How do you determine the size of a Unlimited boat ?

[Tall Fella]

Hello everybody .

This is a enquiry from Australia . I have some Newton Marine plans and have read the Rule book of both AMPBA ( Australia ) and NAMBA which states that basically all dimensions have a allowance of 10 % . So , when checking the NAMBA MHR and not finding any dimensions listed behind the boats I am interested in running - how do I determine what size the Original boat was ? .I look forward to reading your replies . I have heard and seen several Scale boats racing over the years and noticed that sometimes members use a piece of wiper blade under the front to reduce the lift generated at speed for example .

Regards

Ian Baas

Tall Fella Racing

 

[glenng]

Ian, the NAMBA website should have in the MHR in the Scale section giving the size of the real boat in feet and inches and also the dims. for 1/8 scale in inches +- 10%. What hull are you building?

 

[Mike Cathey]

Some clubs like UNW and RCU only allow +/- 5% on the length. You can do away with the air dams if you lower the angle of the break in the bottom and move it forward at least to the sponson transoms. You also want no more than a couple of degrees of angle of attack on the running surfaces. On a pickle fork you go to maximum depth. On some of Roger's older plan sets the boats were only going 35-40 mph and required packing more air underneath them for more lift. Now it is routine to see boats moving at 55-60 mph. We now have more power with lighter boats. UNW point leader Adam Putich 's Beacon Plumbing carbon fiber hull, built by his dad Jim, is less than 3 lbs bare hull. When you go faster everything changes accordingly. A good analogy might be that in the big boats that when they made them start using more stock parts in the turbines to reduce costs it also reduced power and all of the boats that had huge vents mid way back (like the Bud/Exide/Circus/Truckgear boats) went away because they didn't have enough lift at slower speeds and sagged off so bad in the turns.

As we continue to work on the new gas scale class and we seem to be getting lots more power and speed my guess is that the next generation of hulls built will have almost no break in the bottom, a minmum tunnel width, almost flat running surfaces, belly pans to lower CG and the motor as far forward as possible to keep them on the water w/o using air dams or a lot of weight in the nose. One of the biggest issues seem to get getting enough air to the motors to really let them develop max power in a scale cowling arrangement.

Right now many of the hulls that are essentially a ramped up 1/8th scale nitro hull are having a hard time staying on the water.

 

[hugh hargett]

Mike, about air - even though its 1/8 scale FE im going to get air in the motor bay by incorporating a naca duct inside the cowling the water spray will pass right over while still forcing air down onto the motor.... just an idea im using on my scale.

 

[Hydro Junkie]

Ian, Mike's information is pretty much on the money as far as the scale boats go. If you want to compute the actual scale size for a scale boat to make it an exact match to the full size, take the max and min sizes, add them together and divide by two, This will give you the size of a perfectly scaled boat. Here is an example, using the 1984 Atlas Turbine hull 8401:

Full size length= 28.5 feet scale length= 42.75 inches allowable lengths are 41.75 to 43.75 inches

Full size width= 13.5 feet scale width= 20.255 inches allowable width are 18.23 to 22.28 inches

Full size tunnel= 7.416 feet scale tunnel= 11.13 inches allowable tunnel is 10.02 to 12.24 inches

Full size hull depth= 2.25 feet scale depth= 3.375 inches allowable depth is 3.04 to 3.71 inches

Full size after plane=15.916 feet scale length= 23.875 inches allowable length is 21.49 to 26.26 inches

Full sized picklefork=11 feet scale depth= 16.5 inches allowable depth is 14.85 to 18.15 inches

Hope this helps

 

[Dasboatman]

"........ how do I determine what size the Original boat was ? "

Hey Ian,

I read that you are looking for dimension not listed in the MHR for a hull you'd like to model.

Check the sanctioning acivity you run under (AMPBA). It probably specify something like:

"The true scale dimensions of any Scale Unlimited Hydroplane will be derived from the unlimited dimensions listed on the Scale Unlimited Hydroplane Master Hull Roster".

If not listed there, I'd assume you would have to wait until the dimensions are listed in the MHR to comply with sanctioning activities Rule Book.

What specific hull are you looking for??? CHEERS !! Bob

 

[Hydro Junkie]

Okay, I think I get the question. You need to know about boats like the 2003 Trendwest, 2007 Oberto, 2007 Red Dot and the new Degree. There isn't much you can really do on those boats except pattern them off of similar boats. That being said, most of the boats I just listed(Trendwest is a different animal all together) are loosely based on the T-6 and Elam/Qatar hulls. If you use them as a baseline, you will probably be in the ballpark. Another option would be to contact the race team itself and ask for the approximate dimensions and scale accordingly. That won't work for some of the teams until after the final "Stateside" race in San Diego since the U-5, 6 and 22 are all going to be on the west coast rather than in their home shops

 

[PakMan]

To Answer your question, check the MHR... listed on WWW.RCUNLIMITEDS.ORG check out the information page. It has the dimensions with the tolerances for RCU... check your org. for similar compliance.

Now that the Gas Scale class is 'official' ( In NAMBA)... let me know when their (6 lap) record is within 5 seconds of the Nitro's and I'll start listening to this chatter (Mike). The talk is interesting...

Bring on the SLUGS... Kinda kidding guys... you all know me.. I'm not trying to be mean.... but let's do this!!! Us Nitro Guys need some motivation....

Thanks,

David

 

[jwo]

To Answer your question, check the MHR... listed on WWW.RCUNLIMITEDS.ORG check out the information page. It has the dimensions with the tolerances for RCU... check your org. for similar compliance.

Now that the Gas Scale class is 'official' ( In NAMBA)... let me know when their (6 lap) record is within 5 seconds of the Nitro's and I'll start listening to this chatter (Mike). The talk is interesting...

Bring on the SLUGS... Kinda kidding guys... you all know me.. I'm not trying to be mean.... but let's do this!!! Us Nitro Guys need some motivation....

Thanks,

David

Hey David, The 2 lap records will be in Sept. My U-95 gasser will be there. It is faster than the nitro hulls.

 

[Tall Fella]

Hello everybody .

I have been looking around a few websites - NAMBA MHR , Newton Marine and RCU to get the best information posslble in order to sort out my enquiry without much successs . I have a Australian built fibreglass hull that was originally going to be a U - 100 American Spirit ~ 1991 that has a sad face cowl - like the Circus Circus and T - Plus boats had . I made several enquiries over time to get a Colour Sheet for it and apparently none were available . What did get supplied in it's place would make a later American Spirit / Dream - PICO boat . Now my thoughts are to change the identity of the boat to the 1998 Llumar boat because I already have the cowl for it . So that's where I am up to in regards to this project . Hopefully this helps in getting a guide to the correct information to have this boat completed and up and running .

Regards

Ian Baas

Tall Fella Racing

Australia

 

[Mike Cathey]

To Answer your question, check the MHR... listed on WWW.RCUNLIMITEDS.ORG check out the information page. It has the dimensions with the tolerances for RCU... check your org. for similar compliance.

Now that the Gas Scale class is 'official' ( In NAMBA)... let me know when their (6 lap) record is within 5 seconds of the Nitro's and I'll start listening to this chatter (Mike). The talk is interesting...

Bring on the SLUGS... Kinda kidding guys... you all know me.. I'm not trying to be mean.... but let's do this!!! Us Nitro Guys need some motivation....

Thanks,

David

John's Tempo with a mod motor in it was doing the mid 60's last year in Tri-Cities but it was getting confused about whether is was a boat or an airplane. Spectaculat altitude on the blow overs! Marty's Oly boat was continually going over at the last race with the added HP. It was built by Kerry Case and is a large version of the hull that he and John Hruby run in nitro.