Arneson 'Hydra Trim'?
 

Hi all,

Who has experience with one of these or a similar device? As shown on the below famous Donzi (the bit below the prop), it's a little horizontal fin mounted on the bottom of the skeg at a slight angle to give bow lift with a surface drive by giving downward thrust on the drive. This in theory allows boats with no natural bow lift to use surface drives.

I'm looking for info on whether these work and how well in real life situations? I'm guessing they're best on trimmable surface drives like the arneson so the angle of attack can be adjusted, but I assume they could also work on a fixed drive if set to give the correct bow lift for flat water, which can then be countered for rough water.

I know they will cause a little extra drag, but in most applications I've seen such as the donzi they've really gained from it. If it allows a surface drive to be used on a straight bottom V then I'm sure a little extra drag would be offset by the ability to run something other than a bravo!!

Cheers, James

I have one on my Donzi. It does make quite difference. You will want try it without first. What hull are using?

The one in the picture was made by the owner of the boat not Arneson.

Jeff

Fixx
 

you wil get more answers @ donzi.net on this ..i think this was done on mighty mouse for several reasons..

Haven't got anything installed yet. I'm building a 25ft revenger, it's a very narrow and light straight bottom mono based on the don shead hull design, excuse the fuzzy pic!

I'm building a blown big block for her and just don't want to trust a bravo drive as it will be driven hard and raced. I've been over the surface drive idea before and have been told it won't work due to lack of bow lift, but I'm determined to find a way of making it work! There's too many people with surface drives on straight bottom boats for me to believe it won't work!

James

Yeah, I've spent several nights on there looking at the reasons including the increased stability, which would also be a nice addition! I'd rather do a stable and reliable 75 than a scary 80 never knowing when my drive will blow again!
I don't believe Geoo posts on there any more though does he?

Cheers, James

Fixx
 

pm mattyboy,,,Scott Pearson,,,mr.x or buiszilla..one of them can give you a in def story,most likely mattyboy..mattyboy is also on facebook under http://www.facebook.com/#!/group.php...18449494841496

matthew v

did you watch some of the vids of mighty mouse,geoo had plenty of bow lift...you can also try to pm him on donzi.net..GEOO is his screen name..

View post 45,,some vids of geoo
http://www.donzi.net/forums/showthre...y+mouse&page=3

Thanks very much for all of that, I'll PM them this evening. I've avidly watched all the mighty mouse vids I can find, it's an amazing boat driven and owned by an amazing guy. I can't believe all the 'tributes' to him on donzi.net, he's like a god to them! Would be great if I could get in contact with him, seems he's very friendly and would most likely know all the answers to my questions!

Cheers, James

George is a great guy... He took a boat and a setup that everyone said would never work and he proved he was right.

You can read about my installation here--

http://www.donzi.net/forums/showthre...arneson&page=2

Jeff

Cool, I'll have a look through that too then!
I'm a lot like George in that I won't take no for an answer unless someone can prove to me that there is absolutely no way of doing something. If no one ever tried to be different we wouldn't be where we are today!

I've added about an inch of rocker to the bottom when I did the build anyway so that should help and 99% of my boating will be done in very rough water, so it won't matter if the bow isn't pointing at the sky naturally!

Cheers, James

And what drive are you going to be using?

Well this is the big question!!

At the moment the boat is rigged for bravo with a crazy high x dimension, the bullet is only a couple of inches or so below the bottom. Considering that I'll be running about 600hp, I just won't believe that the bravo (which is thin floor) will hold with race use, it's not like I can just take it easy! That said, the boat is quite light, about 3000-3500lbs.

Ideally I'd actually like to go with an arneson as I feel I'll need the manouverability it offers, we have a lot of tight harbours and this boat will also be used for leisure. Also this will obviously be the best option with the little trim tab etc. Only issue for me is getting props and price, so I may look into getting a 2nd hand drive as it'll be a trial more than anything else!

If anyone wants to discuss anything off the board for any reason, feel free to PM me.

Hope this helps,

Cheers, James