Dunlap 30 WOF TWIN 3.5 Os build.....

[Mike Larson]

Guys, Marty and I may team to build this hull as a winter project, I've been in R and D mode for weeks determining issues......

Got a few questions for the knowledge on here.... ( Everyone's saying Jerry D, is the man to ask, so Jerry, help us out!)

Any of you twin guys I met at the champs feel free, too... I was impressed, and this will be the pinnacle of my meager experience...

What aspect, will most help compensate for the serious amount of weight this boat will support on the rear?

Thoughts of A: wider boat, overall.

B: deeper tunnel, ie: more air, more lift?

C: airfoil/wing center, more forward, or back to help balance/support

D: what effect is gained, or lost, actually building a wedge shape from front to back, or

vice versa, effectively funneling/releasing the air in the bottom of the center section?

E: wider sponsons only, C/S the same

F: what effect of building more or less angle into the C/S vs the sponsons example,

front of C/S higher than the rear?

Input would be great! For the most part, without building 10 proto's a few steps in the right direction, would be appreciated.... thanks Mike

 

[MarkScott]

Mike, don't qoute me on this, but thought that most of the twin motor boats at this years OB Champs were running 7.5 boats.. You might want to rethink using the 30" length for this project.. Look into building a 34" or 36" for the twin.. One of these years I may build one up myself.. But as it is, too many projects and not enough time until next March.

 

[John Knight]

Mike, don't qoute me on this, but thought that most of the twin motor boats at this years OB Champs were running 7.5 boats.. You might want to rethink using the 30" length for this project.. Look into building a 34" or 36" for the twin.. One of these years I may build one up myself.. But as it is, too many projects and not enough time until next March.

Mark,

At this past Tunnel Champs race, the twin boats were actually twin OS engines that ran in the 40 classes. Some were mounted on WOF's and others, like Mike Talley, were on a Shaman. I also believe that most were 40 hulls if not all. I believe that Talley proved that a longer and wider hull is more stable for the twins, especially in the turns. Gabe tried a twin wood (not sure if it was a Villain or Nemesis) with a narrow stance and it spun out badly in the turns.

BTW, Carl Van Houten told me last night that Talley has a new and improved twin coming to the race in March. It is a new hull design and it is quite a bit faster - Shaman. So look out.

John

 

[Jerry Dunlap]

A 33" - 34" boat with typical 7.5 dimensions should provide a pretty good hull.

JD

 

[Mark Poole ModVP]

I would agree that twins on a 30" hull is too much. The OS motors are taller, heavier and the prop is back more than a K&B. A 40 size hull will handle this better. I am sure Gabe would share his experiences with you since he has tried several different set ups.

 

[Ronald van Essen]

Mike, don't qoute me on this, but thought that most of the twin motor boats at this years OB Champs were running 7.5 boats.. You might want to rethink using the 30" length for this project.. Look into building a 34" or 36" for the twin.. One of these years I may build one up myself.. But as it is, too many projects and not enough time until next March.

Mark,

At this past Tunnel Champs race, the twin boats were actually twin OS engines that ran in the 40 classes. Some were mounted on WOF's and others, like Mike Talley, were on a Shaman. I also believe that most were 40 hulls if not all. I believe that Talley proved that a longer and wider hull is more stable for the twins, especially in the turns. Gabe tried a twin wood (not sure if it was a Villain or Nemesis) with a narrow stance and it spun out badly in the turns.

BTW, Carl Van Houten told me last night that Talley has a new and improved twin coming to the race in March. It is a new hull design and it is quite a bit faster - Shaman. So look out.

John

Take alook at this page:

http://www.ovalexpressracing.com/

Scroll down and there you see a Nemesis twin os from Gabe

I believe this combo could work if not for the special behaviour of the Nemesis in the turns.

The twins are mainly OS max since you can run them quite the same compared to K&B's.

Gabe will give his comment on this.

Ronald.

 

[topfuel443]

Guys, forget the big 40 size hulls. Far too much boat for the size props these engines turn. The Nemesis I had would have been ideal, as it is close to the size of a Shaman. It showed great speed, and the issues in the turns were from the boat itself, NOT the fact that it had twins mounted on the back. I have had a problem with that boat from day one, with a single or twins, it just didnt turn.

We all at that time thought the twins would be better suited on a 40 sized HTB 360 type hull. Shane and Terry from bermuda built these exact boats, both with sport modified twin OS's on the back. They ran them at the last Charleston race a month or so ago, and they were kind of pigish. They handled nicely, but most boats do when they arent running that fast. I firmly believe it was simply to much boat. Too much tunnel, too much length, too much weight etc. You cant turn a big enough prop to get the boat to get up to where it should be.

You guys also need to remember, the Shaman is a very small size 40 boat. In fact many peple run this boat with a strong modified .21 engine.

I think the ideal Twin boat would be a HTB 290 that was 32 inches long and a 1/4 inch wider in the tunnel. Unfortunately, that boat desnt exist. so you will have to build it, or find a shaman.

~James

 

[MarkScott]

At this past Tunnel Champs race, the twin boats were actually twin OS engines that ran in the 40 classes. John

John,

That was my point.. Guess it wasn't stated clearly enough. Twin motors on a 7.5 hull to run in the D class..

 

[Mark Poole ModVP]

I bet the HTB 340 would be a good one. 2 inches less length would go a long way towards riding more freely but would have the same handling characteristics as the 360. The 360 is a boat that will handle all the power you can hang on it. I also think how far back the props are becomes even more critical.

 

[Mike Larson]

Thanks Guys.... In discussion with Marty, basically we can do anything..... hence the hull engineering questions. The boat is just in infant stages of R and D, forcing a great amount of brain to paper work, before it moves forward......

Basically, to this point, a general agreement of small adjustments length and width.......

It'll be a one off, anyway, and if you aint fightin a proto what else makes you happy, so.....

Any testing at all done with wider sponsons, and a possible greater tunnel depth to help the boat turn? Benefits?

Theory, on to this point, correct if you would, wider spoons to allow the overall weight easier access to full plane, and, higher tunnel to allow more air to keep it there once achieved?

Thanks for the help, right now, it's a massive knot of thought.... ....

Mike

 

[moparbarn]

guys, check out screamandfly.com. A LOT of pics and info on full size tunnels and what it took to turn them into twins. and most of the drivers, hull designers/builders, and ob factory engineers who set them up. easy and free to join, about like here. look at the racing history and rigging and setup forums for the most help. have a rc forum and a KILLER fiberglass & composit forum, also. might see some names you recognize from here, and racing. plus, just a bunch of REALLY COOL boats. imo, a worthwhile site to check out-just about everything that affects our boats affects big ones the same way. there is a wealth of info there. not trying to imply that iw isn't the same, just adding another source.