Villain 29.5 SC(Slightly Copied)

[Jerry Dunlap]

Had the opportunity to test out the stretched version of the Villain S1. The boat is all WOF(Wood Over Foam) and features the same motor offset as the S1 and basically the same center section wing shape(only lengthened 1"). The tunnel width is the same. The sponsons are the same - only lenghtened 1 1/2". The center section extends to the back of the sponsons.

The motor mount plate is 1 1/2" inset and I'm using a LawLess outdrive and a CMB Gold Head 3.5.

The weight is about 5 1/2 pounds RTR. The boat rides flat like the S1 and corners great - without front "stumble blocks." 3 oz. of lead was added under the front cowling chin. A X640 cut to 37mm dia. seemed to be the best working prop. The 1440 that runs great on my S1 didn't work - pushed the bow down. I suppose I could have made a prop thrust change, but decided to just stick with the cut 640.

We have a points race this weekend and I'm going to race the boat in 3.5 Mod Tunnel. It will be interesting to see how it does in competition.

Jerry Dunlap

 

[TimD]

Jerry,

Thanks for the feedback! Do you have any Pic's available and an idea of the speed you were reaching??

Tim.

 

[Kris Flynn]

Jerry,

i liked your boat so much that i put it as my desktop background hope you dont mind?

5 1/2 lbs RTR hey, is that how much you guys normally run them with?

my Electric Tunnel comes in at around 2.76 lbs RTR with 6 cells alot of difference there

Kris

 

[Jerry Dunlap]

Kris,

A couple of things:

1. Regarding the Dumas 7.5 Sprint cowling, purchasing one from Mike Z. would probably be the quickest way to get one. Fitting the cowling to the center section is basically a matter of cutting away material until the desired size is obtained. Mike's cowlings have a cut line for Villain, but it would provide a good reference. The Dunlap 27 doesn't have as much crown in the top of the center section, however. Anyway, cut a little at a time is a good approach.

2. The weight of a 3.5 mod tunnel varies depending on size of boat and construction. My HTB 290 is fiber glass and weighs 6 1/2 lbs RTR. It runs fine, but something a pound lighter should accelerate faster .

Jerry

 

[Kris Flynn]

Jerry,

i've spoken to Mike Z. about getting one of his canopies and they are a great price, im just going to check out the Guy TimD told me to ring, who is also in us, to see if he would happen to have any spare Canopies from his Nice Tunnel...

ill have to wait and see, because they are both pretty good canopies, but ill have to see which one is easier to get a hold of

btw i only just noticed the other day that you have had ALOT of contribution to RC boating (in my view anyway), pretty successful stuff

Kris

 

[TomMoorehouse]

we all feel very lucky to have a bunch of great tunnel hull designers/builders/racers on the board!

thanks guys for your contrabutions!

Jerry..... how do you attach your wood to the foam.... I might have a weight saving trick to share with you....

 

[Jerry Dunlap]

Tom,

I've been coating the underneath side with a thin layer of West Systems epoxy. A couple of guys have suggested I try contact cement like the kind they use to sheet foam wings on model airplanes. The other method that would save me weight would be to use frame built sponsons like Mikie Z. does with the Villain. Only thing is, I can make a WOF sponson so much faster. But, maybe this winter I'll try building some frame sponsons.

Had the boat out again today for a few practice runs. Really working nice. ;D If I didn't have my CMB Green Head on my HTB 290 I'd be tempted to change powerheads. But, I'll hold off on that till after the NAMBA Nats.

I'm going to run the Villain 29 SC this weekend and a new model boater is going to race the HTB 290. We're both going to run on the same frequency, so we won't race each other unless we get enough boats for a final heat.

Jerry Dunlap

 

[TomMoorehouse]

ok Jerry here is my secret try double sided tape... the stuff i use i get from work.... but it is essentially carpet tape. its sticks instantly and it's light weight. i use it for my wof rigger sponsons with no problems.... i'd be glad to send ya a roll to try if ya want.

tom

PS do you think it is a good trick Mike Z.

 

[chunk t]

Tom,

Specificly what brand and series VHB adhesive have you used? In the bicycle industry we worked on reliable "glueless" patches for tubes. The problem was either the adhesive gave out 6 mo down the road or the adhesive was so agressive that it would eat through the substrait it was applied to (plastic, rubber or foam). that's why glueless-patches are temporary. If it's still holding 12 months later you must have found the magic combination for foam adhesion. ;D

chunk

 

[Kris Flynn]

i make all my boats using the frame method, easier for me because i dont know how to get big blocks of foam down here or even how to cut the stuff properly...what type of foam do you guys actually us4? blue foam or something different again?

also may i ask...does anyone know if making the center sction into a wing shape improve performance much in an RC Tunnel? because i see some real Tunnels that dont have a wing shape, yet i read somewhere that a wing shape should provide more lift therfore less boat in the water. What are you opinions in this subject?

 

[TomMoorehouse]

i have no idea what kind of adhesive it uses.... but i've seen it last more than a couple years without a problem.

 

[Jerry Dunlap]

RACE REPORT

The Villain 29.5 SC had a successful first race. The boat won all three heats and tied for first in 3.5 Mod Tunnel at the District 8 Championship Series race on Sunday, the 23rd.

The racing conditions were somewhat windy and the boat handled the choppy water nicely. There were smaller boats entered in the class and they experienced handling problems in the rough water.

Jerry

 

[chunk t]

Kris,

I use the pink or blue foam sheets that are used for insulation. 3 inch thick and I pick it up at home improvement stores. Usually there are cracked pieces in the bin so the store will gladly sell them cheep. I think the easiest way to cut the foam is with a table mount band saw. Start at the transome (use it to set the table angle) and cut forward following the contour of the deck. Once you get the hang of it, it's amazing how fast a hull can be built.

Can't speak for anyone else but I'm a firm believer in shaping the center section "wing." The underside shape can move the center of pressure forwards or backwards toward the transome to help balance the hull (i.e. a C.P. too far forward will cause a stable & balanced boat -at low speed- to have a tendancy to blow off the water at high speed). I don't feel there is much lift benefit from the upper surface until the hull is running 45+ mph. Keep in mind that lift is a by-product of drag and compression increases resistance. But that's a discussion for later .

chunk t.

 

[Grimracer]

Chunk

I dont follow.. please explane. Also where did 45 come from. Does this come from testing tunnel designs.

Allways learning

Keep me posted,

Grimracer

 

[ggillman]

Grim,

On the full size hulls, at speeds less than 50 mph the aerodynamic lift counts for less than 10% of the total lift, with the sponsons supporting nearly all the weight of the boat.

Here is the link to the info, about midway down on the page:

http://www.boatdesign.net/articles/tunnel-hull-design/

Gene ;D

 

[TimD]

Gene,

That is a great link! Well worth a look as there is some great stuff there for those of us who want to know "how" it all works the way it does.

Tim.

P.S does anyone own that book at all?

 

[Kris Flynn]

hmmm seen that just wanted to make sure that the same principles did apply to RC Tunnels, though probably not mine because it wont be going those speeds for a little while longer

always looking to get a little more out of things if i can, but now i realise that it wont make much difference i might not make the center section a wing shape for now...dunno just yet- in your opinion what do you think would be better for a bit slower (electric) tunnel?

Kris

 

[chunk t]

Grim,

I wouldn't call anything I've done as serious testing. I'd call it a mix of tinkering, casual observation & enough exposure to fluid mechanics to get me in a whole lot of trubble.

In regards to the center of pressure... Most tunnels I've seen (and read about) have the center section set at a positive 1-3 degree angle (I think you use 1 deg. on the S1). We know as the air travels in the tunnel it becomes compressed, increasing the pressue. That area w/in the tunnel where the average pressure is located, is the center of pressure. At high speeds when the hull is "flying" (for lack of a better term) the further apart the c.p. and the center of gravity are from each other the more unstable the hull will be because the two centers are working against each other.

45+?? I'm thinking of a hull with a pretty severe camber in the upper deck. It's about the only way for the boundry layer of air to be of much help in providing lift (what little you get). 10% benefit, I'll take it. anything is better than nothing in my book.

Again Grim, I'm not an expert, just someone who's listend to what other boaters have tried, read a bit and tinkered a little.

chunk

 

[ggillman]

Tim,

At $69.95 for the book thats a little pricy fer this old fart, It would come in handy though.

Chunk, I am not a expert either, I am good at rippin off sponsons and flipping. I have rebuilt my SAW Sprint three times now!!!!! :

As far as the speed vs. lift thing, In the R/C tunnels, the hull becomes very touchy at speeds approaching 50 mph resulting in a blow off if setup is not correct, so I would think the same principles apply.

Grims wing shaped center section in the Villain helps to control this set at the 1 degree said before.

In the full size tunnels, the Molinari that I had the rare chance to drive was just about like any other fast boat till you got past 50, at about 55 to 60 you can feel the hull lifting and the steering gets very lite, past 75 the hull gets real serious and all the forces described come into play.

Gene ;D

 

[Grimracer]

Chunk

Good information and understood. The Villain was developed CP was a focus of mine in regards to the CG..

However here is the ugly part.

What happens to the air as it passes through the tunnel.. it speeds up right...right.. does this raise the boat in the air??? Nope,, not at all, Not the way i see it..

The low pressure from this speed change buries the back of the boat in the water. ( got to have that dam AOA) ugly surface tension with the water is happening and over she goes. "blow over"

The boat begins to rotate (lift off) at the CG,,not the front of the hull..

The faster the boat goes the more the water and air passing through the tunnel pulls the sponsons in the water.

Your boat (without upper airfoil) would be slower then mine with.

Did I explain that well at all? :

Grim