NAMBA strut question

[Terry Keeley]

From page H4 of the IMPBA Rule Book:

"The drive dog must not extend beyond the transom unless the prototype's strut and/or drive dog did so. Photo documentation may be requested for proof by race CD or district scale director."

 

[Randy Rapedius]

I have no horse in this race however, I did race Scale for many years when I was into nitro. These rules are so outdated and require changing to simplify the sport.

IMPBA and NAMBA should try and mirror their rules.

To keep things simple, there should be one rule.

Option 1 - No part of the drive dog my protrude past the transom.

Option 2 - Struts may be mounted either under the hull or off the rear of the transom. No part of the hardware may protruded 3” past the transom.

Personally, I like option 1. Plain and simple rules. No exception for newer hulls. No measuring. No having documentation.

With option 2 it’s more like the Sport 40 rule.

 

[Ray Sametz]

I think drive dog has to replace with hub of the propeller. Then pick a number, 1/2"- 3/4". Totally eliminates homemade drive dogs.OMHO

 

[Rokieboater]

Seems NAMBA's rule is clear.

[SIZE=12pt]The propeller drive dog may extend one drive dog length beyond the transom.[/SIZE]



Not sure how that isn't clear. Does not give allowance for newer or older boats. It does give allowance for outdrives, articulating shafts, sponson pads, rudder and turn fins. But drive dog location is very clear.

It may be something that needs updating but..........

Hey Robert,

I just started a new business. Custom drive dogs. How long would you like yours? LOL Using a standard length for drive dog, then it would be 1/2 inch. I have a lathe and a mill. Should be able to whip out some 1" long ones to be in the gray area of that rule. Heck how about 2". Would need to build some shafts then.

It is still clear Mike. One drive dog length. Send me a couple of those when you have them done. I suppose we could read every rule and say its not clear enough for me.

Book Bag says hi.

 

[Mike Hughes]

Give the old book bag a hug and squeeze for me.

 

[Matt Smith]

Seems NAMBA's rule is clear.

The propeller drive dog may extend one drive dog length beyond the transom.

Not sure how that isn't clear. Does not give allowance for newer or older boats. It does give allowance for outdrives, articulating shafts, sponson pads, rudder and turn fins. But drive dog location is very clear.

It may be something that needs updating but..........

Hey Robert, I just started a new business. Custom drive dogs. How long would you like yours? LOL Using a standard length for drive dog, then it would be 1/2 inch. I have a lathe and a mill. Should be able to whip out some 1" long ones to be in the gray area of that rule. Heck how about 2". Would need to build some shafts then.

It is still clear Mike. One drive dog length. Send me a couple of those when you have them done. I suppose we could read every rule and say its not clear enough for me.
Book Bag says hi.

Thank you for the sarcasm

 

[Michael Costanzo]

don't know what all the fuss is about,have tried it father out and does not do a dam thing for the handling of the the hull (i run a twin wing). i personally think the boat turns quicker and more aggressive with the drive dog BEHIND the transom. just my 2 cents...

 

[Hydro Junkie]

So much for my recon run. When I got to the HARM, I found that the "Dreamliner" had been loaned to a museum in Oregon, making my "modern" boat unavailable. Sorry guys, but I did try

 

[Joe Wiebelhaus]

I think a diagram of this "unclear" problem should be put in the rule book for clarity.

1. the leading end of the prop hub would be a common datum point 'A'

2. Older hulls maybe pre 89', didn't have extended struts beyond the transom, so to take the "drive dog" out of the question, we could reference datum 'A', not to be extended beyond the transom.

3. Newer hulls have extended struts anywhere from 2" to 6" , this is a scaleable dimension, and can relocate the datum point 'A' as required.

4. Documentation would be required by the owner.

Years ago Roger Newton and myself started taking pictures of the new boats with extended struts, we talked, but the issue was never put to the test, maybe its time.

I'll put a simple diagram together so we got something to complain about.

impba strut.pdf

 

[Ray Sametz]

I think a diagram of this "unclear" problem should be put in the rule book for clarity.

1. the leading end of the prop hub would be a common datum point 'A'

2. Older hulls maybe pre 89', didn't have extended struts beyond the transom, so to take the "drive dog" out of the question, we could reference datum 'A', not to be extended beyond the transom.

3. Newer hulls have extended struts anywhere from 2" to 6" , this is a scaleable dimension, and can relocate the datum point 'A' as required.

4. Documentation would be required by the owner.

Years ago Roger Newton and myself started taking pictures of the new boats with extended struts, we talked, but the issue was never put to the test, maybe its time.

I'll put a simple diagram together so we got something to complain about.

Can"t wait!

 

[Matt Smith]

I think a diagram of this "unclear" problem should be put in the rule book for clarity.

1. the leading end of the prop hub would be a common datum point 'A'

2. Older hulls maybe pre 89', didn't have extended struts beyond the transom, so to take the "drive dog" out of the question, we could reference datum 'A', not to be extended beyond the transom.

3. Newer hulls have extended struts anywhere from 2" to 6" , this is a scaleable dimension, and can relocate the datum point 'A' as required.

4. Documentation would be required by the owner.

Years ago Roger Newton and myself started taking pictures of the new boats with extended struts, we talked, but the issue was never put to the test, maybe its time.

I'll put a simple diagram together so we got something to complain about.

Great explanation. This should be an IMPBA scale rule. Set a max drive dog length.

 

[Samuel Hagan JR]

Agreed.

Maybe a dumb question being that I'm the Scale Director for D14 but how easy is it to find documentation on length of the real boat for the drive dog rule?

Is it documentation based on photos?

 

[Matt Smith]

Agreed.

Maybe a dumb question being that I'm the Scale Director for D14 but how easy is it to find documentation on length of the real boat for the drive dog rule?

Is it documentation based on photos?

No documentation to this point that Im aware of, but dont worry Sam, these veteran boaters will chime in with their 2 cents.

 

[Samuel Hagan JR]

Agreed.

Maybe a dumb question being that I'm the Scale Director for D14 but how easy is it to find documentation on length of the real boat for the drive dog rule?

Is it documentation based on photos?

No documentation to this point that Im aware of, but dont worry Sam, these veteran boaters will chime in with their 2 cents.

That's what I'm afraid of. There are a lot of knowledgeable people on this site and who we race with but sometimes the true to Scale guys ways get in the way of progress of getting more people in. I won't say names but he know who he is would make racing a Scale boat in his district not very fun.

I think a measurement of the common drive dogs used from various sources and make a good measurement for that rule.

 

[Hydro Junkie]

I have to agree with you on measuring the drive dogs, Samuel. You can pretty much assume any boat prior to roughly 1988 should have the prop at least partially, if not fully, under the hull. Anything newer, your thought on the drive dog measuring would be something that is techable and easy to do at the pond.

 

[Michael Costanzo]

I have to agree with you on measuring the drive dogs, Samuel. You can pretty much assume any boat prior to roughly 1988 should have the prop at least partially, if not fully, under the hull. Anything newer, your thought on the drive dog measuring would be something that is techable and easy to do at the pond.

this sound's like common sense...

 

[Mike Cathey]

Perhaps something to consider is that model boats have a higher power to weight ratio and the props, rudders and turn fins are proportionally larger. The full size boats also have fixed struts and make the boats work mostly with prop and gearbox selection, lighter weights, aero and balance. Model boats have evolved just as much as the full-sized boats with more power with new generations of motors, lighter hull weights and improved sponson design and the props have really gotten more aggressive in pitch and diameter. As our models have gotten faster it's been necessary to build boats that pack less air to keep them on the water by decreasing the break angle and making the sponsons shallower and that has required shallower strut settings.I know the last 2-3 boats I have built I have had to start routing the cooling line from the rudder outboard to keep the prop from cutting the cooling line. When I had a 20lb. boat with a K&B (w/ 457, 250 props) that wasn't going 60mph in race trim this definitely wasn't an issue.

Perhaps the drive dog rule should state that the front of the drive dog should not exceed the transom rather than the back of it. The drive dogs from the recognized manufacturers could set the length standard as they are all about the same.

I suppose someone could machine outlaw length pieces. Cheating on purpose, where's the honor in that? Man, this is just an interesting hobby enjoyed by a pretty small group in the RC world, not life and death.

 

[shann harrison]

Okay here we go the 1/8 scale strut ruling should addressed it is a very grey area due to the modern hydroplanes on circuit now I started planning a boat last August I got in touch with the Leland team and asked a lot of question about the boat which included strut I was informed the strut was placed at the rear of the sponson not the Hull transom which is 18inches inwards so I did exactly that so here was what I did with my hull is with all measurements requierments according to NAMBA length width tunnel ect now the transom to rear of sponson is 3/4 inche in model form I put my extended strut at first 5/8 past transom after doing some math decided to go with 1/2 to be legal to IMPBA rule which is where I was scratching my head over not a problem I have more then enough picture evidence as proof so I get that part but this really does need to be addressed after reading my friend and last district scale director I was under Joe Wiebelhaus I do not agree with the picture he provided at all that has no bearing on the modern hydroplanes of today Here we are to model a hull as close as possible to the real thing but using old rules??? doesn't apply to the new boats of today this does not make anything but more confusion at all So there needs some major changes under these circumstances of the new boats now a days just my two cents positive communication is all I am after here fellas Shann

 

[Joe Wiebelhaus]

Perhaps something to consider is that model boats have a higher power to weight ratio and the props, rudders and turn fins are proportionally larger. The full size boats also have fixed struts and make the boats work mostly with prop and gearbox selection, lighter weights, aero and balance. Model boats have evolved just as much as the full-sized boats with more power with new generations of motors, lighter hull weights and improved sponson design and the props have really gotten more aggressive in pitch and diameter. As our models have gotten faster it's been necessary to build boats that pack less air to keep them on the water by decreasing the break angle and making the sponsons shallower and that has required shallower strut settings.I know the last 2-3 boats I have built I have had to start routing the cooling line from the rudder outboard to keep the prop from cutting the cooling line. When I had a 20lb. boat with a K&B (w/ 457, 250 props) that wasn't going 60mph in race trim this definitely wasn't an issue.

Perhaps the drive dog rule should state that the front of the drive dog should not exceed the transom rather than the back of it. The drive dogs from the recognized manufacturers could set the length standard as they are all about the same.

I suppose someone could machine outlaw length pieces. Cheating on purpose, where's the honor in that? Man, this is just an interesting hobby enjoyed by a pretty small group in the RC world, not life and death.

Shannon, This is why I wanted to get out of using the term drivedog, Im sure the leading face of a prop can turn into a can of worms also, in terminology,

But I would bet, 99% of us would use a standard prop we all purchase, and the leading edge of the hub on the prop is pretty consistent.

 

[Joe Wiebelhaus]

Agreed.

Maybe a dumb question being that I'm the Scale Director for D14 but how easy is it to find documentation on length of the real boat for the drive dog rule?

Is it documentation based on photos?

Sam,

No documentation that I know of, I;ll pull some pics from home to show 3-4 typical examples of current and old struts.

Matt, if you use the leading edge of the prop as your datum point, it doesn't matter what size your drive dog is in length.