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Dumas Drag'n Fly 40 - Vintage Build

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Old 07-05-2009, 02:57 AM
  #26
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

THANK YOU VERY MUCH I found the new versions at the MECOA site and it appears they have parts for my engine so I am going to clean it up and put it back into service in my dragon fly 40 rebuild.and I figured that was what the tap off the crancase was for ill just plug it off and run exhaust pressure to the tank....again thanks....
and what do you guys have against top secret hardware???im just curiouse why you prefer the aeromarine stuff over it?
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Old 07-20-2009, 03:35 AM
  #27
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

Week # 3 - 7/20/2009

I've been pretty busy doing other activities around the house but I was able to get some of the basic glueing done on the bulkhead pieces and cockpit sides.






One problem I ran into was that no marine hardware manufacture makes an isolated engine mount that will fit between the cockpit sides. It measures about 3 1/2 inches between the sides and all available mounts are 4 or 5 inch. I'll probably just fabricate something myself, modify one of the available mounts, or use the harwood block mounts that came with the kit.

This week I'll probably order the rudder, turning fin, engine, flywheel, and engine side universals.

This is the rudder I plan on using:





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Old 07-21-2009, 09:01 AM
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

Hi Fastkat
It's looking good so far. With regard to the engine mount thought you might be interested in the response to my 'hard mounting' in my AvL. Try this link - reply #7 onwards http://www.modelboatmayhem.co.uk/for...?topic=18573.0.

I was well past the stage of being able to do anything about it without a lot of pulling about but it looks like you still have the opportunity. All the advice I have received, on the forum and local guys is not to go hard mounting because of the stresses involved with vibration and the noise issue - it'll be the last time I do it - Hope it helps.

Might also pay you to check out Hydro Junkies replies on 'First Hydro' on this forum - he's been a great help to me.

Keep up the good work, know what you mean about household interference!

Regards - Ramon
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Old 07-23-2009, 06:10 AM
  #29
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

Nobody has mentioned using rubber washers or grommets on the mounting plate I don't think..

I will be going with plate mounts with my Drag N's (20, 40 & 60) and will be using neoprene washers top and bottom with a plastic tube spacer in the bolt holes so the screws stay isolated from rubbing the plate, and also keep it located.

I can't see any drawbacks to this other than maybe adjusting how many washers are needed. It will change the motor height but have a good guess with how many washers to start with while building to help locate the stuffing tube.

The drawing is crude but it shows the order and placement of the idea. The plastic spacer will obviously have to be trimmed to be a little shorter than the stack height of the assembly to let the washers do their work.

It does not take much to take the "shock" out of plate mounts, and most the trouble that comes with this type of mount is not pinning the bolts through the hardwood blocks and the epoxy that is holding them in cracks and then starts the damage from oil and water.

I think that those iso-rubber deals rob RPM's myself. I know the effects of a loose motor in its mounts from my 1/2A control line days. You loose most of the top rpm's badly when that happens. Back then it meant it either it could pull itself or it couldn't and you ditch it, and there was no audiable difference to tell you when it existed.
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Old 07-23-2009, 09:42 AM
  #30
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

Thanks. Your design for the isolated plate mount may be exactly what I need.
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Old 07-23-2009, 11:47 AM
  #31
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

Jetpack, up here in the backwoods of the Pacific Northwest, we use the rubber isolators all the time without any loss of power or RPM. The trick is to use them vertically, fastening them to the bottom of the boat and then bolting the mount to them. If used in this manner, they are stiffer than if used horizontally, support the engine and still absorb vibration. Just so you know, the scale boats at the NAMBA NATs were almost as fast as the larger riggers in lap times using this set up. I would stay away from using the block mounts if at all possible for two reasons:
1) they add weight that really does nothing except take up space
2) they transmit vibration right into the hull which can cause radio problems and break glue joints

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Old 07-23-2009, 05:02 PM
  #32
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

I guess iso-pads would work under a motor plate then just as well and just go with a shorter, thinner lighter version of the motor blocks if not wanting to bolt through the bottom of the boat.

For me, a plate mount is prefered over rail mounts because of the strength factor it adds to the engine, but getting it isolated well enough is the challenge.

They can be home made quite easily for any engine you want to try in your boat and makes swapping out different engines a pretty simple process, plus you are putting no wear on the engine lugs if your keep your motors with the plate.

Granted, they don't have as much bling as machined soft mount systems (or can they) but for me there's a couple better points to stay with using them besides having to be trapped inside the narrow cockpit width.
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Old 07-24-2009, 01:46 AM
  #33
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

Don't even have to be machined to use the isolators. A piece of 6061-T6 aluminum 1/8th sheet stock will work. You can go thicker but you would probably have to tap the mounting holes to hold the isolators. Just cut to size, drill out the holes for the isolator studs to go through, cut a big enough slot to accept the engine and drill holes for the mounting screws. If you use self tapping screws you don't even need a tap. Heck, you can even use one of those Octura extruded mounts the same way, just cut the flanges to fit between the engine bay bulkheads and call it good. NOW IN MY CASE, since I have a mini-mill, I would be making mounts to go along with the isolators. I'd be dropping the engine down as low as I can get and going from there since I want the CG as low as I can get. As I said, thats me
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Old 07-28-2009, 01:54 AM
  #34
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

Fastcat, just curious, which side do you plan on mounting that rudder on? If you're going to mount it on the right side, the one in the picture is fine. If you're going to mount it on the left side, you need to get a rudder assembly set up for the left side. This puts the rudder arm on the right side of the rudder. I have the same set up in my scale Muck hull, at least until I replaced the blade pivot. My bracket is now mounted reversed from the picture with the arm on the right. BE AWARE THAT THE PIVOT CANNOT BE JUST INVERTED AND STILL HAVE THE BREAKAWAY WORK PROPERLY

Just had a thought, you might want to order a "short" mount that places the front edge of the pivot assembly against the transom. That 1" can make the boat corner much tighter if set up right. I wouldn't get any of the bracket extenders with the holes milled into them as they move the rudder away from the boat which increases turning radius and adds unneeded weight. Dont' know if you can tell, but I'm a fanatic about eliminating excess weight
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Old 07-28-2009, 06:28 AM
  #35
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

Hydro Junkie - I'm mounting the rudder on the right hand side. The pic below shows the rudder and how it will sit on the transom. That's a good point about the turning radius of the boat with a longer mount. I ordered the shortest mount they had but for appearance sake ( Didn't think about turning radius ).

Rudder Part Number: Speedmaster SPDR-010-40SB

Thanks FastKat

P.S. Anyone looking to purchase a rudder. The Speedmaster rudder is an awesome piece, the machine work is fantastic.

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Old 07-28-2009, 07:38 AM
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

Speedmaster is a good one. I have that same rudder on my sport 40. Pricey but it is machined professionally with good sharp tooling.

I've kicked around what I plan on doing for my hardware and I think I'll build in a secondary transom far enough forward to mount an Octura aluminum strudder assembly with the drive dog even with the back of the hull. Still sketching on that one...

Meanwhile here's a pic from a 1960 kilo record run of a cabover. 115mph that day took the record. Check out how high the transom is riding.
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Old 07-28-2009, 09:51 AM
  #37
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

Jetpack - That would be an interesting way to mount the strudder. I guess you would just have a slot in the transom and a slot in the bottom for the strut to protrude through. I think once you had everything mounted it would look very similiar to the seperate rudder/strut setup. How would you seal the rear transom to the strut bracket? Rubber boot?

That cabover is really flying. I always find old racing pics interesting because of the minimal safety gear they used to wear. These days they would have breakaway safety capsules, parachutes, breathing systems, etc...
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Old 07-28-2009, 10:54 AM
  #38
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

It would turn out looking like the back of a Hot Shot IV tunnel. Instead of an outboard mount, the strudder bracket would be mounted in its place. Nothing would have to be sealed. Maybe a drain hole in the transom plate to let whatever gets thrown in in front of it a place to go, or cap that area with the canopy. The bottom doubler plate can be omitted this way because there won't be any load of a strut to the bottom sheet. The cockpit sides are being used as the load bearers. Another plus there will be no holes having to be put through the bottom surface.

The only drawback I can figure is it will look a little odd.
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Old 07-28-2009, 06:42 PM
  #39
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

Like boat, like builder
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Old 08-08-2009, 02:00 AM
  #40
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

Hi
Saw your posting re the HP40 engine. Was trolling around and saw the Drag'n Fly and remembered I always hankered after one but being in Africa they were never imported here and US outlets usually weren't interested in exporting single kits, too much hassle.

I used to use these motors in RC boat races and they are/were fine engines. Still have one somewhere around I think but if memory serves correct they were made - in Austria as you know - by a company called Hirtenberger Prazionstecknik. Spelling may be a little off there. I see that yours is the manufacturers marinised version and that was one of the reasons I bought them, no problems with using them in boats or clamp on water jackets. I used to run a tuned exhaust on a home made manifiold and when that motor hit the pipe it used to fly!

Only problem i ever had was the rear bearing which used to get hammered quite quickly, mainly I think as bearings available here were not such great quality, never lasting as long as the original bearing.

The pipe from the crankcase is to allow you to use a presurised fuel tank. It makes a big performace difference when the motor is flat out, especially on a tuned exhaust.

You've got some fun ahead of you. Hope you enjoy and hope this is of some interest. If you like I'll see what i can find here, may still have a leaflet hanging around but haven't looked at this stuff in years. I was active back in the early 70's so that'll date the engine - and the Drag'n Fly too I guess.

All the best with the new boat

Regards

Graham
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Old 08-10-2009, 11:28 PM
  #41
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

Thank you very much..I am planning on re using that engine in my dragon fly40...and wheres the rest of the build???
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Old 08-11-2009, 03:00 PM
  #42
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

Week # 5 - Progress Update.

We'll been waiting for some "spare" cash to buy the engine. But I finally got it today. I went with the O.S. VX-M .46 Hopefully it will be enough to get some speed out of this boat. I couldn't mount the bottom center sheeting until I had a reference on how the engine was going to sit in the boat and get the correct angle for the drive shaft. Also I wanted to mount the drivetrain and radio before I put the final top and bottom sheeting.

I did get the sponson sides and bottoms, non-trip chines glued onto the framework and profiled. I think the shape of the boat is going to be awesome.

For the motor mount, I decided to use a speedmaster aluminum mount, but I won't be able to use the provided ISO mount. ( Because of total width ) Instead I'm going to use a 1/4" piece on neoprene on each side of the cockpit side and a rubber sleeve over the bolt. This won't be as good as the ISO rubber mount but should effectively isolate the engine from the boat and still keep me from having to do alot of metal fabrication.

Something Like This : Red is neopene sheet, Green is cockpit sides, blue is rubber bolt sleeve.




Here's some other pics of the progess so far.





Boat Bottom: Sheet not glued in yet.






O.S. Engine and Speedmaster Mount.



Well next update everything should be mounted in and have the sheeting completed. I'm shooting for Mid-October completion to see how she'll run before it gets too cold here.

Take Care,
FastKat
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Old 08-11-2009, 04:49 PM
  #43
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

[8D] The sheeting is turning out niiiice. Good job on sanding the sponsons and leaving the ride pad thickness along the sides. Most just sand it to the same angle as the non-trips, but you loose doing that with a soupy ride.

Your new D-port should move out just fine. Looking right at home in the cockpit, and well protected with this design from those occasional deck rides others can't help from happening. I plan on putting addional strenth to the sides with mine by using a maple strip on each outside edge drilled and pinned full length. It will also help to add thickness to the end grain ply for chips and splinters.

One thing I've really wanted to build into mine is movable air traps, or at least detachable ones with a few different sets to try out.
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Old 08-11-2009, 05:43 PM
  #44
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

Jetpack - That's quite a collection of dragnflys you have there. Do you have any videos of them running? I've looked around and haven't found any. I notice the one white boat has a "modified" sponson on one side. Does that help speed/handling?

I like the idea of the maple strips mounted to the cockpit sides to increase strength. I had thought about building the cowl / tunnel cover, but make it half length sloping towards the rear. I'll probably do the strips inside to provide a mounting surface for the cowl.

You mentioned movable/detachable air traps. What do those look like? How do they work?

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Old 08-11-2009, 09:03 PM
  #45
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

None of those are my dragons, just a couple years of saving pics on ones that turn up for sale on ebay. I've had thoughts of this kit way back when it was new in the catalogs and always kept an eye out along the way. Sorry no video. The only thing I have of one in action is a snapshot but it gives you a taste how one looks on the lake. This one was an older 40 motor I believe with a normal strut arrangement under the boat if I remember right.

About the modified outside sponson, you probably mean how the side is sanded smooth with no ride pad lip? Can't spot the detail, maybe point it out some more.

You already know what air traps are but never knew the name, they are the skirts formed by the cockpit sides under the boat past the sponsons that form the air tunnel under the hull. If you play with the depth and length of them, you can help fine tune the ride of your hull. If the back of your boat is heavy, you try and capture as much air as you can and carry it back through the tunnel using deeper skirts.

Actual full size hydros are able to change these traps to adjust for conditions and handling, but there are also rule dimensions you have to stay within, but there is room for playing.

To make removable traps on scale hulls, the easiest way I guess would be to use sheet aluminum and bend the proper degree in a sheet metal brake to match the sides of the non-trip section and fit fairly well to the ends of the sponsons. The bend would then be screwed into cleats built into the hull along its length.
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Old 08-11-2009, 09:25 PM
  #46
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

You mentioned your boneyard of pics is empty of dragons and you're working on the cowl, here's some work others have done that you might be able to use for thinking.[8D]
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Old 08-11-2009, 10:06 PM
  #47
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

Air trap pic. Hard to find the right one to show you.

To build them into the hull as movable, it will require building in a pocket for it to slide and tighten into the cockpit sides. They should be made to allow independent depth settings both front and rear.

Having trouble with a high sponson down the straight? Spill more air out the high side by sliding up the air trap more near the rear of that sponson and get rid of that air early...
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Old 08-12-2009, 05:17 AM
  #48
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

Jetpack - Thanks for all the information. There's alot I need to learn. The pictures give me alot of great ideas for building the cowl.

The white boat left sponson appears to have the left sponson widened behind the normal sponson area. Maybe it helps the boat get on plane more quickly??

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Old 08-16-2009, 11:21 AM
  #49
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

I think what you are seeing there is just a bad picture due to the gloss of the boat, but if it is widend it would stem from wanting the boat to have more front lift on the outside during the turns because that is where most of the weight is being thrown to.

There are places on a hydro where things aren't necessarily symmetrical to get it to handle because of them normally being oval racers, such as blending the outside sponson's non-trip into the sides of the bottom to get it to skate better sideways when turning.
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Old 08-17-2009, 01:22 PM
  #50
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Default RE: Dumas Drag'n Fly 40 - Vintage Build

GREAT enjoyment reading you post air trap .air escape STOP blow overs, we hope My Atlas Vanline did a great 440 flip 360 +180 A guy in the North West area showed me this . Hydro Junky may have seen this setup . That hull hasn't seen water with this setup results I don't know . Notice holes for air fin on frount canard
Here is another option
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