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ZoomZoom Trimable engine mount
- Thread starter COLD
- Start date
ZoomZoom
Well-known member
Cold, I will be glad to, it will take me little time to send you some pictures, but I will not forget. I'll write myself a note. It works quit well I got the idea from stern drive outboards. What I do is make an engine mount that has it's pivot point in front of the engine, (all thought this may not be entirely necessary), it does slow down the rate of pitch angle change when you are changing such angle. I then go to the rear and mount a jacking device. I have used two kinds ele. over hyd. and ele. over mechanical (jack screw), with a safety device to keep the engine travel safe even if the jacking device fails. I’ve thought about of going into some kind of production, but airboats can sometimes be a bit funny about new ideas. It has a greater effect for trimming because you are trimming the thrust angle. I hope this info will help you, where do you boat? ZZ
Just building. Actually just came in from welding the forward stringers. That sure stiffened it up. River in my Back yard and boat launch 2 block's away. It's a 16'9' by 8' Deckover built out of 12 Gauge steel (0.105"). It is powered by a 489 CID BBC with a Rotator 2.68 and 82" 3Blade Superwide Sensenitch, (now you think i'm a lamb?) I think it should be pretty cool? 8)
I have brought up the tilt idea before however I was thinking tilt rear mounts on the "Rotator" and a frame attached to those mounts and the front of the engine to a 3" ram I have. I figured with the greater distance from the prop as well as larger diameter cyl you would get a gentler adjustment when you pressed the switch. It has 6" travel however I figured I would cut that back to about 3" and If I need to limit stroke more I can put some stroke limiters in the cyl. Have a trim pump sitting here and was all free so only cost would be seal kit for cyl and hoses.
Edit: Oh yeah, I'm going to mount the rad in front of the engine like a car and use a Clutch fan and shroud. Another reason the engine needs to be on a frame because the rad will move with the engine. Clean air to rhe prop, It's way cooler up here, 90 degrees is smokin hot!
I have read guys say trim the engine down, (riding on nose) to run dry as well as trim up? It might give you better options with diferent loads and surfaces? :?
I have brought up the tilt idea before however I was thinking tilt rear mounts on the "Rotator" and a frame attached to those mounts and the front of the engine to a 3" ram I have. I figured with the greater distance from the prop as well as larger diameter cyl you would get a gentler adjustment when you pressed the switch. It has 6" travel however I figured I would cut that back to about 3" and If I need to limit stroke more I can put some stroke limiters in the cyl. Have a trim pump sitting here and was all free so only cost would be seal kit for cyl and hoses.
Edit: Oh yeah, I'm going to mount the rad in front of the engine like a car and use a Clutch fan and shroud. Another reason the engine needs to be on a frame because the rad will move with the engine. Clean air to rhe prop, It's way cooler up here, 90 degrees is smokin hot!
I have read guys say trim the engine down, (riding on nose) to run dry as well as trim up? It might give you better options with diferent loads and surfaces? :?
dantheairboatman
Well-known member
I have bought the parts to build a electric jack for the bottom of the boat. I 'm calling it my trim jack. I bought a gear reducted electric screw jack with micro switches to limet movement. If your motor is close to level with your stringers a jack can bring up or pull down on the nose of the boat. Lots of people have a hook in their boat and don't know it. The boats i run on respond well to jacks. The problem is i have them set for cruise or wide open and i get tired of laying down adjusting them. and this jack has a remote up and down. Will see if it a good idea or not? Might not make me rich but if it works good i will be happy. I didn't want to jack your thread. Just made me think about it again.
ZoomZoom
Well-known member
Cold, in my set up I also run my water rad up front and I don't over heat but my rad is rather large, it is hard mounted( in rubber for shock) to the eng. stand and works find I also don't run a fan, but it sounds like a good idea. I've only got over 200 degs. once when I got stuck for awhile and that lead me to PVC, and that outcome turned out fine for me. My ram has about 4" of travel, but what's more important is the degree of angle change of thrust, and that is determind by how far the ram is from the pivot point on the eng. I will try and ck. mind and see how many degrees of thrust change that I have. ZZ
Just thinking out loud here, so I'm not trying to scatter anybodies biscuits.
In my mind it is a bad idea to have a remote controlled bottom jack in a boat, either glass or AL. Reason being fatigue of the bottom. It certainly seems to me that will shorten hull life expectancy by a lot.
One of the issues with a remote controlled engine centerline trim is the same as with the wings people have tried to trim with, and that is, that you only get trim when you are on the throttle. As opposed to an in the water tab that trims even if you do let off the throttle.
The in the water trim tabs that are remotely adjustable allow fine tuning at any hull speed and any engine speed.
It would make sense to me to trim the engine for best dry running then bolt er down right there. If there is further trim needed in deep water and or high speeds, I would use one of the electric or hydraulic in the water tabs.
I generally make my own trim tabs using electric car window motors and mechanisms. Never had one fail and its dirt cheep and infinitely adjustable.
Scotty :wink:
In my mind it is a bad idea to have a remote controlled bottom jack in a boat, either glass or AL. Reason being fatigue of the bottom. It certainly seems to me that will shorten hull life expectancy by a lot.
One of the issues with a remote controlled engine centerline trim is the same as with the wings people have tried to trim with, and that is, that you only get trim when you are on the throttle. As opposed to an in the water tab that trims even if you do let off the throttle.
The in the water trim tabs that are remotely adjustable allow fine tuning at any hull speed and any engine speed.
It would make sense to me to trim the engine for best dry running then bolt er down right there. If there is further trim needed in deep water and or high speeds, I would use one of the electric or hydraulic in the water tabs.
I generally make my own trim tabs using electric car window motors and mechanisms. Never had one fail and its dirt cheep and infinitely adjustable.
Scotty :wink:
FL Kracker
Well-known member
I'd love to see pictures of this stuff being built! Also, Whitebear, can you pm me with pics of your window motor trim tabs?
thanks, FK
thanks, FK
Scotty! I agree with pretty much everything you said. I just thought the extreme thrust angle changes might assist in stuck situations. If you trimmed it bow up could you spin a boat around in it's boat length or the video's you see with the bow dancing side to side and not going anywhere if you trimmed bow down might you break the back end out? I agree a trim tab is easier for cruise trim.
FL Kracker, I dont build boats anymore, except for myself or friends but I think you can cee the unit in this picture.
Cold, I only have experience with boats here in the south. A lot of heavy work boat experience in the shop with a fleet of 35 boats and before that I was partners in manufacturing hulls and complete airboats. Our solution was to form a ball under the first 1/3 of the boat from the nose, that allowed the boat to spin on the ball in its own length. It also has some benefits we didnt think of initially. The boat was a very light handler. A simple flick of the wrist and a blast from the prop and you could dart in any direction at any speed. At normal cruise in winding canals or rivers it required slight counter steer. These things were a dream to run. Truth is though, there isn't much of a demand for glass hulls that are hand layed one at a time anymore. We finally gave it up and went and got real jobs rather than re rig the whole yard for metal hull fabrication.
You can go to my web site and browse the 1970s style pictures and see what you can see there. Most arent really great pics. They are polaroids that layed in a drawer until flat bed scanners got cheep enough to own. Then I scanned them and at least saved that much of them.
Heres the link to my Airboat pictures, look for 70s Style album.
http://www.ursinecom.com/gallery2/main.php
Thats the main page, look down on the third row for my airboat goodies.
Scotty
Cold, I only have experience with boats here in the south. A lot of heavy work boat experience in the shop with a fleet of 35 boats and before that I was partners in manufacturing hulls and complete airboats. Our solution was to form a ball under the first 1/3 of the boat from the nose, that allowed the boat to spin on the ball in its own length. It also has some benefits we didnt think of initially. The boat was a very light handler. A simple flick of the wrist and a blast from the prop and you could dart in any direction at any speed. At normal cruise in winding canals or rivers it required slight counter steer. These things were a dream to run. Truth is though, there isn't much of a demand for glass hulls that are hand layed one at a time anymore. We finally gave it up and went and got real jobs rather than re rig the whole yard for metal hull fabrication.
You can go to my web site and browse the 1970s style pictures and see what you can see there. Most arent really great pics. They are polaroids that layed in a drawer until flat bed scanners got cheep enough to own. Then I scanned them and at least saved that much of them.
Heres the link to my Airboat pictures, look for 70s Style album.
http://www.ursinecom.com/gallery2/main.php
Thats the main page, look down on the third row for my airboat goodies.
Scotty
ZoomZoom
Well-known member
Cold, here's more info on my trim tab set up, I'm also sending picks. The ram that I used has 3" of travel and changes the eng. thrust angle 5 deg. There is 2 ft. between the eng. pivot point and the ram. The number of degrees up or down will depend on were the (cg) of your boat is, but roughly it should be about the same. The pics are of the ram, power unit and relays and the eng's two pivot points some are better than others, I will PM you with some more info. ZZ
PS pics are in members gallery under Zoom Zoom[/img]
PS pics are in members gallery under Zoom Zoom[/img]
So what do you think the best benefit is of having a trimable motor mount? I was kinda surprised at the shaft size of the cylinder. The one I have has a 1" shaft.
Yeah the cylinder I have is 3" diameter and 6" long. I could trim some inches from it save a few pounds. as Is I would guess it weighs about 16 lbs. OMC trim pump assy is probably 10 lbs. hoses and a qt. of atf. Extra fabrication probably a 40 to 50 lb. hit. I'm really trying to get this thing fueled and ready to hit the river under 2600 Lbs. Not going to be a light boat so just really want to know if this idea would be a benifit? Thanks!! 8)
Yeah the cylinder I have is 3" diameter and 6" long. I could trim some inches from it save a few pounds. as Is I would guess it weighs about 16 lbs. OMC trim pump assy is probably 10 lbs. hoses and a qt. of atf. Extra fabrication probably a 40 to 50 lb. hit. I'm really trying to get this thing fueled and ready to hit the river under 2600 Lbs. Not going to be a light boat so just really want to know if this idea would be a benifit? Thanks!! 8)
ZoomZoom
Well-known member
Cold, the ram that I use is all alu. and is about 3" dia and 6" long the service lines are 1/4" alu and the power control unit weighs less than 10 lbs. I would say that the entire unit weighs only 10 to 15 lbs. I hope this info. will help. In testing it only took about 75 lbs of air pressure to raise the eng. The advantage is that you can trim the boat to run more efficiently, depending on the load in the boat, it can also help when you get stuck by using eng. thrust. In the ram that I use the ram's shaft is only about 1/2" in dia. The front pivot points have no rubber in them I use Delron which is a from of plastic, which means that there is lateral movement, which means the only load on the ram is vertical, it takes no thrust loads. ZZ