Raymondpb

Hello All, I am about to embark upon my first boat build and have lots of questions. This first build will be a Dumas Miss Unlimited. I have built a few airplanes in the past and have many years of experience in my home wood shop so I have the woodworking skills; I just need solid advice on boat building techniques and processes. I was over in another thread asking questions and have already gotten allot of good advise. Someone suggest that I start my own thread that chronicles this build and after a day or two of this idea kicking around in my mind I decided to do it. At first I thought I would start it after the build starts so I can keep the pace flowing along but then I remembered that I have a million questions and that if I start this from the “git-go� I could use the forum as a coach to help me where my questions lye. If you all don’t mind I would like you to follow my progress and act in a mentor capacity to help me take my skills to the next level. To help you understand me a bit more I will give you my RC background in my next installment.

Ray
Mattawan, MI.
[email protected]

Raymondpb

I have been in the RC hobby for about 8 years (excluding the stuff I did when I was a kid) playing with an electric RC stadium truck. I spent the past three years building a Sig Kadet LT40 and GP Super Sportster and have just finished those builds this winter. I will learn to fly them this coming spring. I have had a Miss Vegas since the summer of 05 or 06 (the years are running together) and during that time I have been looking for the time to build this first boat; here I am.

Ray

Raymondpb

Ok, I am off to open up my kit’s box of parts and study the plans. FYI; My goal for this build is 1) a professional looking build 2) meet IMPBA Sport 40 nitro specs and 3) a boat that will hold up to an overgrown kid who plays hard with his toys.

Ray

Ron Olson

My Feedback: (1)

Ray, nice meeting you yesterday.
You might find that the wood quality isn't the best with the Dumas kits plus they use die-cutting instead of CNC routing or laser cutting. A lot of the owners will substitute aircraft lite ply and use the parts for templates.

Raymondpb

Hi Ron, Yes, I was glad to have the privilege to meet with you yesterday at the Kalamazoo RC show. Funny how small this world is huh? I got a good deal on a 7 channel 2.4gh Futaba receiver at the show. I needed one for a GP Sportster I have just finished up.

Thanks for the lead on the boat club; I am exited at the prospect of doing some racing this summer.

Thanks for the info on the quality of the Dumas kits content. I have plans to scrutinize each part as a candidate for replacement; substandard parts will not help me reach my goals for this project. Is this issue prevalent across all the Dumas Kit lines? It may not matter as my next build may be from plans anyway.

Ray
Mattawan, MI
[email protected]

Ron Olson

My Feedback: (1)

It's a heavy kit also. You can lose a lot of weight by removing some of the centers of the bulkheads.
We'll get you up to the club lake once the weather breaks or we'll meet up somewhere around here.
I'll have to get Hydro Junkie in here as he has a lot of experience with Dumas hydro's.

Hydro Junkie

You called Ron?

Ron Olson

My Feedback: (1)

Your ears burning?
I figured that you were one of my picks to give Ray a hand as the only experience that I have with any Dumas boats were the 'glas ones but I've read plenty of your postings on them.

Hydro Junkie

Okay Ray, you want a professional looking build, don't bother with the Dumas supplied Doorskin framing, use it for templates. Cut out all the frames from 1/16th aircraft grade plywood. If your boat uses the laminated transoms, use 1/4 aircraft ply for it. Use the inside frame as the pattern and leave excess on the sides for a more exact fit. Add some length to the glue tab on the back of any internal lengthwise framing, you will see why later. Not sure what the plans say about the skid fin, but if it's directed to go on the inside of the sponson, ignore it. Make the right sponson transom out of 1/4 ply and the left from 1/8ply. At this point, if you could post a picture of the frame parts, I can give you more exact directions.

Raymondpb

Thanks Ron and Hydro Junky. I have started a build notes log that I am copying your suggestions to so they will be readily at hand in the shop. Believe me I will need them; I suffer from CRS. That stands for can’t remember stuff�. Give me a few days to get the parts separated from the excess they are still loosely attached to and take the pics. Even though I have not really studied the parts yet you all have be sold on upgrading many of the parts.

Ron, I will take you up on the offer to get together this summer. I would really like to run with other boats. So far all my RC Boating experience has been by myself.

Ray

Raymondpb

Please excuse my ‘slowness’ in getting this build started. I am trying to plan as much detail before I start gluing so I can anticipate any required modifications to the hull/systems.

I am planning on building this boat to be compliant with IMPBA Sport 40 nitro specs. Yea, I know that this may not be the best hull from a competitive standpoint but remember; this is my first build and would rather make my learning mistakes on a $50 kit than a more expensive one. That more expensive one IS coming later If I understand prop shaft strut placement in that class correctly…�No part of the strut may protrude behind the transom of the boat, or have a width greater than 9/16 inches or a length longer than 3 inches". I am thinking about cutting a slot in the bottom of the hull just forward of the transom for the strut attachment end to slid through and attaching it to a set of ‘L’ brackets that are mounted on the forward side of the transom (inside the boat). Would the bolt heads protruding on the back side of the transom create compliance issues? Does anybody have any pictures of how they achieved their compliant strut set up that they would not mind sharing with me so I can gain some ideas? Is there a better way to mount the strut and still have tune-ability?

Under the assumption (at this point) of employing the design idea mentioned above I am looking for suggestions on how to cleanly make the ‘cut’ to slide to strut mounting bracket though. It MUST be on centerline and it MUST run parallel to the hulls centerline. And it should (read must) be sized with a close tolerance fit with the strut to help reduce drag and leakage. Thinking of leakage, assuming I would ‘seal’ up the slot once an optimum height and attitude is set, how would I minimize leakage during test and tune runs?

This is gonna be fun!

Ray

Ron Olson

My Feedback: (1)

Ray, when I built mine I mounted the strut bracket to the transom but most mount theirs on the floor of the boat so, yes, it's legal. The drive dog and prop can extend beyond the transom.

jetpack

My Feedback: (1)

I would have to ask how thick the transom is, and how much width between the rails.

You must consider transom mounting can severely weaken the glue joints due to flexing if it is not a "boxed" transom, meaning it is still open at the top, like just an "L" shaped corner. Perforations for the four bolts weaken it even more, providing it with stress lines.

Any time there is flex, there is danger of hairline cracks down to the wood, and you'll have aging problems with it way sooner than you'll like. Epoxy is very strong, but at the same time very brittle with no real way around it.

You almost cant even trust well supported areas staying prone from cracking, just due to the nature of expansion and contraction of sealed wood with just an epoxy spread and paint. This is why people fiberglass their wood hulls. It will add weight but the hull will last a lot longer down the road. It is your call on what you expect out of your build.

The more conventional way is mounting the angle brackets for the strut to the bottom of the boat, where the entire strut bay is reinforced with a plywood doubler plate.

You then use countersunk head screws through the bottom, and nuts and washers on top the angle.

You can cheat a little on thickness of the doubler pad, and go with another doubler on top of that to provide additional thickness to compensate for the depth of the countersinks. The final doubler is just cut large enough to cover the square area of the angles.

Cutting the strut hole is a matter of drilling a series of holes, and then filing with a wood file to your pencil layout. I would not try for a snug fit which would lock your strut alignment in without being able to compensate for any misalignment.

Give it play room, so when you install your strut, you can insert a long 3/16" rod through the strut itself, and compare your measurements near the strut, and then at the end of the rod at the front of the boat between the sponsons or as far as you possibly can.

Some will even add in an amount of left thrust to compensate for prop walk to take some of the load (drag) off of the rudder trim amount to keep the boat handling straight.

You then can fill any gaps with plumbers putty around the strut at first until you have run the boat and settled on where the best trim position is. After you are close you can substitute the plumbers putty with silicone caulking, and fill the screw heads with wax and scrape smooth.

If you plan on never ever changing props or strut angles, balance, ect...and will be making no further adjustments to the strut forever, save painting the hull after the strut is set and just run it with your epoxy coat, then after the strut is locked in, tape off the gap and fill from the inside with epoxy, sand and paint with the strut masked.

Them's my thoughts...

(Blueprint photo: Dumas Eagle Sport 40)

Hydro Junkie

WOW!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Jet and I are on the same page for once!!!!!!!!!!!!!!!!!!!!!!!!! Miracles do happen.
My thought on transom mounting the strut is for a boat like the Miss Unlimited, it will be totally outclassed by more modern designs. The newer boats have the strut mounted on the transom for easier adjustments and all out racing. Your round nosed boat will have much less transom area than most(exception being the whiplash) so why put the stress of hanging the rudder AND strut off that small piece of wood? As Jet already said, you will have weak areas due to the screw holes for the rudder, so why compound the issue by adding more for a strut. Go through the bottom and call it good

Raymondpb

Thank You Gentlemen for you help, this is very good stuff!

My thoughts on mounting on the transom vice the bottom were rooted in every attempt to reduce/eliminate drag. My new schooling on transom stresses make bottom mounting with countersink screws a very appealing way to approach it. It would also make a cleaner look on the transom.

The tip for cutting the slot and aligning the strut makes very good sense; thanks.

With regards to offset to compensate for prop forces, how many degrees should be considered optimal or is that number a function of the engines power rating and prop selection? Is this also a prop tuneability issue? Should I design my strut brackets with this potential tuning movement in mind?

Is prop fore and aft location relative to the transom critical to performance? If so how is this position determined? I can easily see how it can affect balance fore and aft but…..should there be some (however so small) adjustability designed in to allow for tuning? If so what would the range be so as to make the proper initial location?

Ron, Is the boat in the pic yours? I could not help but notice, what is the third servo for?

Hydro Junkie, I see you live in Marysville. If it is the same Marysville I am thinking of you may be interested to know that I used to live out on Whidbey Island. I moved back here to MI in 06. My internet surfing on the RC topics suggest that RC boat racing is very popular out there in WA. I did not notice when I lived out there.

Ray

Ron Olson

My Feedback: (1)

That was mine. I ran into some money problems shortly after I got it finished after a stay in the hospital so it had to go as my SUV blew a motor. Really hated to sell it. That's a Phil Thomas Super-Sport 45 with a MAC engine and pipe with Speedmaster hardware and Hi-tec radio.
The third servo controlled the fuel mixture. Good eye!

Raymondpb

Sorry to hear it still does not reside in your marina Ron.

Speaking of servos, surfing all the message boards I have not seen a single thread (yet) that discusses rudder forces and the required torque needed to move it as needed in a race boat; do you have any leads for me on this topic?

Ray

Ron Olson

My Feedback: (1)

For a rudder I like to use servos that have around 100oz.in. of torque and use Hi-tec HS-645MG's in just about every boat that I own and have used those from .21 mono's up to my gas boats. Throttles don't need a lot as you can use mini's or any standard servo there.

Hydro Junkie

To answer your location qustion, I was on Whidbey Island yesterday. I agree, finding the boaters isn't all that easy. I ran across R/C Unlimiteds totally by accident at Gissberg Twin Lakes Park. That was back in the late 1980's, before the internet really took off.
I normally mount my struts so that the prop is legal in all three, APBA/NAMBA/IMPBA, by moving the strut far enough forward to have the drive dog and front of the prop hub under the boat.

jetpack

My Feedback: (1)

[sm=biggrin.gif]HJ,

I wouldn't think we're buddies quite yet. I had to delete most of what you typed to create the quote and it actually felt quite good to have to do it. [sm=bananahead.gif]


Ray,

It might pay to study your prop height and strut location and plan ahead a little by gluing in a wood block inside the transom in that area in case you need to scallop the outside of the transom out to clear the lead of the prop if the block doesn't get in the way of the strut brackets.

The block will fit and glue better while your still working with your mockup and provide some filler and strength you'll loose in case you do have to scallop it.

Check it out and keep it in mind so there's no having to back-track to fix. Adding it now will be easier and neater while your still working with your mockup then having to go back and work around previous glue fillets.

It might not even be anything to worry about with what you have going but something worth mentioning and can save a headache.

(Pic: Dumas Eagle Instructions)

f16man

Hey Raymond it's been quiet here for a while, how are you comming along with the miss unlimited? And whats up between jet and hj I must have missed something?

Raymondpb

Hi F16man, Yea, I know I am off to a slow start but…..I have good reason: I have been spending most of my limited hobby time researching all I can before I make my first move. I am exercising patience trying to plan every move and alteration to the kit so as to anticipate ahead of the glue. This is my first boat build and I am finicky about the details so…..I will get things moving along soon.

Thanks to all the good mentorship provide above I have the strut configuration set up figured out in my head. Currently I am researching engines and servo options.

Ron, thanks for the servo suggestions.

I have also been distracted helping my 16 year old son lay out the framing structure of a 1:84 scale scratch built Arleigh Burke class destroyer. Yea, it will be six foot long and yea, this is his first boat build also. He has his building table erected and patterns laid out as per ‘his’ drawings and has started cutting out the spine and bulk heads. I love the smell of saw dust

Jetpack, I am picking up what you are putting down wrt the planning but I am curious about the need to ‘scallop’ the transom like that. Not that I have lots of experience here but I have never seen a transom scalloped like that. What else can you tell me about it? Is it purely a measure used to get the prop up as high as possible as needed by some hull types? Are you suggesting that my shovelnose may need that extra clearance?

Can we talk flotation? I have seen swimming pool noodle foam and heard of some people using air bags. What is the best approach and why would you recommend it? Has anyone considered helium filled airbags? In theory wouldn’t it make the boat ‘lighter’? And lighter can be converted to faster right?

Ray

Ron Olson

My Feedback: (1)

Tay, wait for a little time if you have to to get some pool noodles. I don't know if Meijer's or anyone else has them in stock yet. I've got a couple if you need them. I got mine at Dollar General. I don't know what you've got out there around Mattawan as I don't get out that way much. The last time I was there I went to Formula-K Raceway to drive the go-carts.
Walt contacted me last week and said that you joined the club!

advanced builder

The reason for most transom setups is ease. My 43" Atlas Van lines has a bottom rudder, To adjust rudder ,is almost work ,My fingers don't work like they use to. Looking at the Miss Vegas the rudder is mounted on the transom from what I see.Legal? My Atlas Van Line can be carried by my rudder, If I wanted to. How, bigger rear stringers at the end ,small screw's & 2 layers of birch ply or airplane ply.

Raymondpb

Hi Ron, I have a few pool noodles lying around that I could use. I was wondering though if one were to use air bags and filled them with helium if you could ‘lighten’ the boat and fine tune balance. I think helium is inert is it not? If so it would not creat a safety hazard so......Interesting idea if nothing else.

Ray