dave frank oberto plan

[dave weagel]

thinking about using the dave frank / garry finlay 1/12 scale oberto plan to build a 1/10 scale electric for counter-clockwise, left turn racing ?

as you know, this plan is a sport hydro version of the 8255 hull, has good scale hull outline and excellent running characteristics for right turn racing.

are more changes required other than switching the sponson bulkheads left side with right side and mounting the turn fin on the inboard edge of the left sponson ?

this will be my first FE scale hydro project and i would appreciate all the advice and experience with this hull you can provide.

thank you,
dave

[JimClark]

What are the sponson angles and the dihedral angles?

[Allan]

From memory the sponsons are the same but if not you need to reverse the formers and build on the opposite side.

Personally I don't like the Dave Frank internal support and favour the Garry Finlay approach. I guss it is not really important.

Also from memory the hull is not offset - but if it is then you just need to switch all the formers around. ( E.G for shaft access) and offest the drive the other side.

[dave weagel]

jim, alan,

thank you for replies.

don't know the sponson angles. i am talking about the long notches / steps that make the ride surfaces different. i'm pretty sure the sponsons are designed for right turns.

the right sponson is stepped on the outboard side and stepped on the left inboard side. the angles not given on plan but appear to have same dihedral left and right. but not certain. don't know the AOA angle(s). the hull is not offset, the sponsons being equally spaced from centerline.

i'm looking for copy of the construction article that was published in rc boat modeler. and dave's construction video would be helpful. dave should have drawn pictorial views of the hull assembly and added construction notes like garry finlay's plans.

that's garry's next assignment, re-draw the oberto plan with all of the great finlay features.

i think that just switching the left and right sponson frames will work for left turns. but would like comment from someone that has built it for CCW running before i start building it.

alan, i understand your concern about the internal framing structure. dave designed this hull to be built with 3 sub assemblies, center box and 2 sponson structures. the potential weakness is the lack of positive attachment and alignment between the the sponson assemblies and the center box.
the lack of full width frames and slotted stringers is not immediately obvious until you study the template sheet.

i like the overall simplicity of this hull and the cowl would be relatively easy to make with wood. but would definitely be interested in a 1/10 scale glass cowl if available.

several paint scheme choices available and no rear wing to deal with.
MHR 8255, NEWTON 138

i built a 43 inch gas version as drawn several years ago. doweled the sponsons to the center box before installing the deck skins. runs great turning right with a zenoah 260. used the non-scale phil thomas 82U55 gas cowl to enclose the engine and exhaust system.

thank you,
dave

[DJ Campbell]

I have a built but unfinished Oberto and a set of hard copy plans with the article. If there is interest, I can scan the article and make a pdf available. Seems like though the article may be out there in electronic form somewhere.

There is also some negative thoughts on the steps being both inboard and outboard. Some of the racers in the MN club have changed the steps to be both inboard - as the hull would not turn left at all without mishap. (sometimes you gotta turn a little left-nobodys a perfect driver all the time. I have not run the hull so I don't know from first hand.

[Allan]

If you build from the plans for counterclockwise racing then you need to reverse the plans left to right. You will need a counter rotating drive and Counter rotating prop also.

The plans and write up used to be available online but seem to have gone. RumRunner and I have the plans on site.

Allan

[dave weagel]

dan,

thank you for reply. i understand the thinking re steps on the inboard side both sponsons and is reasonable. many hydros use that feature.

but i'm pretty sure dave f. optimized his sponson design for best performance in the straights and turns.

i'm building this boat for scale CCW left turn racing. that's what my questions are about. sounds like your club is running CW, right turns. as you know, most hydros won't turn opposite the turn fin side very well.

upon closer inspection of plans i think the right sponson has more dihedral than the left which makes sense for a right turn boat in my opinion.

the most logical and simple approach would be to exchange the left and right sponson frames putting the outboard step and dihedral on the left and the inboard step on the right.

if you can put the construction article in a a pdf and email or post it here i'd appreciate it. i'm thinking that dave might have commented about his sponson design in that article. can't find it and doubt that the back issue of rc boat modeler is still available.

as i said, i built a 43 inch gas version which runs very well. of course the structure of the center box is modified for the gas engine but otherwise built as drawn except use of 1/8 and 1/16 birch ply for frames and skins.

finish that hull if you can, it runs great.

thank you,
dave w.

ndu7@aol.com

Originally Posted by DJ Campbell

I have a built but unfinished Oberto and a set of hard copy plans with the article. If there is interest, I can scan the article and make a pdf available. Seems like though the article may be out there in electronic form somewhere.

There is also some negative thoughts on the steps being both inboard and outboard. Some of the racers in the MN club have changed the steps to be both inboard - as the hull would not turn left at all without mishap. (sometimes you gotta turn a little left-nobodys a perfect driver all the time. I have not run the hull so I don't know from first hand.

[dave weagel]

alan,

i understand what you're saying about counter rotating drive and props. evidently this stuff available because some scale clubs like my local club do run CCW. i'm new at elec scale boating and still learning.

upon closer look at the plans it appears that just switching the left and right sponson frames will give the hull the same great running characteristics turning left as it does as drawn for right turns.

awaiting more tech info from left turn racing scale builders.

thank you for making the finlay plans available. i built a 43 inch gas version of this hull from the frank plans available from rc boat modeler magazine several years ago but do not have the construction article.

thank you,
dave

Originally Posted by Allan

If you build from the plans for counterclockwise racing then you need to reverse the plans left to right. You will need a counter rotating drive and Counter rotating prop also.

The plans and write up used to be available online but seem to have gone. RumRunner and I have the plans on site.

Allan

[chuckc]

Dave, check your email.. I'll walk ya through it...

[dauminator]

I think a quick trip through the rules is in order to avoid certain pitfalls:

1. Hull 8022 is by the definition under NAMBA Rule Section 28e.iii)(b) is in the Modern Class. The rules in this sup part apply only to Modern boats as defined by the Master Hull Roster number.

2. Unlike Vintage Class Hulls, Anhedral/Dihedral sponsons, inside nontrips, recovery surfaces, steps and grooves are all allowed. Also unlike the Vintage Class, the turn fin of a Modern boat can be hung off the sponson transom.

3. The biggie: "Any shaft may be used." and that means just what it says, ANY! Wire drive, flex, articulated or solid straight shaft is OK and it does not have to be a straight shot from where it exits the bottom of the hull to the strut, just make sure part of the prop is under the transom of the boat.

On most hulls of a modern design and even the vintage 1/8 Scale hulls, the inside sponson geometry typically differs from the outside when viewed from the back of the boat relative to the turns are to be made. Some modern hulls are even more asymetric in that the cockpit and cowling are offset to the inside of the turn as well.

Given all this information, to turn a right hand turning (CCW) design into a left hand (CW) turning design, you need to build reversing the plans left to right as Alan suggests above. This can easily be achieved by cutting and marking all your bulkheads and longitudinals per plan then swap the inboard longitudinals left to right and bulkeads facing back to front.

If you are going to use flex drive, get the kind for opposite hand rotation.
Start with a Graupner K45L prop for initial testing and transition to an Octura 447R with what ever secret speed mods you can put on it and not burn up the speed control.

One more thing to think about, if you actually want to be able to race in either direction, you will need to make sure your sponsons are symetric, e.g. no anhedral-dihedral. Both sponsons with three degree dihedral and 5 degree runners with a 3-4 degree tunnel should perform well. Hard points on both sponson transoms and both sides of the transom to allow for opposite handed mounting of hardware and you should be good to go have fun. Also for 1/10 Scale, use 1/16 ply everywhere the larger scale plan calls for 1/8 and 1/32 wher 1/16 is called for. Sides and sponson nontrips that are backe up with foam, use 1/64" ply. Don't believe it? That is how my Such Crust III is built.

Will we see you at the Nats in CO?

[dave weagel]

ron, chuck,

thank you for the very informative replies. ron's explanation of the 1/10 rules really helps.

based on my reading of the namba 1/10 rules and ron's posting i'll use a flex shaft and mount the turn fin on the left sponson transom.

the dave frank plan is a sport hydro version of mhr 8255. the hull outline looks very close to scale to me. so i will build the hull 1/10 size of the real hull, 28ft 6in, 34.2 inches unless i'm allowed to use the +/- 1 inch length variation shown on page 3 of the 1/8 scale mhr. the other hull dimensions should fall within the 10% variation rules if i build it an even 35 inches. i'll verify all this before enlarging the frank 1/12 plan.

i will simply switch the sponson frames , left and right, which should provide same great running characteristics for CCW left turns. i know my 43 inch gas version of this dave frank plan runs great. that's why i want to build this hull as my first 1/10 scale electric.

all this pending final approval of the local club, MME.

this being my first elec, i have a lot to learn and i appreciate all the help.

thank you,
dave

[DJ Campbell]

I'll get those pages scanned into a pdf pretty soon and make it available. I think too I'm going to setup that hull I have with a SV27 package.

Originally Posted by dave weagel

dan,

thank you for reply. i understand the thinking re steps on the inboard side both sponsons and is reasonable. many hydros use that feature.

but i'm pretty sure dave f. optimized his sponson design for best performance in the straights and turns.

i'm building this boat for scale CCW left turn racing. that's what my questions are about. sounds like your club is running CW, right turns. as you know, most hydros won't turn opposite the turn fin side very well.

upon closer inspection of plans i think the right sponson has more dihedral than the left which makes sense for a right turn boat in my opinion.

the most logical and simple approach would be to exchange the left and right sponson frames putting the outboard step and dihedral on the left and the inboard step on the right.

if you can put the construction article in a a pdf and email or post it here i'd appreciate it. i'm thinking that dave might have commented about his sponson design in that article. can't find it and doubt that the back issue of rc boat modeler is still available.

as i said, i built a 43 inch gas version which runs very well. of course the structure of the center box is modified for the gas engine but otherwise built as drawn except use of 1/8 and 1/16 birch ply for frames and skins.

finish that hull if you can, it runs great.

thank you,
dave w.

ndu7@aol.com

[Allan]

The free versionis on my site www.astecmodels.co.uk/plans.htm

[dave weagel]

thank you for making the garry finlay plans available allan.

we need to talk garry into re-drawing the dave frank plan adding pictorial views of the hull assembly with construction notes clarifying the assembly sequence of building the separate hull sections, 2 sponson assemblies and the center box and a method of positive alignment when attaching the sponsons to the center box.

this is not readily apparent looking at the plan. dave frank's construction article and build video were very helpful when i built my 43 inch gas version.

it's an excellent running hull.

[JimClark]

The question is how will the design of the hull hold up to today's power and lighter lipos? It could need a complete redesign of the air trap and sponsons to work well today. Garys atlas plans already have Brushless and in some cases Lipos taken into considderation
Jim

[Garry Finlay]

I did the best I could putting the Oberto into CAD format by copying the shape and size of the parts from two paper sheets of Dave’s original plans (Rev_B) that I had.

The dilemma is that this is his design and I did not want to change that. I copied each part outline as close as possible. Unfortunately, hand drawn shapes on paper may not be perfect. Add to that that, I had a third, or fourth generation copy from the original. There were places that the part outlines were at conflict with each other. I tried to minimize that without interjecting my own interpretation of how the boat should be designed.

The plans of my hulls are derived from a solid CAD model of the hull. All the pieces are modeled in the computer and the assembly of each part is checked for fit. Even then, there are discrepancies due to things like the need for bevels on parts that are cut by laser or band saw. And often I leave a bit of safety stock so builders will have a bit to sand down instead of a gap, in places where the fit is critical and the assembly may vary a large amount due to “building style”.

Bottom line, I can’t easily (or even with great effort) draw up a new Dave Frank Oberto in CAD. It is a fine hull as he originally drew it up many years ago. Like the multitude of plans drawn by Roger Newton, I liken these to fine works of art and I won’t try to improve on them.

But, it is about time I got off my duff and started some new projects. A drop sponson 1950-60 Luaterback (sp?) hull comes to mind. Or a hybrid of classic, mixed with more modern tunnel and sponson shapes for the REALLY high power systems available now,, or a cross between a supper-vented turbine style hull with an outrigger.

Too many project, too little time – and the lawn needs mowing.

Garry

[DJ Campbell]

Originally Posted by JimClark

The question is how will the design of the hull hold up to today's power and lighter lipos? It could need a complete redesign of the air trap and sponsons to work well today. Garys atlas plans already have Brushless and in some cases Lipos taken into considderation
Jim

I've seen a racer in the Minnesota club (QuietLee) build and run lipo/aquacraft LSH powered versions of the 1/12 Oberto hull. The opinion was that they ran great and are very competitive. I don't know exactly what Lee did (if any) in modifications. I have heard from some guys there about the anhedral sponsons being modified, but now I remember this may have been a Larsony hull -it has similar anhedral sponsons-that was modified by Dan Proulx.

Anyway, I think the Frank hull is worth a test or two for proof of concept in LSH. I'm gonna try the one I got off of ebay. It was built well and came with original plans and instructions.

[Allan]

I did the best I could putting the Oberto into CAD format by copying the shape and size of the parts from two paper sheets of Dave’s original plans (Rev_B) that I had.

been there - done that - its not easy!!

The plans of my hulls are derived from a solid CAD model of the hull. All the pieces are modeled in the computer and the assembly of each part is checked for fit. Even then, there are discrepancies due to things like the need for bevels on parts that are cut by laser or band saw. And often I leave a bit of safety stock so builders will have a bit to sand down instead of a gap, in places where the fit is critical and the assembly may vary a large amount due to “building style”.

wish I had the 3d modelling capability. My Cad software does - I don't!!

Any one that thinks translating from drawings to cuts is easy needs their head eaxmined - OR I have one of U8 Tide that they could do for me.

Before anyone asks it is copyright and therfore not published. If I ever figure out the right former sizes I may publish as that and with changes to key things better and improve cutting ability.

SO Garry - thanks for what you do!! I now have the vanlines and thriftway in 1/16th in kit form, vanlines and PaynPak and U7 Notre Dame at 1/12th ( Paynpak available and U7 close, and cuts for the thriftway too prototype being built.

[DJ Campbell]

Originally Posted by Allan

been there - done that - its not easy!!

Before anyone asks it is copyright and therfore not published. If I ever figure out the right former sizes I may publish as that and with changes to key things better and improve cutting ability.

Hey Allan, can you clarify what is meant by copyright? Do you have copyright to it? It would be good to know to have a brief explanation for everybody about that about those plans and plans and use of them in general. Just to note that on the Oberto plan it says "Public Domain".

[Allan]

U8 Tide plan was/is owned by a magazine and were being sold on Ebay. Andy Kunz drew them originally so I checked with him - I don't know who owns the copyright now. Unless I find out it has lapsed I'm not putting them online.

Allan