in the water. In fact, that was one of my issues in racing mine. If it ever dropped off plane in a heat race you were dead. The boat would not get back on plane.

Enjoy the build and the on water experience. Be sure to seal the entire interior with thinned epoxy before the deck goes on. Water gets in where you least expect it and will ruin the boat if it soaks into the wood. Of course you will build with Epoxy! You can do a lot towards weight reduction by placing lightening hole in the sponson bulkheads. Use the kit supplied bulkheads, but I'd suggest you trash the Luan plywood they supply for the skin and use some good 1/16" marine plywood. I also used Epoxy paint on mine, but today there are a lot of good paints available.
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Old 06-22-2004, 08:26 AM
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Default RE: Dumas Drag 'N Fly 20?

I have one also, the pickle fork version. I built it to run for fun not racing, it has a .40 airplane engine with a kool klamp on it.
Top speed is probably around 45 mph, haven't had any blow over problems. I too put in a flex drive line, just bought a hardware kit from Dumas for one of their other boats, call them they can fix you up.

Like John said, epoxy coat the complete interior before putting on the deck, and don't forget to install some styrofoam for floatation. I would also highly recommend getting some 3/4 ounce fiberglass cloth and covering the whole boat with it or at least the deck and over lapping the sides. Wooden boats tend to develop small cracks from engine vibration which over time let water in and the hull will gain weight and slowly come apart. The boat will last a lot longer if you fiberglass it, it also gives a better surface for painting.

John, could you post some photos of your tunnel air dump mods?
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Old 06-22-2004, 03:42 PM
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Default RE: Dumas Drag 'N Fly 20?

Thanks for all the info guys!!

John, is it possible to get some pics of your boat? And maybe some good pics of the flex drive system. I've never put in a drive system, either solid or flex.....so some pics would surely help!!

Thanks again,


Oh, I will be putting in an O.S. 15CV - MX (pull start version).
Any help with flex shaft size would be of some help!
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Old 06-22-2004, 04:22 PM
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Default RE: Dumas Drag 'N Fly 20?

Dumas has a web page, look at some of their smaller boats and see what hardware kits they use with them.
They have a small hydro called Lil Rascal that uses a .10 engine and requires a flex drive kit.
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Old 06-22-2004, 04:27 PM
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Default RE: Dumas Drag 'N Fly 20?

Thanks Painless!

I've also been suggested Prather running hardware kit #1050. Haven't been able to find out what all is included with this hardware kit. I might just email Prather and find out. Have been to the Dumas site and there is an actuall running hardware kit for the Dran 'N Fly 20 that has a flex shaft instead of the solid shaft. I'm up in Canada and it's hard to find a hobby shop around me to get marine parts. And I also can't do online shopping because I don't have a Credit Card.

Thanks again!!
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Old 06-23-2004, 07:14 AM
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Default RE: Dumas Drag 'N Fly 20?

I will have to beg borrow or steal a digital camera. I don't think my Brownie Hawkeye will do. The hull is empty - engine, tank, radio and running gear are all out but I'll get some detail photos. I can't be of much help with hardware kits. I refuse to pay good money for something I can make myself. But that's another issue.
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Old 06-23-2004, 08:48 AM
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Default RE: Dumas Drag 'N Fly 20?

Thanks John......

I know the feeling about the digital cameras!!

What I need is a good pic on where the turn fin is located! I've been looking at different manufactures of turn fins, and they all look the same....I guees placement it the question here!!

Thanks again!
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Old 06-23-2004, 08:39 PM
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Default RE: Dumas Drag 'N Fly 20?

Here are a few picture of mine, hope it helps.
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Old 06-23-2004, 09:05 PM
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Default RE: Dumas Drag 'N Fly 20?

Hey Painless,

Thanks for the pics......

Helps alot. I notice you cut off the "Wings" from the non-trip chines. The pic of the underside is good too. This will help me alot.

Again, Many Thanks!!
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Old 06-30-2004, 11:02 AM
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Default RE: Dumas Drag 'N Fly 20?

OK guys, I've got pictures of my boat and the details we discussed. How the heck do I post the pictures??????????? I can't find any Help topics that tell you how.
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Old 06-30-2004, 12:46 PM
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Default RE: Dumas Drag 'N Fly 20?

Down in the lower left there is a link that says "upload images". This will open up another window where you can attach the files from your hard drive. There is a file size limit too, but it will tell you if you are exceeeding it.
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Old 06-30-2004, 01:20 PM
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Default RE: Dumas Drag 'N Fly 20?

OK, I'll give it a go. I hope this will be relatively PAINLESS.

Note in the pictures that there is also a mod I did to the sponsons to prevent the sponsons from digging in if the boat encounters wakes or generally rough water.
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Old 06-30-2004, 01:23 PM
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Default RE: Dumas Drag 'N Fly 20?

More. And a glimpse at my other side.
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Old 06-30-2004, 01:28 PM
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Default RE: Dumas Drag 'N Fly 20?

More again! And another chance to view my other side. Don't know why the other photos didn't go
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Old 06-30-2004, 01:49 PM
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Default RE: Dumas Drag 'N Fly 20?

Interesting tunnel mod. I'm surprized you had blow over problems with the engine mounted so far forward.
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Old 06-30-2004, 02:36 PM
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Default RE: Dumas Drag 'N Fly 20?

Painless:

If you look at the overall top view you can just make out a 1" square by about 1/2" piece of lead mounted to the bottom of the engine mount plate. The boat ran quite well in this configuration. I said it had a K&B .21 in it. That was a case of memory fade. The K&B is in my Mongoose Rigger. The D Fly had an OPS .21. Rough water was never it's friend.
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Old 10-08-2004, 08:18 AM
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Default RE: Dumas Drag 'N Fly 20?

I was thinking of parting with the silver boat in the photos above. email john10121@msn.com if interested.
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Old 12-02-2004, 12:26 AM
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Default RE: Dumas Drag 'N Fly 20?

I have a Drag N' Fly 20 MkII kit, still in the box and can't wait to get to it. I just need to polish out one more coat of K& B colors on my Sport 40 Eagle kit that I enjoyed...my first powerboat build.

Looking at the size of the MkII, and what the overall weight might be...I'm thinking of buying probably an OS Max pull-start motor...not going up fully to a .21 size motor. I think a hot .15 or maybe .18 would be good...looking for a rear exhaust mainly to get away from a sidepipe, but options seem slim on that.

Running gear will probably be an Octura setup. I'll have to get a current catalog and figure out what kind of strut is close enough to work...struts that I've shopped for and bought needing some cutting to fit the thin transom height. With running something smaller than a .21, could a fast electric strut and rudder work OK? They seem to be built lighter but strong enough for the .15-18 size engine. Has anyone thought of adding a flywheel to a nitro car motor? Would that type of engine and its tuning be good for a boat?

Looking at the plans, there is one area that I am concerned about building, and that is the trailing edge of the hull. The plans are showing the decks simply glueing straight to the floor sheeting...sort of a "V" shaped glue joint going on there...nothing to glue to except for another thin sheet of ply)...Has this caused any clamping (warpage) with it? When I go to epoxy it closed, thoughts of standing up the jig so the glue piles up in the "V" seam might help build the bond width, if it all doesn't run out first! I need help here.

I am also thinking about replacing all of the kit wood with clear aircraft birch ply...only because I would like just a simple clear finish this time with some trim colors added. What thicknesses or problem areas should be corrected when the templates are drawn from the kit pieces? Does it all fit OK?

Although I am planning on staying with the inboard version, I have often wondered about how the outboard version would handle. The KB .21 outboard motor I am pretty familiar with now would seem like too much weight swinging around back there and add top weight, but for right now, I am not familiar enough with RC boats to really predict the combo.

Overall...the MkII so far just from looking at the plans now that I OWN one...lol...looks to me like a really fun hydro to have to hang in a turn. My opinion looking at the sponson depth and the air dam angle....seems like it has too much angle of attack for high speeds. Would decreasing this help from the start? Or should it be left alone for the size of engine I am planning?

The motor plate mounts are designed as wooden with captured bolts acting as studs...Not good if one happens to strip out or breaks loose and turns..is there any way this can be improved or failsafed?
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Old 12-02-2004, 10:42 AM
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Default RE: Dumas Drag 'N Fly 20?

Jetpack, take a look at the photos of my (retired) DragonFly. There are a lot of modifications incorporated to keep the boat on the water. The final engine in the boat was an OPS 21. It was very competative in light wind conditions but in wind it would blow over in an instant. Also had to add the mods to the sponsons to try and resolve the tendancy to nose dive if it hit rough water. I never had an issue with the deck joint at the rear of the boat. I'd suggest you use only sloooow cure epoxy. It will give you a better bond with the birch plywood. As I recall, Dumas uses glorified mahogany door skin for for their boat kits. I'd dump the junk in a barrell and use the aircraft birch ply as you plan. Should be no issues with changing to birch. The DragonFly is an old design and will not take the power of a modern fire breathing 21. Putting in a tamer engine in the .19 cu.in. range is prudent.
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Old 12-02-2004, 05:31 PM
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Default RE: Dumas Drag 'N Fly 20?

Here are some updated pics of my [link=http://home.cogeco.ca/~probinson76/boats.html]Drag 'N Fly 20[/link] . Hope you enjoy.....any question I will be happy to try an answer.
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Old 12-18-2004, 03:44 AM
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Default RE: Dumas Drag 'N Fly 20?

Thats comming along pretty good. Looks like you chose the right strut and rudder and was wondering what you used. I would like to use the same with mine. What are your plans for a turn fin?
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Old 12-18-2004, 09:43 AM
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Default RE: Dumas Drag 'N Fly 20?

Bonehead, dump that battery pack system you have. Vibration has been known to cause intermittant contact with the battery cells and result in radio problems. Spring loaded packs work OK in the transmitter but are not a good idea in the boat. Also, depending on the engine you plan to use, the plastic prop is going to be marginal at best. At high RPM, you may loose the blades. Get a berillium prop. My Drag n Fly seemed to be happy with an Octura X445 and an X642 prop. That was with an OPS 21 engine. Other than that, it looks like you have a good handle on construction. Are you using thinned slow set epoxy to seal the wood - inside and out?
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Old 12-18-2004, 10:30 AM
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Default RE: Dumas Drag 'N Fly 20?

Hey John,

The battery pack is just being used for testing purposes....I will be changing to a Ni-MH pack when the boat is completed. Plastic props will be used to see what the boat will work best with, then I will switch to a berillium prop. Engine still has not been determined, will be in the .15 - .18 range for starters. And yup, thined 30min epoxy is what is being used for sealing.

Jetpack, stru and rudder are from Octura: OC6SBCOML-150 for the strut and flex cable and OC4WR for the rudder.
As for the turn fin, it will be custome made, and when I get to that part and finished, I will post a pic for ya.

Any pics that anyone else has I would love to see.

Thanks all
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Old 12-18-2004, 06:03 PM
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Default RE: Dumas Drag 'N Fly 20?

Bonehead, you may be disappointed with a .15 or a .18 engine. The power isn't there to push this boat. I'm guessing these are front intake engines as opposed to the rear intake with a drum valve or disk. The problem with the front intake engines is they are limited in intake area because they have to flow through the crankshaft. Where as a rear intake has much more intake area because it take the fuel air mixture through a rotating valve driven by the crank pin directly into the crankcase. I mentioned before that this is an old design that will not take the power of a modern racing .21 but would be happy with a tamer .21 like a K&B or an OS.
Also when you install the flex drive housing make sure you make smooth bends and make the last few inches line up center line to centerline with the strut thrust line. I've seen many installations with a hard bend at the entrance to the strut. You're asking for shaft failures with that kind of installation.
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