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Re-Engineering A Dumas Pay'N Pak

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Re-Engineering A Dumas Pay'N Pak

Old 08-11-2011, 12:41 PM
  #1  
Hydro Junkie
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Default Re-Engineering A Dumas Pay'N Pak

After several weeks of urging by other members of both this and another forum, I finally gave in and ordered a Dumas 20 sized Pay'N Pak kit and, rather than build it, decided to use it as the basis for a totally redesigned boat using nothing from the kit in the build. Upon opening the box, I found the usual Dumas garbage die cut 1/8 mahogany framing and the 1/16" birch skin. Unlike most of what I've bought from Dumas years ago, it was all surprisingly flat. I punched out the framing from the supplied sheets and went to work dry fitting the frames. Needless to say, I found little changed from when I built this boat back in 1982 except for the addition of 1/8" glue blocks added to the inside of the sponson insides. I decided right then that there was no way to make this into a boat that would meet my requirements so I began remanufacturing and reworking the parts into what I felt was going to be a much better boat. I've attached a picture of the dry fitted frame so you all would know what I started with
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Old 08-11-2011, 01:00 PM
  #2  
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Default RE: Re-Engineering A Dumas Pay'N Pak

My first changes after tracing out the sponson insides onto 1/16" birch was to change the bottom of the parts. Knowing the kit was designed around a Veco .19, I felt that the boat needed to be able to handle the power of a newer engine design. I picked the Nova Rossi .21 5 port to rework this kit around, requiring a wider boat that packed less air than a stock kit would. To this end, I decided to move the bottom break aft from the sponson transom to frame 6 as recommended to someone else by Grimracer if I remember right. This had the effect of changing the bottom angle forward of the break from 10 down to 5 degrees as well as moving the primary pressure point of the bottom further aft, helping take weight off the prop at speed. After drawing the new bottom profile onto the the part, I decided that to decrease the amount of air under the boat it would be advantagious to remove some depth from the sponson bottom. I decided on an arbitraty amount of 3/8" to start with and drew that onto the part. This now cut into the factory air trap, requiring a redesign there as well. Taking my cue from a Roger Newton color sheet for the 1973 Pak, I scaled down the shape and drew it onto the sponson inside, including the air trap extension back to the bottom break. After removing all the now not needed traced part outline, I started looking to the transom. Here I had to add length to accomodate the transom to keep the boat at 30". I added enough material to allow the part to extend flush to the outside face of the transom and again removed the factory lines. I now realized I needed to make one more change, the height of the sponson inside at the transom. The kit has an incorrectly arced top, not the flat top of the full sized boat. This required reshaping the top of the sponson inside so that it still had a slight curve and yet matched the height of the engine bay wall. With all the outside changes made, I cut the redesigned sponson insides from the ply and set them aside while I worked on the transom. This was an easy rework. I allowed more space for the engine and pipe using a 180 degree header, totaling 4" of width. I then decided to widen the boat further for better handling, adding to each side of the hull an additional 3/8" for a total increase of 1-1/16" up to 8-13/16". To get an idea of how the new design compared to the old, I now made a widened frame 1 and dryfit the parts of the frame. Seeing that everything was looking good, I cut lightening holes in the sponson insides and frame 1. I decided at this point to take another page from the Roger Newton play book and made some additional frames, NONE HAVING THE COWL INCLUDED. I also deleted the center part of several of the frames to clean up the inside of the engine bay. I had to change the bottom of the sponsons due to the new depth and in so doing, the left sponson retained the stock diheral while the right sponson now had no dihedral at all. After getting these parts finished, including the new bottom profile and engine bay walls, I dryfit the kit and reworked frames to get this set of pictures.
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Old 08-11-2011, 01:15 PM
  #3  
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Default RE: Re-Engineering A Dumas Pay'N Pak

I learned on my first boat to preplan everything and make allowances for changing as you go as every boat starts out one way and ends another. That's one of the reasons I hate kits is you can't easily make changes without having to fabricate new parts. I figure if I'm going to need to make new parts, I might as well remanufacture the kit. Here are some intermediate pictures I took to show how I've preplanned the build. The first two pictures show how the width was changed as well as where the engine will be located. The third shows the framing with some of the frames still needing to be finished.
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Old 08-11-2011, 01:31 PM
  #4  
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Default RE: Re-Engineering A Dumas Pay'N Pak

After making frames 6 and a pair of frame 7s, I decided to start assembly. I installed glue blocks to the bottom of the sponson insides and engine bay walls as well as the inboard end and bottom of frames 7. To keep weight down in the afterplane, I made frames 5 and 7 out of 1/32 ply rather than the 1/16 ply everything else except the transom was made from, it was 3/16". In the end, I ended up puting both sponson insides, both engine bay walls, the transom and the previously mentioned frames 6 and 7 together using West Systems 105 resin and 209 hardener while at the same time installing a resized and cut aft bottom. The bottom was installed to keep the hull square during the rest of the build. When the epoxy had cured, I added glue blocks to the frames for attaching the nontrips as well as adding frames 5 with it's glueblocks. The glueblocks were all installed at 45 degrees to match the angle I used on the ends of the transom as again drawn on Roger's plans. I included a third picture showing how the frames were clamped together taken from the kit build I ended up doing for the wife(build is being documented in another thread)
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Old 08-11-2011, 01:35 PM
  #5  
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Default RE: Re-Engineering A Dumas Pay'N Pak

The next step was to install the redesigned sponson transoms. This turned into a two step process. The first step was to get the locations of the glue blocks required to support the front end of the nontrip panels. Knowing the nontrips are set at a 45 degree angle, it was a matter of computing the location of the bottom end of the block. This worked out to 3/32" above the bottom of the boat due to the thickness of the nontrip panels. After the glue blocks were installed, the sponson transoms were attached with epoxy. The catch here is to make sure the transoms, especially the right one, is at 90 degrees to the sponson inside. To those that have never built a sport or scale hydroplane, this is one of the most critical parts of building the boat. Since the skid fin is mounted on the right sponson transom face, any deviation from square will affect handling or must be compensated for when setting up the boat later. It's better to get it right from the beginning and not have to worry later.
With the framing all installed, the outside top corner of the cross frames were notched and a 1/4X1/8" spruce glue rail was installed to the top of the glue blocks with the wide face out. It's important that the rail be high enough to extend above the finished height of the nontrip panel as this will be the surface the deck is epoxied to later. At this point, the nontrip panels were installed with epoxy and left to cure. In the second picture, the air trap and the extension are clearly visible at the base of the nontrip.
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Old 08-11-2011, 01:46 PM
  #6  
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Default RE: Re-Engineering A Dumas Pay'N Pak

With the sponson transoms installed and secured to the nontrip panels, I now turned to the sponsons. A 1/8" square spruce glue rail was installed to the inside the bottom edge of the sponson inside. Frames that were not finished previously were now finished, including the addition of lightening holes and epoxied to the sponson insides and engine bay walls with 1/8" square spruce glue blocks. I made two partial frame 2s from 1/32 ply, again to cut weight, while the previously completed frame 1 and now completed frame 3 were fabricated from 1/16". Frame 3, like frame 1 that was made earlier, extended across the full width of the hull, adding rigidity to the hull where it was needed most, in front of the skid fin. With the frames now mounted, the sponson sheer rails were fabricated from 1/8" ply and installed. Once again, I had to deviate from the directions with how the sponson chines were done. The directions said to "glue on the 1/8" mahogany parts into slots on the bottom of the cross frames, sand the sheers and chines to match the angle of the frames and attach the sponson side". To me, the sponsons need to be built heavier than that so they won't fall apart. To this end, I cut out two sponson chines from 1/8" ply and epoxied them into place. I then added a 1/8" glue rail and attached it to the outside of the chines to increase the strength and gluing area. Another glue rail was added to the inside to increase the area to attach the sponson bottom. A 1/4X3/16" glue block was now attached to the outside of the sheer/chine joint and the sheers and chines were now sanded to give them parallel gluing surfaces and glue blocks added to the outside edge of each frame. Since the chines were now heavily overbuilt, I removed a considerable amount of ply above the glue blocks using a Dremel tool. A final sanding and the sponson frames were now ready for skinning. At this point, I got away from woodworking and into set up. Rather than fight around the skin later, I machined a skid fin bracket and installed it using machine screws and blind nuts. I also installed threaded inserts into the bottom inboard corners of the sponsons as well as the bottom left corner of the underdeck area through the boat's transom. I'll stop here for the day and continue tomorrow. I have several boats that need building and a couple that are being reworked so...................................
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Old 08-11-2011, 06:41 PM
  #7  
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Default RE: Re-Engineering A Dumas Pay'N Pak

Time for a building break so I figure why not add a little more to the story?
I've come to the point where I have to look at set up, plumbing and all of the running gear going into the boat. My first task was to fabricate a doubler for the strut to pass through. Since I want a boat that will be legal to run anywhere, that and it would look tacky, I refused to mount the strut on the outside of the transom. I instead mounted the two "L" brackets to the bottom of the boat on top of a 1/8" ply doubler. A slot was cut into the bottom and a .21 sized .187 Aeromarine strut was then installed. Next, I machined a mirror image bracket for the Speedmaster .21 sized rudder assembly and installed it with machine screws and blind nuts. I next drilled a hole in the transom for the rudder pushrod, tobe installed later with the radio. Having everything else in the boat, I next drilled holes through most of the left side underdeck framing and transom for the installation of the cooling water supply tube. This was followed by a discharge tube through the left nontrip aft of the sponson transom. With all of this now in the boat, the last of the glue blocks were glued in and sanded to shape. The sponson sides were next added and, after the epoxy cured and the bottom edges sanded flush with the chines, the sponson bottoms were added. At this point, I again deviated from the instructions. The instructions say to add a running pad on the bottom of both sponsons, mounted along the edge next to the hull's tunnel. Since this boat is so radically different from the stock kit, I decided to forgo the runner until the boat shows it's needed. At this point, with everything that is under the deck installed except the fuel system, I installed any still needed glue blocks and sanded down the top of the frames and skin panels already on the boat to make the hull ready to accept the left side deck. Finding that I didn't need as much material for the sponson sheers, I used the Dremel tool again and removed almost all of the excess material. With the underdeck woodworking done, I now coated everything not previously coated with West Systems slow set epoxy. After the epoxy had cured, I test fit the kit deck on the hull. As I expected, it was considerably narrower than required so, using the kit's panel for a template, I traced out the edges of the deck onto a sheet of 1/16" ply and made the required corrections to fit the new hull. After cutting out the reworked deck, I used it as a template for a right side deck and then installed the left side deck. Since the reight side was already traced, I repeated teh sequence and installed the right side deck the next day. With the decks installed, the edges were sanded flush and the curve behind the sponson was finished, again based on the Newton Pak color sheet as I liked the curve from it better than the curve on the Dumas supplied deck panels
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Old 08-11-2011, 06:56 PM
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Default RE: Re-Engineering A Dumas Pay'N Pak

I realized after I made that last post that I didn't have any pictures of the strut or rudder installations so here they are. I included a shot of my remanufactured kit along side the Dumas stock kit frame so you could see some of the differences
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Old 08-12-2011, 05:23 AM
  #9  
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Default RE: Re-Engineering A Dumas Pay'N Pak

Thank you for taking pics along the way. A very good builder your are . Great presentation.
Old 08-12-2011, 05:31 AM
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Default RE: Re-Engineering A Dumas Pay'N Pak

looks awesome. makes me wish I read around here before sealing up my Miller, probably could have lightened it up a ton.

Out of curiosity, what is the target weight for scale hydros both this size and 1/8 scale? Mine is about 8lbs right now with everything but the engine, but I have no idea if thats within target range or not. I also have to check how much weight is on the prop once everything's together.
Old 08-12-2011, 07:42 AM
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In all actuallity, there is no right answer on either case. I've seen scale boats as low as 8 pounds ready to go(including fuel) as well as in excess of 20 pounds. The differences in performance were in acceleration and stability. The lite boat could outrun everyone but also blew over easily. By and large, the average falls in the 12-15 range for a scale and 4-7 for a sport 20. Prop weight needs to be kept to a minimum but, more importantly, the boat needs to be balanced just aft of the sponsons. If you can keep a majority of the weight forward, added weight can be kept to a minimum and prop weight will be normally in the acceptable range. That is why, in this build, I've tried to reduce weight as much as possible. It's easy to add weight to balance a boat, it's very difficult to remove it from a finished boat
Old 08-12-2011, 07:45 AM
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Default RE: Re-Engineering A Dumas Pay'N Pak

I'll bet many of you are saying "Wait a minute, what about the forward bottom panel? Doesn't that go on prior to the deck?" In this case, I left it off as I still need to install the fuel system as well as it made taping down the decks considerably easier. I was able to wrap the tape around the the hull through the bottom rather than stopping on the engine bay wall and hoping it would hold. Easiest decks I've ever installed
Getting back to the build, I installed two 4 ounce Sullivan tanks under the deck, one on either side just behind the sponson transom. I routed the system as follows:
pipe pressure to right tank vent
right tank outlet across engine bay to left tank vent
left tank outlet to remote NON-R/C needle valve and on to the carb

And again, something sounds wrong, needle on the left and going to the carb? My plan was to run the exhaust down the right side of the engine bay and, not wanting to get the fuel line against the header or pipe, I had Glenn Quarles modify the carb to be backwards, throttle on the right side, fuel inlet on the left. Anyway, with the tanks and fuel lines all in, I went to work on the bow blocks and cowl.
Old 08-12-2011, 07:51 AM
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Default RE: Re-Engineering A Dumas Pay'N Pak

The cowl and bow blocking has probably been the hardest part of the build. The cowl build started with fabricating a cockpit rear panel, part 7A in the kit. Tracing this part was not possible due to the wider width of the engine bay so, using dimensions from the kit supplied part, a wider one was fabricated. I then traced around the tail doublers and lower cowl sides and cut them out of 1/32 ply. To get the tails to the desired width up to the back of the cockpit, I fabricated a framework using 1/8" thick spruce stick stock with widths of up to 1/4" to fill out the tail and sidewall thickness. The vertical tail frames were then sanded to get a scale like taper along the rear edge of the tails. The precut skins were then glued to the inboard side of the vertical tails. The tails were then glued to a false floor that comprised the deck between the tails as well as the cockpit rear panel. To get the front of the cockpit width, I again turned to the Newton color sheet as well as pictures of the full sized Pak to make the new part 5A. I then glued a 1/8" square piece of stick stock to the outside of the tail framing, cockpit rear and the newly fabricated 5A, tapering the rear to get the right angle to the cockpit side. New frame upper halfs were fabricated using the height of the kit parts but with the widths adjusted to the wider engine bay. I now moved to the front of the hull and fabricated a nose cowl bottom block, adjusting the width and shape to match the wider profile and attached it to the front of frame 1. Before going further on the cowl, I added 1/8" glue blocks to all the vertical and top edges to assist in holding the skin. I now installed the lower cowl sides from tail to the front of the center nose block. I next attached glue rails along the top of the cowl frames on both sides to attach the cowl top and upper cockpit sides. At this point, the boat was starting to show that it actually was going to look somewhat like the Pak from the kit.
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Old 08-12-2011, 07:55 AM
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Default RE: Re-Engineering A Dumas Pay'N Pak

At this point, I attached the top of the cowl from the nose block to the top of frame 5A. After installing glue blocks to the upper vertical sides of the engine frames, I installed the upper cowl sides from nose block to the rear of the cockpit. The ledge panels were next installed from bow block to tails, giving a smoother look than with a stock kit build. Since the front of the cowl was glued to the deck, I coated the inside of the cowl from the bottom. I left the center of the cowl frames bare as that area is to be removed. I next laid out cut lines using dimensions listed in the kit directions and cut the cowl, removing the rear section that covers the engine and stock build radio box location. I next removed all of the excess material from the cowl frames and sealed up the remaining bare wood. With the cowl now completed except the wing, I installed the forward bottom. The left and right bow blocks were then shaped and installed. The outside of the boat was then coated with West Systems except the center of the bottom. This was left bare until the engine mounts and stuffing box were installed. I next fabricated a wing in the same manner as an airplane wing. Using the wing dimension from the Pak color sheet, I cut a piece of 1/32 ply to 12X3-1/2". I next installed a leading edge made of 1/4" square spruce stick stock. I followed this with a trailing edge made of 3/8X1/8" spruce stick stock. Using the wing tip shape from the color sheet, I cut 7 wing ribs from 1/16" ply and sanded to the rough finished shape. At this point, the wing top was sanded to get the correct airfoil EXCEPT the leading edge. I next attached the wing top skin and, after the glue cured, sanded the leading edge to shape. I didn't attach the wing at this point as it was still unsealed. I also still needed to round the front edge of both tails. This was the boat's configuration when I took the boat east. The picture on the right shows the boat as it was in Grand Rapids Michigan
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Old 08-12-2011, 02:25 PM
  #15  
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Default RE: Re-Engineering A Dumas Pay'N Pak

And now comes the fun part, INSTALLING THE DRIVETRAIN!!!!!!!!!!!!!!!!!!!!
I'm going to tell you all what I did while on the road on this one and then go back and document the changes I feel I need to make to do a proper install. My first step was to make some engine mounts. I used .091" thick 6061 aluminum plate purchased at Hub's Hobbies in the Mineapolis south side suburbs and, using a Dremel with a cut off wheel,. cut off approximately 1" from the end. I next cut the strip in half giving me two pieces roughly 1X3". I next placed the engine in roughly the center of the factory edge and, using a small drill bit as a punch, centerpunched the locations of the mounting lug screw holes. Using the appropriately sized bit, I drilled a hole as located earlier, followed by running a 4-40 tap to make threads. I next screwed the plate to the mounting lug and verified the second punchmark was in the center of the screw hole. Finding it slightly off, I used a smaller bit and, turning the bit by hand, started drilling a starter hole. With the location now corrected, I removed the screw holding the plate to the engine. I then drilled and tapped the plate to complete the second screw hole. This led to the fun part, locating the hole location for the second plate. I took the easy way out on this one, laying a square on top of the first plate and drawing a line from the center of the screw holes to the edge of the plate. I then laid the second plate beside the first and marked where the lines ended on the first plate. The square was then used to draw lines from the marks across the second plate. With the locating lines now drawn, I punched starter points for the screw holes, followed by drilling and and tapping them. To verify I got it right, I screwed the plates to the engine lugs and found one of the plates was drilled too far in, forcing it upward at the outer end. This was cured with the Dremel, bevelling the edge of the plate enough to get it horizontal. I then laid out and drilled a 1/4" hole in each outboard corner for mounting the plates into vertically placed "Humdinger" rubber isolators. Using the same dimensions as on the aluminum plates, I made a "template" of the engine mounts and drew it onto the inside of the boat's bottom.

To locate the holes through the bottom of the hull for the retaining screws, I took the 1/4" drill bit and used it to make a pilot dimple in the template. I tacked the template down with a couple of drops of CA and ran a small drill bit through the template and the bottom. I next removed the template and fabricated a pair of doublers from 1/8" plywood, securing them to the bottom of the boat with a line of CA down the middle, followed by weighting them down to cure.
Once the CA had cured, I back drilled the bottom and doublers with a 5/32 drill bit and followed that with a 1/4" bit. I next used a coundersink and bevelled out the holes on the bottom and inserted four flat head screws through the botton, securing them with the Humdinger rubber inserts. The last step(so I thought) was to install the mounting plates and engine onto the rubber mounts. It was at this point that I realized I had a problem What I found is in my rush to get the boat ready to go, I forgot to consider two things when I cut the plates:
1) The pressure line to the right side tank and how far out it would protrude
2) The width of the wide part of the pipe
The first one wasn't a big deal, just trim the plate until there was room, no problem....... IF I WAS AT HOME AND HAD MY MILL TO WORK WITH!!!!!!!!!!!!!!! It took over an hour with my limited tools to get the plate cut back enough to clear the pressure tubing
The second turned into a real problem. I cut the pipe so it would telescope over the header for easy adjustment later.......forgetting that the carb barrel extends out as you open the carb. This gave me two choises, smash in the side of the pipe and hope it still worked or leave the pipe long enough so the carb didn't reach the pipe. This was a no-brainer, the pipe stayed long.
With the engine in, it was time to bend and fit the stuffing tube. With a lot of patience, I slowly put a bend in the tube so that the tube would pass through the bottom just forward of frame 6. With a little more patience, I got the tube to line up perfectly with the engine collet......until I cut the tube and installed it into the front of the strut.Now I found the hole in the bottom was too round and needed some slotting to make it work while the tube itself had a side bend from me working around the strut. After another 30 or so minutes, I had the stuffing box in . By comparison, the flex cable was easy:
1) install drive dog and thrust washers(if used)
2) insert flex cable into strut and stuffing tube
3) run the shaft all the way to the back of the collet and measure
4) measure from back of strut to drive dog, allow for cable wind up
5) Cut cable, grease and install
6) DOUBLE CHECK TO BE SURE THE COLLET IS ASSEMBLED CORRECTLY!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!! I was fortunate to find that mistake before cutting the cable
Next on the list was install the skid fin. Again, no big deal, the transom is already set up with hardware and the bracket is drilled to match...........except for the machine screws holding the blade to the bracket. Once again, I had the hardware and drill, what could go wrong? I made the bracket out of 6061-T6 and Mike Hughes made the fin out of 7075, a much harder variety. I had grabbed a set of old drills in that last minute scramble to get out the door and on the road that didn't want to hardly scratch that fin. After what seemed like an eternity(it was now almost 1:00 in the morning and the boat was supposed to be on the water in 9 hours) I finally got the fin drilled, only to find the fin had slipped by around 5/32" down. Too late to fix that so I bolted on the fin and went to work with epoxy. I had bought a package of Z-Poxy in Missoula Montana so I mixed up a batch and secured the stuffing tube as well as started to seal the bottom................and then the stuff cooked off. I had to mix up a total of 5 1/2 ounce batches of the stuff to finish sealing the boat. Unlike the West Systems I had back at home, this went on thick and didn't flow out. Since it's what I had I made due. After getting the boat sealed, I called it a night.
It's now 10:30, the fun run has been going on for 30 minutes and I'm working on the radio. Servos are servo taped to the bottom, horns drilled as needed and installed, pushrod hardware is ready to go...................and I'm fighting with 4-40 pushrods that I don't have the proper tools to cut or bend. I finally got everything together(so I thought) and we headed for the lake, 45 minutes away. Upon arriving, the new boat gremlins attacked in force putting me back in build mode for another hour. FINALLY, the boat was ready:
Fuel in tank.....check
Glow ignitor charged......check
TX and RX battery packs charged.........check
starting belt installed.........check
12VDC starter and battery are on, won't spin the new engine The top was so tight that one of the others had to grab his 24VDC set up and that finally got it going, but not until his starter was too hot to touch. After a few minutes, we were going to launch the boat and stupid me had forgot to turn on the transmitter. Hit the switch only to kill the engine as the throttle was in full closed position
After letting the starter and engine cool a bit, we tried it again. This time the engine fired up on the second or third try so we threw it on the water and off it went, until the servo tape on the throttle servo let go The engine slowly wound down and died about 15 feet from shore so we got a ball on it and drug it in. All in all, the boat showed promise and acted like it wanted to get up and really run.

That ended on July 2nd. The question is, did I learn anything? HELL YES!!!!!!!!!!!!!!!!!!!!!!
1) Dont rush a build just to get it done. You'll end up taking more time in the long run
2) be sure to have more tools and materials than you think you will need as I was forced to buy building supplies and tools in Montana, Minnesota, Michigan and Ohio just to get it into a runable condition

Now that the boat and I are back home, it's time to talk rework. I decided to try and take the Z-Poxy off with a heat gun, only to find that the stuff gets fragile extremely quick. It took only a coule hours to strip the bottom as it flaked off in chunks.
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Old 08-12-2011, 02:31 PM
  #16  
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Default RE: Re-Engineering A Dumas Pay'N Pak

Since I'm reworking the engine mounts and radio arrangement, I figured I should show you all what I'm starting with. A quick glance should show how rough the engine mounting plates are, not to mention a few other things that need to be taken care of. Now that you have all seen what's what, on the the "disassembly"

The first step is to loosen the collet so I can put the drive cable free. Then with the removal of the throttle servo clevis, the engine is free to be removed. I'm sure some will be asking why I posted the picture of the boat's bottom. The screws holding the rubber isolators are sticking up from the bottom up to 1/8", so fixing that is definately a must.
With the engine removed, I decided to remove the stuffing tube as well. As suggested by someone else in another thread, a heat gun made that easy. What I wasn't happy about is I found that fuel that had been spilled inside the hull had attacked the Z-Poxy and turned it brown. While stripping it out of the engine bay, I found the bottom of the boat was stained brown in places but not from fuel contamination. My task now is to make new engine mounts as I wasn never happy with what I had come up with on the road, plate wise. They had the engine raised up almost 1/4" above the hull bottom, way too high in my opinion. Since I now have a Sherline mill and lathe to work with, I've decided to fabricate a pair of mounting plates with a lowered center so I can drop the engine down to around 1/16" or so above the bottom. I may also make a few minor changes to the fuel system as well, not sure about that one yet.
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Old 08-12-2011, 02:34 PM
  #17  
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Default RE: Re-Engineering A Dumas Pay'N Pak

I found a 1/2X1-1/2X12" piece of 6061-T6 aluminum in the garage a bit ago. With a little bit of drilling and a whole lot of milling, it will make a nice pair of engine mounts. The fun part now is to get the final mount shape laid out on the block and then start making aluminum chips. I know the machinists in the forum love this kind of stuff. Any volunteers in the crowd
I've designed a set of engine mount mounting rails and started working on the first one. With my little Sherline mill, it tends to take time for any major part work so...............................................
One thing I have managed to get finished is shaving down the heads of the engine mount retaining screws that hold the rubber isolators to the bottom of the boat. When I originally set everything up, the heads stuck up from 1/16 to 1/8". Since I don't want the screws visible after the boat is painted, I broke out the Sherline Minilathe(first time this has happened and I've had the lathe for several years) and clamped an appropriately sized nut in the chuck. I ran the screws down into the nut and VERY SLOWLY cut down the height of the head. The next step will be securing the screws in the recessed holes with epoxy and resealing both inside and out of the bottom so I will be able to install the mounting rails and engine when the rails are completed. For those wondering why I'm making new engine mounting rails, here's a picture of one of them. The engine sits over 1/8" off the table in that shot, way to high for my taste so....................................
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Old 08-14-2011, 05:49 PM
  #18  
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Default RE: Re-Engineering A Dumas Pay'N Pak

Over the weekend I was able to get some work done on the boat. I resealed the bottom and right nontrip on the outside of the hull as well as the inside of the forward bottom panel. In the process, I epoxied in the through bottom screws so that they are sealed in as well. While the epoxy cures over the rest of the evening and overnight, I'll be working on the engine mounts so I can install them over the next few days. I'll post pictures later after I get more of the rework done
Old 08-15-2011, 11:14 PM
  #19  
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Default RE: Re-Engineering A Dumas Pay'N Pak

Due to schoolwork and a wife's reworking the kitchen, my total build progress for today was installing the rubber isolators and dropping the engine(still screwed to the old mounting plates) back into the boat to verify everything was still lined up. Finding all still fit, I'll be hitting the mill again tomorrow to continue the work on the engine mounts
Old 08-21-2011, 09:12 PM
  #20  
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Default RE: Re-Engineering A Dumas Pay'N Pak

Just a quick update on the engine mounts. It's taking forever to machine the first one since I've had problems with end mills slipping in the collet, kind of like a flex shaft. Anyway, here's how far I've gotten
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Old 08-28-2011, 07:03 PM
  #21  
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Default RE: Re-Engineering A Dumas Pay'N Pak

With school over for the quarter, or longer, I'm finally able to get back to the boats. I'll be posting updates later in the week
Old 08-29-2011, 05:33 AM
  #22  
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Default RE: Re-Engineering A Dumas Pay'N Pak

Nice job on the mounts HJ I'll kick back and watch. not much to say ,except great boat build
Old 08-29-2011, 10:13 AM
  #23  
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Default RE: Re-Engineering A Dumas Pay'N Pak

I did learn a lesson in machining on the first mount. I made a major mistake by not thinning down the aluminum block to closer to the finished thickness. This would have made removing the unneeded material MUCH EASIER. I've actually had to almost fight one of the endmills due to the depth I've had to go to get the end thickness I want. I may end up making another left side mount when all is said and done, all depends on if it holds up without bending OR if I like the finished appearance. Is it possible that I'm too picky
Old 08-29-2011, 11:38 AM
  #24  
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Default RE: Re-Engineering A Dumas Pay'N Pak

lesson number # 1 dont make boat parts on machines built for making doll house furniture lol
Old 08-29-2011, 12:00 PM
  #25  
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Default RE: Re-Engineering A Dumas Pay'N Pak

No Yota, you're not even close. Rule number one is to remember the capabilities of your equipment and work within those capabilities, not outside of them. This applies to mills, lathes, saws, sanders, drills and any other tool you may use to complete a task. Would you use a 1/4" drive ratchet to break loose a 1" torqued down bolt?

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