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Dumas Hot Shot IV - Need help...

Old 03-31-2006, 11:03 PM
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Skiddz
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Default Dumas Hot Shot IV - Need help...

About 20 years ago I bought a Dumas Hot Shot IV kit (wood) and a K&B 3.5 outboard. (Like the 8907, but without the gold carb) Got the boat built and running and ran it a couple times then dinged it up and stripped it down to bare wood to refinish it. Lost interest in the boat as soon as I picked up my 1st helicopter and now am looking to get the boat back on the water and have some questions:

When I built the boat, I coated the entire thing with resin (Sorry, don't recall it it was epoxy or polyester) and sanded it smooth before painting with Epoxy enamel. The hull, for being in storage for nearly 20 years, is in great shape with no cracks or dings anywhere. When I stripped it, I sanded the entire hull back to bare wood. Will I need to resin the hull again, or can I get away with primer/paint/clearcoat? Any particular clearcoat I should use to provide a fuel proof surface?

The engine was oiled up well before it was put away and I pulled it out a little bit ago to check it out. No rust and it turns freely if I pull the glowplug out. Putting the plug back in it seems to have good compression. I do plan on disassembling it to check for rust on bearings and to grease the bottom end drive well.. Anything else I should do to the engine while I've got it apart? Would a Prather 220 be a good prop to start with? Should I set the prop depth so the centerline of the prop is just below the bottom of the hull? Should I set it up with downthrust to help keep the nose down as she runs? I've got a McCoy tuned pipe (long, "straight" sucker - no it's not for an inboard) for it and the bottom end will require machining to get it to fit.. is it worth it to fit this thing or get a newer style pipe? Will the pipe quiet it down at all? As I recall it was pretty loud when it ran without it.

I know the prop needs to be sharpened and polished as well as the turn fin (if I can find it.. hehe) should I also smooth out the bottom drive? I can polish it to a mirror finish on my buffer if it'll help... What's a decent starting point for turn angles??

I have no idea if I still have the docs that came with the kit; where would be a good CG point to start from?

Lastly (for now) what's the best way to keep the upper cowl on. The old method with the rubber band is just cheesy.

I'm sure I'll have more questions, but any little bit of help I can get from you folks would be very much appreciated.

Thx!



Old 03-31-2006, 11:41 PM
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ob nut
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Default RE: Dumas Hot Shot IV - Need help...

WOW, questions galore!! I built too many of the HS IV kits, lets see if I can help..

ORIGINAL: Skiddz

About 20 years ago I bought a Dumas Hot Shot IV kit (wood) and a K&B 3.5 outboard. (Like the 8907, but without the gold carb) Got the boat built and running and ran it a couple times then dinged it up and stripped it down to bare wood to refinish it. Lost interest in the boat shame on you as soon as I picked up my 1st helicopter and now am looking to get the boat back on the water and have some questions:

When I built the boat, I coated the entire thing with resin (Sorry, don't recall it it was epoxy or polyester) and sanded it smooth before painting with Epoxy enamel. The hull, for being in storage for nearly 20 years, is in great shape with no cracks or dings anywhere. When I stripped it, I sanded the entire hull back to bare wood. Will I need to resin the hull again, or can I get away with primer/paint/clearcoat? If you don't recall what was used, there can be problems mixing the two. Or at least what I've been told. One will go over the other, but not the other way around (epoxy / resin). Think you could get away without another coat. Any particular clearcoat I should use to provide a fuel proof surface? I'm using PPG 2021. 65% won't touch it.

The engine was oiled up well before it was put away and I pulled it out a little bit ago to check it out. No rust and it turns freely if I pull the glowplug out. Putting the plug back in it seems to have good compression. I do plan on disassembling it to check for rust on bearings and to grease the bottom end drive well.. Anything else I should do to the engine while I've got it apart? Looks like you have it covered. Maybe a new plug. K&B 1L or MC9. Would a Prather 220 be a good prop to start with? Maybe a P215, X440/2, X438, X437/3 or a M440 Should I set the prop depth so the centerline of the prop is just below the bottom of the hull? Depends on prop. Good starting point is 1/8" - 3/32" above the bottom of the spoons. Should I set it up with downthrust to help keep the nose down as she runs? Set the CG first, then adjust +/- angle accordingly to how the boat handles or flys I've got a McCoy tuned pipe (long, "straight" sucker - no it's not for an inboard) for it and the bottom end will require machining to get it to fit.. is it worth it to fit this thing or get a newer style pipe? Can't say I've seen a McCoy tuned pipe. If it's is a tuned pipe and not a muffler it should be worth it. Will the pipe quiet it down at all? Some pipes are loud. If it is, put an internal stinger in the pipe exit. If you go that route, let me know. I'll futher explain. As I recall it was pretty loud when it ran without it.

I know the prop needs to be sharpened and polished as well as the turn fin (if I can find it.. hehe) should I also smooth out the bottom drive? I can polish it to a mirror finish on my buffer if it'll help... A big performance gain is getting the skeg in line with the prop shaft. That alone will pick up 3 - 5 mph. Get that done then polish. Doing a polish job is one of those subjects ready for debate. What's a decent starting point for turn angles?? ??? Do you mean turn lock to lock? Those boats can be touchy. Turn down/up the turn ratio deflection (if posible on the transmitter) to give a good turn length. Race course have 30' turn diameters.

I have no idea if I still have the docs that came with the kit; where would be a good CG point to start from? Each boat is different. 27% to 33% is typical of tunnels.

Lastly (for now) what's the best way to keep the upper cowl on. The old method with the rubber band is just cheesy. Go to a hardware store and buy a cabinet door latch. Plastic rollers that grap onto a metal point.

I'm sure I'll have more questions, but any little bit of help I can get from you folks would be very much appreciated. Hope something helped.

Thx!
PICS????
Old 04-01-2006, 12:54 AM
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Default RE: Dumas Hot Shot IV - Need help...




shame on you

Yeah, I know.. No pond close enough to run it on and the home owner's association fined me for running it in the pool. (Olympic sized - PERFECT for the boat. heheh)


? If you don't recall what was used, there can be problems mixing the two. Or at least what I've been told. One will go over the other, but not the other way around (epoxy / resin). Think you could get away without another coat.

That's what I'm thinking, but I'll probably give the innards a quick coat of epoxy just to make sure it's water tight.

I'm using PPG 2021. 65% won't touch it.

I'll hit up the local supply store next week.. Should have some color on the hull this weekend.

Looks like you have it covered. Maybe a new plug. K&B 1L or MC9.

I've got some MC9s in my old parts bins.. Most are still in their blister packs so I'm sure I'll find a couple good ones.

Maybe a P215, X440/2, X438, X437/3 or a M440

Don't want scary fast speeds.. (I'll be running it on my sister's pond - 200' x 50' approximate size) at least not yet.. Just want to get it running again..


Depends on prop. Good starting point is 1/8" - 3/32" above the bottom of the spoons.

OK, potentially stupid question.. WTH are "the spoons"?

Set the CG first, then adjust +/- angle accordingly to how the boat handles or flys

I'm hoping to avoid option 2 if at all possible.

Can't say I've seen a McCoy tuned pipe. If it's is a tuned pipe and not a muffler it should be worth it.

Definitely a tuned pipe. I remember buying it from Tower. Haven't laid my hands on it yet, but I'm sure it's in the same box in the attic I dug the engine and radio gear out of.

Some pipes are loud. If it is, put an internal stinger in the pipe exit. If you go that route, let me know. I'll futher explain.

Noice willbe a bit of a consideration. My sis lives in an uppity neighborhood, but has a large lot. She doesn't care about the noise, but I don't want to wear out my welcome with the neighbors when I run the boat. (Her neighbors always complain when I fly a helicopter over her house - full scale, not model - and blade slap the hell out of it.)

A big performance gain is getting the skeg in line with the prop shaft. That alone will pick up 3 - 5 mph. Get that done then polish. Doing a polish job is one of those subjects ready for debate.

OK, ya lost me a bit there.. How can I tweak the bottom to line up with the prop shaft? (kinda sounds like you're talking about an inboard here, not an outboard)


??? Do you mean turn lock to lock? Those boats can be touchy. Turn down/up the turn ratio deflection (if posible on the transmitter) to give a good turn length. Race course have 30' turn diameters.

Radio is an older Futaba Magnum and I have lots of adjustments possible.. What would be a good place to start on high rate, i.e. lock to lock. I can tweak expo and ATV travel on the fly from there.

Each boat is different. 27% to 33% is typical of tunnels.

From the transom, right?

Go to a hardware store and buy a cabinet door latch. Plastic rollers that grap onto a metal point.

Cool. have a few of those in the junk drawer in the kitchen...

Hope something helped.

Very much so, thanks!

Thx!



PICS????

No pics of the boat at all, but I can certainly take some and post 'em as I rebuild it.


Old 04-01-2006, 06:33 AM
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Default RE: Dumas Hot Shot IV - Need help...

Even though the P220 is recommended for the motor/boat, it's still a tad bit too much prop. With that boat, you won't get "scary" speeds.

Spoons = sponsons. The outter ride pads or some call them pontoons. The boat should ride on about 1/4" - 1/2" of water on the sponsons when running in top form.

CG is measured from the back of the sponsons, not the transom. It's been too many years, can't recall if the IV has an insetted transom or not.

Pipe stinger is a brass tube that will slide inside the pipe. Use JB Weld to secure it in place. Make a thin cut (dremel cut off wheel) on this tube right after where it will clear into the pipe. This will allow any oil/fuel residue to have a run out hole. Below is what I did to one of my pipes before using JB Weld.


Lineing up the skeg to output shaft is an outboard thing. Especially K&B. What needs to be done is to lock the skeg on a wood clamp that has a straight line back behind it. Take an old prop shaft a brass tube over it. Believe a 3/16" will be the ticket. The brass tube should line up with the line from the skeg. To line them up, take material off the opposite side of the skeg. Don't bend the skeg, it will break. It's a quick explanation of a easy process once it's known what/how it's done.
Old 04-01-2006, 09:03 AM
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Default RE: Dumas Hot Shot IV - Need help...

A Prather 220 won't fit under the cavitation plate nor will any Octura prop over 40mm.
Race courses hasve 35 feet radius or 70 foot diameter turns.
Old 04-01-2006, 01:05 PM
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Default RE: Dumas Hot Shot IV - Need help...

Even though the P220 is recommended for the motor/boat, it's still a tad bit too much prop. With that boat, you won't get "scary" speeds.

Ok, Ran out to the shop and dug through all my old RC junk and found 3 props.. 2 Dumas 3105s (1.75" diameter) and some unknown that's maybe 1.125" in diameter. The smaller one looks like the one that was on the engine when it was stored. Can't find any other info on the Dumas props - must be discontinued. Looks like they're too big to fit under the cavitation plate anyways.. Looks like I'm headed to the store..

Spoons = sponsons. The outter ride pads or some call them pontoons. The boat should ride on about 1/4" - 1/2" of water on the sponsons when running in top form.

ok, so centerline of the prop about 1/8" below the bottom of the sponsons to start got it..

CG is measured from the back of the sponsons, not the transom. It's been too many years, can't recall if the IV has an insetted transom or not.

yep, the transom is inset from the rear of the sponsons, maybe an inch or so..

Pipe stinger is a brass tube that will slide inside the pipe. Use JB Weld to secure it in place. Make a thin cut (dremel cut off wheel) on this tube right after where it will clear into the pipe. This will allow any oil/fuel residue to have a run out hole. Below is what I did to one of my pipes before using JB Weld.

[pic snipped]

Can't exactly tell what you're talking about, but I'll save the pic and enlarge it to check it out. I took a couple pics of the pipe/engine andw as going to post 'em, but the battery in my dig-cam pooped out and I don't have a card reader. Once the batt is recharged, I'll post the pics..


Lineing up the skeg to output shaft is an outboard thing. Especially K&B. What needs to be done is to lock the skeg on a wood clamp that has a straight line back behind it. Take an old prop shaft a brass tube over it. Believe a 3/16" will be the ticket. The brass tube should line up with the line from the skeg. To line them up, take material off the opposite side of the skeg. Don't bend the skeg, it will break. It's a quick explanation of a easy process once it's known what/how it's done.

OK, gotcha.. Looking at the skeg, I see what you're talking about. I'll get that taken care of this morning as I'm "overhauling" the engine/drive unit.
Old 04-01-2006, 01:38 PM
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Skiddz
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Default RE: Dumas Hot Shot IV - Need help...

OK, here are some pics of the pipe/props/engine.
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Old 04-02-2006, 09:06 PM
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Default RE: Dumas Hot Shot IV - Need help...

Despite my wife's insistence that I go look at furniture with her all weekend, I found some time to work on the hull. It not as sound as I thought it was with several small delaminations of the sponson steps and a couple cracks where the deck sheeting mates with the hull which I discovered after the 1st coat of primer. Entirely servicable, but will require a bit more work and lot of sanding to get smooth. Thinking abut painting it pearl white like the '05 Lexus line, with pearl blue/green accents..

Pulled the engine apart and it's *really* clean inside. Forgot the prop shaft nut was reverse thread so it took me a while to get the bottom end apart. Aside from some slight discoloration on the water pickup tube, the bottom end was also very clean inside. Not bad for an engine that's been in a zip-loc bag for about 20 years...

I probably could have just bolted the thing on the boat and let 'er rip, but better to be safe than sorry.

Question. Is this black K&B carb - The metal one, not the plastic one (Perry?) the 3.5 sometimes came with - a servicable unit or should I drop the $20 on the gold carb?
Old 04-02-2006, 09:45 PM
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Default RE: Dumas Hot Shot IV - Need help...

If there is nothing wrong with the black carb, use it. If you want to drop the money for a gold one then do it, both a vr\ery good carbs.
Whenever I run into a new K&B OB owner, that's the first thing that I tell them about, the left-handed thread on the propshaft. I was just telling one of our new members in here on AIM about a tool that comes in handy when working on the 3.5 OB engine. I was looking for a thin wrench to take off the propshaft with and found the tool that comes with Cox .049 engines. On the end, it is the right size to remove the propshaft and on the side there is a spot that fits the prop nut. It's not my preferred way to take off the nut but it's there in a pinch. It's a cheap stamped part so it may not be an exact fit as I've found some that were tight, nothing that a few strokes with a file that wouldn't take care of it.
Old 04-03-2006, 12:09 AM
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Default RE: Dumas Hot Shot IV - Need help...

Naw, not really interested in spending much money on this "restoration".. If I can get away with just paint and labor, (maybe a couple props and a few odds and ends too) I'll be happy. If the black carb works, I'm gonna leave it on there. Not sure if I'm going to bother with this pipe though. Modifying the bottom end won't be that big of a deal, but it looks kinda stupid with 8" of pipe sticking straight out the back. I *MIGHT* look at a tuned pipe solution before the thing hits the water...

To fix these delaminations, can I used thinned epoxy and force it into the openings/cracks and then clamp overnight? I'm kinda hoping capillary action will wick the epoxy in far enough to get a good bond and prevent these few areas from coming apart again...
Old 04-03-2006, 01:33 AM
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Default RE: Dumas Hot Shot IV - Need help...

Hey Skiddz. I just wanted to give you a few pics of my boat with a Magic Muffler pipe on it. It will give you an idea of what it woudl look like with the pipe sticking out the back, I dont think it is all that ugly looking to be honest. My complete pipe length from center of the manifold to the end of the stinger is 7.5 inches, so it shoudl give you a good idear of what it looks like. Enjoy, they are [link=http://gallery.intlwaters.com/albums/userpics/10271/normal_boat%20pics%20015.jpg]HERE[/link] [link=http://gallery.intlwaters.com/albums/userpics/10271/normal_boat%20pics%20016.jpg]AND HERE[/link] (click the HERE AND HERE for the pics)
Old 04-03-2006, 08:30 AM
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Default RE: Dumas Hot Shot IV - Need help...

Those props look really old and I'm guessing that they are JG props that were sold under the Dumas name. Some of them are collectables.
If you don't want to hack up the lower unit and have that pipe hanging out, fine. I'm guessing that it is another rare piece also. What does it say on the label?
Old 04-03-2006, 11:45 AM
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Skiddz
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Default RE: Dumas Hot Shot IV - Need help...

The props were purchased before I finished building the boat and I think I bought the kit while I was still in college. (early-mid 80s)

They don't fit under the cavitation plate so at this point, I don't have a use for them.

As far as the pipe goes, the label doesn't say much: "McCoy Racing Products by C&H Inc." Wonder if it's the same C&H that sells sugar.
Old 04-08-2006, 01:03 AM
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Default RE: Dumas Hot Shot IV - Need help...

Pics of the various damaged areas I need to address before the hull is ready for paint. Can I thin some epoxy and wick it into the damaged areas then sand & prime? Not too worried about the cowl crack as it's cosmetic, but I want to make sure the hull is sound. Looks pretty decent in primer even after 20 years in storage...

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