Building the fastest Donzi Classic

[DickB]

I’ve owned boats for over 25 years and been a radio controlled modeler for longer. I’ve gotten the bug to build an RC model of the full-size boat that I’ve owned at the time several times, but never done it. I recently got the urge again, and this time I’ve started. I’m working on a quarter-scale Donzi Classic 18.
There are no scale model Classic hulls of which I’m aware, so I need to build one. Tom Lang was kind enough to send me some construction data on the Wynn Mill II and also a higher-resolution copy of the early Donzi ad that featured “engineering” drawings (a low-res version is on this site at http://www.donzi.net/cat/cat66/ ). The latter provided a surprising amount of useful data. Along with some photos, I was able to draw up plans for a scale wood model. To date I’ve cut and assembled the frames, along with a keel, chine, and sheer strips made from 6mm marine plywood. I’m about to add the transom. The frame will be covered with 3mm marine plywood and fiberglassed using West System epoxy. A complete scale interior is planned.
Power is coming from a weedeater-type engine made expressly for RC marine models. I’m using a Zenoah engine from Japan. It’s a 2-cycle, 25.4 cc displacement, runs on gasoline and oil mixed, is water cooled, and uses a pull starter. It’s rated at 2.16 kW at 12,000 rpm.
Scale outdrives are a rare breed. I’m using a semi-scale outdrive from RCM in South Korea. It’s loosely based on a Mercury Blackhawk drive and it is a surface drive. Most model boats of this type are running surface drives. My own full-size boat has a Mercury Alpha, so this is one concession to absolute scale accuracy. I plan to make some cosmetic additions to the upper portion of the drive to make it appear more like my Mercury Alpha.
So, where does the fastest Donzi Classic claim come from? I figured, as this is a power forum and not a modeling one, that I needed a tag line like that. But, at ¼ scale, the model needs only to exceed 30 mph actual to break 120 mph scale. The power plant, hull, and drive should be capable of 35 and perhaps 40. Hopefully I can complete the model by spring and test the theory.

[catch 22]

Very cool outdrive. Looks like a #6 to me. Keep us posted on this cool project.:cool!:

[gold-n-rod]

Awesome. Keep us posted and good luck!

[gcarter]

Folks, my hat's off to this member!:eek!:
This is hard to do, particularly from scratch. I'm VERY impressed.
Good luck!!!:)

[zimm17]

I have a Dumas scarab 55" RC boat with a surface drive and Zenoah engine. It's no Donzi classic though. It's run 48mph on GPS so far.

Here's some pics: I've since put on a cooler looking exhaust pipe.

http://zimm17.com/id22.html

It might be for sale if anyone is interested. These things cost $1000 and take a few months to build even with a pre-made fiberglass hull. Making a wood one from scratch....that's a little out of my league!

Keep us posted (no pun intended) with the progress on the Classic.

[rustnrot]

Bravo! When I asked him what modeling program he was going to use....he said Pencil and Paper! Great start, can you bring this to the Mt. Dora, FL Classic Boat show March 2007?

PS, my thanks to GEOO for providing copies of the original drawings to me of the Wynn Mill II.

Can you post a pic of a human next to this as I am trying to grapple with the size of 1/4 scale in my head...4 foot or so long...wow.

[boxy]

So, where does the fastest Donzi Classic claim come from? I figured, as this is a power forum and not a modeling one, that I needed a tag line like that. But, at ¼ scale, the model needs only to exceed 30 mph actual to break 120 mph scale.
Looks great, I can't wait to see pics of it on the water.
Just so you know though, you are going to need a little more than a scale 120 MPH to make the claim of fastest Classic hull. I think Mighty Mouse might have seen the dark side of a buck twenty a couple of times .... :D

[LKSD]

Neat project! You have to share more pics!:yes: :yes: It looks like it will scream! Jamie / Lakeside

[MOP]

Very neat project and quite a bit of work but so rewarding in the end! Thinking about the speed thing 30=120 35=140 40=160 I think you may well achieve your goal. I too hope you will keep us regularly updated as the bits and pieces come together.

Phil

[DonziJon]

Bravo! When I asked him what modeling program he was going to use....he said Pencil and Paper! Great start, can you bring this to the Mt. Dora, FL Classic Boat show March 2007?

PS, my thanks to GEOO for providing copies of the original drawings to me of the Wynn Mill II.

Can you post a pic of a human next to this as I am trying to grapple with the size of 1/4 scale in my head...4 foot or so long...wow.

Quarter Scale is .25 times (1/4) ANY dimension from the original. A quarter scale C-18 will be 4.5 feet long. The beam will be 1/4 the beam of the original. EVERY dimension on the model will be 1/4 the dimension of the original. John

[DickB]

Thanks all for the comments and encouragement. I will post more pictures as I go, but it may take a week or two for me to make significant progress. While scratch-built is a lot of work, it's not a lot more than some kits. I built a Dumas Chris-Craft a couple years ago. Construction is very similar, plywood over frames. But then each mahogany plank, top and bottom, must be individually placed. That takes some time.

The model is 54" long with a 21" beam. I'll try to get a picture that shows the scale in the near future.

My clutch arrived today. It bolts to the engine and allows the model to be stopped in the water. It also makes it much safer to start and launch.

[BGH18]

What a great piece of craftsmanship! Can't wait to see end results.....

[mphatc]

Very very cool!

You've made some great progress to be this far. Likely it will be faster than some real Donzi Classics .

Have you considered making a fiberglass mold of the hull and deck? I'd be interested n one for sure!

This project reminded me of another model maker . . .
http://video.google.com/videoplay?docid=-5721579124059513186&q=ferrari

Mario L.

[Donzi Dreaming]

To be totally scale...
http://www.floridaame.org/GalleryPages/g1m0115.htm

http://videos.streetfire.net/video/2121aa46-58d2-43cf-8f85-98570153b3d6.htm

[gcarter]

Not to detract from these wonderful pieces of astounding craftsmanship, but in the early to mid '50's, Motoguzzi built a liquid cooled 500 cc V-8 powered Grand Prix motorcycle. It produced about 85 HP versus about 50 HP for the competition's 500 cc twins but wasn't as competitive as the competition due to lack of development. Here are some pics;

[Donziweasel]

I noticed you said you were doing a complete interior. Are you going to make a little scale person of yourself driving the boat?:) If you do, are you going to have a little Donzi girl in a bikini in the passenger seat? :wink: I think we would all like to see that!:yes:

[rustnrot]

Yes, and you wouldn't have to scale all the parts of the Donzi girl exactly to one fourth size!!!!

[boxy]

Not to detract from these wonderful pieces of astounding craftsmanship, but in the early to mid '50's, Motoguzzi built a liquid cooled 500 cc V-8 powered Grand Prix motorcycle. It produced about 85 HP versus about 50 HP for the competition's 500 cc twins but wasn't as competitive as the competition due to lack of development. Here are some pics;

Huhhh ??????

[gcarter]

Huhhh ??????
Steve, I think my post followed three (3) links to sites that featured model running multi-cylinder engines.
My reference is to not a model engine, but to a tiny 4 cam V-8 motorcycle engine of remarkable output. Not a copy of anything, but although it's 50 years later, this engine is still outstanding for its miniscule size and compactness.

[DickB]

I noticed you said you were doing a complete interior. Are you going to make a little scale person of yourself driving the boat?:) If you do, are you going to have a little Donzi girl in a bikini in the passenger seat? :wink: I think we would all like to see that!:yes:
Not sure if my better half would approve.

I started planking the hull today. It's important to clamp the frame securely to the bench so that the end result will be perfectly straight. A cardboard template is made first to get the shape. Then the plywood is cut and attached with epoxy using a lot of clamps and screws. The screws will be removed when the epoxy sets, and the holes filled.

I wasn't planning to make a mold, but I'll give it some thought. Some modelers build fiberglass hulls this way. Others form a core out of foam, then lay fiberglass on top of it. I thought the frame and stringer approach would be easier for me to get the classic hull shape.

Making a scale model always involves trade-offs. The model V-8's are sweet, but would put my project into a whole other league. My model will be more of a "stand-off scale" - stand back a few feet, and it will look like the full-size boat.

[boxy]

Steve, I think my post followed three (3) links to sites that featured model running multi-cylinder engines.
My reference is to not a model engine, but to a tiny 4 cam V-8 motorcycle engine of remarkable output. Not a copy of anything, but although it's 50 years later, this engine is still outstanding for its miniscule size and compactness.
OK, I've got it now ..... :D

[Donziweasel]

DB, I really like what you are doing. I have done some modeling myself in years past as the winters here will slowly drive you insane. I only built one boat and it was a Dumas Swamp buggy. Still have it and it runs like a scalded cat over snow, water, swamps, whatever. I had the same idea as you a few years ago about building a classic and then kinda lost interest. I was going to power with this engine-

http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXHZA0&P=0

It is 5cc bigger than what you are using, but I am not sure about the power. I have really enjoyed reading about your progress. Please keep us informed about how it is coming along. Great pics by the way.

[DickB]

DB, I really like what you are doing. I have done some modeling myself in years past as the winters here will slowly drive you insane. I only built one boat and it was a Dumas Swamp buggy. Still have it and it runs like a scalded cat over snow, water, swamps, whatever. I had the same idea as you a few years ago about building a classic and then kinda lost interest. I was going to power with this engine-
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXHZA0&P=0
It is 5cc bigger than what you are using, but I am not sure about the power. I have really enjoyed reading about your progress. Please keep us informed about how it is coming along. Great pics by the way.
I built and ran a couple of Dumas kits long ago - a Little Swamp Buggy and a Sk Daddle Jr. I had lots of fun with those, and they just ran and ran.
I competed planking the hull bottom on the Donzi model. I think the hull looks quite Donzi-like. Attached also is a picture with yours truly to give some sense of the size.
The more I think about it, the more I want remote electric start for this model. I've got a couple of ideas on using the guts of an unused cordless 9.6V drill for this. I may spend some time on that this weekend.

[DickB]

I completed the deck. Next is the hatch and then fiberglass top and bottom. The interior will drop in and probably be removable for access.

[Barry Eller]

Great job!

What color will your boat be? Your wood looks too good to paint, a mahogany stain and clear urethane would look sooo good, but wouldn't look like a true Donzi?

I would have a hard decision, paint or natural, paint or natural...

[rustnrot]

Unless it is Mike Yobe's Classic 16...
http://www.donzi.net/forums/attachment.php?attachmentid=17178&d=1136947467
http://www.donzi.net/forums/attachment.php?attachmentid=20146&d=1145738511
http://www.donzi.net/forums/attachment.php?attachmentid=20144&d=1145738511
http://www.donzi.net/forums/attachment.php?attachmentid=20145&d=1145738511

[Barry Eller]

I see your point.
Is that going to be a complete re-fabrication of the deck?

[DickB]

Great job!
What color will your boat be? Your wood looks too good to paint, a mahogany stain and clear urethane would look sooo good, but wouldn't look like a true Donzi?
I would have a hard decision, paint or natural, paint or natural...
I like wood too, but this is to be a model of my 18 so it will be green on white.
Mike's 1/2-breed looks gorgeous.

[boatnut]

I completed the deck. Next is the hatch and then fiberglass top and bottom. The interior will drop in and probably be removable for access.

Gee, you mean you won't have to rip the entire deck off to replace the gas tank ---- I thought this was a true replica??:) Fantastic project!! Ed

[Donziweasel]

JW's posting of the mini-blown V-8 got me wondering how the project is going. How is it progressing?

[Ted Guldemond]

As always you guys have got me thinking. I've been looking for a project to do with my 13 yr. old son, like a small boat build 11-14ft. I was going to go will an old Glen-L design. But now you got me thinking that maybe a 3/4 scale Wyn-Mill or 18 classic with a period correct 20-30 hp Merc would be the way to go. How can I get plans, table of offsets etc? Thanks.

[Johntrip]

Calling DB..!!!!!! Hows the Donzi 18 :wink: :wink: comin along....???? We need an update!!!!

[MOP]

As always you guys have got me thinking. I've been looking for a project to do with my 13 yr. old son, like a small boat build 11-14ft. I was going to go will an old Glen-L design. But now you got me thinking that maybe a 3/4 scale Wyn-Mill or 18 classic with a period correct 20-30 hp Merc would be the way to go. How can I get plans, table of offsets etc? Thanks.

I am pretty sure Lenny has a copy of the plans, he is pretty sharp and may be able to help in scaling it down.

EDIT: There was a post a few months back about a scaled down Donzi built on wood that may be another good source for you.

Phil

[faverod]

That's amazing. I've been building a Dumas Chris Craft Barrel Back for 2 years now during the winters. Just recently I finished all the sub-planking and have started sanding before applying the mahogany. Granted, I glue a plank a night but I can't foresee the boat hitting the water for at least another year. Great job, after my project I can see the appreciate the work you've put in.

[DickB]

As is often the case with my projects, other priorities took over. I got sidetracked into a couple of other projects from January until just a few weeks ago, so the Donzi model progress has stalled. The basic hull is done and about 1/2 of the basic interior.

I'm away on vacation right now, but will post a couple of pictures when I get back.

[DickB]

I've done a bit more work on the interior, but as you can see I've got considerable work yet to do even on the basic shape.
I added the 18's 'power dome' to the engine hatch using a couple of plywood sheets. The fillet is a mixture of West epoxy and silica filler. Apply, let cure, and sand to shape.
The most significant recent work has been the lifting strakes. Forming and applying these was a fairly involved process. For the strakes themselves, I ripped triangular strips of maple on the table saw of uniform thickness. To taper the strakes, I first made a jig. Using a dado at an angle, I cut a long slot in a pine board to accept the strake blank upside down - that is, the surface of the strake that will be glued to the hull is facing up on the jig. next, I nailed that pine board to another base board, using shims along the length to gradually raise one end of the jig. Using this jig, I loaded the strake blanks one at a time into the jig and fed the whole works into my planer, short (stern) end first, thus shaving the bottom bow end of each strake off a bit at a time. I repeated until the strake at the raised, bow end of the form was nearly gone. This yielded strakes of the desired shape, narrow at the bow and thicker at the stern. These were glued, a few inches at a time, using super glue and held in place by hand. They were finished with fillets of silica epoxy and sanded. Well, actually only two have been sanded so far; I have two to go. I sometimes think I have sanded off more epoxy than remains on the model!
The full-scale boat is coming out of storage this weekend, further competing for time spent on the model.